Report No. 31303 Towards a More Effective Operational Response Arsenic Contamination of Groundwater in South and East Asian Countries (In Two Volumes) Volume II: Technical Report March 28, 2005 Environment and Social Unit South Asia Region Water and Sanitation ProgramWSP Document of the World Bank Acknowledgments This study was conducted by the World Bank and the Water and Sanitation Programs o f South and East Asia, with additional financing from the Bank Netherlands Water Partnership Program. It was prepared by a team composed o f Karin Kemper and Khawaja Minnatullah (co-task leaders); Amal Talbi, Ede Ijjasz-Vasquez, and Carla Vale (World Bank); StephenFoster and Albert Tuinhof (World Bank Groundwater Management Advisory Team - GWMATE); and Jan-Willem Rosenboom (WSP- East Asia). The background papers were prepared by Pauline Smedley (British Geological Survey), Amal Talbi (World Bank), Feroze Ahmed (Bangladesh University o f Engineering and Technology) and Phoebe Koundouri (Reading Universityiuniversity College London and GWMATE). Valuable comments were provided by Caroline van den Berg, John Briscoe, and Nadim Khouri beer reviewers); and Junaid Ahmad, Guy Alaerts, Ejaz Ghani, Rachel Kaufinann, Smita Misra, Rick Pollard, Jamal Saghir and Luiz Tavares. In addition, the study benefited from numerous comments from participants at the sessionheldat the World Bank Water Week inWashington, D.C. inFebruary 2004 and at the Regional Operational Responses to Arsenic Workshop held inKathmandu, Nepal, in April 2004. The team would like to express their gratitude to Jeffrey Racki (Acting Director, South Asia Social and Environment Unit) and Alastair McKechnie (Country and Regional director, South Asia Region) for their guidance during the study. The team would also like to thank Shyam Ranjitkar (World Bank, Nepal Office) and Dibya Ransatkar from the Department of Irrigation in Nepal for hosting the workshop inKathmandu, the respondents o f the study survey and the many colleagues in the World Bank, WSP and numerous organizations who provided information for this study. - The study documentation was edited by Joh n Dawson. Vandana Mehra (WSP) managed design and publication arrangements. This volume is a product o fthe staff o fThe World Bank and o fthe Water and Sanitation Program. The findings, interpretations, and conclusions expressed inthis document do not necessarily reflect the views o f the Executive Directors o f The World Bankor the governments they represent. The World Bankdoes not guaranteethe accuracy o fthe data included inthis work. The boundaries, colors, denominations, and other informationshown on any map inthis work do not implyany judgement on the part o fThe World Bankconcerning the legal status o f any territory or the endorsement or acceptanceo f such boundaries - 3 - Table of Contents Acknowledgments 3 ExecutiveSummary of Volume I-PolicyReport 11 Abbreviations and Acronyms 15 Paper 1: Arsenic Occurrence in Groundwater in South and East Asia: Scale, Causes, and Mitigation 17 Summary 18 1. Introduction 22 1.1 PathwaysofArsenic Exposure 22 1.2 Drinlung Water Regulationsand Guidelines 22 1.3 World Distribution of High-Arsenic Groundwaters 23 2. Arsenic Distributionin Southand EastAsia 25 2.1 Overview 25 2.2 Alluvial, Deltaic, and LacustrinePlains 26 2.2.1 Bangladesh 26 2.2.2 BengalDeltaandAssociatedAquifers, India 32 2.2.3 Terai Region, Nepal 34 2.2.4 Irrawaddy Delta, Myanmar 36 2.2.5 QuatemaryAquifers, Taiwan, China 37 2.2.6 Alluvial Plains,Northem China 38 2.2.7 RedRiver Plain, Vietnam 41 2.2.8 Mekong Valley: Cambodia, Laos, Thailand, andVietnam 43 2.2.9 IndusPlain, Pakistan 45 2.3 Miningand Mineralized Areas 46 2.3.1 RonPhibun, Thailand 46 2.3.2 RajnandgaonDistrict, MadhyaPradesh, India 48 2.3.3 Other Areas 48 3. Hydrogeochemistryof Arsenic 49 3.1 Overview 49 3.2 Arsenic Sources 49 3.3 ProcessesInvolvedinMobilization 52 3.3.1 Oxidation of Sulfide Minerals 52 3.3.2 Releasefrom Iron Oxides 52 3.3.3 Release from Other Metal Oxides 53 3.3.4 GroundwaterFlow and Transport 54 3.3.5 Impact of Human Activities 56 3.4 At-Risk Aquifers 56 3.5 Variability inArsenic Concentrations 58 3.5.1 SpatialVariability 58 3.5.2 Temporal Variability 58 4. Groundwater Managementfor DrinkingWater and Irrigation 61 4.1 Overview 61 - 4 - 4.2 MiningandMineralizedAreas 61 4.3 Sedimentary Aquifers 61 4.3.1 Shallow Groundwater 61 4.3.2 Groundwater from Deep (Older) Aquifers 63 4.3.3 Surface Water 64 5. Recommendationsfor SurveyingandMonitoring 67 5.1 Overview 67 5.2 Aquifer Development andWell Testing 67 5.2.1 Aquifers o f Low Potential Risk 67 5.2.2 Potentially High-Arsenic Aquifers 68 5.2.3 Deep Aquifers below High-Arsenic Aquifers 70 5.3 Monitoring 70 5.3.1 Shallow Sedimentary Aquifers with Recognized Arsenic Problems 70 5.3.2 Deep (Older) Aquifers inArsenic-Prone Areas 71 5.3.3 FurtherResearchNeededto AssessTemporalVariations 71 6. ConcludingRemarks 73 Glossary 75 References 76 Tables Table 1. Summary o fthe Distribution, Nature, and Scale o f DocumentedArsenic Problems (>50 pgL-')inAquifers inSouth andEast Asia 27 Table 2. Frequency Distributionof Arsenic inGroundwater from Tubewells from Quaternary Alluvial Aquifers inBangladesh 30 Table 3. Frequency DistributionofArsenic Concentrations inAnalyzed Groundwater Samples from Nepal 36 Table 4. Frequency Distributiono fArsenic Concentrations inGroundwaters from the Alluvial Aquifer ofMyanmar 37 Table 5. Frequency Distributiono fArsenic Concentrations inGroundwater fromthe Huhhot Basin, Inner Mongolia 41 Table 6. Summary Arsenic Datafor Groundwater from DugWellsinthe High-Arsenic Groundwater Region o fthe Huhhot Basin 41 Table 7. Summary Arsenic Datafor Groundwater from Tubewells inthe RedRiver Plain, Vietnam, Divided into Those from the Holocene and Pleistocene Aquifers 42 Table 8. Summary Arsenic Datafor Groundwater from Tubewells inthe MekongValley o f Cambodia 44 Table 9. Summary Arsenic Datafor Groundwater from Tubewells inthe MekongValley o f Lao PDR 45 Table 10. Frequency Distributiono fArsenic Concentrations inGroundwater Samples fromNorthern Punjab 46 Table 11.Frequency Distributiono fArsenic Concentrations inWater from RonPhibunArea 47 Table 12. Frequency Distributiono fArsenic Concentrations inGroundwater from Chowki Block, Madhya Pradesh, India 48 Table 13. Typical Arsenic Concentrations inRock-FormingMinerals 50 - 5 - Table 14. Typical Arsenic ConcentrationRangesinRocks, Sediments, and Soils 51 Table 15. Risks Associated with the Use o f Drinking Water from Various Sources at Various Scales andPotential Mitigation Strategies 66 Table 16. Arsenic Testing Strategies inPotential High-Arsenic Groundwater Provinces 68 Figures Figure1. Summary o fthe World Distribution o fDocumentedProblems with Arsenic inGroundwater andthe Environment 24 Figure2. Map of South andEast Asia Showingthe Locationso f DocumentedHigh-Arsenic Groundwater Provinces 25 Figure3. SmoothedMap of Arsenic DistributioninGroundwater fromBangladesh 28 Figure4. Maps of the DistributionofArsenic inShallow Groundwater fromthe Chapai Nawabganj Area, Northwest Bangladesh 29 Figure5. Variation inConcentrationofArsenic andOther Elements with Depthina Purpose-Drilled Piezometer in Chapai Nawabganj, Northwest Bangladesh 29 Figure6. Map of West Bengal Showing Districts Affected byHighGroundwater Arsenic Concentrations 34 Figure7. Map o fChina Showing the DistributionofRecognized High-Arsenic (>50 pg L-1) Groundwaters and the Locations o f Quaternary Sediments 39 Figure8. Regional Distributiono fArsenic inGroundwaters fiomthe Shallow andDeep Aquifers o f the Huhhot Basin 40 Figure9. Geological Map of Cambodia Showing Distributionof Potentially High-Arsenic Aquifers 44 Figure 10. Simplified Geology o f the RonPhibunArea, Thailand, Showing the Distribution of Arsenic inAnalyzed Groundwaters 47 Figure11.Schematic Diagramo fthe Aquifers inSouthern Bangladesh Showing the Distribution of Arsenic and the Configuration o f Wells 54 Figure 12. Sea Level Changes duringthe Last 140,000 Years 55 Figure 13. Classification of Groundwater Environments Susceptible to Arsenic Problems from Natural Sources 57 Figure14. MonitoringData for Groundwater from Selected Wells and Specially DrilledPiezometers inFaridpurArea, CentralBangladesh 59 Boxes Box 1. Analysis o f Arsenic 26 Box 2. Shallow versus Deep Aquifers 31 Box 3. Dug Wells 33 Box 4. Frequently Asked Questions 55 - 6 - Paper 2: An Overview of CurrentOperationalResponsesto the Arsenic Issue inSouth andEastAsia 81 Summary 82 1. Introduction 83 2. Arsenic: HealthEffects, RecommendedValues, and NationalStandards 84 2.1 International andNational Standardsfor Arsenic Intake 84 2.2 Major Limitations of Existing Epidemiological Studies 85 2.3 Major HealthEffects 87 2.4 Arsenic Ingestedthrough the FoodChain 87 2.5 OperationalResponsesof CountriesinSouthand EastAsia 88 2.6 Initial Responsestowards SuspectedArsenic Contamination 88 2.6.1 Screeningand Identification ofContaminationLevels inWater Sources 89 2.6.2 Well Switching, Painting of Tube Wells, and Awareness 93 2.6.3 PatientIdentification 95 2.6.4 Treatment ManagementofArsenicosis Patients 98 2.7 Longer-Term Responses 99 2.7.1 Institutional Longer-Term Responses(Arsenic Country Policy) 99 2.7.2 Technical Longer-Term ResponsesBasedon Surface Water 100 2.7.3 Technical Longer-Term ResponsesBasedon Groundwater 102 2.8 Disseminationof Information 106 2.8.1 RegionalArsenic Networks andNational Databases 106 2.8.2 SummaryRemarks 107 3. Arsenic Mitigationinthe Context of the OverallWater Supply Sector 108 3.1 Background 108 3.2 Access to Improved Water Sources inAsian Countries 108 3.3 Arsenic Priority Comparedto Poor Bacteriological Water Quality Priority 108 3.4 Definition and Indentification of Arsenic ContaminationHotspots 110 3.5 RemainingIssues and Recommendations 111 4. Incentives for Different Stakeholdersto AddressArsenic Contamination 112 4.1 Number of Peopleat Risk 112 4.2 NumberofArsenicosis Patients 112 4.3 RuralandUrbanAreas 112 4.4 National and International Media 113 4.5 Institutional Aspects 113 4.6 Short-Termversus Long-Term Solutions 113 4.7 ReputationalRisk 113 5. Conclusion 115 Annex 1.OperationalResponsesUndertakenby Southand East Asian Countries 117 Annex 2. Matricesfor Implementation ofOperationalResponsesto Arsenic Contamination 118 Annex 3. OperationalResponsesto Arsenic Contamination: QuestionnaireResults 123 Annex 4. Government, NGOs, International OrganizationsInvolvedinOperationalResponses 129 Annex 5 HealthEffects ofChronic Exposureto Arsenic inDrinking Water 131 References 137 - 7 - Tables Table 1.Currently AcceptedNational Standardsof Selected Countriesfor Arsenic inDrinking Water 84 Table 2. Chronology ofRecommendedWHO Values for Arsenic inDrinkingWater 85 Table 3. Current Populationat RiskinAsianCountries 96 Table 4. Summary of Responsesto Arsenic ContaminationBasedon Surface Water 103 Table 5. Summaryof Responsesto Arsenic ContaminationBasedon Groundwater 106 Table 6,Access to ImprovesWater SourcesinSelected AsianCountries 108 Table 7.Percentage ofPopulationinSelectedAsianCountrieswith Sanitation 109 Table 8. Child MortalityRatesinSelectedSouthandEastAsianCountries 109 Table 9. ConceptualizedIncentive Matrix: Stakeholder Incentivesfor Action on Arsenic Issues 114 Boxes Box 1.Comparisonof FieldTestingand Laboratory Analysis 89 Box 2. Parametersto Assess the Capacity of LaboratoryAnalysis 90 Paper 3: ArsenicMitigationTechnologiesinSouth and EastAsia 140 Summary 141 1. Introduction 142 2. Treatment of Arsenic-ContaminatedWater 143 2.1 Oxidation-SedimentationProcesses 143 2.2 Coagulation-Sedimentation-FiltrationProcesses 144 2.3 Sorptive Filtration 148 2.4 MembraneTechniques 152 2.5 ComparisonofArsenic RemovalTechnologies 152 3. Laboratoryand FieldMethodsof Arsenic Analysis 156 3.1 Laboratory Methods 156 3.2 FieldTest &t 156 4. Alternative Water Supply Options 160 4.1 Deep Tubewell 160 4.2 Dugor RingWell 161 4.3 SurfaceWater Treatment 162 4.4 RainwaterHarvesting 163 4.5 PipedWater Supply 164 4.6 Cost Comparisono fAlternative Water Supply Options 165 5. Operational Issues 166 5.1 TechnologyVerificationandValidation 166 5.2 SludgeDisposal 166 5.3 Costs 167 6. Conclusions 169 References 170 Tables Table 1.Comparisonof MainArsenic Removal Technologies 153 - 8 - Table 2. ComparisonofArsenic RemovalMechanismsand Costs inBangladesh 154 Table 3. Comparisonof Costs of Different Arsenic TreatmentTechnologiesinIndia 155 Table 4. Laboratory Analysis Methods for Arsenic 157 Table 5. Comparison of Arsenic FieldTest Kits 158 Table 6. Advantages and Disadvantagesof Rainwater Collection System 163 Table 7. Costs of Alternative TechnologicalOptions inArsenic-Affected Areas 165 Table 8. Cost of Water Supply Options for Arsenic Mitigation 168 Figures Figure 1.Double Bucket HouseholdArsenic TreatmentUnit 146 Figure 2. StevensInstituteTechnology 146 Figure 3. DPHE-Danida Filland Draw Arsenic RemovalUnit 146 Figure 4. Tubewell-Attached Arsenic RemovalUnit 147 Figure 5. CorrelationbetweenIronand Arsenic Removal inTreatmentPlants 147 Figure 6. Alcan EnhancedActivated Alumina Unit 149 Figure 7. GranularFerric Hydroxide-BasedArsenic RemovalUnit 149 Figure 8. Three Kalshi Filterfor Arsenic Removal 150 Figure 9. ShaplaFilter for Arsenic Removal at HouseholdLevel 150 Figure 10. TetrahedronArsenic RemovalTechnology 151 Figure 11.Deep Tubewell with Clay Seal 160 Figure 12. PondSandFilterfor Treatmentof Surface Water 162 Figure 13. Plastic Sheet Catchment 164 Paper 4: The Economics of Arsenic Mitigation 174 Summary 175 1. TheIssue 176 1.1 Aims ofThis Paper 176 1.2 SituationalAnalysis 177 2. An Ideal Approachto Evaluation ofArsenic Mitigation Measures 178 2.1 Uncertainty andthe IdealApproach 178 2.2 An IdealModel 179 2.3 Problemswith the Ideal Model 180 2.4 The NthBest Model 181 2.5 I s Passing a Cost-Benefit Test Sufficient? 183 3. The Cost of Arsenic Mitigation Measures: Review of PossibleActions 185 3.1 Health Effects of Arsenic inDrinlungWater 185 3.1.1 Cancer Health Effects 185 3.1.2 Treatmentof Arsenicosis Sufferers 186 3.2 MitigationofArsenic inDrinking Water 186 3.2.1 Groundwater 187 3.2.2 Surface Water 188 3.2.3 Technology Choice 189 4. Applyingthe Model 199 4.1 Methodology for the Model 199 - 9 - 4.2 Data andEstimates for the Model 199 4.3 Results for the Model 203 5. Summary and Conclusions 209 Annex 1.DetailedTechnologyCosts 210 References 217 Tables Table 1.RankingofProjects 183 Table2. Arsenic MitigationTechnology Options 189 Table 3. Small Village: Capital andOperation andMaintenance Costs 191 Table 4. Small Village: Technology-Specific Levelof Service 191 Table 5. MediumVillage: Capital andOperationandMaintenance Costs 192 Table 6. MediumVillage: Technology-Specific Level of Service 192 Table 7. Large Village: Capital andOperation andMaintenance Costs 193 Table 8. Large Village: Technology-Specific Level of Service 193 Table 9. Small Villages: PresentValue Analysis ofTechnology Costs 194 Table 10. MediumVillages: PresentValue Analysis ofTechnology Costs 195 Table 11.Large Villages: PresentValue Analysis ofTechnology Costs 195 Table 12. Small Villages: Total Costs ofMitigationTechnology Options 197 Table 13. MediumVillages: Total Costs ofMitigationTechnology Options 197 Table 14. LargeVillages: Total Costs ofMitigationTechnology Options 198 Table 15.All Villages: Total Costs ofMitigationTechnology Options 198 Table 16. PresentValue ofCosts ofArsenic MitigationOptions for Whole Population 199 Table 17. Bangladesh: EstimatedHealthImpact ofArsenic Contamination ofTubewells 201 Table 18. NPV (inBillionUS$)o fArsenic MitigationPolicies, Discountedat 5% 205 Table 19.NPV (inBillionUS$) ofArsenic Mitigation Policies, Discounted at 10% 206 Table20. NPV (inBillionUS$) of Arsenic MitigationPolicies, Discountedat 15% 207 -10- Executive Summary of Volume I-Policy Report Background and Introduction i. Thedetrimentalhealtheffectsofenvironmentalexposuretoarsenichavebecomeincreasingly clear in the last few years. High concentrations detected in groundwater from a number o f aquifers across the world, including in South and East Asia, have been found responsible for health problems ranging from skin disorders to cardiovascular disease and cancer. ii. Theproblemhasincreasedgreatlyinrecentyearswiththegrowinguseoftubewellstotap groundwater for water supply and irrigation. The water delivered by these tubewells has been found in many cases to be contaminated with higher than recommended levels o f arsenic. In the study region, countries affected include Bangladesh (theworst affected), India, Myanmar, Nepal, and Pakistan (South Asia); and Cambodia, China (including Taiwan), Lao People's Democratic Republic, andVietnam (East Asia). iii. This studyconcentratesonoperational responsesto arsenic contaminationthatmaybeof practical use to actors who invest in water infrastructure in the affected countries, including governments, donors, development banks, andnongovernmental organizations (NGOs). ObjectivesandAudience of the Study iv. The objectives o f this study are (a) to take stock of current knowledge regarding the arsenic issue; and (b) to provide options for specific and balanced operational responses to the occurrence o f arsenic inexcess o fpermissible limits in groundwater inAsian countries, while takinginto account the work that has already been carriedout bymanydifferent stakeholders. v. The study provides information on (a) occurrence o f arsenic in groundwater; (b) health impacts o f arsenic; (c) policy responsesby govemments and the international community; (d) technological options for and costs o f arsenic mitigation; and (e) economic aspects o f the assessment and development o f arsenic mitigation strategies. The focus o f the study i s on rural rather than urban areas, due to the particular difficulties associated with applying mitigationmeasures inscattered rural communities. vi. The study is structured as follows: Volume I:Policy Report. This report summarizes the main messages o f Volume 11, and highlightsthe policy implications of arsenicmitigation. This Volume I1comprises four specialist papers: Paper 1. Arsenic Occurrence inGroundwater inSouth and East Asia: Scale, Causes, and Mitigation Paper 2. An Overview o f Current Operational Responsesto the Arsenic Issue inSouth and East Asia Paper 3. Arsenic Mitigation Technologies in South andEast Asia Paper 4. The Economics o f Arsenic Mitigation The Scaleof the Arsenic Threat vii. In South and East Asia an estimated 60 million people are at risk from high levels o f naturally-occurring arsenic ingroundwater, and current data show that at least 700,000 people in the region have thus far been affected by arsenicosis. However, although the negative healtheffects of arsenic ingestion ingeneral, and the specific impact of ingestion of arsenic- contaminated groundwater, have both beenwidely studied, there is still no clear picture o f the epidemiology o f arsenic in South and East Asia, and uncertainty surrounds such issues as the spatial distribution o f contamination; the symptoms and health effects o f arsenic-related - 11- diseases, and the timeframe over which they develop; and the impact o f arsenic compared to other waterborne diseases whose effects may be more immediate. ... v111. While arsenic is clearly an important public health threat, it needs to be noted that morbidity and mortality due to other waterborne diseases is also a serious health issue. Therefore, mitigation measures to combat arsenic contamination in South and East Asia need to be consideredwithin the wider context o f the supply o f safe water. ix. Due to the carcinogenic nature o f arsenic, the World Health Organization (WHO) recommends a maximumpermissible concentration for arsenic in drinking water o f 10 pg L-' (micrograms per liter), which has been adopted by most industrial countries. Most developing countries still use the former WHO-recommended concentration o f 50 pg L-'as their national standard, due to economic considerations and the lack of tools and techniques to measure accurately at lower concentrations. Further studies are needed to assess the relationship between levels o f arsenic and health risks in order to quantify the inevitable trade-offs at different standards between such considerations as healthrisks, the ability o f people to pay for safe water, and the availability o f water treatment technology. Distributionof Arsenic Contamination x. The concentration of arsenic in natural waters globally, including groundwater, is usually below the WHO guideline value o f 10 pg L-'. However, arsenic mobilization in water is favored under reducing (anaerobic) conditions, leading to the desorption o f arsenic from iron (and other metal) oxides. In South and East Asia such conditions tend to occur in shallow aquifers in Quaternary strata underlying the region's large alluvial and deltaic plains (Bengal basin, Irrawaddy delta, Mekong valley, Red River delta, Indus plain, Yellow River plain). (Some localized groundwater arsenic problems relate to ore mineralization and mining activity, which are not the focus o f this study.) Recent hydrogeochemical investigations have improved our knowledge o f the occurrence and distribution o f arsenic ingroundwater, though much uncertainty remains regarding the source, mobilization, and transport o f the element in aquifers. xi. One o f the important findings o f recent detailed aquifer surveys has beenthe large degree o f spatial variability in arsenic concentrations, even over distances o f a few hundred meters. Temporal variability also occurs, though insufficient monitoring has been carried out to establish a clear picture o fvariations inarsenic levels over different timescales. Arsenic MitigationMeasures xii. Arsenic mitigation requires a sequence o f practical steps involving enquiry and associated action. Assessing the scale o f the problem (now and over time) involves field testing, laboratory testing, and monitoring; identifying appropriate mitigation strategies involves technological, economic, and sociocultural analysis o f possible responses; and implementation involves awareness raising and direct action by governments, donors, NGOs, and other stakeholders at local, national, and regional levels. Sustainability in the long run remainsamajor challenge. xiii. The two main technological options for arsenic mitigation are (a) switch to alternative, arsenic-free water sources; or (b) remove arsenic from the groundwater source. Alternatives in the first category include development of arsenic-free aquifers, use of surface water and rainwater harvesting; alternatives in the second category involve household-level or community-level arsenic removal technologies. For each option there will be a wide range o f design specifications andassociated costs. xiv. Despite continuing uncertainty regarding arsenic occurrence and epidemiology, the lethal nature and now well-established effects o f arsenic exposure in South and East Asia make it necessary that informed choices and trade-off decisions are made to address arsenic contamination o f drinking water sources and the scope and extent o f mitigation measures, withn the context o fthe development o fthe water sector andthe wider economy. - 12- xv. Accordingly, a simple cost-benefit methodology has been developed that takes into account data limitations and provides decisionmakers with an approach for rapid assessment o f the socioeconomic desirability o f different mitigation policies under various scenarios. In particular, the methodology permits an analysis o f options in order to choose between different approaches indealing with (a) the risk that arsenic mightbe found inan areawhere a project is planned; and (b) the risk mitigation options where a project's goal i s arsenic mitigationper se. xvi. Demand-side perspectives are an important consideration for designing arsenic mitigation measures that meet the requirements o f households and communities. For example, are users willing to pay for an alternative such as pipedwater? Demandpreferences can be assessed through contingent valuation or willingness to pay studies and can provide important guidance to decisionmakers. There is a need to strengthen institutional capacities in the countries to carry out such assessments. The PoliticalEnvironmentof Arsenic Mitigation xvii. Arsenic has become a highly politicized topic in the international development community and within some affected countries due to its carcinogenic characteristics and due to the earlier failure to consider it as a possible natural contaminant in groundwater sources. This factor makes rational analysis o f the issue difficult and highlights the fact that application o f mitigationmeasuresneeds to consider the political as well as the social and economic climate. The scattered rural communities most affected by arsenic contamination often have limited political presence and are inparticular needo f support. xviii. Governments that want to address the arsenic issue will therefore have to take a stronger lead role in their countries and on the international plane. This goes both for more strategic research and knowledge acquisition regarding arsenic in their countries, as well as for the choice and scope o f arsenic mitigation activities. The Importanceof an EffectiveOperationaland StrategicApproach xix. Significant strides have been made since arsenic was first detected in dnnking water tubewells in Eastern India and Bangladesh in the late 1980s and early 1990s. However, a range o f factors - including projected population growth in the region, continuing private investment in shallow tubewells, and the drive towards achevement o f the Millennium Development Goal related to safe water supply - add to the urgency o f adopting a more strategic approach for effective action at project, national, and international levels. xx. At project level, any interventions that consider using groundwater as a source must involve an assessment ofwhether occurrence o f arsenic would affect the outcome o fthe project. Such an assessment would include consideration o f technical factors (such as screening and possible mitigation technologies), social and cultural factors, and economic factors (including a cost-benefit or least-cost analysis). xxi. Some countries have taken arsenic to the national level o f attention, including Bangladesh, Nepal, and Cambodia. Others, such as India, Pakistan, and China, have only started to address the issue, while in others international organizations such as UNICEF and local NGOs and universities are the focal points for arsenic-related activities. Although the characteristics o f arsenic contamination are unique to each affected country, study results suggest that three simple steps would help governments more effectively address the problem now and in the hture: (a) encourage further research in potentially arsenic-affected areas in order to better determine the extent of the problem; (b) ensure that arsenic i s included as a potential risk factor in decisionmaking about water-related issues; and (c) develop options for populations inknownarsenic-affected areas. xxii. At the global level, focused research on the chemistry o f arsenic mobilization and the dose- response relationships for arsenic are o f vital importance in formulating a more effective approach. If governments and the international community are to achieve the MDGs inwater - 13 - supply and sanitation then the knowledge gaps regarding arsenic needto be filled, notably by (a) further epidemiological research directly benefiting arsenic-affected countries; (b) socioeconomic research on the effects o f arsenicosis, understanding behavior and designing demand-based packages for the various arsenic mitigation techniques; and c) hydrogeological andhydrochemicalresearch xxiii. It also needs to be made clear that, due to the nature of arsenic itself, in the not-so-distant hture there will be diminishing returns on investments in scientific arsenic research to reduce uncertainty. The important challenge will be to identifythose areas where improved research- level data collection i s likely to provide a major return. For other areas the main question will behow to manage inthe face o f unavoidable and continuing uncertainty. xxiv. Accordingly, the international dialogue should shift towards targeted research priorities that address these issues. This would also include the pursuit o f the research agenda regarding arsenic in the food chain. Both the World Bank and a number o f development partners are contributors to the Consultative Group on International Agricultural Research (CGIAR) and this organization would lenditself to buildingup a coherent and focused research agendaon this topic in order to provide decisionmakers with guidance regarding arsenic-contaminated groundwater. - 14- Abbreviations andAcronyms The following list includes all abbreviations and acronyms usedthroughout Volumes Iand I1o f the report. AAN AsianArsenic Network AAS atomic absorption spectrometerhpectrometry A E S atomic emission spectrometry AIIH&PH All IndiaInstitute ofHygieneandPublic Health APSU Arsenic Policy Support Unit(Bangladesh) As arsenic ASV anodic strippingvoltammetry AusAID Australian Agency for International Development A W W A American Water Works Association BAMWSP Bangladesh Arsenic Mitigation Water Supply Project BGS BritishGeological Survey BUET BangladeshUniversity o fEngineering and Technology CBA cost-benefit analysis CCA chromated copper arsenate CEPIS PanAmerican Center for Sanitary Engineering and Environmental Sciences (Peru) CGIAR Consultative Group on Intemational Agricultural Research Danida DanishAgency for International Development DF discount factor DOC dissolved organic carbon DPHE Department o f Public HealthEngineering (Bangladesh) DWSS DepartmentofWater Supply and Sewerage (Nepal) EAWAG Swiss Federal Institute for Environmental Science and Technology EPA Environmental ProtectionAgency (United States) GDP gross domestic product GF-AAS graphite finace-atomic absorption spectrometry GPL General Pharmaceutical Ltd. GPS global positioning system GWMATE World BankGroundwater Management Advisory Team HG-AAS hydride generation-atomic absorption spectrometry HG-AFS hydride generation-atomic fluorescence spectrometry ICP inductively coupledplasma ICP-MS inductively coupledplasma-mass spectrometry IRC International Water and Sanitation Center (formerly International Reference Center for Community Water Supply) JICA Japan International Cooperation Agency Lao PDR Lao People's Democratic Republic MDG MillenniumDevelopment Goal M S mass spectrometry NAMIC National Arsenic Mitigation Information Center (Bangladesh) NASC National Arsenic Steering Committee (Nepal) NGO nongovemmental organization - 15 - NPV net present value NRC National Research Council (United States) NRCS Nepal RedCross Society NTU nephelometric turbidityunit PAHO PanAmerican HealthOrganization P V present value SDDC silver diethyldithiocarbamate SORAS solar oxidation andremoval of arsenic TCLP toxic characteristic leachingprocedure UNCHS UnitedNations Centre for HumanSettlements UNDP UnitedNations Development Program UNICEF UnitedNations Children's Fund WHO World Health Organization WRUD Water Resources UtilizationDepartment (Myanmar) UnitsofMeasurement Pg microgram mg milligram kg kilogram L liter PgL-l micrograms per liter mgL-' milligramsper liter cm centimeter m meter km kilometer Units of Currency(January 2004) 1US$ =58 taka (Tk) (Bangladesh) 1US$ =48 rupees (Rs) (India) - 16- Paper 1 Arsenic Occurrence in Groundwater inSouth andEastAsia: Scale, Causes, and Mitigation Prepared by Dr.PaulineSmedley, BritishGeological Survey Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1 Paper 1 Arsenic Occurrence in South - - andEastAsia: scale, causes, and mitigation Summary The detrimental health effects o f environmental exposure to arsenic have become increasingly clear in the last few years. Drinking water constitutes one o f the principalpathways of environmental arsenic exposure in humans and high concentrations detected in groundwater from a number o f aquifers across the world have been found responsible for health problems ranging from skin disorders to cardiovascular disease and cancer. Food represents a hrther potential exposure pathway to arsenic, particularly where crops are irrigated with high-arsenic groundwater or where food is cooked inhigh- arsenic water. However, the relative impact on human health is as yet unquantified and in need o f hrther study. The concentration o f arsenic in natural waters globally, including groundwater, is usually low. Most have concentrations below the World Health Organization (WHO) provisional guideline value for arsenic in drinking water o f 10 pg L-I.However, arsenic mobilization inwater is favored under some specific geochemical and hydrogeological conditions and concentrations can reach two orders o f magnitude higher than this in the worst cases. Most occurrences o f high-arsenic groundwater are undoubtedly o f natural origin. Major alluvial and deltaic plains and inland basins composed o f young sediments (Quaternary; thousands to tens o f thousands o f years old) are particularly prone to developing groundwater arsenic problems. Many o f the identified affected aquifers are located in South and East Asia. High concentrations have been found in groundwater from such aquifers inthe Bengal basin o f Bangladesh and eastern India; the Yellow River plain and some internal basins of northern China; the lowland Terai region o f Nepal; the Mekong valley o f Cambodia; the Red River delta o f Vietnam; and the Irrawaddy delta o f Myanmar.Problems may also emerge in similar alluvial and deltaic environments elsewhere inthe world. Unfortunately, such flat-lying fertile plains are often densely populated and so poor groundwater quality can have a major impact on large numbers o f people. The increasing incidence o f arsenic-related health problems inthese areas largely coincided with the change to using groundwater from tubewells, which beganinthe 1970s and 1980s. The detailed mechanisms by which the arsenic mobilization occurs in sedimentary aquifers are still not well understood. However, the development o f reducing (anaerobic) conditions inthe aquifers has beenrecognized as a key risk factor for the generation o f hgh-arsenic groundwater. Indicators o f such conditions include lack o f dissolved oxygen and highdissolved iron and manganese concentrations. High-pH, oxidizing (aerobic) groundwater conditions have also been linked with high groundwater arsenic concentrations insome parts o f the world, though there i s as yet no evidence for this means o f occurrence in aquifers o f South and East Asia. And inlandbasins such as occur innorthern China and Mongolia represent possible areas for such conditions, but few data exist for such areas. Slow groundwater movement i s also considered an important risk factor since under such conditions arsenic can be dissolved from minerals in the aquifer but is not readily flushed out o f the system. Flat-lying sedimentary basins and delta plains are typically areas o f such slow groundwater movement. One o fthe key findings o f the last few years has been that the sediments inthese high-arsenic aquifers do not contain unusually high arsenic concentrations. Typical concentrations are o f the order o f 5- 10mg kg-'; values rather close to world averages. Nor do the sediments contain unusual arsenic minerals. It is therefore feasible that any young sedimentary aquifers could develop high-arsenic groundwater, given the special geological and hydrogeological conditions outlined above. Hence, other regions inAsia and elsewhere with young sedimentary aquifers may contain groundwater with high arsenic concentrations, but have not yet been identified. Given the increased awareness of arsenic problems and increased groundwater testing that is currently beingundertaken invarious parts o f Asia, it is likely that other areas with problems will be identified more rapidly thanwas previously the case. The existence o f unrecognizedproblems on such a large scale as that identified inthe Bengal basin is not impossiblebut is considered unlikely. Mineralized areas, particularly areas o f mining activity, are also at increased risk o f groundwater arsenic contamination, although, unlike young sedimentary aquifers, the affected areas are typically o f local extent (a few kilometers around the mineralized zone). Some geothermal areas may also give - 18 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEast Asia: scale, causes, and mitigation rise to increased groundwater arsenic concentrations, though this i s also a less regionally significant occurrence. Despite the advances made in recent years in understanding where high-arsenic groundwaters are likely to exist on a regional scale, predictability on a local scale is still poor andprobably will always be so. Short-range (well-to-well) variability ingroundwater arsenic concentrations is often large. This means that individual wells used for drinking water need to be tested in recognized arsenic-affected areas. Despite common associations between arsenic and a number o f other trace elements (for example iron, manganese) in groundwater, observed correlations in water samples are usually weak. Hence, although other elements may signal potential problems regionally, they are not reliable as proxy indicators o f arsenic concentrations inindividual wells. Temporal variations in groundwater arsenic concentrations are also poorly defined. Significant seasonal and longer-term variations have been claimed to occur in some groundwaters from affected aquifers, though the information is largely anecdotal and difficult to verify. Temporal variation has major consequences for mitigation efforts and i s in need o f further investigation. However, in the interim, major short-term changes in groundwater arsenic concentrations are not expected in most cases. Hence, it is reasonable to assume that an initial determination is likely to be representative, provided the result is analytically reliable. In areas affected by high-arsenic groundwater, there has been much investigation into finding alternative sources o f safe (low-arsenic) drinking water. Many o f the options focus on the use o f surface water (including rainwater), water from dugwells, and water from deep aquifers. Surface waters usually have low dissolved arsenic concentrations. This i s because o f the low so1id:solution ratios in surface conditions compared to aquifers, and to the oxidizing conditions that pertain inmost surface environments. Under oxidizing conditions, adsorption o f arsenic to sediments and soils occurs andmobilizationinsoluble form i s not favored. Exceptions can occur locally insome mining environments as a result o f direct contamination or insurface waters with a major proportion o f discharging high-arsenic groundwater. However, the normally strong adsorption o f arsenic to stream sediments is likely to remove the dissolved arsenic from these sources over time. Arsenic may persist in some surface waters affected by geothermal inputs or evaporation (under high-pH conditions) but highconcentrations related to these processeshave not been identified inAsia and are not considered o f major importance in the region. Some arsenic in surface waters may be associated with particulate matter rather than being truly dissolved, especially if the water is turbid. The overwhelming drawback o f surface waters is their often poor bacterial quality. This also has major health implications and has been an important factor indetermining the shift towards increased use o f groundwater from tubewells in Asia over the last few decades. Surface waters therefore usually require sanitary treatment before use for potable supply. Dugwells have also often been found to contain groundwater with low concentrations of arsenic in areas where tubewell groundwaters yield high concentrations. As with surface waters, groundwater in dug wells is typically relatively oxidizing, comprising a high proportion o f freshly recharged rainwater and being open to the atmosphere. Most groundwater samples analyzed from dug wells in Bangladesh, West Bengal, Myanmar, and Nepal have been found to contain arsenic concentrations less than 50 p g L-' (the national standard for most countries in Asia). As a result o f this, dug wells have beenpromoted insome high-arsenic areas as alternative sources o f drinkingwater. However, the concentrations cannot always be guaranteed to be low. Sporadic occurrences above 50 p g L-' have been found in groundwater from dug wells in a number o f the recognized high-arsenic provinces. Some may be in the particulate rather than dissolved fraction, but such details are rarely specified in reports from the affected regions. Nevertheless, dissolved concentrations o f up to 560 p g L-' have been found in dug well water from Inner Mongolia (China) where anaerobic conditions have been maintained in low-lying areas o f groundwater discharge that are characterized by sluggish groundwater movement. More chemical analysis i s requiredto obtain an improved database of arsenic concentrations for dug wells. As with surface waters, shallow dug wells are vulnerable to contamination from surface pollutants and pathogenic organisms. They are also more prone to drying up inareas with large water table fluctuations. They are therefore unlikely to represent a major long- - 1 9 - Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEast Asia: scale, causes, and mitigation term solution to the arsenic problems identified in most areas o f South and East Asia, although they may provide a suitable interim solution (given adequate sanitary protection) in some affected areas if their arsenic concentrations canbe demonstrated to be reliably low. Insome arsenic-affected regions of Asia, low-arsenic groundwater hasbeen found indeeper aquifers underlying the young affected sediments. Groundwater with low arsenic concentrations ( 4 0 pg L-') has been found in, for example, deep aquifers inthe Bengal basin (Bangladesh, India) and the Nepal Terai. The depth at which these aquifers occurs varies considerably (tens to hundreds o f meters) and so considerable confusion has arisen over the descriptions o f these aquifers. The stratigraphy o f the aquifers i s poorly defined in most countries. More investigation has been canied out in Bangladesh than elsewhere. Here, the deep aquifers with low-arsenic groundwater are mineralogically distinct from the younger overlying sediments and are relatively oxic. They are likely to be o f Pleistocene age (Quaternary; greater than 10,000 years old) and are considered to have undergone more flushing by groundwater over their geological history than the sediments bearing high-arsenic groundwater that overlie them. These older aquifers in Bangladesh, West Bengal, and Nepal represent a potential altemative source o f safe (low-arsenic) drinkingwater for the affected populations. However, considerable uncertainty exists over their long-term sustainability in the event o f significant exploitation. Further hydrogeological research i s required to investigate whether, and to what extent, they would be susceptible to drawdown o f high-arsenic groundwater from overlying aquifers or saline water in coastal areas following significant aquifer development. However, research effort on these aquifers should be complementary to the implementation o f mitigation measures and not a reason for delaying them. Although older, deeper Quaternary aquifers inthe Bengal basin andNepal have been found to contain low groundwater arsenic concentrations, this has been found not to be the case insome other regions. Inparts of northern Chma, high arsenic concentrations have been found in groundwater from both shallow (young Quaternary) and deeper (older Quaternary) aquifers. Here, the inland deep aquifers are thought not to have beenwell flushed duringthe Quaternary ice ages because o f slow groundwater flow and closed-basin conditions. Some groundwaters in Pleistocene aquifers o f Vietnam also appear to have high arsenic concentrations. Aquifer depth i s therefore not an indicator o f susceptibility to arsenic mobilization. Rather, dissolved arsenic concentrations are determined by a combination o f geochemical conditions suitable for mobilizing it and hydrogeological conditions which prevent its removal. Hence, groundwater quality with respect to arsenic concentrations must be considered on an aquifer-by-aquifer basis and good hydrogeological and geochemical understanding o f young sedimentary aquifers is a prerequisite to groundwater development. On a regional scale, our understanding o f arsenic mobilization processes i s sufficiently developed to allow some kind o f prediction o f where arsenic problems are likely to occur and where not. Young sedimentary aquifers in alluvial and deltaic plains and inland basins are obvious areas for priority groundwater testing. Randomized reconnaissance groundwater arsenic surveys o f such areas are the logical first step in identifying problem areas, followed by more detailed surveys and mitigation if problems emerge. In identified arsenic problem areas, ideally every well used for dnnkmg water should be tested for arsenic. Given the high toxicity o f arsenic to humans, there i s an argument for reconnaissance testing o f groundwaters from any aquifer used for potable water supplies regardless o f aquifer type and lithology. However, groundwater testing in Asia necessarily involves prioritization, with greatest emphasis on the aquifers at greatest risk. A central tenet of both understanding the nature and scale of arsenic problems in groundwater and mitigating them is the acquisition o f reliable analytical data for arsenic. Poor data can lead to erroneous conclusions and hence inappropriate responses. However, reliable chemical analysis o f arsenic in water is not a trivial undertaking and requires continual attention to quality assurance. Many groundwater arsenic analyses in Asia have been carried out using field test kits and these are particularly prone to problems with poor precision and accuracy. Great emphasis should be placed on obtaining good-quality analytical data during testing and monitoring programs. Such programs need -20 - Arsenic Contaminationof Groundwater in South and East Asian Countries:Volume I1 Paper 1- Arsenic Occurrence in South - andEast Asia: scale, causes, and mitigation to take account o f local laboratory arsenic analytical capability and build in capability development where necessary. Although a numbero f groundwater provinces have beenfound with high arsenic concentrations, it is important to keep the scale o f contamination in perspective. Groundwater from most aquifers has acceptably low arsenic concentrations and in most cases is less prone to bacterial contamination. In many areas o f Asia and elsewhere, groundwater represents a reliable source of safe dnnking water. Indeed, in some arid areas it constitutes the only source o f water. Even in Bangladesh, which has suffered by far the greatest impact from groundwater arsenic problems, national statistics based on randomly collected groundwater samples indicate that 27% o f shallow groundwaters (from tubewells 4 5 0 mdeep) have arsenic concentrations greater thanthe Bangladesh standardo f 50 pg L-' and46% have concentrations greater than 10 pg L-I. This means that 73% and 54% respectively have concentrations below these values and are therefore deemed to be o f acceptable quality. Given that considerable investment has been made in groundwater in countries such as Bangladesh over the last few decades, it would be costly and overreactive to abandon groundwater in favor o f alternatives without first carrying out testing programs and, where necessary, further hydrogeological investigations. This report provides an overview o f the current state o f knowledge on the occurrence, distribution, and causes of arsenic problems inwater supplies in South and East Asia. It also characterizes likely at-risk aquifers and the types of indicators that may be used to identify them. Response strategies in terms o f analytical testing and monitoring will vary widely depending on factors such as the scale o f the arsenic problem, the numbers o f operating wells, the population served, the water use, and the scope for alternative water sources. Some o fthese issues are investigated and strategies for testing and monitoring outlined. -21 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1 - Arsenic Occurrence in South andEastAsia: scale, causes,and mitigation 1. Introduction 1.1 PathwaysofArsenic Exposure The dangers associated with long-term exposure to arsenic are now well known. The most prominent health problems in affected populations are skin disorders (melanosis, keratosis, skin cancer) but a large range of other disorders, including intemal cancers (bladder, lung, kidney), cardiovascular diseases, peripheral vascular disorders, respiratory problems, and diabetes, have also been linked to chronic highdoses o f ingested arsenic. Drinlung water can be one o f the most important pathways o f exposure to arsenic inhuman populations and groundwater sources are thought to be responsible for the majority o f the world's chronic arsenic-related health problems. Despite this, most groundwaters have low or very low concentrations o f arsenic (well below regulatory and recommended limits) and in a global context they often constitute the most reliable sources o f safe dnnking water. Groundwater is also less vulnerable to contamination from the waterborne diseases that can be a serious problem in many surface waters. It appears to be only when certain geological and hydrogeochemical conditions arise inaquifers that arsenic problems occur on a regional andproblematic scale. This report describesthose occurrences andthe geochemical processes controlling them and attempts to provide guidance on the criteria for identifymg,monitoring, anddealing with theseproblemareas. Although drinking water i s known to be closely linked to chronic arsenic-related health problems, the sometimes poor relationship observed between arsenic intake from water and health symptoms poses the possibility that other pathways of arsenic exposure may also occur. Food i s one potential source. Crops irrigated with high-arsenic groundwater are potentially vulnerable to arsenic take-up, particularly following long-term groundwater use and soil arsenic accumulation. Some studies have shown higher-than-background concentrations o f arsenic in vegetables. Higher concentrations have typically been found in roots than in stems, leaves, or economic produce. However, few results have been published so far. Meharg and Rahman (2003) considered that rice irrigated with high-arsenic groundwater could represent a significant contribution to the arsenic intake in some o f the Bangladeshi population. Ina study o f dry rice grainproduced by groundwater irrigation, they found concentrations up to 1.8 m g kg-' (compared, for example, with the 1m g kg-' Australian standardfor inorganic arsenic in food). However, few samples were analyzed and the values found are higher than those in other studies o f naturally cultivated rice carried out to date (Abedin, Cotter-Howells, and Meharg 2002). The bioavailability o f arsenic in rice is also uncertain and is strongly influenced by the proportions o f organic and inorganic forms present. Comparatively high concentrations have been found inrice straw, which could affect the doses taken by grazing animals (Abedinand others 2002). Clearly, more research needs to be carried out on arsenic uptake by crops in irrigated areas and on food for, and produced from, grazing animals. Since arsenic is phytotoxic, uptake by vegetation may be inhibited and may therefore not be the greatest concern. However, long-term effects on crop yield, especially o f rice, couldbecome an important issue (Abedin andMeharg 2002). Arsenic-contaminated air i s also a potential exposure pathway in some cases. In Guizhou Province, southem China, severe chronic health problems have arisen from the burning o f local coal with very high arsenic concentrations (up to 35,000 mg kg-I), the exposure being both by inhalation and consumption o f chillis dried over domestic coal fires (Finkelman, Belkin, andZheng 1999). This pathway is muchmore localized thanthat from drinkingwater but, in China, an estimated 3,000 people in several villages o f Guizhou Province have arsenicosis symptoms as a result o f exposure from this source (Ding and others 2001). 1.2 DrinkingWater Regulations andGuidelines Regulatory andrecommended limits for arsenic indrinkingwater have beenreduced inrecent years following increased evidence o f its toxic effects to humans. The World Health -22 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1 - Arsenic Occurrence in South - andEast Asia: scale, causes, and mitigation Organization (WHO) guideline value was reduced from 50 p g L-' to 10 pg L-' in 1993 although the recommendation is still provisional pending further scientific evidence. Westem countries are reducing, or have reduced, their national standards in line with this change. Despite ths, national standards for arsenic in most Asian countries (except Japan and Vietnam) remain at 50 pgL-', inline with the pre-1993 WHO guideline value. This is largely a consequence o f analytical constraints and, insome countries, o f difficulties with compliance to a lower standard. 1.3 WorldDistributionof High-ArsenicGroundwaters The concentrations o f arsenic in most groundwaters are low, typically less than the WHO guideline value o f 10 pg L-' and commonly below analytical detection limits. An investigation o f some 17,500 groundwater samples from public supply wells in the United States o f America, for example, found that 7.6% exceeded 10 pgL-' and 1% exceeded 50 pg L-', while 64% contained <1pg L-' (Focazio and others 1999). Despite the usually low abundance in water, high concentrations can occur in some groundwaters. Under geochemically and hydrogeologically favorable conditions concentrations can reach tens to hundredso f pgL-' and, ina few cases, canexceed 1mgL-'. Most o f the world's high-arsenic groundwater provinces result from natural processes involving interactions between water androcks. Some o f the highestconcentrations o f arsenic are found in sulfide and oxide minerals, especially iron sulfides and iron oxides. As a result, higharsenic concentrations inwater are often found where these minerals are inabundance. Mineralized areas are well-documented examples. These contain ore minerals, including sulfide minerals, typically as veins or replacements o f original host rocks and result from past infiltration o f hydrothermal fluids. In mineralized areas, rates o f mineral dissolution can be enhanced significantly by mining activity and arsenic contamination can be particularly severe inwater associated with mine wastes and mine drainage. Some geothermal waters also contain higharsenic concentrations. A map of the distribution of documented cases of arsenic contamination in groundwater and the environment is given in figure 1. Many of these cases are related to areas o f mineralization and mining activity and a few are associated with geothermal sources. While these cases can be severe with often high concentrations o f arsenic in waters, sediments, and soils, the scale o f contamination i s usually not o f large lateral extent. This i s due to the normally strong adsorption capacity o f iron oxides, which leads to removal o f arsenic and other potentially toxic trace elements fromwater. Despite these associations, other areas with recognized high-arsenic groundwaters are not associated with obvious mineralization or geothermal activity. Some o f these occur inmajor aquifers and may be potentially much more serious because they occupy large areas and can provide drinking water for large populations. Unlike mining and geothermal areas, they are also more difficult to detect without chemical analysis o f the groundwater. Several aquifers around the world have now been identified with unacceptably high concentrations o f arsenic. These include aquifers in parts o f Argentina, Chile, Mexico, southwest United States, Hungary, Romania, Bangladesh, India, China (including Taiwan), Myanmar, Nepal, and Vietnam (figure 1). Many differences exist between these regions, but some similarities are also apparent. The majority o f the high-arsenic groundwater provinces are in young unconsolidated sediments, usually o f Quaternary age, and often o f Holocene (42,000 years) age. These aquifers are usually large inland closed basins in arid or semiarid settings (for example Argentina, Mexico, southwest United States) or large alluvial and deltaic plains (for example Bengal delta, Yellow River plain, Irrawaddy delta, RedRiver delta). These aquifers do not appear to contain abnormally high concentrations o f arsenic-bearing minerals but do have geochemical and hydrogeological conditions favorable for mobilization and retention in solution. -23 - Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1- Paper 1- Arsenic Occurrence in South andEastAsia: scale, causes, and mitigation Figure 1 Summary ofthe World DistributionofDocumentedProblemswith Arsenic inGroundwater and the Environment LEGEND Arsenic-affectedaquifers a Arsenicrelatedtominingandmineralization Geothermalwaters - ... - - - - ___--- --- - I .___ I_ Source: Modifiedafter Smedleyand Kinniburgh2002. Note: InChina, arsenic has further beenidentifiedinthe provincesofJilin, Qinghai,Anhui, Beijing,and Ningxia(reportedat RegionalOperationalResponsesto Arsenic Workshop inNepal, 26-27 April 2004). InIndia, further affectedstatesare Assam, ArunachalPradesh,Bihar, Manipur, Meghalaya, Nagaland, Uttar PradeshandTripura. - 24 - Arsenic Contaminationof Groundwater in South and EastAsian Countries: Volume I1- Paper 1- Arsenic Occurrence in South and EastAsia: scale, causes,andmitigation 2. Arsenic Distributionin SouthandEastAsia 2.1 Overview Many o f the world's aquifers with recognized arsenic problems are located in Asia where large alluvial and deltaic plains occur, particularly around the perimeter o f the Himalayan mountain range (figure 2). This section gives an account o f the occurrence and scale o f groundwater arsenic problems in countries where such problems have been identified. There may be other Quaternary aquifers with high groundwater arsenic concentrations that have not yet been identified, but since awareness o f the arsenic problem has grown substantially over the last few years, these are likely to be on a smaller scale than those already identified. Figure 2. Map o f South and East Asia Showing the Locations o f Documented High-Arsenic Groundwater Provinces IBRDAprii 33758 2005 -.._ .._. %. _. Source: Modified after Smedley 2003. The information in this section has been compiled from published literature, as well as various unpublishedreports and websites. Many o f the unpublished data are difficult to access and reports typically not peer reviewed. Data for many countries also lack spatial information, particularly georeferenced sample points. Reporting often merely gives an indication of whether an area i s or is not affected, rather than an account o f percentages o f affected wells in a given area. In some cases, the quality o f analytical data is also uncertain (box 1). These uncertainties make it difficult to assess the scale o f arsenic problems in many parts o f South - 25 - Arsenic Contaminationof Groundwaterin South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - and East Asia: scale, causes, andmitigation and East Asia. Nonetheless, the information available has been brought together to provide a critical assessment o f the current state o f knowledge o f the scale o f groundwater contamination o f the aquifers in Asia and to detail where apparent data gaps exist. A summaryof the recognized occurrences, aquifers involved, andpopulationspotentially at risk (that is, using drinking water with arsenic concentrations >50 pg L-I) is given in table 1. Some of these population statistics are poorly constrained given the present state o f knowledge. Box 1.Analysis of Arsenic Arsenic is a trace element that is present at pg L-' concentrations in most natural waters. Sampling and analyzing such small concentrations is not a trivial task and there have been many examples in recent years where faulty analysis has led to dubious conclusions. All surveys require a planned and maintained quality assuranceprogram to ensure data produced are o f good quality throughout the program. This includes adequate record-keeping, sample tracking, regular use o f analytical standards, interlaboratory (round robin) checks, and duplicate analyses. The most precise and sensitive analytical methods depend on sophisticated laboratory instruments such as hydride generation-atomic absorption spectrometry (HG-AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and hydride generation-atomic fluorescence spectrometry (HG-AFS).The use o f HG-AAS has expanded inrecent years, but many developing countries do not have such sophisticated facilities or have difficulty maintaining them, especially on the scale required. Costs o f analysis by these techniques are typically in the range US$10-20 per sample. The HG-AAS and HG-AFS methods are at the cheaper end o f this range, but the more expensive ICP methods are multielement techniques and so provide information on elements other thanarsenic. There are cheaper andmorerobust instruments, such as that employed by the silver diethyldithiocarbamate (SDDC) method, but these are less sensitive, are slow, and may not be appropriate for large screening programs. Fieldtest kitshave therefore been widely used as a primary source of data inmany surveys, with laboratory methods used for checking some o f the results. Field test kits are relatively simple and inexpensive, usually costing less than US$1per sample for the materials. The early kits were insufficiently sensitive (being barely capable o f detecting less than 100 pg L- I). However, they have improved in the last few years and the best can now detect down to 10 pg L-I, the WHO guideline value. In practice, the reproducibility o f the kits has often proven disappointing and care has to be taken to ensure that good results are obtained consistently during a survey (Rahmanand others 2002). As a result o fthe relatively large errors involved inarsenic analysis, especially with field test kits, it is inevitable that somewells will bemisclassified as "safe" when they are not, andvice versa. Procedures should be in place to assess the scale and significance o f these misclassifications and to minimize their impact, for example by reanalyzing samples that are very different from those taken from neighboring wells. The reliability o f the kits increases for concentrations well above the drinking water standard or guideline and so they tend to be more reliable at detecting the most toxic waters. 2.2 Alluvial, Deltaic, and Lacustrine Plains 2.2.1 Bangladesh O f the regions o f the world with groundwater arsenic problems Bangladesh i s the worst case identified, with some 35 million people thought to be dnnking groundwater containing arsenic at concentrations greater than 50 p g L-' (table 1) and around 57 million drinlung water with concentrations greater than 10 pg L-' (Gaus and others 2003). The large scale o f the problem reflects the large area o f affected aquifers, the high dependence o f Bangladeshis on groundwater for potable supply, and the large population in the fertile lowlands of the - 26 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - and EastAsia: scale, causes, and mitigation Bengal basin. Today, there are an estimated 11 million tubewells in Bangladesh serving a population of around 133 million people (2002 estimate). The scale o f arsenic contamination inBangladesh meansthat it hasreceivedby far the greatestattentioninterms of groundwater testing and more is known about the arsenic distribution in the aquifers than in any other country inAsia (as well as most o f the developed world). However, much more testing is still required. Table 1. Summary of the Distribution, Nature, and Scale of DocumentedArsenic Problems (>50 pg L-')inAquifers inSouth and East Asia Location Areal extent (km') Populationat riska Arsenic range (pg L-') Alluvial/deltaic/lacustrine plains Bangladesh 150,000 35,000,000 <1-2,300 China(Inner Mongolia,Xinjiang, Shanxi) 68,000 5,600,000 404,400 India (West Bengal) 23,000 5,000,000 <10-3,200 Nepal 30,000 550,000 40-200 Taiwan 6,000 (?) 10,OOOb 1&1,800 Vietnam 1,000 lo,ooo,oooc 1-3.100 Myanmar (?)3,000 3,400,000 Cambodia (?)<1,000 320,000d Pakistan - - -Notavailable. a. Estimatedto be drinking water with arsenic >50 pgL-'.From Smedley2003 and data sourcestherein. b.Beforemitigation. c. UnitedNationsChildren's Fund(UNICEF) estimate. d. Maximum. Source: World BankRegionalOperationalResponsesto Arsenic WorkshopinNepal, 26-27 April 2004. Several surveys o f arsenic in Bangladesh groundwater have been carried out over the last few years, both by laboratory and field methods. The Bangladesh Department o f Public Health Engineering (DPHE) and the United Nations Children's Fund (UNICEF) carried out surveys o f 51,000 wells during 1997-1999 usingarsenic field test kits. The British Geological Survey (BGS) and the DPHE conducted a survey o f around 3,500 samples nationwide during 1998- 1999 (BGS and DPHE 2001). Over the last few years, the Bangladesh Arsenic Mitigation Water Supply Project (BAMWSP) and a number o f nongovernmental organizations (NGOs) and international agencies (for example the Japan International Cooperation Agency (JICA), the Asian Arsenic Network (AAN),NGO Forum, UNICEF, World Vision Intemational, and Watsan Partnership) have carried out major screening programs o f groundwaters across Bangladesh. Van Geen, Zheng, and others (2003) also analyzed samples from about 6,000 wells in eastem Bangladesh. To date more than 4.2 million tubewells have been tested for arsenic. However, this i s still only around 39% o fthe wells inthe country. 2.2.1.1 High-ArsenicShallow Aquifers The aquifers affected by arsenic are Quaternary, largely Holocene, alluvial and deltaic sediments associated with the Ganges-Brahmaputra-Meghnariver system. These occur as the - 27 - Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - and East Asia: scale, causes,and mitigation surface cover over a large part o f Bangladesh. Groundwater from the Holocene aquifers contains arsenic at concentrations up to around 2,300 pg L-', though concentrations span more than four orders o f magnitude (BGS and DPHE 2001). Van Geen, Zheng, and others (2003) found concentrations inthe range <5-860 pg L-' ingroundwaters from Araihazar, east o f Dhaka. Several surveys of the groundwater have shown a highlyvariable distribution o f arsenic, both laterally and with depth. This means that predictability o f arsenic concentrations inindividual wells i s poor and each well used for dnnking water needs to be tested. Nonetheless, on a regional scale, trends are apparent, and the worst-affected areas with the highest average arsenic concentrations are found inthe southeast o f the country, to the south o f Dhaka (figure 3). Here, in some districts, more than 90% o f shallow tubewells tested had arsenic concentrations >50 pgL-'. Some areas with low overall arsenic concentrations have localized hotspots with locally high arsenic concentrations. That o f the Chapai Nawabganj area o f western Bangladesh is a notable example (figure 4), where the median concentration in groundwater from Holocene sediments was found to be 3.9 p g L-' but with extremes up to 2,300 pg L-I concentrated in a small area o f around 5 x 3 km. Overall, the BGS and DPHE survey of shallow groundwaters found that 27% exceeded 50 pgL-' and 46% exceeded 10 pg L-'. Investigation o f the depth ranges o f affected tubewells suggests that concentrations are low in groundwater from the top few meters o f the aquifers close to the water table, but that they Figure3. Smoothed Mar, o fArsenic DistributioninGroundwater from Bangladesh EmaWDPHE[;5011 Bo w I wI I I I $rP QP 9 9 Note: Samples are from tubewells 4 5 0 m deep. Source: BGS and DPHE 2001. increase markedly over a short depth range. This is demonstrated by the profile o f groundwater compositions in a piezometer (10 cm diameter, 40 m deep) in Chapai Nawabganj, northwest Bangladesh. Arsenic concentration was relatively low (17 pg L-') at -28 - Arsenic Contamination of Groundwaterin South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEastAsia: scale, causes, and mitigation Figure 4. Maps of the Distribution of Arsenic inShallow Groundwater from the Chapai Nawabganj Area, Northwest Bangladesh b km ia ' pi NAWABGANJand8HiBGAN.J 2.1" Note: Samples are fromtubewells4 5 0 m deep Source:BGS andDPHE2001. Figure 5. Variation inConcentration ofArsenic and Other Elementswith Depthina Purpose- DrilledPiezometer inChapai Nawabganj, Northwest Bangladesh 0 10 20 30 30 40 40 0 60120 1000 1200 0 2M)W 0 5 1015 0 5 10 Eh(mv) sEC (pS mi') Aa,(pg C') Fg(meC') SO, (mg C') Source: BGS and DPHE2001. 10mdepth but increased to values inthe range 330400 pg L-' over the depthinterval 20- 40 m(BGS andDPHE 2001) (figure 5). The largest range and highest concentrations o f arsenic are typically found at around 15-30 m depth below surface, although the depthranges o f the peaks vary from place to place. Table 2 shows the frequency distribution o f arsenic concentrations with depth for all analyzed samples from the BGS and DPHE (2001) survey. - 2 9 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1 Arsenic Occurrence in South - - andEast Asia: scale, causes, and.mitigation Investigation o f other elements o f potential health concem reveals that concentrations o f manganese are often greater than the WHO health-based guideline value o f 0.5 mg L-' and concentrations o furanium are also sometimes high(up to 32 pgL-I).Concentrations o f boron exceed WHO guidelines in some saline groundwaters from the south and east o f Bangladesh. Nitrate concentrations are normally low, as are most other trace elements on the WHO list o f elements considered detrimental to health. Concentrations o f iron and ammonium are often high but these are issues of acceptability on aesthetic grounds rather than health considerations. Table 2. Frequency Distributionof Arsenic inGroundwater from Tubewells from Quaternary AlluvialAquifers inBangladesh Tubewell depth Number of samples (%) Total samples range (m)a 4 0 pg L-' 10-50 pgL-' 250 pg L-' <25 597 (53) 193 (17) 327 (30) 1,117 25-50 740 (57) 211 (16) 354 (27) 1,305 50-100 363 (55) 143 (22) 153 (23) 659 100-150 33 (26) 47 (37) 46 (37) 126 150-200 25 (78) 6 (19) 1(3) 32 >200 286 (97) 7 (2) 2 (1) 295 a. Depth of intake o f groundwater is difficult to determine and may be from several horizons at differing depths. Source: BGS and DPHE 2001. 2.2.1.2 Low-Arsenic Aquifers The BGS and DPHE (2001) map (figure 3) demonstrates the low overall arsenic concentrations o f groundwater from coarser sediments in the Tista Fan o f northem Bangladesh. Low concentrations are also found in groundwaters from aquifers in the older (Pleistocene) upliftedplateaux o f the Barindand Madhupur tracts (north-central Bangladesh). These usually have concentrations less than 10 pg L-' and often significantly less. Similar results for these areas have also been obtained by other workers (for example van Geen, Zheng, and others 2003). Groundwater from these areas i s therefore expected to be normally safe from the point o f view o f arsenic, although concentrations o f other elements, notably iron andmanganese,may behigh. Arsenic concentrations also appear to be mostly low in groundwater from older ("deep") aquifers which occur insome areas below the Holocene deposits. The stratigraphy o f the deep aquifers o f Bangladesh is poorly understood at present, but where studied, the aquifers with low-arsenic groundwater appear to be o f Pleistocene age (BGS and DPHE 2001; van Geen, Zheng, and others 2003). Limitedinvestigations indicate that they are mineralogicallydistinct from the overlying Holocene deposits. They are typically more brown in color and relatively oxidized. The deep aquifer sediments are likely to be akin to the aquifers below the Barind andMadhupur tracts, which occur at shallower depths becauseo ftectonic uplift. Although these sediments are often referred to as the "deep aquifer", the definition o f "deep" varies from place to place and between organizations and the subject has become rather confused (box 2). However, depth ranges for the low-arsenic groundwater are usually at least 100-200m. Recent data produced by the BAMWSP for groundwater samples from 60 upazilas across Bangladesh found that out o f 7,123 samples from tubewells >150 m deep, - 30 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - andEast Asia: scale, causes, and mitigation 97% had arsenic concentrations 4 0 p g L-' (percentage 4 0 pg L-' unspecified; BAMWSP website). The BGS and DPHE (2001) national survey categorized shallow aquifers as those less than 4 5 0 m depth and deep aquifers as >150 m. Of 335 samples analyzed from >150 m depth, 95% were found to have arsenic concentrations 4 0 pg L-*(table 2). Most o f the deep groundwater samples analyzed inthe BGS and DPHE survey were from the southem coastal area (Barisal) and the northeast (Sylhet). Inthese areas, the shallow and deep aquifers appear to be separatedby thick deposits o f clay, which afford some hydraulic separation between the two. By contrast, in a local study o f groundwater inFaridpur area o f central Bangladesh, BGS and DPHE (2001) defined the deep aquifer as being greater than loom, based on the occurrence o f sandy sediments and well depths. Here the deeper aquifer was found not to be well separated from the shallower aquifer and a degree o f hydraulic connection between the two is therefore possible (BGS and DPHE 2001). Chemical analysis o f samples from Faridpur revealed arsenic concentrations up to 52 pg L-' (five samples) in groundwater from >lo0 m depth. Closer investigation o fthe wells with higher concentrations also showed that they were sometimes screened at multiplelevels andhence took inwater from various horizons. Box 2. Shallow versus DeepAquifers It has been observed that groundwater from deep Quatemary aquifers in the Bengal basin (Bangladesh and West Bengal) has low or very low concentrations o f arsenic, often much less than 5 pgL-'.The depth at which these deep aquifers occur variesbut is typically more than 100-150m below surface. Deep aquifers have been tapped in southern coastal areas and northeastern Bangladesh for some time but less so in other areas and their stratigraphy, lithology, and areal extent are often poorly defined. They are often said to be more oxic than the younger overlying deposits with a higher proportion of brown iron oxides. As older formations, they are also likely to have beenbetter flushed by groundwater thanthe overlying young sediments as a result o f increased groundwater gradients and more active water movement during past ice ages. As sources o f low-arsenic groundwater, these deep aquifers could provide drinkingwater for affected populations inthe region. More research is needed, however, to establish whether they would be secure from the effects o f downward leakage o f high-arsenic water (or saline water in coastal areas), given significantly increased groundwater abstraction. Inother regions of Southand East Asia, groundwater from deep Quaternary aquifers doesnot always have low arsenic concentrations. In Inner Mongolia, concentrations o f arsenic up to 310 pg L-' have been found in groundwater from wells more than 100m deep in an area where a shallow aquifer (less than 30 m deep) also has high groundwater arsenic concentrations. The lithology and stratigraphy o f the deep aquifer are poorly characterized. However, i t is clear from the comparisons that groundwater arsenic concentration is not a simple function o f aquifer or well depth. Rather, aquifer geology and groundwater flow history are important controlling factors. Observations show that a good understanding o f the hydrogeology and geochemistry of Quatemary alluvial, deltaic, and lacustrine aquifers is neededbefore significant groundwater development should be allowed to take place. Van Geen, Zheng, and others (2003) also found consistently lower arsenic concentrations at greater depth in the Araihazar area east o f Dhaka. Here the low concentrations were found at depths as shallow as 30 myalthough the rangeof the low-arsenic deep aquifer variedbetween 30 m and 120 m. There is some question over whether the deep aquifer at 30 m results from upliftofthe sediments, as the studyareais onthe eastem edge o fthe Madhupur tract. The results clearly indicate that the depth o f safe aquifers varies in different parts of Bangladesh and it is not possible to define the depth at which low-arsenic water will occur, even assuming a deep aquifer exists in all areas. The variable depths are perhaps not surprising given the heterogeneity o f sediments in the basin and complexities introduced by past tectonic movements. The important criterion for determining the groundwater arsenic concentrations is the sediment type and sediment history rather than depth. - 3 1 - Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1 Paper 1 - Arsenic Occurrence in South - andEastAsia: scale, causes,and mitigation From available data, it also appears that concentrations o f manganese and uraniumare lower in the groundwater from the deeper aquifer (BGS and DPHE 2001). Concentrations o f most other analyzed trace elements were also within acceptableranges. Although a number o f studies have been and are being carried out on the Bangladesh deep aquifers, much remains unknown about their distribution across the country, the degree o f hydraulic separation from the shallow high-arsenic aquifers, and their viability as a long-term source o f water. Questions also remain about why higher arsenic concentrations occur in some samples. Possibilities include drawdown from shallow levels due to hydraulic connection, drawdown via wells due to poor sealing, multiple screening o f wells in both aquifers, or in situ high-arsenic groundwater in some parts o f the deep aquifer. These questions are critical to the future potential of the deep aquifers for water supply and need further assessmentbefore development o f these aquifers takes place on a large scale. 2.2.1.3 Dug Wells A number of studies have concluded that arsenic concentrations in shallow dug wells in Bangladesh are usually low, even in areas where tubewells have high concentrations (box 3). Concentrations are generally <50 p g L-', with most being 4 0 pg L-' (for example Chakroborti 2001). BGS and DPHE (2001) found concentrations in five dug wells from northwest Bangladesh (Chapai Nawabganj) in the range <3-14 pg L-', with a median o f 7.6 pg L-I.Two samples exceeded 10 pg L-', albeit by a small margin. However, these were from an area with lower overall groundwater arsenic concentrations than the worst-affected parts o fthe country. Little difference was observed inthe samples between concentrations in filtered and unfiltered aliquots and the concentrations were therefore considered to be largely dissolved. Concentrations o f uranium up to 47 pg L-', manganese up to 1.7 m g L-', and nitrate-N up to 28 m g L-' were found in the dug wells from the region, all o f which exceed current WHO health-based guideline values. Bacterial counts indug wells are also oftenhigh. 2.2.2 BengalDelta and AssociatedAquifers, India Problems with arsenic in groundwater inWest Bengal were first recognized inthe late 1980s and the health effects are now reasonably well documented. Today, it is estimated that more than 5 million people inthe state are drinkingwater with arsenic concentrations greater than 50 pg L-' (table 1). More recently, problems have also been found in Arunachal Pradesh, Assam, Bihar, Nagaland, Manipur, Meghalaya, Tripura, and Uttar Pradesh. The state o f Mizoram also has important Quaternary sedimentary aquifers that are potentially at risk from highgroundwater arsenic concentrations. Recent findings of healthproblems inthe village of Semria Ojha Patti in Bihar prompted a survey o f groundwater arsenic concentrations. O f 206 tubewells tested, 57% exceeded 50 p g L-' and 20% exceeded 300 pg L-'. Concentrations were up to 1,650 p g L-' (Chakraborti and others 2003). Associated health problems are also severe, with skin lesions reported to be prevalent in 13% o f adults and 6.3% o f children and neurological problems in 63% o f adults. As the water samples were collected from villages with identifiedhealth problems, the concentrations represent worst cases and the statistics are unlikely to be representative o f the arsenic concentrations inthe state as a whole. More than 100,000 groundwater arsenic analyses have apparently been determined for West Bengal. Despite this, there still appears to be a lack o f detailed maps o f arsenic to assess the spatial distribution. Worst-affected districts have been identified but the distributions on a larger scale (within districts) are not clear and it i s thought that no point source maps o f groundwater arsenic concentrations have been produced. The scale o f the problem in other states with similar geology (Tripura, Bihar, Uttar Pradesh, Meghalaya, Mizoram) is also not knOWn. The affected aquifers o f the region are mainly Holocene alluvial and deltaic sediments similar to those o f large parts o f Bangladesh. In West Bengal, they form the western margins o f the Bengal basin. High arsenic concentrations have been identified in groundwaters from some tubewells in up to eight districts o f West Bengal, the five worst affected being Malda, Murshidabad, Nadia, 24 North Parganas, and 24 South Parganas (figure 6). These cover - 32 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - andEastAsia: scale, causes, andmitigation around 23,000 km2to the east o f the Bhagirathi-Hoogli river system. Arsenic concentrations have been found in the range <10-3,200yg L-' (table 1; CGWB 1999). At the time of writing, no data on arsenic concentrations in groundwater from Chinsurah District are available. Groundwaters from the laterite uplandin the western part o f West Bengal, as well as the Barindand Ilambazar formations, the valley margin fan west o f the Bhagirathi River, and the lower delta plain and delta ffont have low groundwater arsenic concentrations (PHED 1991). Box 3. DugWells Concentrations o f arsenic in. dug wells are often low, even in areas where those in groundwater from neighboring tubewells are high. In western Bangladesh, a 30 m deep tubewell with a groundwater arsenic concentration o f around 2,300 pg L-' is located just a few meters from an 8 m deep dug well with an arsenic concentration o f less than 4 yg L-'. Groundwater in the top few meters below the water table is likely to be relatively aerobic because o f recent inputs o f rainfall and more active groundwater movement. However, it is most likely that the tendency for low arsenic concentrations in dug wells relates in large part to their large diameter and opennessto atmosphere compared to tubewells. Despite the tendency for low arsenic concentrations indugwell waters, not all are found to be below acceptable limits. Several dug wells from the Bengal basin have been found with concentrations greater than the WHO guideline value o f 10 pg L-'. Worse, in parts o f Inner Mongolia where tubewell water has high concentrations, groundwater from dug wells has been found with concentrations up to 560 y g L-I.The concentration o f arsenic in dug wells is probably largely controlled by the redox conditions inthe wells; where anaerobic conditions can be maintained, arsenic concentrations may be unacceptably high. Concentrations may also be highwhere locally influencedby mining wastes. The concentrations o f arsenic in dug wells can therefore not always be guaranteed to be low, and testing for arsenic needs to be carried out to assess their safety for potable purposes. Additional problems from dug wells occur because o f their shallow depths. They can be at increased risk from contamination by surface pollutants, including pathogenic bacteria, and will generally require disinfection before use. Enclosure o f the well and adding a handpump may also be necessary. Restricted yields and seasonal drying up o f wells are additional problems affecting their usehlness insome areas. In many parts of South and East Asia, dug wells have been superseded over time by handpumped tubewells as a means o f obtaining improved yields and sanitary protection. Nonetheless, they are still used by significant numbers o f people, and in some areas they provide an altemative to high-arsenic tubewell water. In Bangladesh around 1.3 million people are estimated to be dependent on dug wells for drinking water (Ahmed and Ahmed 2002), though not all o f these draw water from the unconsolidated sediments o f the Bengal basin. The Quatemary sediment sequence increases in thickness southwards (CGWB 1999). Sedimentation pattems vary significantly laterally, but sands generally predominate to a depth of 150-200 min Nadia and Murshidabad, while the proportion o f clay increases southwards into 24 North and South Parganas, as does the thickness o f surface clay (Ray 1997). The Quaternary sediments have a similar configuration to those o f Bangladesh but the aquifers have been categorized slightly differently. A shallow "first aquifer" has been described at 12-15 m depth, with an intermediate "second aquifer" at 35-46 m, and a deep "third aquifer" at around 70-90 mdepth (PHED 1991). Higharsenic concentrations occur in groundwater from the intermediate second aquifer. Shallowest groundwaters (first aquifer) appear to have low concentrations, presumably because many (though not necessarily all) o f the sources abstracting from this depth are open dug wells and are likely to contain groundwater that is oxidized through exposure to the atmosphere. Groundwaters from the deep aquifer also have low arsenic concentrations, except where only a thin clay layer - 33 - Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1 Paper 1 Arsenic Occurrence in South - - andEast Asia: scale, causes,and mitigation separates it from the overlying aquifer, allowing some hydraulic connection between them. CGWB (1999) noted that the depths o f arsenic-rich groundwaters vary in the different districts but where high-arsenic groundwaters exist, they are generally in the depth range o f 10-80 m. As with Bangladesh, therefore, the groundwater arsenic concentration ranges appear to show a bell-shaped curve with depth. As with Bangladesh, the distribution o f arsenic concentrations inthe groundwaters is known to be highly variable. Some particularly highconcentrations (>200 p g L-')have been found in Figure 6. Map o f West Bengal Showing DistrictsAffectedby HighGroundwater Arsenic Concentrations )<,'-. /'-'% SIKKIH B H U T A N Note: Numbers refer to number o f blocks with arsenic concentrations >50 pg L-' relative to total number of blocks. Darker shading shows worst-affected areas (data as of 1999). groundwaters from 24 South Parganas, along the international border o f 24 North Parganas, andineasternMurshidabad (Acharyya 1997; CSME 1997). 2.2.3 Terai Region, Nepal Groundwater i s abundant inthe Quaternary alluvial sediments o f the lowland Terai region o f southern Nepal and is an important resource for domestic and agricultural use. The region is estimated to have around 800,000 tubewells, which supply groundwater for some 11million people (World Bank Regional Operational Responses to Arsenic Workshop, Nepal, 26-27 April 2004). About 15% ofthese wells were supplied by government agencies or NGOs, the rest being private wells. Manyhave been installed within the last decade. Groundwater is also used for irrigation; these wells generally abstract from deeper levels than those used for drinlung water. Both shallow and deep aquifers occur throughout most o f the Terai region, although the thickness o f sediments deposited is significantly less than found in Bangladesh. The shallow aquifer appears to be mostly unconfined and well developed, although it is thin or absent in some areas (Upadhyay 1993). The deep aquifer (precise depth uncertain) is artesian. - 34 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1 - Arsenic Occurrence in South andEastAsia: scale, causes,andmitigation Quaternary alluvium also infills several intermontane basins in Nepal, most notably that o f the Kathmandu valley o f central Nepal (ca. 500 km2),where sediment thickness reaches in excess o f 300 m (Khadka 1993). Recent heavy abstraction o f groundwater inthe Kathmandu valley has resulted infalling groundwater levels (Tuinhof andNanni2003). A numberof surveys of groundwater quality inthe Terai regionhaverevealed the presence of arsenic at highconcentrations in some shallow tubewells (<50 mdepth), though most o fthose analyzed appear to have 4 0 p g Le'.Arsenic-related health problems have been detected in some o f the affected areas. Water analyseshave mostly been determined (usingHG-AAS)by four private laboratories inNepal, with additional analyses from four government laboratories (Tuinhof andNanni2003). The most recent water quality statistics were compiled by the National Arsenic Steering Committee (NASC), set up in 2001 to oversee and coordinate national arsenic testing and mitigation (Neku and Tandukar 2003; Tuinhof and Nanni 2003; Shrestha and others 2004). As of September 2003, some 25,000 water analyses of arsenic had been carried out and results indicate that 69% o f groundwaters sampled had arsenic concentrations less than 10 p g L-',while 31% exceeded 10pg L-',and 8% exceeded 50 pg L-' (Tuinhof andNanni2003; Shrestha and others 2004). Worst affected were the districts o f Rautahat, Bara, Parsa, Kapilbastu, Nawalparasi, Rupandehi,Banke, Kanchanpur, and Kailali o f central and westem Terai. The highest concentration observed (RupandehiDistrict) was 2,600 pg L-' (Shrestha andothers 2004). Results from earlier surveys (table 3) show similar overall statistics to the more recent summary. The Nepal Department o f Water Supply and Sewerage (DWSS) carried out a survey o f some 4,000 tubewells from the 20 Terai districts, mostly analyzed by field test kits but with laboratory replication o f some analyses. Results from the survey indicated that 3.3% o f the samples had arsenic concentrations o f >50 pg L-' (Chitrakar and Neku 2001). The highest observed concentration was 343 pg L-' (Parsa District). From testing in 17 o f the 20 Terai districts, the Nepal Red Cross Society (NRCS) also found 3% o f groundwater sources sampled having concentrations above 50 p g L-', the highest observed concentration being 205 p g L-I.The spatial distribution o fthe worst-affected areas was found to be similar to that reported by Chitrakar and Neku (2001). A Finnida survey found 12% o f analyzed samples exceeding 50 p g L-',while a survey by Tandukar found 9% o f samples exceeding this value (table 3). The hghest arsenic concentrations observed by Tandukar (2001) were around 120 pg L-', most o f the high-arsenic samples being from the River Bagmati area. The high arsenic concentrations occur in anaerobic groundwaters and are often associated with hgh concentrations o f dissolved iron (Tandukar 2001). The percentage o f samples exceeding 50 pg L' is generally small and much lower than the percentage observed in, for example, Bangladesh, but the statistics nonetheless indicate a clear requirement for further testing and remedial action. To date, there has been no substantial mitigation program in the region (Tuinhof andNanni2003). - 35 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1 Arsenic Occurrence in South - - andEast Asia: scale, causes,and mitigation Table 3. Frequency Distribution of Arsenic Concentrations inAnalyzed Groundwater Samples from Nepal Agency Numberof samples(x) Total samples 4 0 pg L-' 10-50 pgL-' >50 pgL-' DWSS 3,479 (89.3) 289 (7.3) 128 (3.3) 3,896 NRCS 2,206 (79) 507 (18) 77 (3) 2,790 Finnida 55 (71) 14 (18) 9 (12) 78 Tandukar 54 (61) 27 (30) 8 (9) 89 NASC (2003) 17,300 (69) 6,000 (23) 2,000 (8) 25,000 Sources: Chitrakar andNeku2001; Tandukar 2001; NekuandTandukar 2003. Surveys appear to indicate that deeper tubewells in the Terai region have lower arsenic concentrations. As with Bangladesh, variation in arsenic concentration with depth appears to show a general bell-shaped curve. The largest variation and highest maximum concentrations occur intubewells with depths inthe 10-30 mrange. Concentrations are generally <50 p g L-' at depths greater than around 50 m (Shrestha and others 2004). Recent analysis o f groundwater from 522 irrigation wells with depths o f >40-50 mwere also found to have low concentrations (Tuinhof and Nanni 2003). This suggests that the deep aquifer offers some possibilities as an alternative source o f low-arsenic water supply. However, as with Bangladesh, the susceptibility o f groundwater from the deep aquifer to drawdown o f high- arsenic water from overlying sediments is a matter for concern and further hydrogeological investigation. At the time of writing, around 13% of wells thought to exist in the Terai region have been tested for arsenic. Data so far available from the Kathmandu valley have revealed no arsenic problems there, although the extent o f testing inthe valley i s not clear. 2.2.4 Irrawaddy Delta, Myanmar As elsewhere inAsia, traditional sources of water for domestic supply inMyanmarwere dug wells, ponds, springs, and rivers. However, inthe Quaternary aquifer o f the Irrawaddy delta, many of these have been superseded since 1990 by the development of shallow tubewells. It i s estimated that more than 400,000 wells exist in Myanmar as a whole, more than 70% o f which are privately owned. Little testing for arsenic in groundwater has been carried out in tubewells from the alluvial aquifer, though a few reconnaissance surveys have been undertaken and arsenic has been found in excess o f 50 pg L-' in some. Save The Children reported from analysis o f 1,912 shallow tubewells in four townships in Ayeyarwaddy Division (southern delta area) that 22% o f samples exceeded 50 p g L-I.The United Nations Development Programme (UNDP) and the United Nations Centre for Human Settlements (UNCHS) detected arsenic at concentrations greater than 50 pg L-' in 4% o f samples (125 samples) from Nyaungshwe in Shan State in southern Myanmar (UNDP-UNCHS 2001). The Water Resources Utilization Department (WRUD) carried out a survey o f groundwater in Sittway township in the western coastal area, and in Hinthada and Kyaungkone townships close to the south coast o f Myanmar (WRUD 2001). In Sittway township, salinity problems occur insome groundwaters and surface waters and most tubewells are less than 15 mdeep as a result. Merck field test kits were used for the analysis o f arsenic. In Hinthada and Kyaunkone townships well depths are typically around 30-50m, although some deeper tubewells (55-70 m) were also sampled. Inthe southern townships o f the delta area, highiron concentrations were noted. The distribution o f arsenic concentrations determined by 2001 is givenintable 4. Exceedances above 50 pg L-' in shallow tubewells from Sittway, Hinthada, and Kyaunkone townships were around 10-13%. One sample from the depth interval 56- - 3 6 - Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1 Paper 1 Arsenic Occurrence in South - - and EastAsia: scale, causes, and mitigation 70 malso exceeded 50 pg L-'.As with a number o f other affected aquifers, dug wells from the WRUD survey generally hadarsenic concentrations of4 0 pgL-' (WRUD2001). More recent results from WRUD surveys have shown 15% o f groundwater samples exceeding 50 p g L-' (8,937 analysesby April 2002). Inthese, dug wells were found to exceed 50 p g L-Iin 8% o f samples. As the analyses from the various surveys were carried out using Merck field test kits, the accuracy o f the results i s uncertain but likely to be limited. As with many other areas, the arsenic concentrations of the groundwaters of Myanmar have not been mapped in detail and investigations are inthe reconnaissance stages. However, the divisions o f Ayeyarwaddy and Bag0 (delta area), and the states o f M o n and Shan, appear to be the worst affected. Table 4. Frequency Distribution of Arsenic Concentrations inGroundwaters from the Alluvial Aquifer o f Myanmar Township Well type Numberof samples (%) Total samples 4 0 pg L-' 10-50 pgL-' >50 pg L-' Sittway STW 17(29.3) 35 (60.3) 6 (10.3) 58 DW 22 (96) 1(4) 0 (0) 23 Hinthada STW 56 (68.3) 15 (18.3) 11(13.3) 82 DW 6 (75) l(12.5) l(12.5) 8 Kyaungkone STW 48 (80) 5 (8) 7 (12) 60 D W 21 (95) 1(5) 0 (0) 22 DTW l(33.3) l(33.3) l(33.3) 3 Key: STW shallow tubewell DW dugwell D T W deeptubewell(55-70 m) Source:WRUD 2001. 2.2.5 QuaternaryAquifers,Taiwan, China Health problems experienced in Taiwan have been the subject o f much research since their initial discovery in the early 1960s and have formed the basis o f many epidemiological risk assessments over the last 30 years. Taiwan is the classic area for the identification o f blackfoot disease (for example Tseng and others 1968; Chen and others 1985) and other peripheral vascular disorders, but many other arsenic-related diseases have also been described from the area. Despite being under considerable international scrutiny from an epidemiological perspective over the last 40 years or so, there appears to have been little effort to understand the distribution or causes o f arsenic problems in the aquifers o f Taiwan. As a result, very little information is available for the region. High-arsenic groundwaters have been recognized in two areas: the southwest coastal area (Kuo 1968; Tseng and others 1968) and the northeast coast (Hsu, Froines, and Chen 1997). Kuo (1968) observed arsenic concentrations in groundwater samples from southwest Taiwan ranging between 10 pg L-' and 1,800 pg L-' (mean 500 pg L-I, n = 126), with half the samples analyzed having concentrations o f 400- 700 pg L-'. An investigation by the Taiwan Provincial Institute o f Environmental Sanitation found that 119 townships in the affected area had arsenic concentrations in groundwater o f >50 pg L-I, with 58 townships having >350 pg L-' (Lo, Hsen, and Lin 1977). Innortheastern Taiwan Hsu, Froines, and Chen (1997) reported an average arsenic concentration o f 135 pg L-'for 377 groundwater samples. - 3 7 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - and EastAsia: scale, causes, and mitigation Inthe southwest, the higharsenic concentrations are found indeep (100-280 m) artesian well waters. The sediments from which these are abstracted are poorly documented, but appear to include deposits o f black shale (Tseng and others 1968). The groundwaters are likely to be strongly reducing as the arsenic is found to be present largely as arsenic(II1) (Chen and others 1994) and some o f the groundwaters contain methane as well as humic substances(Tseng and others 1968). Groundwaters abstracted innortheastem Taiwan are also reported to be artesian butmore typically shallow, with a depth range of 16-40 m(Hsu, Froines, and Chen 1997). As found in several other countries, groundwater from shallow dug wells have low arsenic concentrations (Guo, Chen, and Greene 1994). This is probably a reflection o f relatively oxidizing conditions inthe shallow parts o fthe aquifer immediately around the open wells. The arsenic problems o f Taiwan are largely historical, as alternative treated surface water supplies havebeen provided for the affected communities. 2.2.6 AlluvialPlains,NorthernChina The presence o f endemic arsenicosis has been recognized in China since the 1980s and today the scale of the problem is known to be large. Arsenic problems related to drinking water have been identified inQuaternary aquifers inXinjiang Province and more recently inparts o f Inner Mongolia and Shanxi Province (figure 7). Concentrations o f arsenic up to 4,400 p g L-' have been found in groundwater from these affected areas. These areas represent large internal drainage basins in arid and semiarid settings. Groundwater conditions inthe arsenic- affected areas appear to be strongly reducing. High-arsenic drinking water has also been identified in parts o f Liaoning, Jilin, and Ningxia Provinces in northeast and north-central China (Sun, pers. comm., 2001), although the distribution and extent o fthese occurrences, the geological associations, and the health consequencesare not yet documented or defined. The population exposed to drinkingwater with concentrations inexcess o f 50 pg L-' (the Chinese standard) has been estimated as around 5.6 million (table l), the number o f diagnosed and arsenicosis patients currently around 20,000 (Sun and others 2001). Mitigation measures are being implemented in some areas in China, including where possible the provision o f piped low-arsenic surface water and in some cases the use o f small-scale reverse osmosis plants. However, so far the mitigation efforts have covered relatively little o fthe area affected. 2.2.6.1 XinjiangProvince The first cases o f arsenic-related health problems due to drinking water were recognized in Xinjiang Province o f northwest China (figure 7). The region is arid with an average annual precipitation o f less than 185 mm. The basin is composed o f a 10 km thick sequence o f sediments, including a substantial upper portion o f Quaternary alluvial deposits. Artesian groundwater has been used for dnnking in the region since the 1960s (Wang and Huang 1994). Wang (1984) found arsenic Concentrations up to 1,200 p g L-' in groundwaters from the province. Wang and Huang (1994) found concentrations o fbetween40 pg L-' and 750 pg L-' indeep artesian groundwater from the Dzungariabasin on the north side ofthe Tianshan Mountains (up to 3,800 m altitude). The region stretches some 250 kmfrom Aibi Lake inthe west to Mamas River in the east. Artesian groundwater from deep boreholes (70-400 m) was found to have increasing arsenic concentrations with increasing borehole depth. Highest concentrations were also found intubewells from the lower section o f the alluvial plain.Many o f these are believed to abstract groundwater from Quaternary alluvial sediments but whether some o f the deeper artesian wells abstract from older formations i s not known. Shallow (nonartesian) groundwaters from wells in the depth range 2-30m had observed arsenic concentrations between 4 0 p g L-' and 68 p g L-' (average 18 pg L-I).That inthe saline Aibi Lake was reported as 175 p g L-',while local rivers had concentrations between 10 p g L-' and 30 pgL-'. Wang and others (1997) reported arsenic concentrations up to 880 p g L-' from tubewells from the Kuitanarea o f Xinjiang. A 1982 survey o f 619 wells showed 102 with concentrations o f arsenic >50 pg L-'. High fluoride concentrations were also noted inthe groundwaters (up to 21.5 mg L-I). - 38 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1 - Arsenic Occurrence in South andEast Asia: scale, causes, and mitigation 2.2.6.2 Shanxi Province Investigations during the mid 1990s showed that arsenic in groundwater from wells in the Datong and Jinzhong basins in Shanxi Province exceeded 50 p g L-' in 837 (35%) o f 2,373 randomly selected samples (Sun and others 2001). Concentrations in Shmyin County, the worst-affected o f the regions in Shanxi Province, reached up to 4,400 p g L-' (Sun and others 2001). Figure 7. Map o f China Showing the Distribution of RecognizedHigh-Arsenic (>50 y g GI) Groundwaters and the Locations o f Quaternary Sediments Source: Modified after Smedley and others 2003. 2.2.6.3 YellowRiver Plain, Inner Mongolia InInner Mongolia, concentrations of arsenic in excess o f 50 yg L-' have been identified in groundwaters from aquifers inthe Hetao plain, Ba Menregion, and inthe Tumet plain, which includes the Huhhot basin (Luo and others 1997; M a and others 1999). These areas are also arid, with a mean annual precipitation of around 400mm. The affected areas border the Yellow River plain and include the towns o f Boutou and Togto. In the region as a whole, around 300,000 residents are believed to be drinking water containing >50 pg L-' (Ma and others 1999). Arsenic-related health problems from the use of groundwater for drinking were first recognized in the region in 1990 (Luo and others 1997). The most common manifestations o f disease are skin lesions (melanosis, keratosis) but an increased prevalence o f cancer has also been noted. M a and others (1999) reported that 543 villages in Ba Men region and 81 villages in Tumet had tubewells with arsenic concentrations >50 pg L-'. Around 1,500 cases o f arsenic diseasehad been identified inthe areaby the mid 1990s. The Hetao plain comprises a thick sequence o f young unconsolidated sediments. Ina study o f groundwater from the Wuyuan and Alashan areas, Guo and others (2001) found that, respectively, 96% and 69% o f samples analyzed had arsenic concentrations greater than 50 p g - 3 9 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1- Arsenic Occurrence in South andEast Asia: scale, causes,and mitigation L-'.Concentrations were generally muchhigher ingroundwater from tubewells (depth range 15-30 m) than from open dug wells (3-5 m depth) and the highest concentration recorded was 1,350 p gL-'. The area o f Ba Men with high-arsenic groundwater appears to be around 30Ox20km in extent and the sediments are Quaternary lacustrine deposits. Wells were mostly installed in the late 1970s and well depths are typically 10-35 m.Arsenic concentrations have been found in the range 50-1,800 pg L-' (Ma and others 1999) and around 30% of wells sampled had arsenic concentrations >50 pg L-'. The groundwaters are reducing with arsenic being Figure8. Regional Distribution ofArsenic inGroundwaters from the Shallow andDeep Aquifers o fthe Huhhot Basin Welldepth 5 lo0 m 1108 1110 I112 1114 1116 1118 112 Well depth lo0 m > 1108 i i i o iiiz 1114 i i i e 1118 1120 Source: Smedley andothers 2003. dominantly present as arsenic(II1). Some contain highfluoride concentrations (average 1.8 m g L-')(Ma andothers 1999). The Huhhot basin (area around 80 x 60 km) lies to the east o f the Ba Men area (figure 8). The basin is surrounded on three sides by highmountains o fthe Da Qing and ManHanranges and is itself infilled with a thick sequence (up to 1,500m) o f poorly consolidated sediments, largely o fQuaternary age (Smedley and others 2003). Groundwater has been used for several decades for domestic supply and agriculture. Traditional sources o f water were shallow dug wells that were typically 10mor less deep and tapped the shallowest groundwater. These have now generally been abandoned in favor o f tubewells that abstract at shallow levels (typically <30 m) by handpumps or in some cases by motorized pumps. Groundwater is also present within a distinct, deeper aquifer (typically >lo0 mdepth). Tubewells tapping this deeper aquifer are often artesian inthe central parts o f the basin. -40 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEast Asia: scale, causes, and mitigation Arsenic concentrations inthe Huhhot basin groundwaters range between 4 and 1,480 pg L-' in the shallow aquifer (I m) and between 4 and 308 pg L-' in the deep aquifer 100 (>loom). O f a total of 73 samples, summarized by Smedley and others (2003), 25% of shallow sources and 57% o f deep sources have arsenic concentrations in excess o f 50 pg L-' (table 5). The regional distributions o f arsenic inthe groundwaters from the shallow and deep aquifers are shown in figure 8. Concentrations in the aerobic groundwaters from the basin marginsare universally low. Highconcentrations are generally restrictedto the low-lyingpart o f the basin where groundwaters are strongly reducing (table 6) (Smedley and others 2001, 2003). The redox characteristics o f the Huhhot basin groundwaters have many similarities with those of Bangladesh and it is logical to conclude that the main geochemical processes controlling arsenic mobilizationare similar inthe two areas. Table5. Frequency DistributionofArsenic Concentrations inGroundwater from the Huhhot Basin, Inner Mongolia Well depth Number of samples (%) Total samples <10 pg L-' 10-50 pg L-' >50 pg L-' 900 m 35 (59) 9 (15) 15 (25) 59 >lo0 m 6 (43) 0 (0) 8 (57) 14 Source: Smedley and others 2003. Table6. Summary Arsenic Datafor Groundwater from DugWells inthe High- Arsenic Groundwater Region o f the Huhhot Basin Of a Sample Water level Well depth DOC Arsenic m m mgL-' L-' HB2 1.5 3.5 9.3 560 HB18 2.0 6 - 49 HB58 4.0 8 2.5 50 pg L-' Tong (2001) Holocene 117 (45) 62 (24) 81 (31) 260 Tong (2001) Pleistocene 84 (40) 70 (33) 56 (27) 210 Tong (2002) undivided 740 (60.2) 335 (27.3) 153 (12.5) 1,228 Sources: Tong 2001, 2002. The causes o f the spatial variations are not fully clear, but factors may include differences in sediment thickness, composition, and age, and hydraulic connection between layers. In particular, sediments to the north o f Hanoi with typically low groundwater arsenic concentrations are predominantly o f Pleistocene age and are relatively thin (Berg and others -42 - Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1 Paper 1 Arsenic Occurrence in South - - andEast Asia: scale, causes,andmitigation 2001). One uncertainty inthe distribution o fthe arsenic concentrations inthe groundwaters o f the region is the impact that anthropogenic activity may have had on the mobilization o f arsenic. Since some high concentrations have been found close to the city o f Hanoi, it is possible that urban wastewater recharge to the aquifer may have had some impact on the arsenic distributions. This remains speculation and requires hrther investigation. Berg and others (2001) and Tong (2002) have suggested that significant seasonal variations exist in arsenic concentrations in given wells in relation to strong water level fluctuations. Berg and others (2001) found some very large temporal variations, with often higher concentrations inwells sampled in September (rainy season) than when sampledinDecember (dry season) or May (early rainy season). By contrast, Tong (2002) reported that more samples tended to exceed the national standard o f 50 pg L-' in the dry season than the rainy season. As the datainthe case o f Berg and others (2001) were not reported inrelation to other parameters (for example rainfall, water level), and in the case o f Tong (2002) were presented just as ranges and percentage exceedances, the variations are difficult to interpret and to verify. Subsequent monitoringby the Swiss Federal Institute for Environmental Science and Technology (EAWAG) and others (with more stringent sampling and analytical procedures) has revealed muchless temporal variation, the greatest being found inwells close to the river bank (M.Berg, pers. comm., 2004). Resultshave not yet been documented. Maps have been produced showing the distribution o f arsenic in groundwater in the Hanoi area (Berg and others 2001; Tong 2002) but so far mapping o f the groundwater quality in the plainas awhole hasnot beencarriedout. 2.2.8 MekongValley: Cambodia, Laos, Thailand, andVietnam The Mekong River system i s another large delta with potential for development of groundwater arsenic problems. So far few investigationshave been carried out inthe valley as a whole. Most investigation to date appears to have been carried out in Cambodia. The Mekong has a substantial proportion o f its lengthwithin Cambodia and tubewells provide a significant source o f potable supply in the country. Water testing for arsenic is ongoing and little informationhas so far beenproperly documented. A reconnaissance screening o f around 100 tubewells from 13 provinces carried out by Partners for Development in 1999 included analysis o f arsenic, fluoride, some trace metals, and some pesticides. Approximately 9% o f the samples analyzed had arsenic concentrations >10 pg L-I,with observed concentrations in the range 10-500 p g L-I. Exceedances above 10 p g L-' were found in 5 out o f the 13 provinces investigated. The highest concentrations observed were from Kandal Province, close to Phnom Penh. Several districts in this province have a highpercentage o f wells with water containing arsenic in excess o f the WHO guideline value (Feldman and Rosenboom 2000). Since this initial screening, field testing using portable kits has identified groundwater sources with concentrations above 10 p g L-' in two additional provinces. High iron and manganeseconcentrations and anaerobic conditions are common features o f the groundwaters throughout the lowland areas o f Cambodia. More recently, UNICEF has beencarrying out groundwater arsenic screening in the Mekong aquifers. A map o f perceived "arsenic risk" in groundwater has been produced based on geology (figure 9). Areas o f greatest perceived risk are those with Holocene sediments forming the main aquifer. Groundwater arsenic data produced by UNICEF and JICA for the region so far (June 2003) are summarized in table 8. Around 19% o f samples from the Holocene aquifer were found to contain arsenic at concentrations >50 p g L-I. UNICEF and other organizations continue to support and carry out field testing using portable kits with supplementary laboratory analysis in Cambodia. A planto blanket-test wells in 1,500 villages that abstract groundwater from Holocene sediments is currently being drawn up for the southern part o f the country. One noteworthy feature o f the Cambodian Mekong results i s that some o f the highest arsenic concentrations have been found inurban areas, around Phnom Penh. Whether this reflects an - 43 - Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - andEastAsia: scale, causes,and mitigation Figure9. Geological Map o f Cambodia Showing Distributiono f Potentially High-Arsenic Aquifers vS 0 100 200 300 Kilometers Note: Areas o f perceived "increased risk" are those with aquifers o f Holocene age; areas of perceived"low risk" are Pleistocene aquifers; areas o f "very low risk" are crystalline basement rocks. Geological units are provisional and accuracy o f national boundaries is not guaranteed. Sources: UNICEF, Cambodia; D.Fredericks, pers. comm. 2003. impact o f urbanization (increased groundwater pumping or increased inputs o f pollutants such as organic carbon to the aquifers) is not known and is inneed o f further investigation. Table 8. Summary Arsenic Data for Groundwater from Tubewells inthe MekongValley o f Cambodia Number o f samples (%) Total samples 4 0 p g L-' 10-50 pgL-' >50 pgL-' Holocene aquifer 301 (50) 185 (3 1) 113 (19) 599 Pleistocene aquifer 1,184 (95) 59 (5) 3 (0.2) 1,246 Crystalline rocks 708 (96) 24 (3) 2 (0.3) 734 Sources: Data from UNICEF and JICA; D.Fredericks, pers. comm., 2003. As the Mekong valleyalso covers partsof Laos, Thailand, andVietnam, arsenic problems are also possible inthe alluvial and deltaic parts o f these countries. However, few data are so far available from these regions to assess the scale o f the problem there. Doan (n.d.) provided some arsenic data measured by spectrometry for groundwater samples from the Holocene, Pleistocene, and Pliocene aquifers o f the Mekong delta area of Vietnam. Concentrations were found to be mostly low, with only one sample exceeding 50 pg L-I. Concentrations were in the range 4 - 5 p g L-' for groundwaters from Holocene deposits (9 samples, depth range 4- 19 m), 4 - 3 2 pg L-I for those from Middle and Upper Pleistocene deposits (39 samples, depth range 5-120 m), 4 - 7 pg L-' for groundwater from Lower Pleistocene deposits (12 samples, depth range 113-191 m), and 4 - 5 7 pg L-' for groundwater from Pliocene deposits (39 samples, depth range 85-330 m). Highest concentrations in this Pliocene aquifer were in -44 - Arsenic Contamination of Groundwaterin South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEast Asia: scale, causes,andmitigation the Ben Tre area o f the central Mekong delta. The Pleistocene and Pliocene sediments are the most exploited aquifers in the region. The Holocene sediments appear to be largely low- yielding aquitards and are not heavily used. Doan (n.d.) reported that UNICEF carried out some qualitative arsenic testing o f Mekong groundwaters in Vietnam but did not detect arsenic. UNICEF have also carried out some preliminary testing o f groundwater from wells in the Attapeu, Savannakhet, Champassak, Saravan, Sekong, Khammuane, and Bolikamxay areas o f Lao PDR. Results from 200 samples reported by Fengthong, Dethoudom, and Keosavanh (2002) suggested that some samples had arsenic concentrations greater than 10 pg L-' but only one exceeded50 p gL-I.The highest concentration observed inthe regionwas 112 p g L- ' (Attapeu Province). To date, UNICEF, in collaboration with the government and the Adventist Development and Relief Agency, have tested some 680 samples from drinking water sources and found 1% o f sources having arsenic concentrations >50 pg L-' (table 9, unpublisheddata). Table 9. Summary Arsenic Datafor Groundwater from Tubewells inthe MekongValley o f Lao PDR Number of samples (YO) Total samples 4 0 pg L-' 10-50 pg L-' >50 pg L-' Holocene aquifer 531 (78) 143 (21) 6 (1) 680 Source: Data from UNICEF. 2004. 2.2.9 IndusPlain, Pakistan Quaternary sediments, mainly o f alluvial and deltaic origin, occur over large parts o f the Indus plain of Pakistan (predominantly in Punjab and Sindh Provinces) and reach several hundred meters thickness in some parts (WAF'DA-EUAD 1989). Aquifers inthese sediments are potentially susceptible to high groundwater arsenic concentrations. The Indus sediments have some similarities with the arsenic-affected aquifers o f Bangladesh and West Bengal, beingQuaternary alluvial-deltaic sediments derivedfrom Himalayan source rocks. However, the region differs in having a more arid climate, greater prevalence o f older Quaternary (Pleistocene) deposits, and dominance o f unconfined and aerobic aquifer conditions, with greater apparent connectivity between the river systems and the aquifers. Aerobic conditions are demonstrated by the presence o f nitrate (Mahmood and others 1998; Tasneem 1999) and dissolved oxygen (Cook 1987) in many Indus groundwaters. Hence, the aquifers appear to have different redox characteristics from those o f the lower parts o f the Bengal basin. Under the more aerobic conditions (and near-neutral pH), arsenic mobilization in groundwater should be less favorable. To date, only a limited amount o f groundwater testing for arsenic has been carried out in Pakistan. However, the Provincial Government o f Punjab together with UNICEF began a testingprogram innorthem Punjab in2000. Districts to be tested were selected on the basis o f geology and available water quality information. These included areas affected by coal mining and geothermal springs (Jhelum and Chakwal Districts), areas draining crystalline rock (Attock and Rawalpindi), areas with high-iron groundwaters (Sargodha), and one district from the main Indus alluvial aquifer (Gujrat). A total o f 364 samples were analyzed. The majority (90%) o f samples had arsenic concentrations less than 10 pg L-', although 6 samples (2%) had concentrations above 50 pg L-' (table 10) (Iqbal 2001). Further well testing for arsenic i s ongoing. No confirmed cases o f arsenic-related disease have been found in Pakistan, although epidemiological investigations are also being undertaken in some areas. From the available data, the scale o f arsenic contamination o f Indus groundwaters appears to be relatively small, although hrther results are needed to verify the region affected. -45 - Arsenic Contamination of Groundwaterin South and East Asian Countries: Volume I1 Paper 1 - Arsenic Occurrence in South - and EastAsia: scale, causes,and mitigation Quaternary aeolian sand deposits occur to the east o f the Indus plain (Thar and Cholistan desert areas) as well as over large parts o f the Baluchistan basin o f western Pakistan. Testing o f abstraction tubewells inthese areas i s also required. Under the arid conditions inPakistan, high fluoride concentrations and high salinity appear to be more widespread water-related problems thanarsenic. Table 10.Frequency Distribution o fArsenic Concentrations inGroundwater Samples fromNorthern Punjab District Number of samples(%) Total samples 4 0 pgL-' 10-50 pg L-' >50 pg L-' Gujrat 33 (87) 3 (8) 2 (5) 38 Jhelum 32 (86) 4(11) 1(3) 37 Chakwal 63 (88) 9 (12) 0 (0) 72 Sargodha 49 (83) 7 (12) 3 (5) 59 Attock 68 (92) 6 (8) 0 (0) 14 Rawalpindi 81 (96) 3 (4) 0 (0) 84 Total 326 (90) 30 (8) 6 (2) 364 Source: Iqbal2001. 2.3 Mining and Mineralized Areas 2.3.1 RonPhibun, Thailand Health problems related to arsenic have been well documented in Thailand, in this case related to mineralization and miningactivity rather than alluvial and deltaic aquifers. Interms o f documented health problems from drinking water, Ron Phibun District in Nakhon Si Thammarat Province in peninsular Thailand represents the worst-known case o f arsenic poisoning related to mining activity (figure 1). Health problems were first recognized in the area in 1987 and over 1,000 people have been diagnosed with arsenic-related skin disorders, particularly inand close to Ron Phibun town (Williams 1997). At the time o f first recognition o f the problems, some 15,000 people are thought to have beendrinking water with >50 pgL-' arsenic (Fordyce and others 1995). The affected area lies within the Southeast Asian tin belt. Primary tin-tungsten-arsenic mineralization and alluvial placer tin deposits have been mined inthe district for over 100years, although mining activities have now ceased. Legaciesofthe mine operations include arsenopyrite-rich waste piles, waste from ore-dressing plants and disseminated waste from small-scale panning by villagers. Remediation measures include transportation o f waste to local landfill. Waste piles from former bedrock mining are found to contain up to 30% arsenic (Williams and others 1996). Alluvial soils also contain high concentrations o f arsenic, upto 0.5% (Fordyce and others 1995). Higharsenic concentrations found in both surface and shallow groundwaters from the area around the mining activity are thought to be causedby oxidation o f arsenopyrite, made worse by the former mining activities and subsequent mobilization during the postmining rise in groundwater levels (Williams 1997). Surface waters draining the bedrock and alluvial miningareas are commonly acidic @ H <6) with so4 as the dominant anion (up to 142mg L-') and with high concentrations o f some trace metals, including aluminum (up to 10,500 pgL-I),cadmium (upto 250 pg L-'),andzinc (up to 4,200 pgL-') (Williams and others 1996). Strong positive correlations are observed between SO4 and cadmium, aluminium, beryllium, zinc, and copper. Also, SO4 correlates negatively with pH (Fordyce and others 1995). These associations suggest strongly that arsenic and the associated trace metals are derived by oxidation o f sulfide minerals. - 4 6 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEast Asia: scale, causes, andmitigation Concentrations o f the trace metals diminish downstream o f the mining area. Highest arsenic concentrations (up to 580 pg L-') were found some 2-7 km downstream o f the bedrock mining area (Williams and others 1996). Shallow groundwaters ( 4 5 m) are from alluvial and colluvial deposits and deeper groundwaters (>15 m) are from an older carbonate aquifer. The shallow aquifer shows the greatest contamination with arsenic, with concentrations up to 5,100 pg L-' (figure lo). Inthe Figure10. Simplified Geology ofthe RonPhibunArea, Thailand, Showing the Distribution of Arsenic inAnalyzed Groundwaters aW4;IXbblX ; g y g ; ; 1 4 " pt;,, pJ:zy;n C"Jl 4wux 17E:;: Note: The distributionsare (a) arsenic in groundwater from shallow tubewells ( 4 5 m depth); (b) arsenic in groundwater from deeper tubewells(>15 m).Numbersrefer to samples given inWilliams and others 1996. Source: Williams and others 1996. shallow aquifer, 39% o f samples collected randomly had arsenic concentrations >50 pg L-', while inthe deeper aquifer, 15% exceeded 50 pgL-' (table 11) (Williamsand others 1996). Table 11.Frequency Distributiono fArsenic Concentrations inWater from RonPhibunArea ~~ Aquifer Number of samples (%) Total samples 4 0 pg L-' 10-50 pgL-' >50 pg L-' Surface water 1(4) 2 (8) 20 (83) 24 Groundwater from shallow 7 (30) 7 (30) 9 (39) 23 aquifer (45 m) Groundwater from deeper 9 (69) 2 (15) 2 (15) 13 aauiferG-15 ml Source:Williams and others 1996. The high-arsenic groundwaters of the Ron Phibun area clearly differ from many other high- arsenic groundwater provinces in Asia. Inthe shallow aquifer, conditions are more oxidizing thanthoseprevalent in, for instance, the worst-affected areas ofBangladeshandWest Bengal. The differences reflect the distinct geochemical reactions that are controlling the groundwater -47- Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEast Asia: scale, causes,and mitigation arsenic concentrations (section 3.3). In the groundwaters from the deeper aquifer o f Ron Phibun conditions appear more similar to those from other high-arsenic aquifers in Asia and the maintenance o f arsenic in solution appears to be more o f a function o f the presence o f reducing conditions, although leakage o f high-arsenic water from the overlying shallow aquifer is also a possibility. 2.3.2 RajnandgaonDistrict, Madhya Pradesh, India Water-related arsenic problems first became recognized in Rajnandgaon District, Madhya Pradesh, in 1999. Concentrations in groundwater samples from the worst-affected village, Kondikasa, inChowki block, have been found to range between 4 0 p g L-1 and 880 pg L-1 (Chakraborti and others 1999). Out o f 146 samples analyzed, 8% were found to contain more than 50 pg L-1 arsenic (table 12). Three of these exceeding samples were from dug wells, one containing a concentration o f 520 p g L-1. Most were from tubewells, which were usually less than 50 m deep (range 10-75 m). Arsenic-related skin disorders have been recognized in a number o f the villagers. Gold-mining activity has taken place in the local area, though the extent o f mining and o f mineralization i s not documented. To date, no maps have been produced o f Chowki block to indicate the distribution and scale o f the problem. Table 12. Frequency Distribution o fArsenic Concentrations inGroundwater from Chowki Block, MadhyaPradesh, India Block Numberof samples (%) Total samples 4 0 pg L-' 10-50 pgL-' >50 kgL-' Chowki 109(75) 25 (17) 12(8) 146 Source: Chakraborti and others 1999. 2.3.3 Other Areas Although many areas o f mining and mineralization exist in South and East Asia, few have been documented and the distribution of groundwater arsenic concentrations related to them i s unknown. High concentrations were noted in some surface waters and groundwaters close to the Baumining area o f Sarawak, Malaysia (Breward and Williams 1994), although there is no evidence that affected waters are used for drinkingwater. Arsenic is a well-known risk in sulfide mineralized areas and hence the locations o f such problems can be reasonably well predicted. Despite many mining-related problems, modem mining practices are designed to minimize environmental impacts. Environmental protection measures include criteria for siting and management o f waste piles, control o f effluents, and treatment of acid mine drainage. -48 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - andEast Asia: scale, causes, and mitigation 3. Hydrogeochemistryof Arsenic 3.1 Overview There has been a considerable increase in the amount o f research carried out on arsenic in groundwater and the environment over the last few years and understanding o f the processes involved has improved as a result o f studies carried out in Asia and elsewhere. However, many aspects of the mechanisms of release are still poorly understood. Our ability to predict the variations with time i s limited, yet temporal variations in arsenic concentration are a central issue to mitigation. Below are outlined what we know o f the principal causes o f arsenic mobilization in water and the environment and the information that i s available concerning spatial and temporal variability inthe arsenic-affected aquifers o f Asia. The highest concentrations o f arsenic tend to occur in sulfide minerals and metal oxides, especially iron oxides. It therefore follows that where these occur in abundance, arsenic problems can result ifthe release from the minerals i s favored. Undermost circumstances, the mobilization o f arsenic in surface waters and groundwaters is low because o f retention in these mineral sinks. However, the toxicity o f arsenic i s such that it only takes a very small proportion o f the solid-phase arsenic to be released to produce a groundwater arsenic problem. There are a number o f drivers that can result inthe release o f arsenic from minerals and the build-up of detrimental concentrations in water. These are outlined in broad terms below. 3.2 Arsenic Sources Arsenic occurs naturally inall minerals and rocks, although its distribution withinthem varies widely. Arsenic occurs as a major constituent inmore than 200 minerals, including elemental arsenic, arsenides, sulfides, oxides, arsenates, and arsenites. Most are ore minerals or their alteration products. However, these minerals are relatively rare in the natural environment. The greatest concentrations o f them occur in mineral veins. The most abundant arsenic ore mineral is arsenopyrite (FeAsS). This is often present in ore deposits, but is much less abundant than arsenian pyrite (Fe(S,As)S, which i s probably the most important source o f arsenic in ore zones. Other arsenic sulfides found inmineralized areas are realgar (ASS) and orpiment (As&). Though not a major component, arsenic i s also present invarying concentrations in common rock-forming minerals. As the chemistry o f arsenic follows closely that o f sulfur, the other, more abundant, sulfide minerals also tend to have high concentrations o f arsenic. The most abundant o f these i s pyrite (FeS2). Concentrations o f arsenic in pyrite, chalcopyrite, galena, and marcasite can be very variable but in some cases can exceed 10 weight percentage (table 13). Besides being an important component o f ore bodies, pyrite i s also formed in low- temperature sedimentary environments under reducing conditions. It i s present in the sediments o f many rivers, lakes, and oceans, as well as in a number o f aquifers. Pyrite is not stable in aerobic systems and oxidizes to iron oxides with the release o f sulfate, acidity, arsenic, and other trace elements. The presence o f pyrite as a minor constituent insulfide-rich coals i s ultimately responsible for the production o f acid rain and acid mine drainage, and for the presenceo f arsenic problems around coal mines and areas o f intensive coal burning. Highconcentrations of arsenic are also found in many oxide minerals and hydrous metal oxides, either as part o f the mineral structure or adsorbed to surfaces. Concentrations in iron oxides can also reach weight percentage values (table 13), particularly where they form as the oxidation products of primary iron sulfides. Adsorption o f arsenate to hydrous iron oxides i s known to be particularly strong. Adsorption to hydrous aluminum andmanganese oxides may also be important if these oxides are present in quantity (for example Peterson and Carpenter 1983; Brannon and Patrick 1987). Arsenic may also be adsorbed to the edges o f clays and on the surface o f calcite. However, the loadings involved are much smaller on a weight basis than for the iron oxides. Adsorption reactions are responsible for the low concentrations o f arsenic found inmost natural waters. -49 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1 Arsenic Occurrence in South - - and EastAsia: scale, causes, andmitigation Table 13. Typical Arsenic Concentrations inRock-Forming Minerals Mineral Arsenic concentration range (mgkg-I) Sulfide minerals Pyrite 100-77,000 Pyrrhotite 5-1 00 Marcasite 20-126,000 Galena 5-10,000 Sphalerite 5-17,000 Chalcopyrite 10-5,000 Oxide minerals Hematite upto 160 Fe oxide (undifferentiated) upto 2,000 Fe(II1) oxyhydroxide upto 76,000 Magnetite 2.741 Ilmenite 8) and are accompanied by high salinity. High concentrations of trace elements such as fluoride, molybdenum, and boron are also characteristic. While none o f the oxidizing, high-pHgroundwater provinces recognized so far is from Asia, this is not to say that such - 57 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1 Arsenic Occurrence in South - - and East Asia: scale, causes, andmitigation conditions will not occur. Major deposits o f Quaternary sediments (including loess) cover large parts o f northem China, for example. Quaternary aeolian deposits o f Pakistan, including the Baluchistan basin, also contain high-pH groundwater. It is believed that the groundwaters inthese areashavenotbeentestedfor arsenic. One o f the key findings o f the last few years has been that the affected sedimentary aquifers o f Asia (for example Bangladesh, China) do not have anomalously high concentrations o f arsenic in the sediments. This is important because it implies that potentially any young sediments could develop groundwater arsenic problems, given a combination o f geochemical conditions conducive to the release o f arsenic (reducing conditions or oxidizing, high-pH conditions) and hydrogeological conditions that prevent it from being flushed from the aquifer. Other alluvial and deltaic plains, such as the lower reaches o f the Yellow River plain and Yangtze River o f China and the Chao Phraya River o f Thailand, deserve further investigation. 3.5 Variability inArsenic Concentrations 3.5.1 SpatialVariability A high degree of spatial variability inarsenic concentrations both areally and with depth has been noted in many o f the recognized problem aquifers. Such variability is a natural consequence o f sediment heterogeneity and poor mixing brought about by sluggish groundwater movement. Notable vertical variations in sediment texture, composition, and grain size have been observed from sediments in Bangladesh on a scale o f centimeters. This can have large impacts on groundwater movement between layers, on water-rock interactions, and on local redox conditions. Small differences indepth of closely spacedwells canresult in the tapping o f different horizons (figure 11). Lack o f homogenization o f groundwaters and poor hydraulic connection between layers can maintain chemical differences on local scales. Besides, it should be bome inmind that interms o f thresholds o f acceptability the difference between concentrations o f 10 pg L-' and 50 pg L-' is critical, yet geochemically the differences are very small. Manyhigh-arsenic groundwaters appear to be associated with occurrence of finer-grained and iron oxide-rich deposits, such as accumulate preferentially in low-lying distal parts o f deltas or in low-flow zones o f river flood plains. The occurrence o f local arsenic hotspots observed in, for instance, Bangladesh aquifers may be explained by the localized occurrence of fine- grained sediments in inside meanders and oxbow lakes. Together with locally slow groundwater movement in these areas, this may be responsible for the build-up(and lack o f flushing) o f arsenic. 3.5.2 TemporalVariability 3.5.2.1 High-Arsenic Aquifers The timescales over which temporal variations inarsenic concentrations may exist range from hours (diurnal changes) through seasons to years or decades. The potential causes o f such changes are also variable: changes in groundwater pumping rate over the course o f a day; seasonal variations in recharge, irrigation abstraction, and head gradients; long-term changes inpumpingregimes and climate. Duringthe seasonal or annual cycle of a major abstraction source such as an irrigation well or municipal supply well, the chemical composition o f abstracted groundwater may be affected by the variable contribution from different depths, which changes with time. Initial discharge tends to be dominated by flow from the shallowest horizons with deeper flow becoming more important with time as the cone o f groundwater depression deepens. This influence is likely to be less important for small handpumped tubewells which individually involve much smaller abstractions. Changes in chemical compositions over longer timescales may result from long-term changes in groundwater level. To date, there has been very little investigation of the temporal variations in groundwater chemistry in high-arsenic aquifers from Asia and much more needs to be done to assess whether variations are significant ina practical sense. - 58 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - andEastAsia: scale, causes, and mitigation - - l o I I I * ' ~ ' J ~ * ~ i 8- FPWG:150m 1 - 9 46 : f i - 1 450 I I I I l l l l l l l 400- --L-FHlWl t F W 3 --C-FHTW5 -- v- +FHlWZ -+-FHlW4 -0-FHTWB 350- r*./+----,*_r/ Y 300 - -a i 9 250 - ~.., v: - _ 200- 150 - \ I - 100 5o -Other tubewells 0 ' l l l ' s ' t ' * I from West Bengal groundwaters that groundwater arseni concentration vary seasonally, with minima during the postmonsoonperiod, considered to be due to dilution o f groundwater bymonsoon recharge. However, the conclusion is apparently based on small sample sets (4-6 samples at any given location) collected over a short time interval (less than one year). Chatterjee and others (1995) noted a variation o f around 30% in time series data from monitoring o f groundwaters over the period o f a year in their study o f parts o f 24 Parganas Northand South, but detected no significant seasonal changes inthe variation. - 59 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1- Arsenic Occurrence in South and East Asia: scale, causes, andmitigation 3.5.2.2 Deep (Older) Aquifers I t has often been said inrelation to the deep aquifers o f the Bengal basin that some wells that were once arsenic free have become contaminated with time (for example Mandal and others 1996). However, documentation and data in support of this conclusion are difficult to find. Since the long-term trends in groundwater arsenic concentrations are a critical issue for the sustainability o f the deep aquifers, the data that indicate such variations need to be documented properly and be open to peer review. If temporal trends are apparent in groundwater from deep aquifers, there are a number o f reasons why this may be the case. These include inadequate sealing of tubewells, multiple screening o f tubewells at different depths to improve yields, as well as natural hydraulic connectivity between aquifers (as stated above). They also may represent analytical problems. A statistical approach is needed in interpreting time series data. 3.5.2.3 Dug Wells Few time series data exist for dug wells in arsenic-affected areas. Arsenic concentrations in dug wells may be susceptible to temporal change as the groundwaters abstracted from them are from the shallowest levels and therefore subject to the largest changes in recharge inputs, pollutant inputs, and redox conditions. They may also vary if particulate contents vary with time and water samples taken from them are not filtered. Despite these possibilities, groundwater in three dug wells from northwest Bangladesh monitored by BGS and DPHE (2001) over the course o f a year showed little statistically significant variation. Concentrations were low and in the range 0.5-2 pg L-', with only two individual measurements from the wells exceeding 10 pg L-'.More data are clearly needed to determine whether significant temporal changes occur in other areas, particularly where local groundwater arsenic concentrations are high. The relative contributions o f particulate and dissolved fractions should also be investigated by measurement o f other parameters (notably iron) as well as arsenic. 3.5.2.4 Arsenic in Surface Water Little information i s available on the arsenic concentrations o f surface waters in regions with highgroundwater arsenic concentrations. Even less is available on temporal variations. The greater likelihood o f highsuspended loads insurface waters means that the concentrations are potentially more variable than in most groundwaters as the arsenic associated with particles can be significant. Concentrations in particles are likely to be in the range 5-10 mg kg-', in line with the concentrations o f average sediments, but may be higher in iron-rich particles. There i s also potential that river waters will vary seasonally as a result o f the variations inthe proportion o f baseflow compared to runoff. This has not been studied in detail. However, most o f the evidence points to surface waters generally having low arsenic concentrations, even where groundwater arsenic concentrations are high. - 60 - Arsenic Contaminationof Groundwater in South and East Asian Countries:Volume I1- Paper 1- Arsenic Occurrence in South andEast Asia: scale, causes,and mitigation 4. Groundwater Management for Drinking Water and Irrigation 4.1 Overview The previous sections highlight the extreme variability in arsenic concentrations both within and between aquifers and have shown some of the issues associated with identifying safe sources o f water and determining suitable alternatives. One o f the key developments o f the past few years has been the realization that the mode of occurrence o f arsenic in water can vary substantially. The mechanisms of arsenic occurrence inwater inmining andmineralized areas can be very different from those in young sedimentary aquifers and their distribution and scale can also differ considerably. Some of the options for water supply are detailed further in this section, along with the risks associated with them and potential strategies for dealing with those risks. The choice o f water supply in any given area must depend on many technical and social factors that need to be assessed locally. The options, risks, and potential mitigation strategies are summarized intable 15, at the end o fthis chapter. 4.2 Mining and Mineralized Areas In areas with rich deposits of sulfide minerals, both surface waters and groundwaters are potentially vulnerable to higharsenic concentrations. Other toxic trace elements may also be present in excessive concentrations (for example copper, lead, zinc, cobalt, cadmium, nickel). In these areas, surface waters, groundwaters, and soils are all potentially affected by high arsenic concentrations. However, the scale o f contamination is likely to be localized, on the scale o f a few kilometers around the site o f mineralization. Mitigation of the problem therefore centers on identifying contaminated water sources and finding alternative supplies locally. Both identification o f at-risk sources and mitigation should be less o f a problem than inarsenic-affected sedimentary aquifers. Environmental problems are usually exacerbated by mining activity and are therefore largely predictable. 4.3 Sedimentary Aquifers 4.3.1 Shallow Groundwater 4.3.1.1 Shallow Tubewells O f the sedimentary aquifers in South and East Asia with recognized arsenic problems, the majority are composed o f young sediments at shallow depths o f less than 50-100 mor so. In Bangladesh the highest concentrations and largest range o f concentrations are found in the shallow aquifers, which are dominantly o f Holocene (42,000 years) age. The extreme variability indicates that on a local scale, the scale relevant to mitigation, no reliable method can be used to predict their concentrations accurately and no substitute therefore exists for testing each well for arsenic if it is to be used for drinking water. This is not to say that on a regional scale some sort o f prioritizationwould not be possible given some knowledge o f the distribution o f sediment textures, hydrogeology, and water chemistry. Bangladesh groundwaters tend to have highest arsenic concentrations in the low-lying parts o f the delta. This i s also evident inother aquifers o fAsia (for example Huhhot basin, China) (Smedley and others 2003). However, our understanding o f the distribution o f arsenic in groundwater at present does not allow prediction o f such trends with confidence, even on a regional scale, and hence major testing programs in such susceptible aquifers are needed regardless o f local geological variations. The distributions o f arsenic in different districts o f Bangladesh vary widely (BGS and PDHE 2001). The worst-affected districts identified from the BGS and DPHE (2001) study were (percentage o f samples with arsenic concentrations greater than 50 pg L-' in parentheses): Chandpur (go%), Munshiganj (83%), Gopalganj (79%), Madaripur (69%), Noakhali (69%), Satkira (67%), Comilla (65%), Faridpur (65%), Shariatpur (65%), Meherpur (60%), Bagerhat (60%), and Lakshmipur (56%). In the worst-affected areas it would probably be appropriate to abandon use o f the shallow aquifer in the long term in favor o f alternative sources o f drinking water. -61 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEast Asia: scale, causes,and mitigation On the other hand, on a national scale, the BGS and DPHE (2001) survey showed that for tubewells 4 5 0 m deep, 27% exceeded 50 p g L-' and 46% exceeded 10 p g L-'. This means that 73% and 54% o f wells had concentrations below these limits respectively. Also, 24% o f samples analyzed had concentrations below the analytical detection limit, usually 0.25 pg L-' or 0.5 pg L-'. The districts o f Thakurgaon, Barguna, Jaipurhat, Lalmonirhat, Natore, Nilphamari, Panchagarh, and Patuakhali all had no samples with arsenic >50 pg L-' in the survey. This means that large-scale abandonment o ftubewells inmany parts o f Bangladesh i s unnecessary. The same holds for most other sedimentary aquifers o f Asia where arsenic problems have been encountered. Major investments have been made in shallow tubewells across Asia and in many places these still constitute a reliable source o f safe drinkingwater. There is also the potential for segregation o fwells for different uses. High-arsenic wells could beused, for example, for washing and other domestic purposes,providedthe wells are labeled adequately. Inmanyareas withhigh-arsenic groundwater domestic-scale treatment is beingcarried out in order to remove or reduce the arsenic indrinking water supplies. These usually involve either aeration and sedimentation, coagulation and filtration, adsorption, ion exchange, or membrane filtration (Edwards 1994; Hering and others 1996; Ahmed 2003). While many o f these techniques have been adapted for domestic use in affected areas and the technologies have improved significantly inrecent years, issues remain over their sustainability and the disposal of high-arsenic waste products. They can provide a u s e h l short-term solution in affected areas but are unlikelyto form the basis o f long-term mitigation strategies. Itshouldbeborne inmindthat the shallow high-arsenic groundwaters o fthe Bengalbasin and other areas o f South and East Asia also often have problems with a number of other trace elements that can be detrimental to health (for example high manganese, uranium, boron concentrations) or can cause problems with acceptability (high salinity, iron, ammonium concentrations). Inarid areas (for example northern China) the shallow aquifers can also have problems with high fluoride concentrations. These other elements rarely correlate well with arsenic and so shallow groundwaters o f good quality inrespect o f arsenic concentrations may not necessarily be o f good quality inother respects. Defining acceptability criteria for potable water supplies should therefore .involve consideration o f other potentially detrimental constituents andnotjust arsenic. 4.3.1.2 Dug Wells It has beentraditionally accepted that shallow groundwater from open dug wells usuallyhas low concentrations o f arsenic. Evidence from Bangladesh (BGS and DPHE 2001), West Bengal (Chakraborti 2001), Myanmar (WRUD 2001), and Taiwan (Guo, Chen, and Greene 1994) indicates that many dug wells contain water complying with the WHO guideline value o f 10 p gL-' and most comply with the national standardo f 50 pgL-'. Despite this tendency, a rather different situation i s apparent for groundwater from dug wells inInner Mongolia. As shown insection 2.2.6, dug wells inthe Huhhot basin were found to contain groundwater with arsenic concentrations up to 560 p g L-' in the area where tubewell arsenic concentrations were also high (Smedley and others 2003). Some recent studies in Bangladesh and Myanmar also appear to be findinghigher arsenic concentrations indugwells than previously appreciated, although supporting evidence has not yet been published to verify this. Some of the higher concentrations observed may be due to particulate rather than dissolved arsenic and concentrations may therefore vary depending on the turbidity of the groundwaters. Particulate matter could presumably be removed by some simple filtration or settling. The findings suggest that in any given aquifer, concentrations o f arsenic in dug wells cannot be assumed to have acceptably low arsenic concentrations without a testing program to confirm the concentration ranges. Care should also be taken in analyzing for arsenic that the relative contributions o f dissolved andparticulate arsenic are determined. - 62 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1- Arsenic Occurrence in South and EastAsia: scale, causes,and mitigation Since traditional large-diameter dug wells are normally open to the atmosphere and tap the shallowest levels o f the aquifer, they are also potentially vulnerable to contamination from bacteria and other surface pollutants. Well siting and construction are therefore important criteria for well protection. Locating wells at some distance from latrines and other contaminant sources i s important, as is installation o f adequate sanitary seals. Installation o f handpumps removes potential contamination from introduced buckets and disinfection o f water can give protection against waterbome diseases. Periodic cleaning o f the well can help to reduce suspended material. One o f the major constraints on the use o f dug wells is likely to be well yields. This is especially the case in areas with relatively large water level fluctuations, where dug wells can dry up inthe dry season. Poor water qualityis linkedto this to some extent, as particle settling becomes more difficult when wells dry up. Poor well yields may be the ultimate limit o f the sustainability o f dug wells in some areas. They are also not suitable in areas with thick layers o f superficial clay. Evidence from the BGS and DPHE (2001) study o f Bangladesh suggests that dug wells also contain potentially detrimental concentrations o f uranium (up to 47 pg L-').Dug wells had the highest concentrations o f uranium identified in groundwaters from Bangladesh. Few epidemiological data exist to set a safe limit for uranium in drinking water, but new WHO guidelines include a provisional value for uraniumo f 9 p g L-'.Concentrations o f nitrate also exceeded the WHO guideline value insome wells, presumably as a result o f surface pollution. Hence, for the reasons outlined above, dug wells may offer a suitable short-term solution to arsenic problems in some affected areas o f Asia. However, they are unlikely to form a major component o f long-term mitigation strategies for most areas. 4.3.2 GroundwaterfromDeep(Older) Aquifers Although analyses o f groundwater from deep aquifers in the Bengal basin are still relatively limited, there appears sufficient information available to indicate that deep (older) aquifers in the region have much lower arsenic concentrations than many o f the shallow aquifers above. The BGS and DPHE (2001) results suggested this for areas o f south and east Bangladesh. CGWB (1999) found comparatively low concentrations in the deep aquifers o f West Bengal. Van Geen, b e d , and others (2003) found similar results east o f Dhaka. Data for other elements are also sparse, but where available they suggest that concentrations o f manganese, uranium, and most other trace elements are also low in these deep aquifers. The older sediments therefore offer potentially good prospects as alternative sources o f safe water for the Bengal basin. Van Geen, h e d , and others (2003) reported successes with take-up o f groundwater supplied by six newly installed "deep" (60-140 m, but pre-Holocene) community wells ina badly affected part o f Bangladesh. Inthe short time since the wells have been installed they are said to have proved popular with the local communities and women have been willing to walk up to hundreds o f meters for their h n k i n g water. The authors reported that such wells could provide drinking water for up to 500 people living within 150m o f the well in densely populated villages. Whether willingness to walk for supplies o f drinkingwater would be a widespread phenomenon in arsenic-affected areas is untested and deserves further investigation. Considerable uncertainties remain over the deep aquifers, particularly with respect to (a) their lateral extent; (b) their depth ranges (as demonstrated by the van Geen, Ahmed, and others 2003 example); and (c) the variation in their hydraulic separation from the shallow aquifers. Inmany places these will not have been assessed if adequate supplies of water have been available at shallower depths. An important risk with development o f such deep (low-arsenic) aquifers is from potential drawdown o f high-arsenic groundwater from shallower levels and contamination in the long term (decades or longer). This can occur if intervening layers o f clay are thin or absent, or if seals on wells penetrating the deep aquifer are inadequate. Flow modeling o f the Bangladesh aquifers (BGS and DPHE 2001) suggested that flow down to deep levels (100 m or more) is - 63 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - andEast Asia: scale, causes,andmitigation likely to be slow even underactive pumping conditions. Modeling of aquifers inthe Faridpur area o f central Bangladesh suggestedthat rates o f groundwater movement to a well screened at 110-135 m depth from the water table at a lateral distance o f 500 mwould be o f the order o f 200 years. The rate was found to behighlydependent on local lithology. Detailed hydrogeological investigations are therefore an essential prerequisite to the development o f such aquifers on a regional scale. The quality o f well construction also needs to be high. Subsequent groundwater quality monitoring for arsenic and a number o f associated parameters also needs to be carried out. The greatest threat i s from abstraction o f large volumes o f water for irrigation. Regulation o f water abstraction should therefore be an integral part of water management policy to protect the deep aquifers. Introduction o f abstraction licensing would be a logical step in policy development. Recording o f well log information in a systematic way for newly drilled deep tubewells would also improve the knowledge baseon the aquifers. It is clear from investigations in other regions of South and East Asia that deep aquifers are not always low-arsenic aquifers. The Huhhot basin o f Inner Mongolia i s a case inpoint. Here, groundwater from (probably) Pleistocene aquifers at 100-400 m depth contains arsenic concentrations inthe range 4-308 p g L-I.The variations reiterate the fact that aquifer depth i s not an indicator o f groundwater arsenic status. They also stress the need for detailed hydrogeological investigations in young sedimentary aquifers to identify sources and model their responses to groundwater development before any development takes place. 4.3.3 Surface Water 4.3.3.1 Rainwater O f all the sources o f drinking water available for communities, rainwater is the least likely to face problems with arsenic contamination. Concentrations o f dissolved solids will usually also be very low (perhaps too low). Rainwater harvesting offers a potential source o f drinking water for individual households in areas where other sources are unsuitable. The method requires a suitableroof for collection and storage tank with adequate sealing to protect it from bacterial and algal contamination. It has been estimated that about half o f households in Bangladesh have roofs suitable for collection o f rainwater (for example galvanized iron, tiled surfaces) but that many o f the poorer families would not be suitably equipped (Ahmed and Ahmed 2002). Rainwater harvesting can provide a seasonal supply of water for dnnlung but its period o f use will be more limited inarid areas. Evenso, provisiono frainwater can still be beneficial evenifavailable for only a few months o f the year. 4.3.3.2 Rivers, Ponds Surface water usually has very low arsenic concentrations (typically <5 pg L-'). Exceptions include waters affected by mining activity and some geothermal areas. These are generally easily identified. As noted above, mining-contaminated waters are also usually localized to withn a few kilometers o f the mining activity (Smedley and Kinniburgh 2002), although those affected by geothennal inputscanbe more widespread. Surface waters in the arsenic-affected regions o f South and East Asia usually have low concentrations. Indeed, this is why there are many proponents o f treated surface water as an option for safe water supply in Bangladesh and elsewhere. BGS and DPHE (2001) found concentrations o f <2 p g L-' in five river samples from the affected areas o f Bangladesh. A sixth sample, from the Mahananda River flowing through the Chapai Nawabganj arsenic hotspot area o f western Bangladesh, had a concentration o f 29 pg L-' (in March 1999) although repeat sampling (in December 1999) gave a value o f 2.7 pg L-I, an order o f magnitude lower. Whether t h s difference represents real seasonal changes is difficult to assess on the basis o f such limited data. I t does highlight the possibility that dry season groundwater discharge to the river systems could raise the surface water arsenic concentrations, especially inthe worst-affected areas. Small rivers may be more affected than large rivers with greater volumes o f water. However, oxidation o f the reduced arsenic and - 64 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEastAsia: scale, causes, and mitigation consequent adsorption will lower the dissolved concentration being discharged to a large extent. The extent will depend upon, for example, the initial concentration and the river baseflow index (proportion o f groundwater present). A worse problemassociated with the use of surface water is the potential risk from bacterial and other waterborne diseases arising from pollution. This problemmeans that surface water will probably always require adequate treatment to remove such hazards before use. At the village level this has been achieved through the use o f pond sand filters. At a municipal level water treatment works can be installed for treatment o f larger volumes. I t i s likely that any arsenic present in the initial waters will be removed by both o f these treatment systems to concentrations below the drinking water thresholds. Other potential problems with the quality o f surface water sources include inputs o f nitrate andpossibly organic compounds (pesticides, solvents) in some areas as a result o f pollution. Concentrations o f these will vary depending on local conditions and are difficult to remove by low-technology treatment methods. - 6 5 - Arsenic Contaminationof Groundwaterin South and East Asian Countries: Volume I1- Paper 1- Arsenic Occurrence in South and East Asia: scale, causes,and mitigation Table 15. Risks Associated with the Use of DrinkingWater from Various Sources at Various Scales and Potential MitigationStrategies Source Risk for supply Mitigation strategy Householdscale Village scale Urbanscale Shallow Higharsenic Water testing; Water testing; altemative Altemative tubewells concentration alternative source source if concentration sourceimunicipal (Holocene ifconcentration high treatment plant if aquifers) high concentration high Highconcentrations Water testing; Water testing; treatment Water testing; o f other inorganic treatment difficult difficult treatment plant constituents (e.g. Mn, U,NH4,B) Deep Drawdown o fhigh- n.a. Carry out prior site Carry out prior site tubewells arsenic water from investigations; restrict use investigations; (older shallow aquifers to drinkingwater; regulate restrict use to sedimentary abstraction drinkingwater; aquifers) regulate abstraction Dugwells' Poor yields ifwells Occasional use; Relocate/deepen wells n.a. dryup seasonally altemative source; walk to other wells Bacterial and other Disinfection, Well protection: sanitary n.a. waterborne diseases, filtration seals, handpump highparticulate loads installation, water disinfection, periodic cleaning. Relocate wells away from pollution sources Other inorganic water Difficult Water treatment difficult. n.a. quality problems (e.g. Relocate wells away from nitrate, uranium, pollution sources (nitrate) manganese) Arsenic may exceed Water testing Water testingnecessary. n.a. prescribed limits necessary. Treatment difficult Treatment difficult Surface water Potential bacterial Small-scale water Small-scale water Urban water problems, high treatment (e.g. treatment (pond sand treatment plants particulate loads pond sand filters) filters) Other pollutants (e.g. Difficult Difficult Urban water nitrate, pesticides) treatment plants Rainwater Seasonal, difficult in Partial supply n.a. n.a. arid areas Bacterial Storage protection, n.a. n.a. contamination disinfection n.a. Not applicable. - 66 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEast Asia: scale, causes,and mitigation 5. Recommendationsfor Surveying and Monitoring 5.1 Overview Although our ability to predict arsenic concentrations in groundwater from a given area or aquifer is still rather limited, knowledge o f its occurrence and distribution has improved greatly over the last few years. We therefore probably know enough about where high concentrations tend to occur to make reasonable estimates o f likely at-risk aquifers on a regional scale. Young sediments in alluvial and deltaic plains and inland basins as well as areas o f mining activity and mineralization are obvious target areas for further evaluation. The guidelines for improving understanding o f the arsenic problem and how to go about dealing with it are broadly the same in any region at increased risk from arsenic contamination. First, the scale o f the problemneeds to be assessed. Second, where problems exist, it is necessary to find out whether or not the situation is becoming worse with time. Third, where problems exist, it is necessary to identify the potential strategies or alternatives that are most appropriate for supplying safe (low-arsenic) water. Central to these issues is arsenic testing. In any testing program it is important to distinguish between reconnaissance testing: that necessary for establishing the scale o f a groundwater arsenic problem; and blanket testing: that required for compliance and health protection. Blanket testing involves the analysis o f a sample o f water from every well used for drinking water. For reconnaissance testing the numbers o f samples need not be large; they should however be collected on a randomized basis. Monitoring is the repeat sampling o f a given water source in order to assess temporal changes over a given timescale (as distinct fiom repeat testing to cross-check analytical results). The quality o f analytical results is also paramount; analysis o f arsenic inwater i s by no means a trivial task, yet reliable analytical data are key to understanding the nature and scale o f groundwater arsenic problems as well as dealing with them. Instigation o f any new arsenic testing or monitoringprogram requires consideration of the analytical capability o f the local laboratories. In some cases, development o f laboratory capability (for example quality assurance procedures, training, equipment upgrades, increased throughput) may be required and shouldbebuiltintothe testingprogram. Appropriate mitigation responses for arsenic-affected regions will necessarily vary according to local geological and hydrogeological conditions, climate, population affected, and infiastructural factors. Surface water may or may not be available as an alternative. Other groundwater aquifers at different depths or indifferent locations may be available for use and need additional assessment. Decisions about what action to take in respect o f the arsenic- affected aquifer depend on factors such as percentage o f wells o f unacceptable quality and range in concentrations (degree by which such standards such as 50 pg L-' or 10 p g L-' are exceeded). Below are outlined strategies for assessing the scale and distribution o f arsenic problems in South and East Asian aquifers and for providing the necessary information as a basis for mitigation. 5.2 AquiferDevelopment andWell Testing 5.2.1 Aquifers of Low PotentialRisk Itfollows from section 5.1 that our ability to define with accuracy where low-arsenic aquifers are likely to be is limited. Broadly, they are likely to include carbonate rocks, crystalline basement rocks, and other old @re-Quaternary) sediments that have not been affected by mineralization or geothermal inputs.However, given the potential health risks associated with arsenic in drinking water, there is an argument for some randomized reconnaissance-scale testing o f existing wells for arsenic in areas with little or no information, regardless o f their perceived risk status (based on our current understanding). Provided the testing i s random, survey results will provide information on the concentration ranges o f arsenic to be expected ina given aquifer or region. Testing for arsenic alone may be sufficient inthis casebut other - 67 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - andEastAsia: scale, causes,and mitigation constituents o f health concern could be included, depending on available budgets (for example iron, manganese, fluoride, nitrate; electrical conductance would also be useful). Newly dnlled boreholes should also include analysis o f arsenic, at least on a subset o f samples. Identification of significant numbers o f samples with unacceptably high arsenic concentrations (say )10 p g L-') should trigger a program for more extensive chemical analysis and geochemical investigation. This should involve analysis o f a wider suite o f analytes aimed at identifying the causes as well as the scale o f the arsenic problem. Until a more detailed understanding o f the arsenic concentrations in groundwaters o f different aquifers inthe developing world (and elsewhere) i s available, including arsenic as a chemical analyte is a logical cautious approach. Although correlations between arsenic and other elements (such as iron) have often been noted in groundwaters, the correlations are usually insufficiently good to rely on proxy analytes. 5.2.2 PotentiallyHigh-Arsenic Aquifers As with any other area, aquifers at greater potential risk from high arsenic concentrations require the scale o f any groundwater arsenic problem to be defined and the likelihood o f future changes assessed. In undeveloped areas where little previous information i s available and new groundwater supply projects are planned, merely testing for arsenic will determine the scale o f the problem but will not define the processes involved. These need to be established to understand the aquifer better and ensure that groundwater use will be sustainable and that subsequent investment i s appropriate. There is therefore a need for a detailed hydrogeological and geochemical investigation before any project implementation. This may involve collation o f all available hydrogeological data (for example well depths, water levels, aquifer physical characteristics, pumping rates, groundwater yields), collection o f new water samples for more detailed chemical analysis (a more comprehensive range o f analytes), and assessment o f sediment chemistry and mineralogy (table 16). Such studies can be time consuming and may have large cost implications. Insome countries local institutions may be equipped to cany out these investigations. In others, expertise from external organizations may be required. The size o f the prior investigation work should be commensurate with the size o f the intendedwater supply program, amounting to say 5-10% o fthe projected implementation cost. Table 16. Arsenic Testing Strategies inPotential High-Arsenic Groundwater Provinces Area Existing drinkingwater wells New drinking water wells ~~~ Untestedareas Randomizedreconnaissance Initialhydrogeologicaland geochemical groundwater arsenic survey. Scale of siteiregionalinvestigation.Test drilling; survey dependenton number ofwells, analysis of groundwaterfor arsenic areal extent of aquifer, number of during drilling andon completion. people served. Stratifiedrandom approach(stratification basedon geology, well depth). Blanketarsenic testingof wells usedfor public supply, schools, hospitals. Established Blankettesting for arsenic. Decisionto drill new wells basedon groundwater previousresults. Alternatives necessary arsenic inbadly affectedaquifers.Inmarginal problemareas cases, selectionofwell location, depth, etc., basedon previousinformation. Analysis for arsenic on completion. - 68 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - and East Asia: scale, causes, andmitigation In areas where groundwater is already in use but water quality data are limited or absent, reconnaissance testing is necessary in the first instance to define the scale o f any arsenic problem. Defining the concentration ranges and spatial distributions o f arsenic in groundwater is best achieved by some sort of randomized groundwater survey (most importantly, not based on previous knowledge o f groundwater arsenic concentrations). The scale of groundwater testing should be commensurate with the numbers o f people dependent on the water supply and potentially affected by it. In Bangladesh the density o f wells sampled inthe BGS and DPHE (2001) national survey was 1 per 37km2. The number o f samples tested represented only around 0.05% o f the tubewells believed to be present in Bangladesh. The survey proved inadequate to pick out many o f the localized arsenic hotspots that occur in some areas but did serve to identify the worst-affected parts o f the country and the depth ranges o f the tubewells with the worst problems. I t therefore highlighted priority areas for mitigation. These were seen to be the southeastem part o f Bangladesh. Subsequent surveys by various organizations may have refined the data distributions, but do not appear to have changed the overall conclusions concerning the worst-affected areas and hence the priority areas for mitigation. The BGS and DPHE (2001) survey statistics indicated that 27% o f shallow tubewells in Bangladesh had arsenic concentrations >50 pg L-'. This figure compares well with an earlier estimate o f exceedances above 50 p g L-' for the whole country (26%) based on data from BGS, DPHE, and other organizations (DPHE-BGS-MML 1999). O f course, these data just provide summary statistics and define regional distributions and do not define concentrations inindividual wells. This latter is needed for compliance testing. The BGS andDPHE (2001) survey showed the high degree o f spatial variability in groundwater arsenic concentrations and, as with many other surveys, demonstrated the need for testing of individual wells used for drinking water. Wells usedfor irrigationshould also be tested ultimately as these represent a potential, though less direct and as yet unquantified, threat to health. They are, however, o f a lower priority. Survey samples need to be georeferenced (latitude and longitude data or other national grid) and notes made of aquifer type, well depth, well age, well owner, well number if available, and location. Other aquifers present inthe region (for example the deep (Pleistocene) aquifer in Bangladesh) should also be tested on a randomized basis to assess their potential as altematives. The data needto be analyzed to assess whether statistically significant variations exist in variables such as well depth, well age, and sediment type. The data should be incorporated into a database for ready storage and manipulation. The data should also be mapped. In areas where some initial surveys have been carried out and where arsenic problems have been recognized, spatial pattems may be discemible. If these are significant, they should highlight where mitigation needs to be targeted and where not. Past experience shows that many arsenic-affected aquifers have highly variable groundwater arsenic concentrations on a local scale. Inthis case and where concentrations are high, blanket testing o f wells will most probably be required. This is best achieved by laboratory analysis using reliable local facilities equipped for rapid throughput o f samples. Where these are absent, facilities should be set up and equipped for analysis o f arsenic and a range of other diagnostic elements (see below). Where setting up o f laboratories is not possible or where the scale o f testing is very large and facilities inadequate to cope with the scale of testing required (for example Bangladesh), field test kits can be an alternative. The technology for these has improved in the last few years and while older kits were barely able to determine concentrations o f arsenic at less than 100 pg L-', the sensitivity o f newer designs i s better. Wherever possible, capability to test reliably at 10 pg L-' should be aimed for. Wherever possible, a subset o f samples analyzed by field test kits (say 10%) should be cross-checked by a reliable laboratory analysis. A premiumshould be placed on reliability o f analytical results and quality assurance should be a critical and ongoing undertaking with any groundwater testing or monitoring program (box 1). - 69 - Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - andEast Asia: scale, causes,and mitigation Past hydrogeochemical investigations o f high-arsenic aquifers have shown correlations with other elements (for example iron, manganese) but these are rarely sufficiently significant to be useful in a practical sense. Results indicate that there are no suitable reliable proxy indicators for arsenic concentration ingroundwater. 5.2.3 Deep Aquifers belowHigh-Arsenic Aquifers As the deep (Pleistocene) aquifers of Bangladesh, West Bengal, and Nepal are identified as being potentially suitable sources for drinking water supply and also being vulnerable to contamination from above, it i s important that future development o f such sources on a major scale is precededby detailedhydrogeological and hydrochemical investigations. These should include sedimentological studies to assess physical aquifer dimensions; pumping tests and groundwater flow modeling to determine flow mechanisms and assess the likelihood o f drawdown from shallow levels; and testing o f a wide range o f chemical parameters to determine controlling processes and assess other elements o fpotential health concern. During development o f such deep aquifers, it is o f importance to collate and document as much hydrogeological information as possible. In the case o f Bangladesh, for instance, collection o f information such as sediment texture (sand, silt, clay) and sediment color would be helpful and would demand little extra cost. Texture gives information on water storage capacity and sediment history. Inthe Bengal basin, experience has shown that reddish-colored sediments at depth are most likely to contain groundwater with low concentrations o f arsenic and iron. Color gives informationonredox conditions and stratigraphy and can help date the aquifers. The redox conditions and aquifer age have both proven critical to the quality o f water with respect to many other elements o f health concern as well as arsenic. Databasing o f such information is also important. Collection o f such information on these potentially valuable aquifers i s o f great importance, but should not serveto delay mitigationefforts inareaswithrecognized arsenic problems. 5.3 Monitoring Monitoring can be a major and expensive task. Production o f good analytical data i s paramount and, as stated above, analysis o f arsenic is difficult (box 1). Analytical problems should therefore be expected and variations viewed with skepticism until found to be statistically significant. As a first approximation, it is reasonable to assume that temporal changes will not be major in the short term and that an initial analysis i s likely to be representative for a given groundwater source (unless, as stated above, the analysis is suspect). Hence, single analyses can give an indication o f fitness for dnnking water in the absence o f time series information. In general, larger fluctuations in chemical composition can be expected at shallower levels where groundwater throughputs are higher and compositions more strongly influenced by changing groundwater head gradients. Chemical compositions in deeper aquifers can be expected to be more stable and changes are likely to be dampened and over longer timescales, unless affected directly by flow (leakage) from other neighboring aquifers. 5.3.1 Shallow Sedimentary Aquifers with RecognizedArsenic Problems On the scale o f arsenic problems recognized in countries such as Bangladesh, even initial testing for arsenic is a major logistical and analytical undertaking.Compliance monitoring o f tubewells and dug wells defined to be initially "safe" i s an even more demanding, and in many cases impossible, task. The scale o f monitoring possible in any given region will dependon the numbers of operating drinkingwater wells andthe resources (funds, analytical capabilities) available. Monitoring should be o f secondary priority to initial testing but is a necessary undertaking given the current uncertainty in temporal variations in arsenic concentrations. Monitoring i s required not only for raw groundwater from shallow tubewells but also for water from dug wells (especially those with concentrations >50 pg L-', which should be retested to verify the concentration) and for treated water that has been through an - 70 - Arsenic Contamination of Groundwaterin South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - and EastAsia: scale, causes, and mitigation arsenic removal plant. Recent investigations have shown that not all treated groundwaters have acceptably low concentrations o f arsenic (MahmudandNuruzzaman 2003). The concentration ranges chosen for monitoring wells vary according to the reason for monitoring. For compliance monitoring, priority would be appropriate for wells with concentrations o f the order to 10-50 p g L-' and wells used for major public supply. For research purposes, monitoring o f groundwater sources with concentrations outside this range (both low andhgh)would be o fvalue. The frequency o f monitoring also depends on the objective o f the monitoring exercise. Assessment o f short-term (diurnal) changes requires frequent monitoring over periods o f hours. Observation o f seasonal changes requires weekly or fortnightly monitoring. Longer- term changes require monitoringannually or biannually. 5.3.2 Deep (Older) Aquifers inArsenic-ProneAreas The deep aquifers o f the Bengal basinrepresent a special case inthat they appear to be largely free o f arsenic and are a potentially important alternative source o f drinkingwater, yet their vulnerability to contamination from the high-arsenic shallower aquifer is in large part untested. An important component o f a groundwater protection policy for the deep aquifers o f the Bengal basin (and other aquifers vulnerable to such leakage from contaminated aquifers) is the regular monitoring o f groundwater quality in order to detect any deterioration in the medium or long term and to take mitigating action if necessary. Annual or biannual monitoring o f such tubewells used for public water supply would be appropriate. Arsenic would be the most important analyte but a range o f other parameters (water level, electrical conductance, iron, manganese) would also be usehl. Monitoring for these selected parameters should be conducted for several years (five and preferably longer). That is not to say that the tubewells should not be used until a suitable run o f time series data have been collected. A subset o f samples should also be tested for all health-related parameters. Such monitoring can be a large task, but the number o f deep wells installed is likely to be much smaller than shallow handpumped tubewells. 5.3.3 Further ResearchNeededto Assess Temporal Variations Sufficient uncertainty remains over the temporal variations in arsenic concentrations in groundwaters in affected aquifers that research programs need to be undertaken in specific areas to obtain further monitoring data. On a research scale, this i s a relatively easy program to set up and could have been instigated in many o f the affected areas shortly after their discovery. Accumulated data from the regular monitoring of selected wells over periods of months or a few years would have helpedto identify the periodicity, scale, and causes o f any observed temporal variations andresolve many o fthe uncertainties that persist. Ideally, a program involving monthly monitoring o f selected tubewells in affected areas (monitoring for arsenic as well as water level, electrical conductance, iron, manganese) should be undertaken in some areas in order to identify seasonal trends. Such monitoring should be over the course o f several years (two minimum). Monitoring o f groundwater quality at different depths inrecognized high-arsenic aquifers i s also required. Such programs have been started in Bangladesh and elsewhere but more monitoring is needed to collect a larger body o f time series data. Studies o f diurnal variations inheavily used tubewells are also required to establish water quality variations over the course o f days. Little information is so far available on the temporal variation in arsenic concentration indug wells. Specific monitoringprograms in a few shallow wells, sampled approximately monthly, can be carried out to establish temporal variations, especially in relation to water level changes. Seasonal monitoring o f surface waters in areas with badly affected aquifers would help to establish whether temporal variations exist and whether they are sufficiently significant to cause consistent exceedances above national standards and the WHO guideline value. Monthly sampling o f filtered (0.45 pmpore size or less) river water over the period o f a year - 71 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 1 Arsenic Occurrence in South - and East Asia: scale, causes,and mitigation would provide information on whether variations are significant in an operational sense. It is stressedthat analysis ofunfilteredwater is likely to producehighly variableresultsdepending on the turbidity of the water since arsenic analysisusually involves acidification, and at any given timethe resultwill includesuspendedas well as dissolvedarsenic. - 72 - Arsenic Contaminationof Groundwater in South and East Asian Countries: Volume I1 Paper 1 - Arsenic Occurrence in South - and EastAsia: scale, causes, and mitigation 6. ConcludingRemarks Higharsenic concentrations recognized inmany parts of Asia and elsewhere are dominantly found in groundwater, and many o f the health consequences encountered have emerged in relatively recent years as a result o f the increased use o f groundwater from tubewells for drinlungandirrigation. Interms ofnumbers of groundwater sources affected and populations at risk problems are greatest in Bangladesh, but major problems have also been identified in India (West Bengal, and more recently Assam, h n a c h a l Pradesh, Bihar, Manipur, Meghalaya, Nagaland, Uttar Pradesh and Tripura), northern China, Vietnam, Taiwan, Thailand, Cambodia, Myanmar, and Nepal. Occasional high-arsenic groundwaters have also been found in Pakistan, although the occurrences there appear to be less widespread. High- arsenic groundwaters in affected areas tend to be found in alluvial or deltaic aquifers or in inland basins. Hence, much o f the distribution is linked to the occurrence o f young (Quaternary) sediments in the region's large alluvial and deltaic plains (Bengal basin, Irrawaddy delta, Mekong valley, Red River delta, Indusplain, Yellow River plain).Although groundwater arsenic problems have been detected in some middle sections o f the Indus and Mekong valleys, such problems have apparently not emerged in the lower reaches (deltaic areas). Whether this represents lack o f testing or whether arsenic problems do not occur there i s as yet uncertain. However, the young Quaternary aquifers most susceptible to developing groundwater arsenic problems appear to be less used in these areas as a result o f poor well yields or high groundwater salinity. Other Quaternary sedimentary aquifers in Asia have not been investigatedand so their arsenic status is unknown. Some localized groundwater arsenic problems relate to ore mineralization and mining activity (for example peninsular Thailand; Madhya Pradesh, India). One o f the key hydrogeochemical advances o f the last few years has been in the better understanding o f the diverse mechanisms o f arsenic mobilization in groundwater, as well its derivation from different mineral sources. The most important mineral sources in aquifers are metal oxides (especially iron oxides) and sulfideminerals (especially pyrite, FeS2).Release o f arsenic from sediments to groundwater can be initiated as a result o f the development o f reducing (anaerobic) conditions, leading to the desorption o f arsenic from iron oxides and breakdown o f the oxides themselves. Such reducing conditions are commonly found in fine- grained deltaic, alluvial, and lacustrine sediments. Release o f arsenic can also occur in groundwaters with hgh pH (>8) in oxidizing (aerobic) conditions. These tend to occur inarid and semiarid settings with pHincreases resulting from extensive mineral reaction and evaporation. High-arsenic groundwaters with this type o f association have not been reported in Quaternary aquifers in South and East Asia but are found insome arid inlandbasins inthe Americas (western UnitedStates, Mexico, Argentina). Analogous conditions could occur in some aridparts o f the region, such as northern China or western Pakistan, but there is as yet no evidence for this. Mobilization o f arsenic in mineralized and mining areas is linked to the oxidation o f sulfide minerals. Here, occurrences can affect both surface waters and groundwaters but the affected areas are typically localized (a few kilometers around the mineralized zone) as a result o f the normally strong capacity o f soils and aerobic sedimentsto adsorb arsenic. Despite this improved understanding o f the occurrences and distribution o f arsenic in groundwater, there remainsmuch uncertainty regarding the nature o f the source, mobilization, and transport of the element in aquifers. It is only in the last few years that detailed hydrogeochemical investigations have been carried out in affected regions. Earlier responses to water-related arsenic problems typically involved engineering solutions or finding alternative water sources, with little emphasis on research. It is worthy o f note that, despite the major epidemiological investigations that have been carried out in Taiwan since the discovery o f arsenic-related problems there in the 1960s, there has been little hydrogeochemical research carried out in the region. Even today, the aquifers o f Taiwan are poorly documented and the arsenic occurrence little understood. - 73 - Arsenic Contamination of Groundwaterin South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - andEastAsia: scale, causes,and mitigation One o f the important findings of recent detailed aquifer surveys has beenthe large degree o f spatial variability inarsenic concentrations, even over distances o f a few hundredmeters. This means that predictability o f arsenic concentrations on a local scale is poor (andprobably will always be so). Hence, blanket testing o f individualwells in affected areas is necessary. This can be a major task in countries like Bangladesh where the scale o f contamination is large. There i s also uncertainty inthe temporal variability o f arsenic concentrations in groundwater as very little groundwater monitoring has been carried out. Some studies have noted unexpectedly large temporal variations over various timescales but the supporting data are often sparse and inaccessible and so these reports cannot be relied upon. More controlled monitoring o f affected groundwaters is required to determine the variability inthe short term (daily), the mediumterm (seasonally), and the long term (years, decades). The emerging arsenic problems have revealed the dangers o f groundwater development without consideration o f water quality in tandem with water quantity. Understanding o f the risk factors involved in development of high-arsenic groundwaters has allowed targeting those aquifers perceived to be most susceptible to developing groundwater arsenic problems inrecent years (for example Quaternary sediments inCambodia, Myanmar,Nepal). However, the toxicity of arsenic is such that it should also be given greater attention in other aquifers usedfor drinkingwater supply. There is an argumentfor routine testing for arsenic inall new wells provided in major groundwater development projects, regardless o f aquifer type. Randomized reconnaissance-scale sampling for arsenic is also recommended for existing public supplywells inall aquifer types where no arsenic data currently exist inorder to obtain basic statistics on the distribution o f arsenic concentrations. Groundwater development in previously unexploited but potentially vulnerable young sedimentary aquifers needs to be preceded by detailed hydrogeological and hydrochemical investigations to ensure that groundwater will be o f sufficiently high and sustainable quality. The scale o f investigations should be commensurate with the scale o fproposeddevelopment. - 74 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - and East Asia: scale, causes, andmitigation Glossary Adsorption. Adherence of a chemical or compoundto a solid surface. Alluvial. Depositedbyrivers. Aquifer.Water-bearing rock formation. Desorption.Releaseof a chemical or compound from a solid surface (opposite o f adsorption). Distal.Remote fromthe origin (for example sediments inlower reachesof a delta). Geothermal. Pertaining to the internal heat of the earth. Geothermal zones are areas o f high heat flow, where hot water or steam issue at the earth's surface. They are found close to tectonic plate boundaries or associated with volcanic systems within plates. Heat sources for geothermal systems may be from magmatism, metamorphism, or tectonic movements. Pyrite. Iron sulfide (FeS2), also known as fool's gold. Occurs commonly in zones o f ore mineralization and insedimentsinreducing conditions. Quaternary. Period of geological time extending from about 2 million years ago to the present day. Dividedinto the earliest period, the Pleistocene, andthe subsequent Holocene (the last 13,000 years). Strata o f Quaternary age are very young on a geologicaltimescale. Mineralization. The presence of ore or non-ore minerals inhost rocks, concentrated as veins, or as replacements o f existing minerals or disseminated occurrences; typically gives rise to rocks with high concentrations o f some o fthe rarer elements. Redox reactions. Coupled chemical oxidation and reduction reactions involving the exchange o f electrons. Many elements have changeable redox states; in groundwater the most important redox reactions involve the oxidation or reduction o f iron and manganese, introduction or consumption o f nitrogen compounds (including nitrate), introduction or consumption o f oxygen (including dissolved oxygen), and consumption o f organic carbon. Reducing conditions. Anaerobic conditions, formed where nearly all o f the oxygen has been consumed by reactions such as oxidation o f organic matter or o f sulfide; reducing conditions commonly occur inconfined aquifers. -75 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1- Arsenic Occurrence in South - andEast Asia: scale, causes,and mitigation References Abedin, M. J., J. Cotter-Howells, and A. A. Meharg. 2002. "Arsenic Uptake and Accumulation in Rice (Oryza sativa L.)Irrigated with ContaminatedWater." Plant and Soil 240:311-3 19. Abedin, M. J., M. S. Cresser, A. A. Meharg, J. Feldmann, and J. Cotter-Howells. 2002. "Arsenic Accumulation and Metabolism in Rice (Oryza sativa L.)." Environmental Science & Technology 36:962-968. Abedin, M. J. and A. A. Meharg. 2002. "Relative Toxicity of Arsenite and Arsenate on Germination and EarlySeedlingGrowth of Rice (Oryza sativa L.)."Plant and Soil 243:57-66. Acharyya, S. K. 1997. 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Niedan, D. Brabander, P. M. Oates, K. N. Ashfaque, S. Islam, H. F. Hemond, and M. F. Ahmed. 2002. "Arsenic Mobility and Groundwater Extraction in Bangladesh." Science 298:1602- 1606. Hering, J. G., P. Y. Chen, J. A. Wilkie, M. Elimelech, and S. Liang. 1996. "Arsenic Removal by Ferric Chloride." Journal American Water WorksAssociation 88:155-1 67. Hsu,K.H.,J. R.Froines, andC. J. Chen. 1997."Studies ofArsenic Ingestion fromDrinkingWater in Northeastern Taiwan: Chemical Speciation and Urinary Metabolites." In: C. 0. Abernathy, R. L. Calderon, and W. R. Chappell, eds., Arsenic Exposure and Health Effects 190-209. London: Chapmanand Hall. Iqbal, S. Z. 2001. Arsenic Contamination in Pakistan. UN-ESCAP Report. Expert Group Meeting on Geology andHealth, Bangkok, Thailand. Islam, F. S., A. G. Gault, C. Boothman, D. A. Polya, J. M.Chamock, D.Chatterjee, and J. R. Lloyd. 2004. "Role of Metal-Reducing Bacteria in Arsenic Release from Bengal Delta Sediments." Nature 430:68-71. Khadka, M. S. 1993. "The Groundwater Quality Situation in Alluvial Aquifers of the Kathmandu Valley, Nepal." AGSO Journal of Australian Geology and Geophysics 14:207-211. Kuo, T.-L. 1968. "Arsenic Content of Artesian Well Water in Endemic Area of Chronic Arsenic Poisoning." Reports of the Institute of Pathology of the National Taiwan University 20:7-13. Lo, M.-C., Y.-C. Hsen, and K.-K.Lin. 1977.SecondReport on the Investigation ofArsenic Content in Underground Water in Taiwan. Luo, Z. D., Y. M.Zhang, L.Ma, G. Y. Zhang, X. He, R. Wilson, D. M.Byrd, J. G. Griffiths,S. Lai, L. He, K. Grumski, and S. H. La". 1997. "Chronic Arsenicism and Cancer in Inner Mongolia - Consequences of Well-Water Arsenic Levels Greater than 50 mg 1-l.'' In: C. 0. Abernathy, R. L. Calderon, and W. R. Chappell, eds., Arsenic Exposure and Health Effects 55-68. London: Chapman and Hall. Ma, H.Z., Y. J. Xia, K. G. Wu, T. Z. Sun, and J. L.Mumford. 1999. "Human Exposureto Arsenic and Health Effects inBayingnormen, Inner Mongolia." In: W. R. Chappell, C. 0.Abernathy, and R. L. Calderon, eds., Arsenic Exposure and Health Effects 127-131. Proceedings of the Third International Conference on Arsenic Exposureand Health Effects. Amsterdam: Elsevier. Mahmood, S. N.,S. Naeem, I.Siddiqui, and F.A. Khan. 1998."Studies on Physico-Chemical Nature of Ground Water of KorangdLandhi (Karachi)." Journal of the Chemical Society of Pakistan 19:42- 48. Mahmud, S. G. and M. Nuruzzaman. 2003. "Arsenic Contamination of Production Wells in Pourashavas in Bangladesh." In: M. F. Ahmed, ed., Arsenic Contamination: Bangladesh Perspective 63-71. Dhaka, Bangladesh: ITN-Bangladesh. Mandal, B. K.,T. R. Chowdhury, G. Samanta, G. K. Basu, P. P. Chowdhury, C. R. Chanda, D. Lodh, N.K.Karan, R.K.Dhar, D. K.Tamili, D. Das, K. C. Saha, and D. Chakraborti. 1996. "Arsenic in Groundwater inSevenDistricts of West Bengal, India-The BiggestArsenic Calamity inthe World." Current Science 70:976-986. McArthur, J. M.,P. Ravenscroft, S. Safiulla, and M. F. Thirlwall. 2001. "Arsenic in Groundwater: Testing Pollution Mechanismsfor Sedimentary Aquifers in Bangladesh." Water Resources Research 37:109-117. Meharg, A. A. and M. Rahman. 2003. "Arsenic Contamination of Bangladesh Paddy Field Soils: Implications for Rice Contribution to Arsenic Consumption." Environmental Science & Technology 37:229-234. Neku,A. and N.Tandukar. 2003. "AnOverview of Arsenic Contamination inGroundwater ofNepal and its Removalat HouseholdLevel." Journal DePhysique I V 107:941-944. - 78 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1 Arsenic Occurrence in South - - andEastAsia: scale, causes,and mitigation Nguyen, V. D. and T. D.Nguyen.2002. Groundwater Pollution in the Hanoi Area, Vietnam. Seminar on the Environmental and Public Health Risks Due to Contamination of Soils, Crops, Surface and Groundwater from Urban, Industrial and Natural Sources in South East Asia, Hanoi, Vietnam, December 2002. UN-ESCAP. Oremland, R., D. Newman, B. Kail, and J. Stolz. 2002. "Bacterial Respiration of Arsenate and Its Significance in the Environment." In: W. Frankenberger, ed., Environmental Chemistry of Arsenic Chapter 11. New York: Marcel Dekker. Peterson, M. L. and R. Carpenter. 1983. "Biogeochemical Processes Affecting Total Arsenic and Arsenic Species Distributions inan Intermittently Anoxic Fjord." Marine Chemistry 12:295-321. PHED (Public Health Engineering Department). 1991. Arsenic Pollution in Groundwater in West Bengal. Final Report. Government of West Bengal, Public Health Department, Public Health EngineeringDepartment. Pirazzoli, P. A. 1996.Sea-Level Changes: TheLast 20000 Years. Chichester: John Wiley & Sons. Rahman, M. M., D. Mukherjee, M. K. Sengupta, U.K. Chowdhury, D. Lodh, C. R. Chanda, S. Roy, Q. Quamruzzaman, A. H. Milton, S. M. Shahidullah, T. Rahman, and D. Chakraboti. 2002. "Effectiveness and Reliability of Arsenic Field Testing Kits: Are the Million Dollar Screening ProjectsEffective or Not?" Environ. Scien. & Technol. 36(24):5385-94. Ray, S. P. S. 1997. "Arsenic in Groundwater in West Bengal." In: Consultation on Arsenic in Drinking Water and Resulting Arsenic Toxicity in India and Bangladesh. Proceedings of WHO Conference, New Delhi, May 1997. Robertson, F. N. 1989. "Arsenic in Groundwater Under Oxidizing Conditions, South-West United States." Environmental Geochemistry and Health 11:171-185. Schreiber, M. E., J. A. Simo, and P.G. Freiberg. 2000. "Stratigraphic and Geochemical Controls on Naturally Occurring Arsenic in Groundwater, Eastern Wisconsin, USA." Hydrogeology Journal 8: 161-176. Shrestha, R. R., M.P. Shrestha,N.P. Upadhyay, R. Pradhan, R. Khadka, A. Maskey, S. Tuladhar, B. M.Dahal, S. Shrestha, and K. B. Shrestha. 2004. Groundwater Arsenic Contamination in Nepal: A New Challengefor Water Supply Sector. Environment andPublic HealthOrganization. Smedley, P. L. 2003. "Arsenic in Groundwater - South and East Asia." In: A. H. Welch and K. G. Stollenwerk, eds., Arsenic in Ground Water: Geochemistry and Occurrence 179-209. Boston, Massachusetts: Kluwer Academic Publishers. Smedley, P. L. and D. G. Kinniburgh. 2002. "A Review of the Source, Behaviour and Distributionof Arsenic inNatural Waters." Applied Geochemistry 17:517-568. Smedley, P. L., H. B. Nicolli, D. M. J. Macdonald, A. J. Barros, and J. 0. Tullio. 2002. "Hydrogeochemistry of Arsenic and Other Inorganic Constituentsin Groundwaters from La Pampa, Argentina." Applied Geochemistry 17:259-284. Smedley, P. L., M.-Y. Zhang, G.-Y. Zhang, and Z.-D. Luo. 2001. "Arsenic and Other Redox- SensitiveElements in Groundwater from the Huhhot Basin, Inner Mongolia." In: R. Cidu, ed., Water Rock Interaction 581-584. Lisse: Balkema. Smedley, P. L.,M.-Y.Zhang, G.-Y. Zhang, and Z.-D. Luo. 2003. "Mobilization of Arsenic and Other Trace Elements in Fluviolacustrine Aquifers of the Huhhot Basin, Inner Mongolia." Applied Geochemistry 18:1453-1477. Sun, G., J. Pi, B. Li, X. Guo, H. Yamauchi, and T. Yoshida. 2001. "Progresses on Researches of Endemic Arsenism in China: Population at Risk, Intervention Actions, and RelatedScientific Issues." In: W. R. Chappell, C. 0.Abemathy, and R. L. Calderon, eds., Arsenic Exposure and Health Effects IV79-86. Amsterdam: Elsevier. - 79 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 1 - Arsenic Occurrence in South - andEastAsia: scale, causes, andmitigation Tandukar, E. N. 2001. Scenario of Arsenic Contamination in Groundwater in Nepal. Department of Water Supply and Sewerage, Nepal. Tareq, S. M.,S. Safiullah, H.M.Anawar, M.M. Rahman, and T. Ishizuka. 2003. "Arsenic Pollution in Groundwater: A Self-organizing Complex Geochemical Process in the Deltaic Sedimentary Environment, Bangladesh."Scienceof the TotalEnvironment 3 13:213-226. Tasneem, M. A. 1999. "Impact of Agriculturaland Industrial Activities on Groundwater Quality in Kasur Area." TheNucleus, Quarterly Joumal of the Pakistan Atomic Energy Commission 36. Tong, N. T. 2001. Report on Investigated Results for Arsenic Groundwater Level in Ha Noi City. Geological and Mineral Surveyof Vietnam. Tong, N. T. 2002. Arsenic Pollution in Groundwater in the Red River Delta. Geological Survey of Vietnam,Northern Hydrogeological-EngineeringGeological Division. Trafford, J. M., A. R. Lawrence, D. M. J. Macdonald, N. Van Dan, and D. N. H. Tran. 1996. The Effect of Urbanization on the Groundwater Quality Beneath the City of Hanoi, Vietnam. Technical Report WC/96/22. BritishGeologicalSurvey. Tseng, W. P., H.M.Chu, S. W. How, J. M.Fong, C. S. Lin, and S. Yeh. 1968. "Prevalence of Skin Cancer in an Endemic Area of Chronic Arsenicism in Taiwan." Journal of the National Cancer Institute 40:453-463. Tuinhof, A. and M. Nanni. 2003. Arsenic Testing and Finalization of Groundwater Legislation, Nepal. World Bank Group. UNDP-UNCHS (United Nations Development Programme and United Nations Centre for Human Settlements). 2001. Water Quality Testingin 11Project Townships. UNDPKJNCHS. Upadhyay, S. K. 1993. "Use of GroundwaterResourcesto Alleviate Poverty inNepal: Policy Issues." In: F. Kahnert and G. Levine, eds., Groundwater Irrigation and the Rural Poor: Options for Development in the GangeticBasin. World Bank, Washington, D.C. van Geen, A., K. M. Ahmed, A. A. Seddique, and M. Shamsudduha. 2003. "Community Wells to Mitigatethe Arsenic Crisis inBangladesh." Bulletin of the World Health Organization 81:632-638. van Geen, A., Y. Zheng, R. Versteeg, M. Stute, A. Homeman, R. Dhar, M. Steckler, A. Gelman, C. Small, H.Ahsan, J. H. Graziano, I. Hussain, and K.M.Ahmed. 2003. "Spatial Variability of Arsenic in6000 TubeWells ina25 la2 ofBangladesh." WaterResourcesResearch 39:1140. Area Wang, G. 1984. "Arsenic Poisoning from Drinking Water in Xinjiang." Chinese Journal of PreventativeMedicine 18:105-107. Wang, G. Q., Y. Z. Huang, B.Y. Xiao, X. C. Qian, H.Yao, Y. Hu, Y. L.Gu, C. Zhang, and K.T. Liu. 1997. "Toxicity from Water ContainingArsenic and Fluoride inXinjiang." Fluoride 30:81-84. Wang, L. and J. Huang. 1994. "Chronic Arsenism from Drinking Water in Some Areas of Xinjiang, China." In: J. 0.Nriagu, ed., Arsenic in the Environment, Part 11: Human Health and Ecosystem Effects 159-1 72. NewYork: John Wiley. WAPDA-EUAD (Water and Power Development Authority, Environment and Urban Affairs Division). 1989. Booklet on Hydrogeological Map of Pakistan, 1:2,000,00 Scale. Lahore: Government of Pakistan, WAPDA-EUAD. Williams, M. 1997. Mining-Related Arsenic Hazards: Thailand Case Study. Technical Report WC/97/49. BritishGeological Survey. Williams, M.,F. Fordyce, A. Paijitprapapon,and P. Charoenchaisri. 1996. "Arsenic Contamination in Surface Drainage and Groundwater in Part of the Southeast Asian Tin Belt, Nakhon Si Thammarat Province, SouthernThailand." Environmental Geology 27:16-33. WRUD. 2001. Preliminaly Study on Arsenic Contamination in SelectedAreas of Myanmar. Report of the Water ResourcesUtilization Department,Ministry of Agriculture and Irrigation, Myanmar. - 80 - Paper 2 An Overview of Current Operational Responses to the Arsenic Issue inSouth and East Asia This paper was preparedby Amal Talbi (WorldBank) with contributionsfrom KarinKemper (WorldBank), KhawajaMinnatullah(WorldBankNSP), and StephenFoster andAlbert Tuinhof (WorldBankGroundwaterManagementAdvisory Team - GWMATE). Arsenic Contaminationof Groundwaterin Southand EastAsian Countries: Volume I1 Paper2 - An overviewof current operationalresponsesto - the arsenic issue in South and EastAsia Summary T h i s paper focuses on the operational responses to natural groundwater contamination in affected countries o f South and East Asia. The paper first outlines the health effects o f arsenic ingested through water and the different recommended permissible values o f maximum concentration o f arsenic indrinking water, and presents a critical analysis o f the current status o f epidemiological knowledge. T h i s i s followed by a comprehensive presentation o f the operational responses implementedto mitigate arsenic contamination in the study countries, and an assessment o f such operational responses in the overall context o f the water supply sector. Finally, an attempt i s made to highlightthe political economy o f arsenic mitigation and to assess the options for addressing arsenic from this perspective. The paper also extracts the major lessons learned when implementing short-term and long-term mitigation measures in South and East Asian countries. These are divided into technical, financial and economic, social and cultural, and institutional issues, and are summarized inoverviewmatrices inannex 2. The outcome o f the paper i s a tool that aims to help decisionmakers in government, multilateral and bilateral institutions, nongovernmental organizations, academics, and water practitioners in general address arsenic contamination o f groundwater. By bringingtogether information from a variety o f sources, includingpublishedand unpublishedliterature, results o f a specially administered survey, and outcomes o f a regional workshop heldinKathmandu in2004, the paper collates, synthesizes, and makes accessible the vast range o f arsenic-related information currently available in order to inform and facilitate concrete operational responsesto the arsenic issue. - 82 - Arsenic Contaminationof Groundwater inSouthand EastAsianCountries:Volume I1 Paper2 -An overview ofcurrent operationalresponsesto - the arsenic issue in Southand EastAsia 1. Introduction Natural arsenic contamination o f groundwater affects a number o f countries worldwide, and specifically in South and East Asia. This paper first reviews the operational responses to natural arsenic contamination o f groundwater in Asian countries that have hitherto been developed and carried out; second, it analyzes the success and failure o f these responses; and third, it presents practical guidance for stakeholders, at either the country or project level, to better address the arsenic issue. This i s critical since govemments, the World Bank, and other development partners implement water projects in this region and are responsible for providing safe drinkmg water. Stakeholders need to be aware o f this contamination, have tools to identify it, and have practical information to provide a proactive response or, where the contamination has been identified at a later stage, a reactiveresponse. The countries in South and East Asia so far identifiedas affectedby natural arsenic contamination o f groundwater are Bangladesh, Cambodia, China (including Taiwan), India, Lao People's Democratic Republic (PDR), Myanmar, Nepal, Pakistan, and Vietnam. This paper deals with natural arsenic contamination rather than contamination o f mining and geothermal origins, and with rural rather than urban areas. The focus on natural contamination, which i s due to the release o f arsenic from sediment to water, stems from the fact that this contamination i s still unpredictable, and i s thus far more difficult to address than contamination o f miningand geothermal origin. Similarly, contamination inrural areaspresents a greater challenge than that faced inmore compact urbanareas. The operational responses to deal with arsenic that have been implemented to date include screening o ftubewells, identification andtreatment o f those affected by contamination, sharing o f arsenic-safe wells, awareness raising, and development o f altemative water provision through, for instance, dug wells, pond sand filters, rainwater harvesting, arsenic removal plants, and tapping deep groundwater. The paper i s structured in four chapters. Chapter 1 presents the health effects and the recommended maximum permissible values o f arsenic in water. A critical analysis i s provided regarding the lack o f epidemiological studies on the health effects o f arsenic and the current uncertainty regarding safe levels o f arsenic indrinkmgwater. Chapter 2 presents the operational responses implemented in South and East Asian countries. An assessmenti s made o f the lessons leamed and the remaining issues on which no conclusions can yet been drawn. Chapter 3 discussesarsenic mitigation inthe overall context o f water supply, including an analysis o f the priority accorded to arsenic contamination. Chapter 4 analyzes incentives for stakeholders to be active (or inactive) in implementing operational responses to arsenic contamination. These incentives influence the political economy and are drawn from the lessons leamed and other issues analyzed in chapter 2. Due to the large number of countries affected, and recognizing that the political economy varies from country to country, this paper does not address political economy in depth for each individual country but rather discusses incentives generally. - 83 - Arsenic Contamination of Groundwater in South and EastAsian Countries: Volume I1-Paper 2 -An overview of current operational responses to the arsenic issue in Southand East Asia 2. Arsenic: HealthEffects, RecommendedValues, and NationalStandards Arsenic i s a substance that i s carcinogenic - capable o f causing cancer. Organic arsenic compounds are less toxic than inorganic compounds, which are more commonly found innatural arsenic water contamination. The recommended standards for the maximum acceptable dose of arsenic are based on health risks, but the lack of epidemiological data on low doses o f exposure makes the health risks difficult to assess with certainty. This chapter presents intemational and national standards for arsenic intake in drinking and irrigation water; the major assumptions regarding the interpretation o f epidemiological data used to assess the recommended maximum permissible values and standards; the major health effects o f arsenic; the status o f the debate on arsenic intake from the food chain; and the effects o f trace elements on reducing or increasingarsenic toxicity. 2.1 International and National Standardsfor Arsenic Intake Regarding arsenic concentration in irrigation water, neither intemational agencies nor individual countries propose any recommended maximum permissible values. For dnnkingwater, however, due to the carcinogenic nature o f the substance, the World HealthOrganization (WHO) has issued a provisional guideline recommending a maximum permissible arsenic concentration o f 10 pg L-' (micrograms per liter). WHO guidelines are meant to be used as a basis for setting national standards to ensure the safety o f public water supplies and the guideline values recommended are not mandatory limits. Such limits are meant to be set by national authorities, considering local environmental, social, economic, and cultural conditions. Most developed countries have adopted the provisional guideline value as a national standard for arsenic indrinkingwater. On the other hand, most developing countries still use the former WHO- recommended concentration o f 50 pg L1as their national standard. Table 1 uses a sample o f countries to illustrate the range o f values adopted (7 pgL-'to 50 pg L-'). Table 1. Currently Accepted National Standards of Selected Countries for Arsenic inDrinking Water Countrylregion Standard: pg L-' Country Standard: pg L-' Australia (1997) 7 Bangladesh (1997) 50 European Union (1998) 10 Cambodia 50 Japan(1993) 10 China 50 USA (2002) 10 India 50 Vietnam 10 Lao PDR (1999) 50 Canada 25 Myanmar 50 Nepal 50 Pakistan 50 Source: Ahmed 2003. The fact that some countries have adopted the recommendedmaximum permissible value o f 10 pg L-' while others still use a value of 50 pg L-' is related to the chronology of recommended maximum permissible values proposed by the WHO (table 2). In 1993 the WHO recommended - 84 - Arsenic Contaminationof Groundwaterin Southand EastAsian Countries:Volume I1-Paper 2 -An overview of current operationalresponsesto the arsenic issue in SouthandEastAsia lowering the maximum permissible value from 50 pg L-'to 10 pg L-'as a precautionary measure because o f the carcinogenic effects o f arsenic, especially regarding internal cancers. So far most developed countries have adopted this newrecommended value as anational standard (table 1). Table 2. Chronology o fRecommendedWHO Values for Arsenic inDrinkingWater 1958 FirstWHO IntemationalDrinking Water Standard: 200 pg L-' 1963 WHO recommendlowering guide value to 50 pg L-' 1974, 1984 Affirmationof 50 pg L-'as guide value 1984 WHO Guidelinesreplace IntemationalDrinkingWater Standard, providing a basis for national standards by individual countries 1993 WH0,provisional guidelinerecommendslowering guide value to 10 pgL-' Most developing countries, however, have not lowered their national standards because they feel they couldnot afford the associatedeconomic costs, including treatment and monitoring costs. For further discussion o f this issue see Paper 4. The United States, Environmental Protection Agency (EPA) conducted an economic study with concentrations o f 3, 5, 10, and 20 pg L-' and found that, given the conditions prevailing in the United States o f America, the recommended maximumpermissible value o f 10 pg L-'represented the best trade-off among health risks, the ability o f people to pay for safe water, and the availability o f water treatment technology. The standard o f 10 pg L-'will be further lowered as treatment technology becomes more affordable. The WHO-recommended maximum permissible value for carcinogenic substances i s usually related to acceptable health risk, defined as that occurring when the excess lifetime risk for cancer equals lo-' (that is, 1 person in 100,000). However, inthe case o f arsenic, the EPA estimates that this risk would mean a standard as low as 0.17 pg L-'(Ahmed 2003), which is considered far too expensive even for industrial countries to achieve. The health risks used in the EPA estimate were based on data from an epidemiological study conducted in Taiwan. Since the study only considered the risk o f skin cancer and lacked data on internal cancers, and because o f several conservative assumptions in the EPA model, the health risks may have been underestimated. On the other hand, the actual rate o f skin cancer may be overestimated because o f possible simultaneous exposure to other carcinogenic compounds (Ahmed 2003). Even though the exact health effects of an arsenic concentration o f 50 pg L-'have not been quantified, many correlations between internal cancer and low concentration o f arsenic have been found. Therefore it i s important that localized epidemiological studies are carried out ina strategic manner, to more clearly inform decisionmakers. 2.2 Major Limitationsof ExistingEpidemiologicalStudies Humans are exposed to different forms o f arsenic from the atmosphere, food, and water. An important distinction needs to be made between inorganic and organic arsenic, inorganic arsenic being the carcinogenic form, though organic arsenic also has adverse health effects. Inorganic arsenic i s the only form that occurs inwater, and i s therefore the focus o f this study.' The study o f kinetics and metabolisms o f arsenicals inhumans i s complex due to the following issues (ATSDR 2002): 'See Paper 1regardingorganic andinorganic arsenic andthe oxidation state of inorganic arsenic. - 85 - Arsenic Contaminationof Groundwaterin Southand EastAsianCountries:Volume I1 Paper2 -An overview of current operationalresponsesto - the arsenic issue in Southand EastAsia 0 Physicochemical properties and bioavailability vary with form o f arsenic. 0 There are many routes o f exposure (inhalation, ingestion, and dermal). 0 The intake o f arsenic can be either acute or chronic. 0 Lengthofexposure canbe short, medium,or longterm. 0 The differing susceptibility to arsenic betweenhumans and animals makes the quantitative dose response data from animals unreliable for determininglevels o f significant human exposure. This paper focuses on the human health effects o f chronic exposure to arsenic by ingestion. This focus has been chosen as the main source o f arsenic poisoning i s through contaminated groundwater, and the secondary source i s through the food chain. Inthe literature, thehealtheffects ofarsenic havebeenestimated from data from various regions (for example Australia, Argentina, Chile, Taiwan). Nevertheless, clear linkages between a given concentration o f arsenic in drinking water and its health effects are difficult because o f the following issues: 0 Inmost cases ofingestion, the chemicalforms ofarsenic areunknown. 0 Most studies do not consider the volume o f drinhngwater consumed. 0 Most studies do not report the temporal variations o f the concentration o f arsenic inthe source over a longperiod. 0 There i s a lack o f data about the relative importance o f arsenic intake from sources other than drinlungwater, inparticular from the food chain. Because o f these issues, it i s difficult to assess the exact health effects for a particular concentration o f arsenic in groundwater. The available epidemiological studies present the health effects based on the exposure dose o f arsenic, which i s defined as the quantity o f arsenic that i s ingestedper kgo f weight per day and can be calculated according to equation 1: Equation1.HealthEffects o fArsenic ExposureDose ED=- C*DI BW Where: ED=exposure dose (mgkg-' day") c =exposureconcentration(mgL-') DI=daily intakeofwater (Lday-') BW=body weight (kg) When estimating exposure dose one o f the usual assumptions is that daily water intake i s 2 liters (Ahmed 2003; ATSDR 2002; WHO 2001b). However, based on the literature reviewed, daily intake inrural areas tends to be higher, and varies from 3 to 5 liters (Ahmed 2003; Masud 2000). Importantly, healthrisk estimations increase as daily intake increases. It appears that improved nutrition increases tolerance to arsenic contamination. For example, in some arsenic-affected villages o f West Bengal in India, families with access to nutritious food show almost no arsenical skinlesions compared with undernourishedfamilies, despite the fact that both are consuming the same arsenic-contaminated water. Hence the poor, who are more likely to bemalnourished, tendto bemost affectedby arsenic contamination. - 86 - Arsenic Contaminationof GroundwaterinSouthand EastAsian Countries:Volume I1- Paper2 - An overviewofcurrent operationalresponsesto the arsenic issue in South and EastAsia Insummary, existingepidemiological studiesarestill oftenbasedonsimplifyingassumptionsthat introduce a number o f uncertainties when quantifying the relationship between the concentration o f arsenic and health effects. 2.3 Major HealthEffects This section focuses on the major health effects o f arsenic, which include skin lesions, blackfoot disease, diabetes, hypertension, skin cancers, and internal cancers. Inannex 5 a detailed matrix o f the health effects is provided with (when available) the exposure dose and the concentration of arsenic based on equation 1with sensitivity analysis o f the daily water intake (2, 3, and 5 liters). Arsenic has various health effects ranging from arsenicosis to skin cancers and internal cancers. However, so far there i s still no widely accepted definition o f what constitutes arsenicosis, the term used for the pattern o f skinchangesthat occurs after chronic ingestion o f arsenic. These skin changes are usually the first symptoms to appear inthe presence o f high concentrations o f arsenic indrinkmgwater. However, two epidemiological studies of chronic ingestion suggest that these lesions could appear for concentrations lower than 100 pg L-'.Another primary noncancer health effect i s blackfoot disease, which was first observed in Taiwan. This peripheral vascular disease leads, eventually, to a dry gangrene and the spontaneous amputation o f affected extremities (Kaufmann and others 2001). The cancer effects o f chronic exposure to arsenic through drinkingwater include skin cancers and internal cancers (lung, bladder, and kidney). In 1988 the EPA estimated that in the United States chronic ingestion o f 50 pg L-'results ina skincancer rate o f 1in400; in 1992, the EPA estimated that the internal cancer mortality risk i s about 1.3 in 100 at 50 pg L-'.In 1999 the United States National Research Council (NRC) estimated the overall cancer mortality risk to be about 1in 100 at 50 pgL-'(NRC 1999; Smith and others 2002). Internal cancers are o f primary concern since they account for most fatalities resulting from chronic ingestion o f arsenic through drinkingwater. Skin cancers are not usually fatal if they are identified at an early stage, and their external symptoms make diagnosis more likely than with internal cancers. 2.4 Arsenic Ingestedthroughthe FoodChain The proportion o f inorganic arsenic ingested through food may be significant, even when the arsenic concentration o f drinking water i s higher than 50 pg L-'.For example, a recent study conducted in Mexico (Del Razo and others 2002), where the concentration o f arsenic in dnnlung water was as high as 400 pg L', found that even so 30% o f inorganic arsenic intake came from food. The quantities o f organic and inorganic arsenic in food should always be quantified, since the form o f arsenic affects its bioavailability and thus its toxicity to humans. Unlike water, where arsenic i s always inorganic, food can contain either organic or inorganic arsenic. Different studies have found different proportions o f organic and inorganic arsenic in food. For example, an EPA study found the percentages o f inorganic arsenic inrice, vegetables, and fruit to be 35%, 5%, and 10% respectively (EPA 1988); a study conducted in West Bengal found the percentages o f inorganic arsenic in rice and vegetables to be 95% and 5% respectively (Roychowdhury, Tokunaga, and Ando 2003); and another Bengali study found the percentage o f inorganic arsenic inrice to be 43.8% (Roychowdhury and others 2002). This wide range of values shows that the total amount o f arsenic (both organic and inorganic) in a food sample cannot be taken as an accurate indication o f the toxicity o f the sample. In soil irrigated with water having significant arsenic concentrations, higher concentrations of arsenic were found in the peel or skin o f the crops, while lower arsenic concentration were found - 87 - Arsenic Contaminationof Groundwater in Southand EastAsian Countries:Volume I1 Paper2 -An overview of currentoperationalresponsesto - the arsenic issue in Southand EastAsia inthe ediblepart ofthe raw crops, A studybyDas and others (2004) found the arsenic content of some vegetables to be greater thanthe recommended limit o f 1mgkg-' set inthe United Kingdom and Australia. Another concern regarding the use of contaminated water for irrigation i s the effect of arsenic on the yield, though this has as yet received little study. There is no current precise definition o f what concentration o f arsenic inirrigationwater would have a quantifiable impact on agriculture yield or on human health. The amount o f arsenic infood seems to be related to both the amount o f arsenic inthe water used for cooking and the cooking process used.For example, a study (Roychowdhury and others 2002) showed that the concentration o f arsenic in cooked rice was higher than that in raw rice and absorbed water combined, suggesting a chelating effect by rice grains. Due to water evaporation during the cooking process, the quantity o f water used i s important and this also affects the amount o f arsenic in food. In addition, another study (Devesa and others 2001) reported no transformation o f arsenic at temperatures up to 120°C. Thus, the boiling process used to cook the food probably does not alter the chemical form o f arsenic nor the amount of inorganic arsenic in the food at the end o fthe cooking process (Del Razo and others 2002). There i s no standard maximum level o f arsenic in food in South and East Asian countries. Inthe United Kingdom andAustralia the maximumfood hygiene standard for the arsenic level infood i s 1mgo f arsenic per kg(Warren and others 2003). Studies related to the interaction o f arsenic with other elements are limited. So far, most studies have focused on fluoride, selenium, and zinc. The main findings are that (a) fluoride neither increases nor decreases arsenic toxicity; (b) selenium and arsenic might reduce each other's effects in the body; and (c) a deficit o f zinc might increase the toxicity o f arsenic. Thus it seems that other elements may play a role inthe effective toxicity o f arsenic indnnkingwater. So far, the intake o f arsenic from food seems to depend more on the amount o f arsenic in the cooking water than inthe water usedfor watering crops. However, research i s still needed to fully confirm that cooking water i s more detrimental than irrigation water in the accumulation o f arsenic inthe food chain. 2.5 OperationalResponsesof Countriesin South and EastAsia The operational responses implementedthus far in South and East Asian countries are difficult to compare because most o f the information available i s for South Asia, particularly Bangladesh, Nepal, and West Bengal in India. Information related to East Asian countries i s much more difficult to find in international literature. Therefore, in order to collect more information on operational responses in South and East Asian countries, the study team sent a questionnaire to major stakeholders. The summary o f the questionnaire responses i s provided in annex 3. In addition, in the context o f the study, the World Bank/WSP Regional Operational Responses to Arsenic Workshop was held in Nepal, 26-27 April 2004. The preliminary results o f the study were shared with 50 participants representing 7 out o f the 11 countries facing arsenic contamination, as well as intemational organizations, donors, and researchers. The major information and data collected are included inthis report. A summary o f operational responses implemented in South and East Asian countries is presented inannex 1. 2.6 InitialResponsestowards SuspectedArsenic Contamination Initial responses towards suspected arsenic contamination include well screening and identification o f water contamination in tubewells, switching from contaminated to arsenic-safe wells, painting o f tubewells, awareness raising, and identification and treatment o f arsenicosis patients. These responses are presented in more detail below. Each section outlines the steps that can betaken and, where available, the lessons learned from these mitigation measures. Most o f the - 88 - Arsenic Contaminationof Groundwater inSouthand EastAsian Countries:Volume I1- Paper2 -An overviewof currentoperationalresponses to the arsenic issue in Southand EastAsia lessons learned are from Bangladesh, Nepal, and West Bengal (India), since these are the cases for whichmost information is available. 2.6.1 ScreeningandIdentificationof ContaminationLevels inWater Sources 2.6.1.1 Background Regardless o f the scale o f arsenic contamination inwater, there are two methods o f measurement: the field test kit, and laboratory chemical analysis.' The field test measures are more qualitative than quantitative. The choice o f method for analysis depends on several criteria, including the precision o f measurement required. 2.6.1.2 Choice of Screening Methodology There are two kinds o f field test: those that provide a Yes or N o answer and those that provide a range o f c~ncentration.~ The Yes/No field test does not provide useful information for further analysis or for the implementation o f mitigation measures. The field test that does provide a range of concentration i s only appropriate in certain circumstances. Box 1 outlines parameters that help to determine which test i s appropriate, assuming that the laboratory test i s efficient and subject to quality assurance. Quality assurance i s necessary to ensure reliability o f analysis within a particular laboratory, and consistency o f measurement between laboratories. Box 2 provides parameters to assess the capacity o f a laboratory to performanalyses inorder to facilitate quality assurance implementation and, ultimately, to provide accurate and usable data. West Bengal inIndia i s the only locationwhere the screening o f arsenic i s conducted exclusively using laboratory spectrometer analysis, thereby reducing the risk o f a well beingmisclassified as contaminated and thereby lost as a source o f water. Other Asian countries employ a mix o f field testing and laboratory testing, or field testing only. With field tests there is a higher risk o f well misclassification; this risk can be reduced through, for example, retesting contaminated wells or usingmultiple testing. For example, inPakistan 10% o f field tests are cross-checked usinglaboratory analysis; while inWest Bengal 3% o f the samples analyzed with spectrometer are cross-checked with referenced laboratories using the atomic absorption spectrometer (AAS) (reported at Regional Workshop, Nepal, April 2004). The only country that i s planning large-scale monitoring o f screened tubewells i s Bangladesh, as stipulated in its National Arsenic Policy approved in March 2004. The National Arsenic Policy makes provision for monitoring o f 2% o f the safe (green) tubewells every six months. However, there i s no specification as to whether field or laboratory testing i s to be used, or regarding the procedures to ensure the reliability o f water quality analyses. Another issue to take into account in interpreting test results i s seasonal variability. InCambodia, for example, the major risk aquifer i s connected to a river and arsenic levels recorded intubewells vary seasonally, with lower levels resulting from a wet-season influx o f low-arsenic river water into the aquifer (reported at Regional Workshop, Nepal, April 2004). Box 1. Comparisonof Field Testing and Laboratory Analysis Whether to use a field test kit or laboratory analysis i s not always a clear-cut decision and must take into account a range o f trade-offs related to the cost o f the analysis, accuracy o f the analysis, A detaileddescriptionof field tests and laboratoryanalysis techniques i sprovided inPaper 3. The Yes/No field test kitsdo notprovide any information onthe range ofconcentration. The only information provided is whether the concentration is higher or lower thanthe national standard ofmostAsian countries (50 pg L-'). - 89 - Arsenic Contaminationo fGroundwaterin Southand EastAsian Countries:Volume I1-Paper 2 - An overview of current operationalresponsesto the arsenic issuein South and East Asia time constraints, logistical requirements, and training. Cost of analysis. InBangladesh, for example, the reported cost o f laboratory chemical analysis i s approximately US$8.60 per analysis, while the price o f a field test i s approximately $0.50. However, in West Bengal, the price o f laboratory analysis i s approximately $1.60. Thus the difference in cost between the field test kit and laboratory analysis varies in significance from country to country. Capacity of laboratories (samples/month). Given that there are approximately 11 million tubewells in Bangladesh, there are insufficient laboratories to analyze all samples. Regional laboratories in Bangladesh have a capacity o f about 300 samples per month, so additional screening has to be done usingthe field test kit. Time needed to process the analysis. The field test provides an immediate answer and, depending on the brand, waiting time varies from 5 to 30 minutes (Kinniburgh and Kosmus 2002). The time required to conduct the chemical analysis will depend on the availability of laboratories near the sampling point and the time needed for actual analysis. This can take months, incontrast to the immediate feedback to well owners providedby the field test kit. Logistics.Iti s essential that samples are labeledproperly and that the informationonwhether the well is safe or unsafe is communicated to the communities in a short time and in a reliable manner. Training. Field test kits are easy to use, so related training is far easier to conduct than that neededto ensure good-quality laboratory analysis. However, the number o fpeople to betrained i s higher for field test kitsthan for laboratory analysis. Opportunity for decentralization. The field test kit has considerable potential for decentralization and community involvement inthe identification o f safe or contaminated wells. This community involvement might be lost if only laboratory analysis i s used. Box 2. Parametersto Assess the Capacity of Laboratory Analysis The main argument for the use o f laboratory analysis rather than a field test kit i s the reliability o f the results. However, if a given country has weak capacity for conducting chemical analysis, the value added from laboratory analysis could be negated. Therefore it i s important to assess the capacity of laboratory analysis, taking into account the following: 0 The current availability o f the equipment to conduct analyses. 0 The current status o f the suppliers o f this equipment. 0 The regular availability o f equipment and materials, for example distilled water. 0 Whether the financing o f equipment and supplies i s fkom a central institution or i s done at the laboratory level. This could affect the lengtho ftime it takes for supplies to reachthe laboratories; inthe worst case supply shortages could interruptwork. 0 The current training program for laboratory staff, which should take into account available posts inlaboratories and staffturnover. 0 Sampling and conservation o f samples should follow accepted, standard procedures. 0 The procedures to ensure quality checks and laboratory certificationhave to be assessed. This process o f certification does not needto be nationwide; it could be carried out among smaller units such as departments. An internal track record ofthese processes and - 90 - Arsenic Contaminationof Groundwaterin Southand EastAsian Countries:Volume I1 Paper2 -An overviewofcurrent operationalresponses to - the arsenic issue in Southand EastAsia all analysesperformedshouldbe kept at each laboratory. Whenthere i s a procedure o f certification the level o f transparency mustbe assessed. 2.6.1.3 Choice of Scale of Screening The screening o f water sources can be conducted on a large scale (national, state level) or on a more localized scale (project level). InBangladesh, West Bengal, and Nepal screening has so far been conducted on a large scale. Inother countries where arsenic has been identified, for example Cambodia, Lao PDR, Myanmar, and Pakistan, screening has been conducted on a small scale in some parts o f the countries. So what are the criteria that help assess whether the screening should be conducted on anational or local level? When contamination i s identified hydrogeologists and geochemists can, from the first results o f screening, make certain assumptions about the potential scale o f contamination based on the size and level o f use o f the aquifer. This will enable them to give advice on the scale o f further screening (national, subnational, local) and on the designo f the screening gnd used to check these assumptions. In Bangladesh the decision to adopt blanket screening was based on the heterogeneity o f the aquifers, which meant that a base sample screening would not accurately represent the level o f arsenic contamination o f tubewells used for drinlung water. InPakistan the screening i s divided into three steps: (a) a sample base screening based on a gnd o f 10 km x 10 km; (b) further screening using a smaller grid o f 2.5 km x 2.5 km; and (c) a blanket screening o f the hotspot (reported at Regional Workshop, Nepal, April 2004). When an aquifer is discovered to be contaminated it is important to identify other vulnerable aquifers in the same area. Vulnerable aquifers are those that are naturally connected to the contaminated aquifer, or are not separated and protected from contamination by an impermeable layer. Similarly, when an aquifer i s separated from the contaminated aquifer by an impermeable layer it i s not naturally vulnerable unless a connection i s created, for example through poor well construction. Itis difficult to predict contaminationrates whenthere is water flow from a contaminatedto a safe aquifer. The first step i s to assess the exact impact o f the dilution effect, which affects the rate at which arsenic concentrationwill increase and therefore reach the maximum permissible level. It i s difficult, however, to determine to what extent arsenic will react with the environment; it may be adsorbed, or it may interfere in biological processes. As a result o f these interactions increase in arsenic concentrationmay be delayed, although there i s currently insufficient knowledge and data to correctly model these interactions and to accurately predict this delay. Therefore only the dilution effect i s usually taken into account in such models, even though this may result in an underestimationo fthe period o f delay. Among the factors deciding the scale o f the screening i s the level o f priority accorded by government to the issue o f arsenic contamination. The incentives that lead stakeholders, including government, to be active or inactive are addressed in chapter 4. When an agency finds arsenic contamination during the course o f a project it i s important to define who i s responsible for screening beyond the scope o f the agency's own project and for implementing the mitigation measures. 2.6.1.4 Institutional Arrangementsfor Arsenic Screening in Different Countries Ifthe govemment decides to conduct a large-scale screening an institutional model needs to be chosen. So far in most countries two approaches have been applied. The first i s to treat the screening as a public good and the second i s to consider the screening the responsibility o f the - 91 - Arsenic Contaminationof Groundwaterin Southand EastAsian Countries:Volume I1 Paper2 -An overviewof currentoperationalresponsesto - the arsenic issuein Southand EastAsia tubewell owners. The first model i s by far the most common. In this case government, usually assisted by nongovernmental organizations (NGOs) and international agencies, conducts the screening. For example, in Bangladesh and Nepal the government i s taking the lead, while in Cambodia, Vietnam, Lao PDR, and China the United Nations Children's Fund (UNICEF) i s the main international agency leading the screening. The second model, where screening i s demand based, has been applied inIndia, specifically inWest Bengal. UNICEF and the state authorities o f West Bengal screen all public tubewells, but private tubewell testing i s the responsibility o f the owner. Informationon the availability o f laboratories i s provided and widely disseminated. So far, there i s not enough informationto determine whether one model i s more efficient or effective than the other. 2.6.1.5 Remaining Issues and LessonsLearned Technical issues: Regarding the choice between the field test kit and laboratory analysis, one option proposed in the literature is to use the field test kitfor large-scale screening and cross-check using laboratory analysis when the capacity assessmenti s satisfactory. The best way to reduce the risko f misclassification, for boththe field test kit and the laboratory, i s to provide adequatetraining to ensure precise measurements, and to maximize, whenpossible, the number o frepetitive analyses. Although there i s a highdegree o f heterogeneity inarsenic concentrationwithin a given area, correlation among neighboring wells can help identify some misclassification. Itis importantto consider the scale ofscreening (large scale, project scale) inrelationto other factors. Test for possible interference o f field test kit resultsby other constituents of the water, which may account for some o fthe false positives and negative^.^ The frequency o f the screening i s significant where there i s highseasonalvariability o f arsenic intubewells, as inCambodia. Screening should be conductedbecausearsenic i s flavorless and odorless; the only way to identifyit is to test for it.Inaddition, ifthe measurement i s wrong there i s no simple way to become aware o f the mistake. Social and cultural issues: The use o f the field test kit tends to create curiosity and thus constitutes a tool for awareness raising. Economic issues: The monitoringo f screenedwells i s still an issue inmany countries. After the initial screening, should the priority be to screen all tubewells or only the safe ones? The rationale o f retestinga contaminated well i s to identify any misclassification, knowing that insome hotspots a safe tubewell could be the only source o f arsenic-safe and bacteriologically safe water. Costs, however, are a significant factor, and the benefits o frescreeningschemes need to be assessed. False positives have an actual concentration lower than 50 pgL-',but are falsely labeledunsafe as the field test shows a concentration higher than 50 pg L-'.False negatives have an actual concentrationhigher than 50 pgL-*,but are falsely labeled safe as the field test shows a concentration lower than 50 pgL-'. - 92 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1-Paper 2 - An overview of current operational responses to the arsenic issue in South and East Asia 0 For longer-term decisionmaking, universal sampling has certain benefits compared to sample- based screening. However, it i s worth notingthat one of the lessons leamed inBangladesh i s that if a well i s not tested ina contaminated area and ifpeople do not have convenient alternative solutions, they will use this well assuming that ifit has not been tested then it should be safe. Institutionalissues: 0 The choice o f screening model (the public-good approach or demand-based screening). 0 The dissemination o f data, both for screening conducted by government agencies and by NGOs, i s critical to ensurethe transparency o f information. 2.6.1.6 SummaryRemarks The following guidelines are applicable when deciding on the method o f testing (field test or laboratory analysis): 0 If fieldtestkitisthemethodofscreeningthen3%to10%ofthesamplesshouldbecross- the checked with laboratory analysis. 0 The capacity o f laboratory analysis shouldbe assessed to ensure that quality assurance i s implemented. 0 Ifusinglarge-scale screening, the first screening couldusealargegndwith afew samples, butwith adequateregional distribution to enable hydrogeologists and geochemists to identify contaminatedand vulnerable aquifers. These resultswould provide a first approximation of, where the hotspots are situated and which zones shouldbe prioritized to conduct amore precise screening and to implement mitigationmeasures. 0 Although not operationalized inthe sample o f countries that are the subject o f this study, a monitoringplan i s o futmost importance. 2.6.2 WellSwitching,Paintingof Tube Wells, andAwareness 2.6.2.1 Background When screening i s conducted and arsenic-contaminated wells (those with levels above the accepted standard) are identified, the first step to mitigate the local population's exposure might be sharing o f safe tubewells. Therefore, awareness campaigns need to make clear how to recognize safe tubewells. So far arsenic screening accompanied by the physical marking o f safe or contaminated tubewells takes place inBangladesh, Cambodia, Nepal, Pakistan, and West Bengal inIndia. A tubewell is considered unsafe ifits concentrationof arsenic is higher than the national standard. So far, all the countries that have marked tubewells have done so indifferent ways. InBangladesh, Cambodia, and Pakistan, the spouts o f the contaminated tubewells are painted in red if the concentration o f arsenic i s higher than 50 pg L-' (the national standard) and in green if the concentration o f arsenic i s lower than 50 pg L-'.InNepal, a cross (X) i s paintedon the tubewell if the concentrationis higher than 50 pgL-'and a check (4i s painted if the concentration o f arsenic i s lower than 50 pg L-'.InWest Bengal, it was decided that confusion could best be avoided by marking only the safe tubewells; those with a concentration o f arsenic lower than 50 pg L-'(the national standard) are painted inblue. 2.6.2.2 WideningAwareness of Water Quality There i s a need to make sure that communities use only safe tubewells. Many countries have increasingly developed groundwater supplies because o f the poor bacteriological quality o f - 93 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 2 -An overview of current operational responses to - the arsenic issue in South and East Asia surface water, a common problem inthe surveyed countries. The use o f groundwater reduces the riskof waterborne disease, but hasbrought with it the needto explain clearly that the clean water from some tubewellscontains poison that can neither be seen nor tasted. Inorder to avoid confusion among communities, people should be informedthat clear and clean water might be contaminated with arsenic. InBangladesh and in West Bengal in India UNICEF has developed a well-researched information package. Other materials have also been developed by the BangladeshArsenic MitigationWater Supply Project (BAMWSP) andNGOs.All materials are used widely. In Nepal the National Arsenic Steering Committee (NASC) has developed a standard information package to help clarify the sometimes contradictory messages related to bacteriological and arsenic contamination o f water. However, there i s still further need for the development o f awarenesscampaigns on poor water quality. Participants at the Regional Arsenic Workshop emphasized the need to ensure that awareness campaigns use community-specific communication methods. In Cambodia, for example, awareness campaigns use puppets, a popular form o f entertainment inthe country. 2.6.2.3 RemainingIssues and LessonsLearned Social and cultural issues: Ithasbeenwidely disseminated that dugwells are less arsenic-contaminated thantubewells; therefore some people think that the problem i s associated with the technology beingused.As a result, there i s apossibility that some people may conclude that the problem i s not inthe groundwater quality per se but that it i s associated with their tubewell and the way to fix it would be to purchase another handpump. Since most wells are privately owned, neighbors may be reluctant to share. Inaddition, most tubewellsare situated inthe courtyard o fhouses so there is aprivacy issue. Sharing o f arsenic-safe wells as a solution can therefore not be taken for granted. If densityofusersateachwellincreases,somepeopleareafraidthattheirtubewellswill the become arsenic contaminated as well. The complaints relatedto sharing safe tubewells include excessive wear on equipment; new users do not clean up after themselves; and people come at late hours. Insome hotspots there are simply not enough safe tubewellsto meet demand for drinlungwater. When people say they have no other water source, they may actually mean that they have no other tolerable source. Sharing i s perceived as a reduction inthe quality o f life. Women, who traditionally collect water, mightnot be allowed in some places to leave their immediate householdunaccompanied. InBangladeshthe choice ofredto indicatearsenic contaminationseems, insomecases, tobe confused with ironprecipitation, which leaves an orange-red color. Awareness campaigns must explain clearly that arsenic i s not a germ that can be killedby boiling water. Insomeplacespeoplearehavingdifficultydistinguishingarsenic-related skindiscoloration from other skin diseases or infections. Color and sign interpretation o f marked tubewells i s a new concept for some people. Repetitioni s important, becauseexperience shows that memory and motivation fade intime. - 94 - Arsenic Contaminationof Groundwater in SouthandEast AsianCountries:Volume I1-Paper 2 - An overviewof current operationalresponsesto the arsenic issue in Southand EastAsia 0 Inmany countries theidentification ofarsenic impliesanincrease ofcollection distance and time due to the change inwater source; therefore women's work loadincreases substantially. This also needs to be factored into the provisiono f arsenic-safe water. 0 Awareness campaigns shouldbe carried out regularly and not only at the time o f screening. 0 For years groundwater has beenpresented as the "safe" source of water; thus the arsenic- related messagecontradicts conventional wisdom about safe water. However, the awareness campaignrelatedto poor surface water quality shouldnot stop because o fthe more recent problem o f arsenic contamination. Technical issues: 0 Tubewells shouldbe retested and repaintedregularly, since painting can be altered duringthe rainy season. 2.6.2.4 SummaryRemarks When arsenic i s identified, ensure that safe tubewells are marked and that the choice o f color or marks i s understandable to communities. Whether unsafe tubewells should be marked or not i s still an open question; the consensus seems to be that in the case o f blanket screening the preferable approach i s to mark the unsafe tubewells, while inthe case o f sample base screening it may be preferablenot to mark unsafe tube well^.^ Awareness campaigns should address arsenic contamination, but also maintain awareness about poor surface water quality. There i s a need to address both quality problems and not substitute awareness o f the healthrisks due to arsenic for awareness o f the risks relatedto poor surface water quality. In addition, the awareness campaign should use community-specific communication methods inorder to reach the maximum o f people inthe community. 2.6.3 Patient Identification 2.6.3.1 Background Patient identification, also called case finding, may be passive or active. Passive patient identification i s simply allowing individuals to present themselves for treatment, while active patient identification involves going out to the field to examine individuals for signs o f arsenic- related disease. InBangladesh and Nepal patient identification is often carried out during tubewell screening. Although arsenic can cause a variety o f health conditions, most patient identification has been based on skinlesion-related symptoms. InWestBengalpatientidentificationismainlypassive, althoughtheJointPlanofAction, between the state and UNICEF, has initiated an epidemiology survey. The first step i s the training o f doctors and NGOs to properly identify patients and to suggest appropriate mitigation measures; active identification has also been suggested. 2.6.3.2 Trainingof Testersin Patient Identiflcation When patient identification i s carried out alongside tubewell testing, the testers must be provided with sufficient training to distinguishbetween skin lesions related to arsenic ingestion and other skin lesions, bearing in mind that (a) there is still no universally agreed case definition of arsenicosis disease; and (b) the actual extent to which exposed persons will develop skin lesions Blanket screening means that 100%o f the tubewells ina given region are tested. Sample base screening means that a selection of tubewells i s screened and fiom that data conclusions are drawn as to the levels o f contamination inthe other tubewells. - 95 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 2 -An overview of current operational responses to - the arsenic issue in Southand East Asia and other arsenic-related conditions is difficult to predict. Therefore the capacity building o f testers and health workers i s critical to ensure reliable patient identification. 2.6.3.3 Identification Based on Skin Lesions and on Laboratory Analysis Some people are subclinically affected by arsenic even though they do not show skin lesions. For example, in contaminated areas in Bangladesh, some studies have shown that children and adults without skin lesions at present may have highconcentration o f arsenic intheir hair, nail, and urine samples. Therefore, patient identification based solely on the presence o f skin lesions may underestimate actual numbersaffected by arsenic. However, identification o f arsenic-affected patients using laboratory analysis o f nail, blood, and hair samples i s very expensive and requires strong laboratory capacity, and implementation on a large scale i s not generally feasible. 2.6.3.4 Current Estimate and Projections of Number of Arsenicosis Patients The current estimates o f the number of patients with arsenicosis in South and East Asian countries i s summarized in table 3. A review o f studies conducted in parts o f the world other than Asia projects that, ifthe at-risk population continues to drink arsenic-contaminated water, between 16% and 21% o f the population will be affected (WHO 2001a). This projection i s based on the assumption that the estimation o f the population at risk i s accurate, the clinical case recognitioni s accurate, and survey results of other regions can be generalized. However, the 1621% estimate has no reliable statistical confidence intervals. For example, inBangladesh a study conducted by the Massachusetts Institute of Technology estimated the arsenic health burdenthrough a model of dose-response function (Yu, Harvey, and Harvey 2003). The study predicted that long-term exposure will result in approximately 1.2 million cases o f hyperpigmentation, 600,000 cases o f keratosis, 125,000 cases o f skin cancer, and 3,000 fatalities per year from internalcancer. Another estimate o f the arsenic-related health burden inBangladesh concluded that the total risk o f cancer would be equal to 375,000 affected people (Ahmed 2003). So far, these two figures are the only quantification o f the potential arsenic-related health burden. They depend heavily on epidemiological assumptions and demonstrate how the lack o f reliable epidemiological information adds uncertainties to the projected number o fpeople at risk. Table 3. Current Populationat RiskinAsian Countries Regiodcountry Present estimationo f Number o f arsenicosis Year of first numberat riskinmillions patients identifiedso far discovery (% o ftotal population) East Asia Cambodia Max. 0.3 (2.7%) - 2000 China 3 (0.2%) 522,566 1980s Lao PDR - - Myanmar 5 (10%) 1999 Taiwan 0.2 1960s Vietnam 11(13.7%) 1998 SouthAsia Bangladesh 35 (28%) 10,000 (partial results) 1993 - 96 - Arsenic Contaminationof Groundwater in SouthandEastAsian Countries:Volume I1 Paper 2 -An overviewof current operationalresponses to - the arsenic issue in Southand EastAsia India (West Bengal) 5 (6.25%) 200,000 1978 Nepal 0.3 (3.4%) 8,600 1999 Pakistan - 242 cases per 100,000 2000 people basedon the results of 10 districts -Notavailable. Sources: Bhattacharya 2002; Ng, Wang, and Shraim 2003; Kinniburgh and Kosmus 2002; WHO 2001a; Smith, Lingas, andRahman2000; Bergandothers 2001; informationreported at Regional Workshop, Nepal, April 2004. 2.6.3.5 LessonsLearned and RemainingIssues Social issues: 0 Gender sensitivity: InBangladesh, for example, each team engagedintubewell screening and patient identification surveys includes at least two females. 0 Actively include information that arsenicosis i s not contagious to ensure that the community will not stigmatize arsenicosis patients due to misinformation. Economic issues: 0 Patient identification and medical referrals, along with public education, should be integrated into all tubewell testingefforts. This seems to be the most cost-effective way to actively identifyarsenicosis sufferers. 0 Identificationo f arsenic-affected patients i s generally based on the skin effects, which are not necessarily the first symptoms. However, identificationbased on laboratory analyses i s too expensive to be implemented at large scale. 0 Arsenic can cause a variety o fhealth conditions, thus there i s still the issue o f identificationo f those patients who do not develop skin lesions. The cost o fthe epidemiological survey required to identify all such patients would beprohibitive. However, such studies could be conducted on a small scale inorder to allow estimates o f the scope o f the arsenic problem ina country or regionwithin a country. 0 The most efficient way to conduct a nationwide survey i s inconjunction with an existing population program. Technical issues: There i s a needto ensureproper training o f tubewell testers andhealth workers so that they can distinguish betweenthe skin lesions resulting from arsenic exposure and other skin lesions. Standardized criteria for diagnosing andgrading skinlesions mustbe developed and carefully followed. The WHO i s leading an effort to develop such criteria. When finalizedthey should be widely usedby government institutions and by all organizations engaged incase finding, treatment, and surveillance. 2.6.3.6 Summary Remarks There i s a clear need to improve information about the epidemiology in arsenic-affected populations. This needs to happen in a strategic manner, and can be achieved by combining - 97 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 2 -An overview of current operational responses to - the arsenic issue in South and East Asia patient identification with well screening. At the same time, targeted epidemiological studies need to be carried out inorder to supply data to assist arsenic mitigation activities inAsian countries. 2.6.4 Treatment Management of Arsenicosis Patients 2.6.4.1 Background Although a number o f clinical treatments have been advocated, there i s no universal medical treatment for chronic arsenicosis. The only measure that will prevent future damage i s to supply the patient with drinkingwater that i s free from arsenic and, if it i s administered at an early stage, it seems to remedy past damage causedby arsenic. The first priority should be to remove people from the source o f exposure and then follow up with symptomatic management. To date, there are no well-designed studies to show whether cessation o f exposure leads to improvement in skin keratoses. However, anecdotal interviews o f patients suggest that mild to moderate keratosis improves with cessation o f exposure. Chelation, which i s often presented as a treatment o f arsenicosis, has been proven effective mainly in cases of acute poisoning. The principle of chelation therapy is to provide the patient with a chemical to which arsenic binds strongly, and which i s then excreted in urine. The provision o f such treatment could remove large stores o f arsenic (from acute exposure) from the body in a matter o f hours. However, although chelation might have a positive result in some patients with chronic poisoning, so far there i s no complete study that assesses its effectiveness for chronic exposure. Inaddition, it i s difficult to ascertain to what extent improvement in skin lesions after chelation therapy i s attributable to the therapy, and to what extent it i s attributable to cessation o f exposure. Therefore, patient improvement after chelation therapy does not provide sufficient evidence o f its effectiveness (Kaufmann and others 2001; NRC 1999). Evidence from Taiwan suggests that some nutritional factors may reduce cancer risks associated with arsenic. Ithasbeenproposedthat providingvitamins and improving diet may be o fbenefitto patients. Inparticular, vitamin A i s known to bebeneficial inthe differentiation o f various tissues, particularly the skin. Ifthe doses given are not excessive, there are other nutritional benefits to be gained. Thus, it i s recommended that all patients with skin lesions be given multivitamin tablets and that research projects be undertaken to establish whether or not they are effective for patients with arsenicosis (NRC 1999). Arsenic i s a probable contributor to causation o f diabetes mellitus and hypertension. For this reason, urinary or blood glucose and blood pressure should be tested in all patients with arsenicosis and appropriate treatment and monitoring should be started if necessary (Kaufmann and others 2001). In Bangladesh people identified with skin lesions are given vitamins and ointment. In West Bengal (India), under the Joint Plan o f Action, a network o f clinics will be set up at the district, subdivision, and block level. At the same time, in both countries, studies are being conducted to provide a better estimation o f the arsenic impact on human health. 2.6.4.2 RemainingIssues and LessonsLearned Social issues: 0 The fact that arsenicosis i s not treatable with folk remedies should be emphasized in awarenesscampaigns (Some o f the scarce literature on social issues regarding arsenic suggeststhat some people may spend a considerable portion o f their income trying to find a homemade cure). 0 The fact that the only way to prevent arsenic contamination i s not to drink contaminated water should be emphasized inawarenessprograms. - 98 - Arsemic Contamination of Groundwater in Southand East Asian Countries: Volume I1- Paper 2 -An overview of current operationalresponses to the arsenic issue in South and EastAsia 0 Ensure that treatment protocols are easy to follow. 0 Ensure that people are informed about the fact that arsenicosis i s not contagious. Technical issues: 0 Awareness campaigns should stress that chelation cannot be viewed as a successful treatment while exposure to arsenic-contaminated water continues. 0 Advanced keratoses are extremely debilitating and complications suchas superimposed fungal infections may cause serious problems. Providingmoisturizinglotions and treatment for infections may be beneficial and shouldbepart ofroutine care inadvanced cases. 0 Arsenic has adversehealth effects other than skin lesions, such as diabetes, and these diseases have to be treated as well. 0 Inremoterural areasclinics, equipment, and expertise are generallyunavailable, so trainingo f health workers should be conducted to helppatients inthe absence o f effective treatment. However, in some countries health and population sector programs mightnot have the capacity to conduct the requirednationwide training for all clinical workers within a short periodo f time. Institutionalissues: 0 Healthand water supply institutions needto work together since the major treatment for arsenic i s an alternative safe water source. 0 Doctor absenteeismmightbe another important factor insome countries. For example, a recent study conducted inBangladesh estimated doctor absenteeism to be around 75% inrural areas (Chaudhury and Hammer 2003). This i s a critical issue, especially ifhealthworkers do not have adequatetrainingto help patients affected by arsenic contamination. 2.6.4.3 Summary Remarks The preferable approach i s to ensure that identified patients have follow-up treatment in the local health institution. The capacity building o f health workers in remote rural areas i s critical and health and water sector professionals need to work together to make sure that people have access to information and to medicines. 2.7 Longer-TermResponses Longer-term responses are institutional and technical. The institutional aspects are mainly related to the country's arsenic policy and strategies. Technical longer-term responses can be divided into two types based on the source of water: surface water and groundwater. Surface water responses include pond sand filters, rainwater harvesting, and piped water supply. Groundwater responses include dugwells, deep tubewells, pipedwater supply, and arsenic removal treatment plants. 2.7.1 Institutional Longer-Term Responses (Arsenic Country Policy) 2.7.1.1 Background A country can respondto arsenic contamination by establishing an arsenic policy andor strategy. The objective i s to provide overall direction and guidance for dealing with arsenic and to set priorities for operationalresponsesinthe short, medium, and long terms. So far, Bangladesh i s the only country to have adopted a national arsenic policy (March 2004) and to have developed a detailed plan of action. The policy seeks to identify the nature and extent o f the problem through screening and patient identification and to provide guidelines for mitigation o f arsenic contamination through (a) public awareness; (b) provision o f arsenic-safe water supply - 99 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 2 -An overview of current operational responses to - the arsenic issue in'South and East Asia with a preference for surface water over groundwater, and the promotion o f piped water supply when feasible; (c) diagnosis and management o f patients; and (d) capacity building at all levels (from government to local communities). The arsenic policy also recommends mapping o f the country's deep aquifer to ensure that deep wells will bebuilt inregions where deep groundwater i s separated from the shallow aquifers by a substantial impervious layer. InNepal the National Arsenic Steering Committee (NASC) is chiefly responsible for arsenic strategy. Ithas formulated national guidelines,which detail the steps to be taken to address arsenic contamination o f groundwater and stipulate how safe and unsafe tubewells are to be marked. The NASC has also produced a standard set o f information, education, and communication materials for awarenesspromotionwithin the community. InCambodia a recently established arsenic committee is working closely with UNICEF and a number o f NGOs. The committee organizes screening of tubewells and provides different stakeholders with field test kits.In Pakistan, UNICEF i s also working closely with the provinces inthe screeningoftubewellsandother water sources. InIndia, in 1999,UNICEF enteredinto a strategic alliance with the government of West Bengal through a Joint Plan o f Action, which incorporates the following: (a) a community-based water monitoring system; (b) altemative technologies for supply o f arsenic-free water (including arsenic removal at the household level and piped water supply); (c) health surveillance, patient identification, and early treatment programs; (d) awareness campaigns; (e) research on arsenic health effects inwomen and children; (f)networlung and informationsharing among stakeholders; and (g) monitoring mechanisms at all levels. The Joint Plan o f Action effectively constitutes a strategy to deal with arsenic contamination inthe short and long term. 2.7.1.2 Summary Remarks Itis important for relevantinstitutionsto have short-term andlong-term strategies for dealing with arsenic contamination. As i s apparent in South Asia, no single strategy i s applicable to all countries or localities. InBangladesh and Nepal the government, incollaboration with a variety o f stakeholders, i s the focus o f strategy, while inWest Bengalthe choice has been made to elaborate a plan in conjunction with an intemational agency, inthis case UNICEF. These experiences show that (a) there i s now a body o f information-as evidenced inthis paper -that permits the design o f such policies and strateges, despite continuing uncertainty about many features o f arsenic contamination; (b) more information i s still neededto enable governments and other stakeholders to be more specific indefiningproposed actions; and (c) policies and strategies need to be flexible enough to incorporate any further information that will become available over time. The final challenge i s to ensure that such policies or strategies are enforced. 2.7.2 TechnicalLonger-TermResponsesBasedon SurfaceWater 2.7.2.1 Background Longer-term responsesbased on surface water include pond sand filters, rainwater harvesting, and piped water supply. Technical details for each o f these operational responses are providedinPaper 3. This section focuses on the lessons leamed and their implementation. The pond sand filter technique i s based on a filtration process by which water i s purified by passing it through a porous medium. Slow sand filtration uses a bed o f fine sand through which the water slowly percolates downward. InBangladesh pond sand filter technology hasbeen used for arsenic mitigationbut the level of acceptance has been low, due in part to doubts about the bacteriological quality o f water. One pond sand filter can supply the daily drinking and cooking water requirements for 40 to 60 - 100- Arsenic Contaminationof Groundwater in SouthandEastAsian Countries:Volume I1 Paper2 -An overview of currentoperationalresponsesto - the arsenic issue in Southand EastAsia families. Inthe literature, Myanmar i s the only other country inthe study region usingponds as a mitigation option for arsenic contamination. Rainwater is usedin many parts o f the world to meet demand for fresh water. The principle i s to collect rainwater, either via a sheet material rooftop or a plastic sheet, and then divert it to a storage container. In the study region there have been reports o f use o f this technique from Bangladesh, Cambodia, and Taiwan. Piped water supply can use surface water after simple water treatment. Generally, treatment i s needed to reduce turbidity and includes chlorination to protect against bacteriological contamination o f surface water. Bangladesh and India are employing the piped water option as a major component o f their mitigation strategies, and Cambodia i s also using this technique. Bangladesh i s now embarking on a large pilot operation to implementpiped village water supply. InIndia, inparticular inWestBengal, thisresponsehas alsobeenrecommendedonalarger scale for multiplevillages. Ingeneral, the level o f acceptance for the pipedwater supply option i s high because o f its convenience. 2.7.2.2 RemainingIssues and LessonsLearned Pond sand filters - social and cultural issues: 0 The community should pledge involvement inoperation and maintenance o f the pond sand filter. 0 Increasingly, inBangladesh, ponds have become important sources o f income because o f fish culture, so farmers are reluctant to give up their ponds for pond sand filter construction. 0 Some users have complained about the taste o f water from this source. 0 Pondsand water i s generally contaminated with pathogens. The bacteriological quality of water fluctuates between a little over the WHOD3angladesh standardto hundreds o f times higherthan that. Pond sand filters -economic issues: 0 The initial capital cost o f construction i s high- about US$430-690, depending on the size o f the pond sand filter. Pond sand filters -technical issues: 0 The selected pond should not be usedfor fish culture, watering and washing livestock, or other domestic purposes, and should be protected from such activities. 0 The selected pond should be perennial. 0 The quality o f water varies seasonally and i s improved with the addition o fbleachingpowder solution. Rainwater harvesting- social issues: 0 Some users complain about the taste o f the water. 0 Ithasbeenreported fromBangladeshthat theretumto rainwater harvestingmaybeviewed as a step backwards to several decades ago when it was quite widely used. 0 InCambodiarainwaterharvestinghasbeenpracticedfor alongtimeandisreportedtobewell accepted. Rainwater harvesting-economic issues: 0 InBangladeshthecostofarainwaterharvestingsystemisanissue. - 101- Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 -Paper 2 -An overview of current operational responses to the arsenic issue in South and East Asia 0 Inaddition, this solution doesnot cover the dry season, when another mitigationmeasure must be used, adding to the cost. Rainwater harvesting-technical issues: 0 Rainwater harvestingi s a useful alternative to other sources, but inareas with aprolongeddry season it can only be a partial solution. 0 Water quality i s a concern: the first rain may flushimpurities, including animal feces, o f fthe roof. Not storing the first rain and cleaningthe roofreduces the risk o f inadequate water quality. Pipedwater supply - social issues: 0 This option functions best inlarger villages where density i s highenough to ensure viability. 0 Itis important to ensure that all peopleare connected, inparticularthepoorest segment o fthe population. 0 Appropriate institutional arrangements for operation and maintenance o f the system should be inplace. Pipedwater supply-economic issues: 0 Affordability by differentincome groups within the community needs to be considered. 0 Operation and maintenance needs to be coveredby the price o f the service. Pipedwater supply -technical issues: 0 A highlevel of skillisnecessaryfor design and construction, and capacity buildingamong local artisans i s an important consideration. 0 A highlevelo f skillis also needed for operationandmaintenance. 0 Permits monitoring o f one single source for water quality rather thanmultiple sources inone village. 2.7.2.3 SummaryRemarks This section has examined some o f the advantages and disadvantages o f the operational responses usingsurface water. Taking into account such factors, certain solutions may present themselves as the best trade-off between the range of options that may be applicable in a given situation. However, care mustbe taken to devise solutions that address fully the goal o f providing drinkable water, rather than addressing only the problems related to arsenic contamination. Table 4 summarizes the options. 2.7.3 TechnicalLonger-TermResponsesBasedon Groundwater 2.7.3.1 Background The longer-term responses based on groundwater include dug wells, deep tubewells, piped water supply, and arsenic removal filters or plants. The technical details o f each o f these operational responses are provided in Paper 3. This section focuses on lessons learned from their implementation. Dug wells are excavated below the water table until the incoming water exceeds the digger's bailing rate. They are typically lined with stones, bricks, tiles, or other material to prevent collapse, and are coveredwith a cap of wood, stone, or concrete to prevent contamination from the surface. This option has been used in Bangladesh and Nepal. The UNICEF Plan o f Action proposes dug wells as a mitigation option inMyanmar. - 102 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 2 -An overview of current operational responses to the arsenic issue in South and East Asia Table 4. Summary o fResponsesto Arsenic Contamination Basedon Surface Water Operational Advantages Disadvantages responses Pond sand filter Technically easy to implement Poor bacteriologicalwater quality L o w service level Complaints about the taste o f water Selectedpond sand filter should be used only for drinking water Rainwater Technically easy to implement Poor bacteriologicalwater quality when not harvesting adequately maintained L o w service level Insome regions, cannotprovide water for the entire year Complaints about the taste o fthe water Can only be a partial solution inareas withprolonged dry season Piped water Adequate water quality when Highlevel ofskill necessary for designand supply treatment is carried out construction correctly Issues of operation and maintenance and management Sustainable source o f supply mustbe considered Other issues include affordability and system coverage One major concern related to dug wells i s that recent investigations show that some dug wells are also contaminated with arsenic (APSU 2004). Indeed, some dug wells in Bangladesh, China, Myanmar, and Nepalhave been found to have arsenic contamination. The deep aquifers inBangladesh, West BengalinIndia, andNepal have been found free o f arsenic thus far. However, inother places, including China, deep groundwater has been found to be even more contaminated with arsenic than shallow groundwater. This means that measurement o f the contamination level must be conducted before any exploitation o f deep groundwater. In the case o f Bangladesh, the assumption i s that the pre-Holocene aquifer has been flushed and therefore all mobile arsenic has been leached from this aquifer, while in China this process might not have taken place. A more detailed explanation i s presented inPaper 1. In Pakistan the preliminary findings of UNICEF screening showed no arsenic in the deep groundwater, though the number o f samples was limited (reported at Regional Workshop, Nepal, April 2004). InCambodia the main issue related to use of the deep groundwater is the poor yield o f deep tubewells, which adds significantly to the unit cost o f the investment. In Cambodia the general acceptance o f rainwater harvesting makes it a viable alternative to use o f deep groundwater. InBangladesh and Nepal mapping of groundwater is being conducted to identify at which depth arsenic-safe groundwater i s located and to identify where the shallow groundwater (Holocene plain) i s separated from the deep groundwater (Pleistocene terrace) by a clay layer. The existence o f this clay protects deep groundwater from potential contamination by shallow groundwater. So far, there i s still no wide consensus on whether groundwater mapping should be conducted through geophysical investigations or on a case-by-case basis when drilling wells. InIndia the Central Groundwater Board has conducted research on the deep aquifer in West Bengal. - 103 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 2 -An overview of current operational responses to - the arsenic issue in South and East Asia Bangladesh, Nepal, and West Bengal already use deep groundwater as a mitigation option for arsenic contamination. UNICEF proposes use o f deep groundwater in its Plan o f Action for Myanmar. InBangladesh, as inseveral other countries, the debate centers onthe following issues: whether deep groundwater should be used or not; the risk of arsenic-contaminated water leaking from the shallow to the deep aquifer; and what assurances there are that the deep aquifer sediments will not also release arsenic into the water at some future point. One important way to handle all these uncertainties i s to strengthen groundwater management, which includes a monitoring process, regulation o f deep groundwater exploitation, and a process o f collecting and storing data that would be helpfulfor further research on potential chemical contamination. A detailed explanation of the different arsenic removal technologies is provided in Paper 3. Arsenic removal plants can be located at the household level or community level. At the householdlevel, the arsenic removal unit could be located inthe house or attached to the tubewell. This mitigation measure has been implemented in Bangladesh, Nepal, Vietnam, and West Bengal in India. UNICEF also proposes its implementation in Myanmar. However, concern has been expressed in Cambodia that the unit may be difficult to maintain at the household level (reported at Regional Workshop, Nepal, April 2004). A pilot i s currently being developed inBangladesh to investigate this concern. Community arsenic removalplants can be useful for small villages and have been implemented in Bangladesh, India, Vietnam, and Taiwan. Ingeneral, the main issue on the technical side is how to ensure the effectiveness o f arsenic removal technologies inthe field, and, on the institutional side, how to ensure large-scale implementationand sustainability. 2.7.3.2 LessonsLearned andRemaining Issues Dugwells -social andcultural issues: 0 Inanumberofareasissuesoftasteandodor, andthepossibilityofbacteriological contamination, are hinderingacceptanceo f dug well water for dnnhng. 0 Use o f handpump technology can aid acceptance o f the dugwell but there have been complaints about the smell associatedwith chlorination. Dugwells -technical issues: 0 Bacteriological contamination levels o f dugwell water are often unacceptable. 0 Monitoring o f arsenic contamination i s needed, especially duringthe dry season. 0 Use o f dug well handpumps enablesbacteriological quality to be improvedand maintained at an acceptable level byregular chlorination. 0 Proper lining and a well-designed apron are crucial for prevention o f surface water contamination. 0 The community should ensure that dugwells are kept in sanitary condition. 0 Yield isreducedwhen the water table drops inthe dry season or ifabstractioni s greater than recharge. Deeptubewells-social and cultural issues: 0 Dueto the cost o finstallation, deep tubewells are usually sharedbyseveral (or many) households. This may mean that people have to walk long distances to collect safe water. 0 The shortage o f deep wells means that people have to wait a long time to get water. - 104- Arsenic ContaminationofGroundwater in Southand EastAsianCountries:Volume I1-Paper 2 - An overview of current operationalresponsesto the arsenicissue in South and EastAsia Deep tubewells - economic issues: 0 Initial capital cost i s high, around US$700-800. Deep tubewells -technical issues: 0 Since there i s no clear understanding so far o f the processesby which arsenic i s released into water, there i s still discussion as to whether deep groundwater will remain arsenic safe after medium-term or long-tenn exploitation.6 0 There i s also the need to ensure that the correct technique for drilling deep tubewellsi s used and that it taps the deep groundwater (not the shallow). Deeptubewells-institutional issues: 0 Groundwater management mustbe implemented to ensure that deep tubewells are usedonly for dnnkingand cooking purposes. Piped water supply: 0 Issues are the same as those for pipedwater supply using surface water except that treatment for bacteriological contamination i s usually not necessary; however, arsenic removal treatment may be necessary. Arsenic removal filters at the householdlevel- social and cultural issues: 0 The process i s time consuming, and the smell and taste are not always good. 0 Water becomes warm after standing for the recommendedtime, and cold water i s preferred for dnnking. 0 Too many water storage containers are required. 0 People are not inthe habit o f filtering their water. 0 The uniti s not always easy to operate and maintain. 0 The advantage i s that it allows rural households to continue usingtheir handpumps. 0 There may be difficulties inobtaining the necessary chemicals. Arsenic removal filters at the householdlevel- economic issues: 0 The technology i s expensive, and operation and maintenance costs may be high. Arsenic removal filters at the household level -technical issues: 0 The concentrationofremaining arsenic in some cases remains higher than the standard. 0 When usingalum treatment, the health risk o f alumremaining inwater i s a concern. 0 Monitoring i s more difficult to conduct at the household level. Arsenic removal filters at the community level - social and cultural issues: 0 There i s a needto organize responsibility for maintenance to ensurethe sustainability o f the water treatment unit. Arsenic removal filters at the community level-technical issues: 0 Monitoring i s easier to conduct at the community level than at the household level. This is inthe case ofcountries where deep groundwateri s not contaminated, such as BangladeshandNepal. - 105 - Arsenic Contaminationof Groundwater in Southand EastAsian Countries:Volume I1-Paper 2 -An overview of current operationalresponsesto the arsenic issue in Southand EastAsia Arsenic removal filters at the community level-institutional issues: 0 There needs to be aroutine for checkingthat water i s arsenic safe. 0 Ifthe sourceissurfacewater there shouldalsobeaprocess for checkingitsbacteriological quality. 0 Effective supply chains needto be developed for large-scale and sustainable solutions. Local government should be involved inensuringeffective supply chains. 2.7.3.3 Summary Remarks Table 5 summarizes the advantages and disadvantages o f each o f the described operational responses, enabling an assessment o f the trade-off most applicable to a given situation. However, some operational responses, while addressing the problems related to arsenic contamination, may give rise to water quality problems, and therefore do not address fully the target o f providing drinkable water. Suchpartial solutions should be avoidedwhenever possible. Table 5. Summary o fResponsesto Arsenic Contamination Basedon Groundwater Operationalresponses Advantages Disadvantages Dug wells Technically easy to Poor bacteriological water quality implement Some dug wells might also have arsenic contamination Possible low level of acceptance Low service level Switchto safe aquifer Canprovide potentially Difficult to predict whether the alternative aquifer will good water quality, but become contaminated needs to be monitored Potentiallow level o f service Arsenic removal Good chance o f Provenand sustainable option not yet generally available technology sustainability at the at household level community level Difficult to monitor at household level People do not always like the taste o f the water Operationand maintenance may be complicated 2.8 DisseminationofInformation 2.8.1 RegionalArsenic Networks and NationalDatabases The development of a databaseprovides stakeholders with access to information. Institutionally, it i s useful to ensure that data are stored following a specific process and are checked and cleaned. Dissemination, accessibility, and transparency o f data are critical for an issue as sensitive as water contamination. Scientifically, a database provides a baseline that can aid identification o f a long- term trend. For example, the lack o f a historical baseline in Bangladesh means that it cannot be ascertained whether arsenic has always been present in the groundwater or appeared only after exploitation o f the aquifer. InBangladeshthe NationalArsenic Mitigation InformationCenter (NAMIC),a component o f the BAMWSP, i s responsible for collecting data related to arsenic. N A M I C collects its own data under the auspices o f the BAMWSP and additional data from other stakeholders according to an agreed format. Some of the data are provided online (www.bamwsp.org). In addition, NGO- Forum provides a list o f the major governmental agencies, international agencies, and NGOs that work inarsenic contamination (www.naisu.info). - 106- Arsenic Contaminationof Groundwaterin Southand EastAsian Countries:Volume I1-Paper 2 -An overview of current operationalresponses to the arsenic issue in Southand EastAsia InNepal, with the support of the UnitedStatesGeological Survey, the Environmental andPublic Health Organization has prepared a national database for arsenic, which currently contains 18,000 arsenic level readings. Pakistan and Cambodia (annex 3) also have databases to centralize all the information from arsenic screening. Inthe three countries the contribution to the database is on a voluntary basis; however, in Cambodia, the Ministry o f Rural Development and UNICEF make receipt o f testing kits dependent upon contribution to the database. In India the Central Groundwater Board also has a web page with some arsenic-related data (www.cgwaindia.com/arsenic.htm). Regional information can be exchanged through the Asian Arsenic Network (AAN) (www.asia- arsenic.net/index-e.htm). The global positioning system (GPS) can be used to locate tubewells on a database, though differentiating individual wells may be difficult where the density o f tubewells i s greater than the resolution o f the GPS, as may occur in Cambodia and Bangladesh (reported at Regional Workshop, Nepal, April 2004). Whatever method i s used to differentiate wells in such circumstances shouldbe practical enough to be usedby all stakeholders, allowing levels o f arsenic inindividual wells to bemonitored over time. 2.8.2 SummaryRemarks Once established, a database shouldbe sustainable. Insome cases a database i s developed within a project and the collection o f data i s dependent on project financing. The institutional process to ensure the sustainability of data i s usually not given priority at this time. However, during such projects the technical process o f data collection, including where to measure and at what frequency, should be developed in parallel with the institutional process to make sure that cost recovery of the data collection takes place after project closure. This raises the issue of whether or not access to data should be free o f charge; and, inthe event o f a charge, whether usage would be sufficient to ensure cost recovery. - 107- Arsenic Contaminationof Groundwater in Southand EastAsianCountries:Volume I1 Paper2 -An overview ofcurrent operationalresponsesto - the arsenic issue in South and EastAsia 3. Arsenic Mitigationinthe Context ofthe OverallWater Supply Sector 3.1 Background Most South and East Asian countries where groundwater arsenic contamination has been identified have inadequate surface water quality, mainly due to microbial contamination. Inthese countries solutions to water supply problems may require a trade-off between the long-term health effects o f a contaminant such as arsenic and the short-term health effects o f microbial contamination. 3.2 Access to ImprovedWater Sources inAsian Countries Until recently, most sectoral programs concentrated on the lack of access to improved water supply. Table 6 shows the increase inaccess to improved water sources in South and East Asian countries during the 1990s. However, other problems, such as inadequate sanitation, are still present inthe regon (table 7) and, despite improvements, child mortality remains high (table 8). Table 6. Access to ImprovedWater Sources inSelected Asian Countries Population with access to improved water source (%) 1990 2000 Country Urban Rural Total Urban Rural Total population population Bangladesh 99 93 94 99 97 97 Cambodia - - 54 26 30 China - - 71 - - 75 India 88 61 68 95 79 84 Lao PDR - - - 61 29 37 Nepal 93 64 67 94 87 88 Pakistan 96 77 83 95 87 90 Vietnam 86 48 55 95 72 77 -Notavailable. Sources: World Bank 2003a: www.wsp.org/07-eastasia.asp; www.wsp.orgi07-southasia.asp. 3.3 Arsenic PriorityComparedto BacteriologicalWater QualityPriority Available data indicate that the rate o f mortality due to waterborne diseases i s greater than that resulting from arsenic contamination. Based on information inthe literature, the best estimate of mortality due to diarrhea in Bangladesh i s 120,000-200,000 people per year, of which possibly half can be attributed to dnnlung o f pathogen-contaminated water (Alaerts and Khouri 2004). Similarly, the best estimates put mortality due to arsenicosis at 20,00040,000 people per year. However, it i s not known whether arsenic morbidity i s higher than waterborne disease morbidity. Thus, there are insufficient data to resolve the issue o f how to prioritize between short-term contamination o f surface water and long-term contamination by arsenic. - 108- Arsenic Contaminationof Groundwater in Southand EastAsian Countries:Volume I1-Paper 2 -An overviewofcurrent operationalresponsesto the arsenic issue in Southand EastAsia Table 7. Percentage o f Population in SelectedAsian Countries with Sanitation Populationwith access to sanitation (%) 1990 2000 Country Urban Rural Total Urban Rural Total population population Bangladesh 81 31 41 71 41 48 Cambodia - 56 10 17 China 29 - - 38 India 44 16 61 15 28 Lao PDR - 67 19 30 Nepal - 20 - 28 Pakistan 52 23 36 82 38 62 Vietnam 29 47 -Notavailable. Sources: World Bank 2003a: www.wsp.org/07-eastasia.asp; www.wsp.org/07-southasia.asp. Table 8. Child Mortality Rates inSelected South and East Asian Countries Infant mortality rate (per 1,000) Under-five mortality rate (per 1,000) country 1980 2001 1980 2001 Bangladesh 129 51 205 77 Cambodia 110 97 190 138 China 42 31 64 39 India 113 67 173 93 Lao PDR 135 87 200 100 Nepal 133 66 195 91 Pakistan 105 84 157 109 Thailand 45 24 58 28 Vietnam 50 30 70 38 Source: World Bank 2003a. As regards contamination with arsenic, certain criteria can help assess the level of priority that shouldbe givento the problem: (a) the concentration o f arsenic in drinkingand cooking water; (b) the spatial distribution of the contaminatedtubewells; and (c) the proximity o f other water sources that are safe. - 109- Arsenic Contaminationof Groundwaterin Southand East Asian Countries:Volume I1 Paper 2 -An overview of current operationalresponsesto - the arsenic issue in SouthandEastAsia There i s a positive correlation between the concentration o f arsenic and its health effects. If the only available sources have high arsenic concentrations (more than a few hundred pg L-')and most o f the tubewells are contaminated, there i s practically no access to safe water. Inthis case the morbidity o f arsenic i s very high, and the shift to surface water might be considered, providing adequate chlorination i s carried out or that people are advised to boil water for dnnkingpurposes. If the average concentration of arsenic is less than 100 pg L-', there is a longer timeframe for planning action. Solutions such as either providing surface water safe from arsenic andbacteria, or piped water either from surface water or another aquifer, can be properly planned to ensure that people get access to safe water. Another scenario could be that some tubewells have high concentrations o f arsenic but the percentage o f contaminated wells i s low, which means that people will still have access to safe water within a reasonable walking distance. This kindo f case- by-case or village-by-village analysis can provide insightinto suitable steps to be taken. The financial sustainability o f any water supply technology i s necessary to ensure long-term sustainability o f the supply, and must include operation and maintenance o f the system, be it wells, pond sand filters, or piped water supply. Such recurrent costs and responsibilities for incurring them will vary according to such factors as whether the water supply i s private (for example individually installedhouseholdwells) or operated by the community. Inthe shiftto arsenic-safe options governments will have to involve communities incost sharing, both for capital costs and for long-term operation and maintenance. With water supply provision still free in a number o f countries, this relatively new concept may not be widely accepted by govemment or by users. Indeed, moving from surface water to groundwater allowed people to have clean clear water almost free o f charge in terms o f operation and maintenance costs. Now that some tubewells can no longer be used, alternative safe sources o f water may have high operation and maintenance costs. Users would have to pay for water on a regular basis and receive a quality o f service equal to or less than that available with tubewells. Therefore, as applicable ina given country, willingness to pay studies will be crucial in deciding what mitigation options are not only technologically appropriate but also socially accepted in the long run. Such studies have been carried out by the Water and Sanitation Program in, for example, Bangladesh (WSP 2003) and have played an important role in informing policy decisions regarding the introduction o f pipedwater supply. 3.4 Definitionand Identificationof Arsenic ContaminationHotspots Color coding o f tubewells has been used to signify which wells are arsenic safe and which are not (section 2.6.2 above). There i s no record in the literature o f more than two colors being used to identify degrees of contamination; for example, one color could indicate an arsenic concentration less than 10 pgL-',another could indicate the range 10-50 pg L-',another the range 50-200 pg L- ',and another a concentrationhigher that 200 pgL-'.Such levels o fprecision would be possible in countries where laboratory testing was the norm, but not in countries that rely on field test kits. Also, use o f additional colors would add complexity to any awareness campaign. However, an advantage would be that users could tell which o f the contaminated tubewells were less harmful and which more harmful. A long-term advantage could be that if the national standard in some countries was lowered to, for example, the present recommended maximum permissible value o f the WHO (10 pg L-')tubewells would not have to be rescreened and reclassified, and sufficient data would be available to enable costing o f the measures associated with adjustment o f the national standard. The problem o f prioritizing mitigation measures for arsenic contamination i s illustrated by Bangladesh, where emergency villages are defined as those with more than 80% o f tubewells contaminated. However, this does not always provide a full enough picture on which to base operational responses; for example, 80% o f tubewells contaminated with, say, 60 pg L' may be - 110- Arsenic Contaminationof GroundwaterinSouthand EastAsian Countries: Volume I1 Paper2 -An overview ofcurrentoperationalresponsesto - the arsenic issue in Southand EastAsia less harmful than 70% o f wells contaminated at an arsenic level o f 200 pg L-'.Therefore, when definition of hotspots i s based only on the percentage of tubewells with a concentrationo f arsenic higher than WHO guidelines or national standards, there is insufficient information to develop a plan o f action. 3.5 RemainingIssues and Recommendations Institutional setting o f water quality monitoring i s a concem. Which institution should be responsible for the first screening and the monitoring? Should the operator or an independent organization such as an NGO or the community conduct them? What about sustainability and transparency and access to the related data? Since some countries such as Bangladesh, Nepal, and India also have the option o f using deep groundwater, the legal aspects o f groundwater management will have to be taken into account. Especially where exploitation o f deep groundwater i s concemed, should permits be introduced to ensure that the deep groundwater will be usedexclusively for drinhng and cookingpurposes or i s it assumed that, because of the cost, people will not use the deep groundwater for irrigation purposes? Hence, for long-term planning, there i s a need to develop and strengthen the legal framework for groundwater management. Although arsenic contamination i s covered far more in the international media than waterbome diseases, this should not imply that the bacteriological quality problem faced by South and East Asian countries shouldbe put aside. The decisionregarding the settingo fprioritieshas to be taken based on criteria such as the level o f contamination o f arsenic, and the access to safe water based on bacteriological and chemical parameters. - 111- Arsenic Contaminationof Groundwater in SouthandEastAsian Countries:Volume I1 Paper2 - An overview ofcurrentoperationalresponsesto - the arsenic issue in South and EastAsia 4. Incentives for Different Stakeholders to Address Arsenic Contamination The major stakeholders in natural arsenic contamination are water users, govemment, NGOs, donors, and international agencies. The incentives for each stakeholder to be active in addressing the issue are different. While a govemment would be expected to be more influenced by public pressure, for example inthe run-upto elections, an international agency mightbe more concemed with the reputational risk associated with its choices. The incentives for an NGO may stem less from public pressure or reputational risk (although this could also be possible) than from the wish to influence decisions ina given sector. When no other stakeholder i s addressing the issue, there i s an incentive for the users themselves to act to remedy the situation. Incentives discussed here are the number o f people at risk, number o f arsenicosis patients, rural and urban areas affected, national and international media coverage, cross-sector responses needed, water service pricing, short-term versus long-term solutions, reputational risk, and transparency of the mitigation measures. 4.1 Number of People at Risk The number o fpeople at risk from arsenic contamination does not seem initself to be an incentive for stakeholders to become active. Those at risk are those drinking contaminated water; only a certain proportion will develop the clinical symptoms o f arsenic poisoning. Ahmed (2003) estimated the percentage o f the total population at risk to be about 25% in Bangladesh, 6% in West Bengal (India), and 2.4% in Nepal. Fewer data are available for East Asian countries than for South Asian countries, perhaps due to lack o f identificationo f the problem, though inVietnam the percentage of the population at riskhas been estimated at 13%, or 11millionpeople (Berg and others 2001). Lack o f information, however, prevents an accurate current assessment o f arsenic contamination inEast Asian countries. 4.2 Number of Arsenicosis Patients The number o f actual arsenicosis patients might be considered more o f an incentive for stakeholders to become active. For example, while the estimate o f the percentage o f population at risk inVietnam is double that of West Bengal, the number of (identified) arsenicosis patients is reported to be nil in Vietnam compared to around 200,000 inWest Bengal (WSP 2003). There i s no indication from the literature that Vietnam i s in the process o f providing mitigation measures on a large scale for the at-risk population. It i s important to note that the use o f groundwater in Vietnam i s quite recent (less than 10 years). Since the latency o f arsenic-related diseases i s between 10 and 15 years, Vietnam could register a large number o f arsenicosis sufferers in a few years -which would increase the incentive to address the issue, but unfortunately at already a very advanced stage. Hence, the first identification o f arsenicosis patients i s a greater incentive for govemment, donors, NGOs, and intemational agencies to act than the population-at-risk measurement. This i s not surprising, given the many other issues that developing countries have to contend with, but investments in patient screening and epidemiology now could prevent costly emergency mitigation interventions later. 4.3 Rural and UrbanAreas Except in the cases o f Vietnam and Cambodia, arsenic-contaminated groundwater has mainly been detected inrural areas. Inurban areas it i s easier to deal with the arsenic problem when there i s a point source water supply. For example, in Hanoi water treatment plants use aeration and sand filtration for iron and manganese removal from the pumped groundwater, which also eliminates some arsenic from the raw groundwater, although in some cases this i s not enough to reduce it to levels below the national standard. Insuch circumstances, established facilities can be upgraded to address the arsenic problem. On the other hand, in rural areas, the problem i s far more complicated because water sources are dispersed and difficult to improve on an emergency basis. - 112- I Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 2 - An overview of current operational responses to - the arsenic issue in Southand East Asia Provision o f mitigation measuresby government and donors may take a long time, though NGOs might be more flexible and better suited to act quickly at this decentralized level. Even so, the scale o fthe problemi s significant. Importantly, rural populations often have less political clout than urban populations, which are typically more informed and politicized. Rural populations also suffer from the organizational problems that tends to afflict large groups with many free riders, weakening their voice as a group. This may in tum weaken the incentive for politicians to address arsenic contamination in rural areas. 4.4 NationalandInternationalMedia National media coverage can be an incentive for stakeholder activity since there i s reputational risk associated with providing unsafe water. However, this type of media coverage may act as a disincentive to action; if it i s alarmist or factually inaccurate then certain stakeholders may prefer to avoidpossible controversy. International media coverage might also create an incentive by raising global awareness, encouraging intemational agencies to orient their projects to take into account arsenic issues, and governments to commit more money to this purpose. However, care must be taken that this shift will not cause governments to reallocate resources from other equally important but less p,ublicizedproblems. For the media themselves, there i s an incentive to cover such controversial issues as arsenic contamination because they increase circulation. However, the short-term coverage i s often in contrast to the long-term, chronic nature o f the problem. 4.5 InstitutionalAspects Arsenic i s a cross-sectoral issue in that it involves water supply, water resources management, health, and (rural) development institutions. This can create difficulties if the institutions do not coordinate with one another. Transparency in the choice o f mitigation measures can be an incentive encouragrng stakeholders to be active and to work together. The pricing o f water supply services provides users with an incentive to hold providers accountable for water quality. This i s not always an incentive for government to implement charges for water supply services since they then become accountable. Tubewells in rural areas provide clean water that i s almost free in terms o f operation and maintenance costs. However, most o f the solutions to address arsenic contamination will be less convenient and some mitigation measures will involve a charge for water supply service, which can be a difficult reform to introduce in some countries. 4.6 Short-Termversus Long-TermSolutions Govemment, international agencies, and NGOs might feel greater incentive to implement short- term solutions rather than long-term solutions that are less immediately rewarding. The development o f arsenic policies and strategies can be a means o f increasing the likelihood that long-term solutions will be implementedas well. 4.7 ReputationalRisk Reputational risk can act as an incentive to make government and intemational agencies active. However, as in Bangladesh, the controversy surrounding arsenic contamination may discourage certain stakeholders from risking their reputations by becoming involved in the issue. This has delayed decisionmaking on such mitigationmeasures as the use o f arsenic-free deep groundwater, which could provide safe water inthe short and mediumterm. - 113 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 2 -An overview of current operational responses to the arsenic issue in South and East Asia Table 9 provides a conceptual summary o f the political economy o f arsenic contamination o f groundwater. It provides an indication why - up to now - mainly donors and international agencies and some country governments have been responding to arsenic contamination. Clearly, as more arsenic-affected areas are being identified and as the number o f arsenicosis patients i s going to rise, it can be expected that stakeholders will become more active. It is, however, important that in the meantime a more rational basis for dealing with arsenic contamination is created in order to avoid delayed - or exaggerated -responses. An important aspect inthis regard r i s investment in epidemiological studies and economic analyses, as outlined inPaper 4. Table 9. ConceptualizedIncentive Matrix: Stakeholder Incentives for Action on Arsenic Issues Donors/ Incentive factors Government international NGOs agencies I Key: I Low incentive Mediumincentive Great incentive - 114- Arsenic Contaminationof GroundwaterinSouthandEastAsian Countries:Volume 11 Paper2 - An overview of current operationalresponses to - the arsenic issue in SouthandEastAsia Table 9 provides a conceptual summary of the political economy of arsenic contamination of groundwater. It provides an indication why - up to now - mainly donors and international agencies and some country governments have been responding to arsenic contamination. Clearly, as more arsenic-affected areas are being identified and as the number o f arsenicosis patients is going to rise, it can be expected that stakeholders will become more active. I t is, however, important that in the meantime a more rational basis for dealing with arsenic contamination is created in order to avoid delayed or exaggerated- responses. An important aspect inthis regard - i s investment in epidemiological studies and economic analyses, as outlined inPaper 4. Table 9. Conceptualized IncentiveMatrix: StakeholderIncentives for Action on Arsenic Issues Donors1 Incentive factors Government international NGOs agencies Number of people at risk I Number o f arsenicosis patients I I I I I Key: I Great incentive - 114- Arsenic Contaminationof Groundwaterin Southand EastAsian Countries:Volume I1 Paper2 -An overview ofcurrent operationalresponsesto - the arsenic issue in Southand EastAsia 5. Conclusions In certain areas, natural arsenic contamination of groundwater has made effective access to safe drinlungwater difficult to achieve. Ifthe concentration inwater of a chemical parameter, such as arsenic, is higher than the maximum permissible national drinking water standards, the water i s considered contaminated and no longer potable. In Bangladesh, for example, arsenic contamination has reducedthe amount o f safe drinkingwater by about 20% inthe last decade. Two main issues generate substantial uncertainties in accurately predicting the impact o f specific short-term or long-term mitigationmeasures. The first i s the lack o f understanding o f how arsenic i s released from sediment to water, and the second i s the lack o f epidemiological data on the health impact o f low concentrations o f arsenic in drinking water. Indeed, since the arsenic release process i s not fully understood, it becomes difficult to be certain that a given mitigation measure will always provide arsenic-safe water. Also, since the epidemiology o f arsenic is not fully understood, estimation o f the real health outcome for lower arsenic concentrations provided by a given mitigation measure is difficult. For example, regarding the exploitation of the deep (Pleistocene) aquifer, so far no arsenic has been found in deep tubewell water in Nepal, West Bengal, or Bangladesh. However, due to these uncertainties, whether deep groundwater will remain arsenic safe inthe long term, and what the real health outcome o f usingdeep groundwater compared to other mitigationmeasureswill be, are difficult to determine. Practically speaking, mitigation measures should be implemented as soon as arsenic has been identified. While the success o f implementation depends mainly on socioeconomic factors such as people's acceptance of an option and its capital cost, scientific understanding o f arsenic has value added on the quantification o f impacts, but not on the implementation o f mitigation measures per se. Therefore, instead o f delaying implementation until arsenic contamination i s fully understood, bothimplementation and scientific investigation should be conducted inparallel. At the policy level (that is, action the govemment needs to take), when arsenic contamination is identifiedingroundwater there i s a needto assess: 0 The scale o f contamination: As the first screening results become available hydrogeologists and geochemists shouldrecommend whether the screening needsto be implemented at the project level or ifnational screening needs to be conducted. 0 The emergency levelbased on the populationat risk, the number o f arsenicosis patients, the time o f exposure, and the concentration o f arsenic inwater. Based on the contamination scale and the emergency level, government should implement a regional emergency plan o f action with short-term and long-term components to mitigate arsenic contamination. Potential emergency and short-term responses include dug wells, pond sand filters, rainwater harvesting, arsenic removal filters at the household level, and use o f a safe aquifer. Potential long-term operational responses are arsenic removalplants at the community level, piped water supply, anduse o f a safe aquifer. At the implementation level (that is, action that needs to be taken at the project level), when arsenic i s identified, there i s a needto conduct the following actions: 0 Ensurethat the appropriate government institutionis informedabout the contamination. 0 Ensurethat the data are available andproperly stored for further scientific research on the contamination, and are also available to different stakeholders that either use the water or implement water projects inor beyond the project area. 0 Ensurethat inthe project areathe govemment requiresthe operator to check arsenic on a regular basis and makes the results available to stakeholders. - 115 - Arsenic ContaminationofGroundwater in South and EastAsian Countries:Volume I1-Paper 2-An overview of current operationalresponsesto the arsenic issue in Southand EastAsia Whether the project should be continued i s a decision for both the institution or international agency and the govemment. There i s a need to ensure that arsenic mitigation occurs in an integratedmanner with ongoing projects. One o f the questions for donors and international agencies i s whether a water project where arsenic i s identified should be pursuedor not. Knowing that arsenic has long-term health effects and that poor surface water quality has short-term effects, the question i s how to address both issues in a balanced way. Ifthe project i s to continue, govemment should provide assurances that appropriate measureswill be taken to mitigate the arsenic contamination. Finally, arsenic contamination has changed people's minds about the generally accepted rule that "groundwater equals safe drinking water". Although such water may be bacteriologically safe recent events have cast increasing doubts on its chemical safety. There are still other sources o f water contamination in South and East Asian countries that needto be addressed, such as fluoride, manganese, sodium, iron, and uranium, in addition to bacteriological contamination. A development agency's target should be to ensure that all the mechanisms for water quality monitoring are set and implemented now, either for surface water or groundwater, to reduce the riskofprovidingunsafe drinkingwater. - 116 - x x X X x x x x X X X x x X x x X x x x x x x x x X k x rr 0 x x X x x x " x X X X x x x x 8 i I s X X X X X X 83 aG; il I W 3 3 I 5 '5 N m I I 2 3 3 m .-2 m 0 I I 0 $1 I N aH L ' .-0 4P .-m e, 0 L8 rr &B Y -0 cd !i .-.-e, Y E EE8 8 n s2 Y v) E *0 sx $2cd 2e, ae c m W Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 2 - An overview of current operational responses to the arsenic issue in South and East Asia Annex 3. OperationalResponsesto Arsenic Contamination: QuestionnaireResults Country: Four countries respondedto the survey: Bangladesh, Cambodia, Nepal, and Pakistan Stateprovince (if applicable): Country national standard for 50 pg L-'for all respondent countries arsenic (pg L-'or ppb): Answer provided by: BRAC, AusAID, FAO, UNICEF, Partners for Development, (Name/institution/address/email) Irrigation Ministryo f Nepal The questionnaire was in two parts. The first part focused on general issues regarding the operational responses towards arsenic contamination, and the second focused on implementation aspects o f these operational responses. The tables below indicate the questions inthe left column, and summarize country responsesinthe right column. Part 1.GeneralIssues Water resources availability and use in the country 1.How much groundwater andsurface water InBangladesh,Nepal, andPakistangroundwater is respectivelyis usedcountrywide for drinking water used first and foremost for irrigation(by a large supply, irrigation andindustry? margin), then for drinking water supply, and finally for industrial purposes. 2. What i s the percentage o f groundwater and Not enough answers to provide any regionwide surface water used inthe rural and inthe urban conclusion. areas respectivelyfor drinking water, industry and irrigation? 3. a) When andbywhat institutiodperson was the Except for Bangladesh, where the first screening first discovery o f arsenic ingroundwater made? was conducted in 1993, the first screenings in b) What are the areas, so far, identifiedandwhat Cambodia, Nepal, and Pakistan were conducted percentage o f the country consists o f these between 1999 and 2000. contaminated areas? Distributiono f contaminated areas within the four countries was as follows: inBangladesh, contamination occurred inthe deltaic areas; in Cambodia, inthe areas close to the Mekong River; inNepal, inthe southernTeraiplain; inPakistan, in the provinces of Punjab and Sind. Regulatory framework 4. I s there a specific national policy, law (or Bangladeshi s ahead o fthe other countries with protocols) regarding arsenic? Ifnot, why not? Ifyes, respect to its national arsenic policy. which institution is responsible to implement these? (Please provide a summaryicopy o f the policyilawiprotocolidecree.) - 123 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 2 -An overview o f current operational responses to the arsenic issue in South and East Asia 5. I s there a groundwater law inthe country? When So far there i s no groundwater law inthe four was it instituted? Ifnot, i s one under development countries. However, Nepal i s inthe process of (law already initiated, law under development, or no reviewing a draft groundwater law, and inPakistan law)? UNICEF and the Ministry o f Environment are planning to initiate one during 2004. 6. I s there a surface water or general water law in Cambodia, Pakistan, andNepal eachhave a surface the country? When was it instituted? Ifnot, i s it water law. InNepal the surface water law was under development (law already initiated, law under institutedin 1992. development, or no law)? 7. I s there a national database on arsenic All four countries have a database. contamination? Ifnot, why? 8. I s contribution to the database enforced by law or Itis voluntary inBangladesh, Nepal, andPakistan, is it voluntary? and mandatory inCambodia as the contributionto the database is a condition for receiving a testing kit from UNICEF and MRD. Mitigation measures 9. When was the first regionwide screening All four countries mark tubewells inthe screening conducted? And whenwas the first nationwide process. InBangladesh, Cambodia, andPakistanthe screening conducted? marking is based on colors, specifically green and Was a systematic marking o f the contaminatedsafe red. InNepal, markings take the form o f either a tubewells/other sources done? How was the cross or a check (4. markingdone? Ifnoscreeningconductedeither regionwide or nationwide, why? 10. Which arsenic-related activities are being Patient care has not been implemented so far in undertaken inyour country? Nepal or Pakistan. 11,To your knowledge, which governmental UNICEF is involvedinthe four countries, in institutionlNGOidevelopmentpartner i s carrying out particular inCambodia and Pakistan. InBangladesh these activities? the number o f stakeholders i s muchhigher than in other countries. The major NGOs inCambodia are RDIandPDF. ~ 12. Are the different actors coordinating these Regardingthe coordinating agencies: there was no activities? Ifyes, by whom and how is it done? consensus inBangladesh; inCambodia, UNICEF i s I s the coordinationeffective? Why? Ifnot, why not? seen as taking this role; and inNepal the National Steering Committee for Arsenic is the coordinating agency. Pakistan has not yet begun a nationwide coordination effort. 13. How many tubewellsiother water supply sources The only country for which the number o f tubewells are there inthe country? i s reportedi s Bangladesh, with about 10million How many tubewellsiother sources are there inthe tubewells. The number o f tubewells i s not reported arsenic-affected areas? inCambodia, Nepal, or Pakistan. How many tubewellsiother sources have been screened? Will allthe tubewellsiother sources be screened in the long term? Ifnot, why not? 14. What i s the tone o f the national media coverage The tone o f the national coverage o f arsenic - 124- Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1 Paper 2 -An overview of current operational - responsesto the arsenic issue in South and East Asia regardingarsenic contamination? contaminationhas beenreportedas: alarmist in Bangladesh andNepal; fact based inPakistan; and nonexistent inCambodia. 15. How would you rate, on a scale from 1to 3, the The arsenic problem i s rated as very important in arsenic problem compared with other problems Bangladesh and Pakistan; and o f medium faced by your country? importance inCambodia andNepal. 16. Which institutioniNGOiinternationa1 UNICEF i s seen as the main driver inaddressing organization is the main driver inaddressing the arsenic issues inboth Cambodia andPakistan; in arsenic issue? How did this institution come to take Nepalit i s the Department of Water Supply and the lead? Sewerage; and inBangladesh several agencies have beenreported as beingthe main drivers: DPHE, DANIDA,UNICEF,andthe WorldBank. 17. When exploring a new source o f water, are there Bangladesh and Cambodia have a standardprotocol standardprotocols about the chemical parameters to for drinkingwater supply. check water quality for drinking water supply, or None o f the four countries seems to have a standard irrigation? protocol for irrigation. 18. I s arsenic one o f the parameters o f these Although arsenic i s a parameter o f the protocol in protocols? Bangladesh and Cambodia and shouldbe a factor in Ifyes, isarsenic occurrence afactor inthe decision the decision as to whether to use the water source, it about the choice o f usingthe water source? And ifit does not seemto be implemented. is detected, what are the actions conducted regardingthis contamination? Part2. Specific Implementationof MitigationMeasures Implementationaspectof mitigationmeasures 19. I s there any monitoring for the Inallfour countries limited or nomonitoringis reported. screened tubewells/other water supply sources? Ifyes what frequency andhow is itdone? Ifnot, why? 20. What method i s usedfor the screening? Fieldtest kits are used for screening inall four countries. (e.g. fieldtest kit, laboratory or both). I s Cross-checking with laboratories i s reported inall countries. cross-checking o f field test and laboratory analysis applied? Ifyes, how i s it done? 21.What are the main problems Ensuringthe effectiveness o f the field test. encountered inthe process o f screening, Limitedcapacity o fgovernment staff. both on the technical and on the institutional side? The transport o f samples from the field to laboratory. 22. Describe the present awareness TV, radio, anddistribution o fprintedmaterial are the media campaign (TV, radio, newspaper, etc.) usedfor the awareness campaign. What are the lessons learned on the best Lessons learned: way to communicate information about arsenic? Use community-specific communication methods, e.g. karaoke (whenapplicable), video. Verbal communicationwith the community i s one o f the most effective means o f communication. - 125 - Arsenic Contaminationof Groundwaterin Southand EastAsian Countries:Volume I1- Paper 2 -An overview of currentoperational responsesto the arsenic issuein Southand EastAsia Mitigation should accompany awareness campaigns as providing an alarmist message without providing a solution i s counterproductive. 23. What mitigation measures are already Screening i s the mitigationmeasure that has beenconducted applied and tested (e.g. dug wellisurface inthe four countries. Sofar, allthemitigation optionshave waterhainwater harvestinglwater been tested inBangladesh. InCambodia dugwells, rainwater treatmeddeep groundwateriothers)? harvesting, community water treatment, and ceramic filters for surface water treatment have beenimplemented. InNepal water treatment at the householdlevelhas beentested on an experimental basis. InPakistandug wells are usedand household-level treatment i s being promoted. 24. H o w are mitigationmeasures (dug InBangladeshandCambodiaallthe implementedmitigation well/surface waterhainwater options are selected at the community level. InNepal harvestinglwatertreatmenudeep screening i s selectedby the central agency and donors, while groundwater/others) selected (e.g. householdwater treatment i s only selectedby donors. In feasibility study, community decision, Pakistan the implementation o f mitigationoptions i s based on central agency)? feasibility studies. ~~ 25. What are the major problems It is difficult to operate the pond sandfilter. encountered inimplementation o f the Itis difficult to make people change behavior andswitch from mitigationmeasures andwhat has tubewells to other water sources. functioned well? The capital cost o f the initial infrastructure for altemative water supply is a problem. Health aspect of the mitigation measures 26. a) Which agencies are responsible for InBangladesh manyagencies areresponsible for arsenic patient identification? identification, namely: Dhaka Community Hospital, upazila b) D othey coordinate their work? health complex at upazila level, and the Ministryo f Health c) Ifyes how i s it done? Ifthe coordination and Family Welfare. InCambodia andNepal it is the Ministry i s not effective what are the reasons? o f Health. InPakistanpatient identificationhas not started yet. d) I s the screening basedon skinlesions or are there measurements(arsenic inhair, InBangladeshthereportedinformationisthatthereisno nail, andblood)? coordination among the agencies, while inCambodia it seems to be coordinated. InCambodiathecoordinationisthroughtheArsenic Interministerial Subcommittee and via UNICEF/WHO assistance. The screening is mainly based on skin lesions inBangladesh, Cambodia, andNepal. InPakistan measurement i s also based on arsenic inthe nail. 27. H o w i s medical management o f InBangladesh itis organized mainlythrough government arsenicosis patients organized? hospitals, DCH, andUNICEF. Inaddition, through the What i s the procedure for monitoring financial assistance o fBAMWSP, D C H trained doctors inthe patients? identification and management o f arsenicosis patients. None o f the countries reported any procedure for monitoring patients. 28. What i s the current estimate o f the For Bangladeshthe range i s from 13,000 to more than 19,000 number o f patients with arsenicosis? What arsenicosis patients. InPakistan, there are approximately 140 i s the current estimate o fthe population at arsenicosis cases per 100,000 people inPunjab. It is reported risk? that no patients have been identified as yet inCambodia. Arsenic Contaminationof Groundwaterin Southand EastAsian Countries: Volume I1 Paper 2 -An overview of currentoperational - responsesto the arsenic issuein South and EastAsia Research aspects of arsenic contamination 29. I s there any researchdone inyour There seems to be a lot o f research in both Bangladesh and countryistateiprovince on the origin of the Cambodia involvingboth local and foreign research arsenic inthe sediment, its release to the institutions. Small-scale research inNepal has beenreported groundwater, and the migration with the with involvement ofthe USGS.N oresearchhas beenreported groundwater flow? in Pakistan. Ifyes, what institutionsareinvolved: local universities, local researchinstitutes, government agencies, foreign universities, foreign research institutes, NGOs, etc.? 30. I s there any outcome o fresearch on W h i l e Bangladeshi s the only country where research on arsenic accumulationinthe food chain? arsenic accumulation has beenreported, no conclusions as yet are available. ~~ 31. I s there national quality control o f Nepali s the only country where there i s national control o f laboratories? laboratories. Ifyes,howisitconducted(frequency, InNepal, the Department ofMeteorology andStandards methodology, responsible institution, etc.)? accredits the private laboratories; however, this is not mandatory and i s done on a voluntary basis. Economic aspect of the mitigation measures 32. What is the cost o f eachmitigation Bangladesh i s the only country where most of the costs are measure? How many people were served? available. These costs are summarizedinthe table at the end o f this annex. IInthe case ofPakistanthe following lumpsumwas provided: (Pitcher + awareness raising +testing - . &marking)/HH =Rs 1,500. 33. Ingeneral, inyour opinion, what are the main lessons leamed onthe operationalresponses that have been conducted? Social It is possible to train female village volunteers to test the tubewells for arsenic. Local women with limitededucational background can also be trained onpreliminary identification o f arsenicosis patients, awareness education, alternative water supply, and monitoring o f these options. Community needs to be mobilized inarsenic mitigation. There i s no unique solution because o ftechnical limitations and cultural acceptance o f mitigation options. Communication o f arsenic issues to private individuals installing tubewells is a challenge. Technical Local mason canbe trained inthe constructionand manufacture o f different mitigation options. Monitoring o f safe water options for arsenic and bacteria (when applied, e.g. for surface water) as well as for other potential contaminants. Since there is so far no treatment for arsenicosis, there i s a needto provide arsenic patients with safe water for drinking and cooking purposes. Muchresearchis neededto fiid out effective treatment regimens for patients indifferent stages o f arsenicosis. Many treatment units, either home based or community based, produce sludge that contains a high concentration o f arsenic. A countrywide proper management system for this sludge should be set up so that ruralpeople canmanage this sludge ina convenient way. Economic - 127 - Arsenic Contaminationof Groundwater in South and EastAsian Countries:Volume I1 Paper2 - An overview of currentoperational - responsesto the arsenic issue in SouthandEastAsia ~ Need low-cost solutions. Needfor fee collectionto cover ongoingmaintenance issues. Institutional Set a priority to implementmitigationoptions inthe most-affectedvillages. There shouldbe more coordinationamong differentgovernmentalandnongovernmentalagencies working inthe country. The longer-termsolutionsmust be based on a long-termvision. This may includethe provision ofpiped water supplyto its populationandthe optimumuse of its surface water. The potentialrole that the local governments canplay inthis longervision mustbe fully explored; towardsthis, experimentationandpilot projectsshouldnot wait. Standardizedfield testing and data management are needed. Government needs to be inthe driver's seat inscreening andimplementingmitigation options. I s h : Costs of MitigationMeasures(Response to Questionnaire Item32) Cost per unit (taka) I Number of peopleserved I Tk 30 (total cost Tk 3,000) 100households Screeningwith laboratory Tk 500by AAS analysis Tk 300by spectrometer 1 Awareness campaign Tk 1,500 pervillage meeting 1 100households I Dug well New: Tk 40,00G50,000 40-50 households (Renovation: Tk 10,000 average) Tk 35,00040,000 20-30 families comprising5 members ~~ Pondsand filter Tk 50,000-60,000 50-70 households Tk 30,00040,000 20-30 families comprising5 members Rainwaterharvesting Tk 10,000-12,000 (3,200 liters) 1household Tk 8,000 (3,200 liters) 1family comprising5 members Deep groundwater Tk 40,000 average 50-60 households Tk 35,00040,000 20-30 families comprising5 members Householdtreatment Dependsonthe water treatment I Communitytreatment I I Depends onthe water treatment - 128 - -+P f .I % Hel I 4 aN N .I I b e B I .-C .-00 C v: D I w Y, a I 0 m 3 I 1 I +I m + I N .d 8 8 VI 8 .-C .-0E d -L . 2 1 a Bn 4d 40 &' M -A 2 0 2 I m V m + I N a- .% c N w3 1 - - I I I I Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 2 -An overview of cunent operational responses to the arsenic issue in South and East Asia References Ahmed, M. F. 2003. Arsenic Contamination: Bangladesh Perspective. Bangladesh University of Engineering & Technology. ITN-Bangladesh. Alaerts, G. J. and N. Khouri. 2004. "Arsenic Contamination of Groundwater: Mitigation Strategies and Policies." Hydrogeology Journal 12:103-1 14. Alam, M. G. M., E. T. Snow, and A. Tanaka. 2003. "Arsenic and Heavy Metal Contamination of VegetablesGrown inSamtaVillage, Bangladesh." The Science of the Total Environment 308:83-96. APSU (Arsenic Policy SupportUnit).2004. RiskAssessment of Arsenic Mitigation Options -Phase I. Dhaka, Governmentof Bangladesh. ATSDR (Agency for Toxic Substances and Disease Registry). 2002. Toxicological Projle for Arsenic. www.atsdr.cdc.gov/toxprofiles/tp2.htmlandwww.atsdr.cdc.gov/toxprofilesltp2-c2.pdf. Bae, M., C. Watanabe, T. Inaoka, M. Sekiyama, N. Sudo, M. H. Bokul, and R. Ohtsuka. 2002. "Arsenic inCookedRice inBangladesh." TheLancet 360. Bates, M.N., A. H. Smith, and K. P. Cantor. 1995. "Case-Control Study of Bladder Cancer and Arsenic inDrinkingWater." Am. J.Epidemiol. 141:523-30. Berg, M., H. C. Tran, T. C. Nguyen, H. V. Pham, R. Schertenleib, and W. Giger. 2001. "Arsenic Contamination of Groundwater and Drinking Water in Vietnam: A Human Health Threat." Environmental Science & Technology 35:2621-2626. Bhattacharya,P. 2002. "Arsenic ContaminatedGroundwater fromthe SedimentaryAquifers of South- East Asia." In: D. Bocanegra, H. Martinez, and E. Massones, eds., Groundwater and Human Development 357-363. Proc. XXXII IAH and VI ALHSUD Congress, Mar del Plata, Argentina, 2002. www.lwr.kth.selPersonallpersoner/bhattacharya.pros~Mardelplata.pdf. BRAC (BangladeshRural Action Committee). 2000. Combating a Deadly Menace, Early Experience with a Community-Based Arsenic Mitigation Project in Bangladesh. ResearchMonograph Series No. 16. BRAC, ResearchandEvaluation Division, Dhaka, Bangladesh. Chaudhury, N. and J. S. Hammer. 2003. Absenteeism in Bangladesh Health Facilities. Policy ResearchWorking Paper WSP 3065. Water and SanitationProgram. Chiou, H.Y., W. I.Huang, C. L. Su, S. F. Chang, Y. H. Hsu, and C. J. Chen. 1997. "Dose-Response RelationshipbetweenPrevalence of CerebrovascularDisease and IngestedInorganic Arsenic." Stroke 28:1717-23. Das, H. K., A. K. Mitra, P. K. Sengupta, A. Hossain, F. Islam, and G. H. Rabbani. 2004. "Arsenic Concentration in Rice, Vegetables, and Fish in Bangladesh: A Preliminary Study." Environment International 30:383-387. Del Razo, L. M., G. G. Garcia-Vargas, J. Garcia-Saicedo, M. F. Sanmiguel, M. Rivera, M. C. Hernandez, and M. E. Cebrian. 2002. "Arsenic Levels in Cooked Food and Assessment of Adult Dietary Intake of Arsenic in the Region of Lagunera, Mexico." Food and Chemical Toxicology 40:1423-143 1. Devesa, V., A. Martinez, M.A. Suner, V. Benito, D.Velez, and R. Montoro. 2001. "Kinetic Study of Transformation of Arsenic Species during Heat Treatment." Journal of Agricultural and Food Chemistry 49:2267-2271. Engel, R. R. and A. H. Smith. 1994. "Arsenic in Drinking Water and Mortality from Vascular Disease: An Ecological Analysis in 30 Counties inthe United States." Arch. Environ. Health 49:418- 427. EPA (Environmental Protection Agency, United States). 1988. Special Report on Ingested Inorganic Arsenic. Skin Cancer; Nutritional Essentiality. EPA, Washington, D.C. - 137- Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1-Paper 2 -An overview of current operational responses to the arsenic issue in South and East Asia Ferreccio, C., C. Gonzalez, V. Milosavjlevic, G. Marshall, A. M. Sancha, and A. H. Smith. 2000. "Lung Cancer andArsenic ConcentrationsinDrinkingWater inChile." Epidemiology 11:673-679. Friberg, L.,G. F.Nordberg, and V. B.Vouk. 1986.Handbook on the Toxicology of Metals Volume 11. Hadi, A. 2003. "Fighting Arsenic at the Grassroots: Experience of BRAC's Community Awareness InitiativeinBangladesh." Health Policy and Planning 18(1):93-100. Hanchett, S., Q.Nahar, A. Van Agthoven, C. Geers, and F. J. Revzi. 2002. "Increasing Awareness of Arsenic in Bangladesh: Lessons from a Public Education Programme." Health Policy and Planning 17(4):393-401. Hoque, B.A., A. A. Mahmood, M. Quadimzzaman, F. Khan, S. A. Ahmed, S. Shafique, M.Rahman, G. Morshed, T. Chowdhury, M. M. Rahman, F. H. Khan, M. Shahjahan, M. Begum, and M. M. Hoque. 2000. "Recommendation for Water Supply in Arsenic Mitigation: A Case Study from Bangladesh." Public Health 114:488-494. Hossain, Z., M. Rahman, and M. Jakariya. I n Search of Safe Water: People's Responses to Various Safe Water Devices in Arsenic Affected Bangladesh. Abstract. www.brac.net/red-abs-env.html. International Water Resources Association. 2001. "Extent and Severity of Groundwater Arsenic ContaminationinBangladesh." Water International 26(3):370-379. InVS (Institut de veille sanitaire). 2002. Exposition chronique ci 1'arsenic hydrique en Auvergne: &valuation des risques sanitaires. Institut de veille sanitaire et Ministbre de la santC, de la famille et des personneshandicapees. Jakaria, M. 2003. The Use of Alternative Safe Water Options to Mitigate the Arsenic Problem in Bangladesh: Community Perspective. Research Monograph Series No. 24. BRAC, Research and Evaluation Division, Dhaka, Bangladesh. Kaufinann, R. B., B. H. Sorensen, M. Rahman, K. Streatfield, and L.A. Persson. 2001. Addressing the Public Health Crisis Caused by Arsenic Contamination of Drinking Water in Bangladesh. World Bank. Kinniburgh, D. G. and W. Kosmus. 2002. "Arsenic Contamination in Groundwater: Some Analytical Considerations." Talanta 58:165-1 80. Mandal, B.K.and K.T. Suzuki.2002. "Arsenic Roundthe World: A Review." Talanta 58:201-235. Masud, K. 2000. "Arsenic in Groundwater and Health Problems in Bangladesh." Water Resources 34(1):304-3 10. NAISU(NGOs Arsenic Information and Support Unit). 2002. An Overview of Arsenic Issues and Mitigation Initiatives in Bangladesh. NGO Forumfor DrinkingWater Supply and Sanitation. Ng, J. C., J. Wang, and A. Shraim. 2003. "A Global Health Problem Causedby Arsenic from Natural Sources." Chemosphere 52:1353-1 359. NRC (National ResearchCouncil, UnitedStates). 1999.Arsenic in Drinking Water.NRC. Rahman, M. M., D. Mukherjee, M.K. Sengupta, U.K. Chowdhury, D. Lodh, C. R. Chanda, S. Roy, Q. Quamruzzaman, A. H. Milton, S. M. Shahidullah, T. Rahman, and D. Chakraboti. 2002. "Effectiveness and Reliability of Arsenic Field Testing Kits: Are the Million Dollar Screening ProjectsEffective or Not?" Environ. Scien. & Technol. 36(24):5385-94. Roychowdhury, T., H.Tokunaga, and M.Ando. 2003. "Survey of Arsenic and Other Heavy Metals in Food Composites and Drinlung Water and Estimating of Dietary Intake by the Villagers from the Arsenic-Affected Area of West Bengal, India." TheScience of the TotalEnvironment 308:15-35. Roychowdhury, T., T. Uchino, H. Tokunaga, and M. Ando. 2002. "Survey o f Arsenic in Food Composites from an Arsenic-Affected Area of West Bengal, India." Food and Chemical Toxicology 40:1611-1621. - 138 - Arsenic Contamination o f Groundwater in SouthandEast Asian Countries: Volume I1 Paper 2 -An overview of current operational - responsesto the arsenic issue in South and East Asia Smedley, P. L. and D. G. Kinniburgh. 2002. "A Review of the Source, Behaviour and Distribution of Arsenic inNatural Waters." Applied Geochemistry 17517-568. Smith, A. H., E. 0.Lingas, and M.Rahman. 2000. "Contamination of Drinking-Water by Arsenic in Bangladesh: A Public HealthEmergency." Bulletin of the WorldHealth Organization 78:9. Smith, A. H., P. A. Lopipero, M.N.Bates, and C. M.Steinmaus. 2002. "Arsenic Epidemiology and DrinkingWater Standards." Science296:2145-2146. ehs.sph.berkeley.eddsuper~ndipublications/O2~smith~l .pdf. UNICEF (United Nations Children's Fund). 2002. Mitigation of Arsenic Contamination in Drinking Water Sources of Myanmar: A Proposed Plan of Action. UNICEF. Warren, G.P., B. J. Alloway, N.W. Lepp, B. Singh, F. J. M.Bochereau, and C. Penny. 2003. "Field Trials to Assess the Uptake of Arsenic by Vegetables from Contaminated Soils and Soil Remediation with IronOxides." TheScience of the TotalEnvironment 311:19-33. WHO (World Health Organization). 2001a. Arsenic Contamination in Groundwater Afecting Some Countries in South-East Asia Region. WHO Regional Committee, South-East Asia Region. WHO (World Health Organization). 2001b. Environmental Health Criteria 224, Arsenic and Arsenic Compounds. SecondEdition. WHO, Geneva. World Bank.2003a. WorldDevelopment Indicators. www.worldbank.orgldata/. World Bank. 2003b. Technical Support to World Bank Urban and Water Supply Unit, Hanoi, Vietnam. Water Supply Project CR N-26-VN-ID 4830. WSP (Water and Sanitation Program). 2000. The West Bengal Pilot Project: Responding to Community Demandsfor Safe Drinking Water in an Arsenic Affected Area. Fieldnote.WSP. WSP (Water and SanitationProgram). 2003. Fighting Arsenic, Listening to Rural Communities. Field note presenting findings from a study on willingness to pay for arsenic-free, safe drinking water in malBangladesh. Yu, W., C. M. Harvey, and C. F. Harvey. 2003. "Arsenic in Groundwater in Bangladesh: A Geostatisticaland Epidemiological Framework for Evaluating HealthEffect and Potential Remedies." Water ResourcesResearch 39:6. - 139- Paper 3 Arsenic MitigationTechnologies inSouthandEastAsia This paper was preparedby Professor Feroze Ahmed (Bangladesh University of Engineering andTechnology) with contributions from KhawajaMinnatullah (World Bank/WSP) and Amal Talbi (World Bank). Arsenic Contamination of Groundwater inSouth and East Asian Countries: Volume I1-Paper 3 -Arsenic Mitigation Technologies in South and East Asia Summary 1. This paper presents the technologies for treatment o f arsenic-contaminated water, arsenic detection and measurement technologies, and alternative safe water options. After a brief introduction (chapter l), 2 examines the principles o f arsenic removal from h n k i n g chapter water and explores the major technologies associated with each. Chapter 3 describes the laboratory and field methods o f arsenic detection and measurement. Chapter 4 presents alternative options for arsenic-safe water supplies.Chapter 5 analyzes some operational issues related to the mitigationoptions presented inthe paper. 11. The objective o f the paper is to provide technical staff in govemments, development organizations, nongovernmental organizations and other interested stakeholders with up-to- date information on the technical aspects o f arsenic mitigation in order to familiarize them with the most commonly used mitigation methods. For treatment o f arsenic-contaminated water, there are four basic processes: (a) oxidation-sedimentation; (b) coagulation- sedimentation-filtration; (c) sorptive filtration; and (d) membrane techniques. For alternative water supply options, there are four main options: (a) use o f an alternative safe aquifer, accessedby a deep tubewell or dug well; (b) use o f surface water employing, for example, a pond sandfilter or multistage filters; (c) use o f rainwater; and (d) piped water supplybased on either ground or surface water. ... 111. The paper is designed as a tool to inform the decisionmaking process when deciding which arsenic mitigation option i s best suited to a particular project. It lays out the advantages and disadvantages o f each mitigationmethod, and the related operational issues. - 141- Arsenic Contaminationof Groundwaterin South andEast Asian Countries:Volume I1-Paper 3 -Arsenic Mitigation TechnologiesinSouthandEast Asia 1. Introduction Arsenic is present in the environment and humans all over the world are exposed to small amounts, mostly through food, water, and air. But the presence o f high levels o f arsenic in groundwater, the main source o f drlnking water in many countries around the world, has drawn the attention o f the scientific community. Groundwater, free from pathogenic microorganisms and available in adequate quantity via tubewells sunk in shallow aquifers in the flood plains, provides low-cost dnnking water to scattered rural populations. Unfortunately, millions are exposed to high levels o f inorganic arsenic through drinking this water. Ithas become a major public health problem inmany countries in South and East Asia and a great burdenon water supply authorities. Treatment o f arsenic contamination of water, in contrast to that of many other impurities, is difficult, particularly for rural households supplied with scattered handpump tubewells. In developing countries like Bangladesh and India the highprevalence o f contamination, the isolation and poverty o f the rural population, and the high cost and complexity o f arsenic removal systems have imposed a programmatic andpolicy challenge on anunprecedented scale. Source substitution is often considered more feasible than arsenic removal. The use o f alternative sources requires a major technological shift inwater supply. Treatment o f arsenic- contaminated water for the removal o f arsenic to an acceptable level is one o f the options for safe water supply. Since the detection o f arsenic in groundwater, a lot o f effort has been mobilized for treatment o f arsenic-contaminated water to make it safe for dnnking. Duringthe last few years many arsenic detection and test methods and small-scale arsenic removal technologies have been developed, field-tested, and used under different programs in developing countries. This short review o f these technologies is intended as an update o f the technological developments inarsenic testing, arsenic removal, and alternative water supplies. It is hoped that the review will be of assistance to those involved in arsenic mitigation in South and East Asian countries. - 142- Arsenic Contamination of Groundwater inSouth and East Asian Countries: Volume I1-Paper 3 -Arsenic Mitigation Technologies in South and East Asia 2. Treatment of Arsenic-ContaminatedWater Arsenic ingroundwater is present mainly innonionic trivalent (As(II1)) and ionic pentavalent (As(V)) inorganic forms indifferent proportions depending on the environmental conditions o f the aquifer. The solubility o f arsenic inwater is usually controlled by redox conditions, pH, biological activity, and adsorption reactions. The reducing condition at low Ehvalue converts arsenic into a more mobile As(II1) form, whereas at highEh value As(V) is the major arsenic species. As(II1) is more toxic than As(V) and difficult to remove from water by most techniques. There are several methods available for removal o f arsenic from water in large conventional treatment plants. The most commonly used processes o f arsenic removal from water have been described by Cheng and others (1994), Hering and others (1996), Hering and others (1997), Kartinenand Martin (1995), Shen (1973), and Joshi and Chaudhuri (1996). A detailed review o f arsenic removal technologies has been presented by Sorg and Logsdon (1978). Jekel(l994) has documented several advances inarsenic removal technologies. Inview o f the lowering o f the standard o f the UnitedStates Environmental Protection Agency (EPA) for the maximum permissible levels of arsenic in W i n g water, a review o f arsenic removal technologies was carried out to consider the economic factors involved inimplementing more stringent drinking water standards for arsenic (Chen and others 1999). Many o f the arsenic removal technologies have been discussed indetails inthe AWWA (American Water Works Association) reference book (Pontius 1990). A review o f low-cost well water treatment technologies for arsenic removal, with a list o f companies and organizations involved in arsenic removal technologies, has been compiled by Murcott (2000). Comprehensive reviews o f arsenic removal processes have been documented by Ahmed, Ali, and Adeel (2001), Johnston, Heijnen, and Wurzel (2000), and Ahmed (2003). The AWWA conducted a comprehensive study on arsenic treatability options and evaluation o f residuals management issues (AWWA 1999). The basic principles o f arsenic removal from water are based on conventional techniques o f oxidation, coprecipitation and adsorption on coagulated flocs, adsorption onto sorptive media, ion exchange, and membrane filtration. Oxidation o f As(II1) to A s 0 i s needed for effective removal o f arsenic from groundwater by most treatment methods. The most common arsenic removal technologies canbe grouped into the following four categories: Oxidation and sedimentation 0 Coagulation and filtration Sorptive filtration 0 Membrane filtration The principal mechanisms and technologies for arsenic removalusingthe above technological options are described indetail inthe following sections. Oxidation-Sedimentation Processes Most treatment methods are effective in removing arsenic in pentavalent form and hence include an oxidation step as pretreatment to convert arsenite to arsenate. Arsenite can be oxidized by oxygen, ozone, free chlorine, hypochlorite, permanganate, hydrogen peroxide, and Fulton's reagent, but atmospheric oxygen, hypochloride, and permanganate are commonly used for oxidation in developing countries. The oxidation processes convert predominantly noncharged arsenite to charged arsenate, which can be easily removed from water. Atmospheric oxygen is the most readily available oxidizing agent and many treatment presses prefer oxidation by air. But air oxidation o f arsenic is a very slow process and it can take weeks for oxidation to occur (Pierce and Moore 1982). Air oxidation o f arsenite can be - 143 - Arsenic Contaminationof Groundwater in SouthandEast Asian Countries:Volume I1-Paper 3 -Arsenic Mitigation Technologiesin SouthandEastAsia catalyzed by bacteria, strong acidic or alkali solutions, copper, powdered activated carbon, and high temperature (Edwards 1994). Chemicals such as chlorine and permanganate can rapidly oxidize arsenite to arsenateunder a wide range o f conditions. Hypochloride is readily available in rural areas but the potency (available chlorine) o f the hypochloride decreases when it i s poorly stored. Potassium permanganate is also readily available in developing countries. I t is more stable than bleaching powder and has a long shelf life. Ozone and hydrogen peroxide are very effective oxidants but their use indeveloping countries is limited. Filtration o f water through a bed containing solid manganese oxides can rapidly oxidize arsenic without releasing excessive manganeseinto the filtered water. In situ oxidation of arsenic and iron inthe aquifer has been tried in Bangladesh under the Arsenic Mitigation Pilot Project o f the Department o f Public Health Engineering (DPHE) and the Danish Agency for International Development (Danida). The aerated tubewell water is stored infeed water tanks and releasedback into the aquifers through the tubewell by opening a valve in a pipe connecting the water tank to the tubewell pipe under the pump head. The dissolved oxygen inwater oxidizes arsenite to less-mobile arsenate and the ferrous iron inthe aquifer to ferric iron, resulting in a reduction o f the arsenic content in tubewell water. Experimental results show that arsenic in the tubewell water following in situ oxidation is reduced to about half due to underground precipitation and adsorption on ferric iron. The method is chemical free and simple and is likely to be accepted by the people but the method i s unable to reduce arsenic content to an acceptable level when arsenic content ingroundwater is high. Chlorine and potassium permanganate are used for oxidation o f As(II1) to As(V) in many treatment processes in Bangladesh and India. SORAS (solar oxidation and removal o f arsenic) is a simple method o f solar oxidation o f arsenic in transparent bottles to reduce arsenic content o f drlnking water (Wegelin and others 2000). Ultraviolet radiation can catalyze the process o f oxidation o f arsenite inthe presence o f other oxidants such as oxygen (Young 1996). Experiments in Bangladesh show that the process on average can reduce the arsenic content o f water to about one-third o f the original concentration. As a process, passive sedimentation has received considerable attention because of rural people's habit o f drlnking stored water fkom pitchers. Oxidation o f water during collection and subsequent storage in houses may cause a reduction in arsenic concentration in stored water. Experiments conducted inBangladesh showed zero to high reductions in arsenic fkom drinking water by passive sedimentation. Arsenic reduction by plain sedimentation appears to be dependent on water quality and in particular the presence of alkalinity and precipitating iron in water. Passive sedimentation, in most cases, failed to reduce arsenic to the desired level o f 50 pgL-'ina rapid assessment o f technologies conducted inBangladesh(BAMWSP- DFID-WaterAid 2001). 2.2 Coagulation-Sedimentation-Filtration Processes Intheprocess ofcoagulationandflocculation, arsenic is removed from solution through three mechanisms: 0 Precipitation: The formation o f insoluble compounds Coprecipitation: The incorporation o f soluble arsenic species into a growing metal hydroxide phase Adsorption: The electrostatic binding o f soluble arsenic to external surfaces o fthe insoluble metal hydroxide (Edwards 1994) Precipitation, coprecipitation, and adsorption by coagulation with metal salts and lime followed by filtration i s a well-documented method o f arsenic removal from water. This method can effectively remove arsenic and many other suspended and dissolved solids from water, including iron, manganese, phosphate, fluoride, and microorganisms, reducing turbidity, color, and odor and resulting in a significant improvement in water quality. Thus - 144- Arsenic Contamination of Groundwater inSouth and East Asian Countries: Volume I1-Paper 3 -Arsenic Mitigation Technologies in South and East Asia removal o f arsenic from water using this method is associated with other ancillary health and aesthetic benefits. Water treatment with coagulants such as aluminium alum (A12(S04)3.18H20),ferric chloride (FeC13), and ferric sulfate (Fe2(S04)3.7H20)is effective in removing arsenic from water. Oxidation o f As(II1) to As(V) is required as a pretreatment for efficient removal. It has been suggested that preformed hydroxides o f iron and aluminium remove arsenic through adsorption, while in situ formation leads to coprecipitation as well (Edwards 1994). In alum coagulation the removal is most effective in the pH range 7.2-7.5, and in iron coagulation efficient removal i s achieved in a wider pH range, usually between 6.0 and 8.5 (Ahmed and Rahaman2000). The effects of cations and anions are very important in arsenic removal by coagulation. Anions compete with arsenic for sorptive sites and lower the removal rates. Manning and Goldberg (1996) indicated the theoretical affinity at neutral pH for anion sorption on metal oxides as: PO, > Se03>As04>As03>> SiO, > SO2>F> B(OH)3 The presence o f more than one anion can have a synergistic effect on arsenic removal. Addition o f either silicate or phosphate has some effects on arsenic removal but presence o f both can reduce arsenate removal by 39% and arsenite removal by 69% (Meng, Bang, and Korfiatis 2000). Based on arsenic removal studies in Bangladesh, Meng and Korfiatis (2001) concluded that elevated levels o f phosphate and silicate in Bangladesh well water dramatically decreased adsorption o f arsenic by ferric hydroxides. The technologies developed based on the coagulation-sedimentation-filtration process include: 0 Bucket treatment unit StevensInstitute technology 0 Filland draw treatment unit 0 Tubewell-attached arsenic treatment unit 0 Iron-arsenic treatment unit The bucket treatment unit, developed by the DPHE-Danida Project and improved by the Bangladesh University o f Engineering and Technology (BUET), is based on coagulation, coprecipitation, and adsorption processes. It consists o f two buckets, each with a capacity o f 20 liters, placed one above the other. Chemicals are mixed manually with arsenic- contaminated water in the upper redbucket by vigorous stirring with a wooden stick and then flocculated by gentle stirring for about 90 seconds. The mixed water is allowed to settle and then flow into the lower green bucket and water is collected through a sand filter installed in the lower bucket. The modified bucket treatment unit shown in figure 1has been found to be very effective inremoving iron, manganese, phosphate, and silica along with arsenic. The Stevens Institute technology also uses two buckets, one to mix chemicals (iron coagulant and hypochloride) supplied inpackets and the other to separate flocs using the processes o f sedimentation and filtration (figure 2). The second bucket has an inner bucket with slits on the sides to help sedimentation and keep the filter sand bed in place. The chemicals form visible large flocs when mixed (by stirring with a stick). Clean water is collected through a plastic pipe fittedwith an outlet covered with a cloth filter to prevent the entry o f sand. The fill and draw system i s a community-level treatment unit designed and installed under the DPHE-Danida Project. I t has a 600 liter capacity (effective) tank with a slightly tapered bottom for collection and withdrawal o f settled sludge (figure 3). The tank is fitted with a manually operated mixer with flat blade impellers. The tank is filled with arsenic- contaminated water and the requiredquantity o f oxidant and coagulant are added to the water. The water is then mixed for 30 seconds by rotating the mixing device at the rate o f 60 revolutions per minute (rpm) and left ovemight for sedimentation. The settled water is then - 145 - Arsenic Contaminationo f Groundwater in South andEast Asian Countries:Volume I1- Paper 3 -Arsenic Mitigation Technologies in South andEast Asia drawn through a pipe fitted at a level a few inches above the bottom o f the tank and passed through a sand bed, and i s finally collected through a tap for drinking. The mixing and flocculation processes in this unit are better controlled to effect higher removal o f arsenic. The experimental units installedby the DPHE-Danida project are serving clusters o f families and educational institutions. Figure 1.Double Bucket Household Arsenic Treatment Unit (Ali and Others, 2001) Figure 2. StevensInstitute Technology (Drawn by Ahmed, 2003) Transferof chemical Chemic r Mixing Mainbucket stick Interior bucki Slits Outlet with cloth filter Plastic pipets deliver treate water Figure 3. DPHE-Danida Filland Draw Arsenic Removal Unit (Drawn by Ahmed, 2003) Gear svstem\ The tubewell-attached arsenic removal unit was designed and installed by the All India Institute o f Hygiene and Public Health (AIIH&PH) (figure 4). The principles o f arsenic removal by alum coagulation, sedimentation, and filtration have been employed in this compact unit for water treatment at the village level in West Bengal, India. The arsenic removal plant, attached to a handpump-operated tubewell, has been found effective in removing 90% o f the arsenic from tubewell water. The treatment process involves the addition o f sodium hypochloride (Cl,) and aluminium alum in diluted form, mixing, flocculation, sedimentation, and upflow filtration ina compact unit. -146 - Arsenic Contamination o f Groundwater in South and East Asian Countries: Volume I1-Paper 3 -Arsenic Mitigation Technologies in South and East Asia Figure 4. Tubewell-Attached Arsenic RemovalUnit (Ahmed and Rahman, 2000) I A A Mixing:B Flocculation; C Sedimentation:D - Filtration(upflow) - 1 ~ ~ Iron-arsenic removal plants use naturally occurring iron, which precipitates on oxidation and removes arsenic by adsorption. Several models o f iron-arsenic removal plants have been designed and installed in Bangladesh. A study suggests that As(II1) is oxidized to A s 0 in the plants, facilitating arsenic removal (Dahi and Liang 1998). The iron-arsenic removal relationship with good correlation in some operating iron-arsenic removal plants has been plotted in figure 5. Results shows that most iron removal plants can lower arsenic content o f tubewell water to halfto one-fifth o f the original concentration. The main problem is to keep the community system operational throughregular washing ofthe filter bed. Figure 5. Correlationbetween Iron and Arsenic Removalin Treatment Plants (Dhai and Liang, 1998) 1w2 0.8718~+0.4547 *I F?=O.6911 / * I 20 30 40 50 0 70 80 90 100 IronRemoMl,% I Some medium-scale iron-arsenic removal plants with capacities o f 2,000-3,000 m' day-' have been constructed for water supplies in district towns in Bangladesh. The main treatment processesinvolve aeration, sedimentation, andrapid sand filtration with provisionfor addition o f chemicals ifrequired. The units operating on natural iron content o f water have efficiencies varying between 40% and 80%. These plants are working well except that the water requirement for washing the filter beds is very high. Operations o f small and medium-sized iron-arsenic removalplants inBangladesh suggest that arsenic removalby coprecipitation and adsorption on natural iron flocs has goodpotential for arsenic content up to about 100 pug L-I. Water treatment by the addition o f quick lime (CaO) or hydrated lime (Ca(OH)*) also removes arsenic. Lime treatment is a process similar to coagulation with metal salts. The precipitated calcium hydroxide (Ca(OH)*) acts as a sorbing flocculent for arsenic. Excess lime will not dissolve but remains as a thickener and coagulant aid that has to be removed - 147 - Arsenic Contaminationof Groundwater in SouthandEastAsian Countries:Volume I1- Paper 3 -Arsenic Mitigation Technologies in SouthandEast Asia along with precipitates through sedimentation and filtration processes. It has generally been observed that arsenic removal by lime is relatively low, usually between 40% and 70%. The highest removal is achieved at pH 10.6 to 11.4. McNeill and Edward (1997) studied arsenic removalby softening and found that the main mechanism o f arsenic removal was sorption o f arsenic onto magnesium hydroxide solids that form during softening. Trace levels o f phosphate were found to slightly reduce arsenic removal below pH 12 while arsenic removal efficiency at lower pH can be increased by the addition o f a small amount o f iron. The disadvantage o f arsenic removal by lime is that it requires large lime doses, in the order o f 800-1,200 mg L-',and consequently a large volume o f sludge is produced. Water treated by lime would require secondary treatment in order to adjust pH to an acceptable level. Lime softening may be used as a pretreatment to be followed by alum or iron coagulation. 2.3 Sorptive Filtration Several sorptive media have been reported to remove arsenic from water. These are activated alumina, activated carbon, iron- and manganese-coated sand, kaolinite clay, hydrated ferric oxide, activated bauxite, titanium oxide, cerium oxide, silicium oxide, and many natural and synthetic media. The efficiency o f sorptive media depends on the use o f an oxidizing agent as an aid to sorption o f arsenic. Saturation of media by different contaminants and components o f water takes place at different stages o f the operation, depending on the specific sorption affinity o f the medium to the given component. Saturation means that the sorptive sites o f the mediumhave been exhausted and the medium is no longer able to remove the impurities. The most commonly used media for arsenic removal insmall treatment plants include: 0 Activated alumina 0 Granulated ferric oxide andhydroxide Metallic iron 0 Iron-coated sand or brick dust 0 Cerium oxide 0 Ion exchange media Arsenic removal by activated alumina is controlled by the pH and arsenic content o f water. Arsenic removal is optimum in the narrow pH range from 5.5 to 6.0 when the surface is positively charged. The efficiency drops as the point o f zero charge is approached and at pH 8.2, where the surface is negatively charged, the removal capacities are only 2-5% o f the capacity at optimal pH (Clifford 1999). The number o f bed volumes that can be treated at optimum pHbefore breakthrough is dependent on the influent arsenic concentration. The bed volume can be estimated using the following equation, where As is the initial arsenic concentration inwater inmicrograms per liter (Ghurye, Clifford, and Tripp 1999): Bedvolume = 210,000 The actual bed volume is much lower due to the presence o f other competing ions innatural water. Arsenic removal capacities o f activated alumina have been reported to vary from 1m g g" to 4 m g g-' (Fox 1989; Gupta and Chen 1978). Clifford (1999) reported the selectivity o f activated alumina as: Regeneration o f saturated alumina is carried out by exposing the medium to 4% caustic soda (NaOH), either inbatch or by flow through the columnresulting inhigh-arsenic-contaminated caustic waste water. The residual caustic soda is then washed out and the medium is neutralized with a 2% solution o f sulfuric acid rinse. During the process about 5-10% o f the alumina is lost and the capacity o f the regenerated medium is reduced by 3040%. The activated alumina needs replacement after 3 4 regenerations. As with the coagulation process, - 148- Arsenic Contaminationof Groundwater in South and East Asian Countries:Volume I1- Paper 3 -Arsenic Mitigation TechnologiesinSouth andEast Asia prechlorination improves the column capacity dramatically. The activated alumina-based sorptive mediaused inBangladesh and India include: BUETactivated alumina 0 Alcan enhancedactivated alumina Apyron arsenic treatment unit Oxide (India) Pvt.Ltd. RPMMarketingPvt. Ltd. Arsenic is removed by sorptive filtration through activated alumina. Some units use pretreatment (for example oxidation, sand filtration) to increase efficiency. The Alcan enhanced activated alumina arrangement is shown attached to a tubewell in figure 6. The unit i s simple and robust in design. No chemicals are added during treatment and the process wholly relies on the active surface o f the media for adsorption o f arsenic from water. Other ions present in natural water, such as iron and phosphate, may compete for active sites on alumina and reduce the arsenic removal capacity o f the unit.Iron present in shallow tubewell water at elevated levels will eventually accumulate in an activated alumina bed and interfere with flow o f water through the bed. The unit can produce more than 3,600 liters o f arsenic- safe drinking water per day for 100 families. APYon Inc. 6.AlcanEnhancedActivatedAluminaUnit Figure (United States of America) has (mambyu e d ,2003) developed an arsenic treatment unit inwhich its Aqua-BindTMmedium is used for arsenic removal from groundwater. Aqua-Bind contains activated alumina and manganese oxides that can selectively remove As(II1) and As(V). The BUET activated alumina units have oxidation and prefiltration provisions prior to filtration through activated alumina. Granular ferric hydroxide (AdsorpAs@)i an adsorption capacity o f 45g kg-' for arsenic and 16 g kg-' for phosphorus on a Gravel filter bed Adsorption bed dry weight basis (Pal 2001). M / S Pal Trockner (P) Ltd, India, and Sidko Limited, Bangladesh, have installed several granular ferric hydroxide-based arsenic removal units in India and Bangladesh. The proponents o f the unit Contaminate claim that AdsorpAs@ has very high water inflow arsenic removal capacity, and produces relatively small amounts o f residual spent media. The typical residual mass o f spent ~~ ~ AdsorpAs@is in the range o f 5-25 glm3 o f treated water. The typical arrangement of the SidkoPal Trockner unit cfigure 7) requires aeration for oxidation o f water and prefiltration for removal o f iron flocs before filtration through active media. Chemicon and Associates has developed and marketed an arsenic removal plant based on adsorption - 149- Arsenic Contaminationof Groundwaterin South andEast Asian Countries:Volume I1- Paper 3 -Arsenic Mitigation Technologiesin SouthandEastAsia technology in which crystalline ferric oxide is used as an adsorbent. The unit has a prefiltration unit containing manganese oxide for oxidation o f As(II1) to A s 0 and retention o f iron precipitates. The Sono 3-Kolshi filter shown infigure 8 uses zero valent iron filings (cast-iron turnings), sand, brick chips, and wood coke to remove Figure8. Three Kalshi Filterfor Arsenic arsenic and other trace metals from Removal (Drawn by W e d , 2003 based groundwater in Bangladesh (Munir and others on Khanand Others, 2000) 2001; Khan and others 2000). The filtration system consists o f three kalshi (burned clay pitchers), widely used in Bangladesh for storage o f drmking and cooking water. The top kalshi contains 3 k g cast-iron tumings from a local machine shop or iron works and 2 k g sand on top o f the iron turnings. The middle kalshi contains 2 k g sand, 1 k g charcoal, and 2 kg brick chips. Brick chips are also placed around the holes to prevent leakage o f finer materials. Tubewell water is poured in the top kalshi and filtered water i s collected from the bottom kalshi. . .. .. ... . .. .. .. Nikolaidis and Lackovic (1998) showed that 97% o f arsenic can be removed by filtration through a mixture o f zero valent iron filings and sand. The authors postulated that coprecipitation, mixedprecipitation, and adsorption onto the ferric hydroxide solids mightbe the mechanisms by which arsenal was removed duringthe process. Thousands o f units using this technology were distributedin arsenic-affected areas but the feedback from the users was not very encouraging. If groundwater contains excess iron the one-time use unit quickly becomes clogged. Field observations indicated that the iron filings bond together into solid mass over time, making cleaning and replacement o f materials difficult. The unit has been renamed Sono 45-25 arsenic removal technology and the materials o f the upper two units have beenput into two buckets to overcome some o f the problems mentioned above. The BUET iron-coated sand filter was constructed and tested on an experimental basis and found to be very effective in removing arsenic from groundwater. The unit needs pretreatment for the removal of excess Figure9. Shapla Filter for Arsenic Removal at iron to avoid clogging of the active filter Household Level (Ahmed, 2003) bed. Iron-coated sand is prepared I following a procedure similar- t o that adopted by Joshi and Chaudhuri (1996). Lid The Shapla arsenic filter (figure 9), a 1 household-level arsenic removal unit, has h Flexible water been developed and is beingpromoted by delivery pipe Intemational Development Enterprises, Bangladesh. The adsorption medium is iron-coated brick chips manufactured by treating brick chips with a ferrous sulfate solution. It works on the same principle as iron-coated sand. The water collected from contaminated tubewells is allowed bucket to pass through the filter medium, which is placed in an earthen container with a drainage system undemeath. - 150- Arsenic Contamination o f Groundwater in South and East Asian Countries: Volume I1- Paper 3 - Arsenic Mitigation Technologies in South and East Asia The READ-F arsenic filter is promoted by Shin Nihon Salt Co. Ltd., Japan, and Brota Services International, Bangladesh, for arsenic removal in Bangladesh. READ-F displays high selectivity for arsenic ions under a broad range of conditions and effectively adsorbs both arsenite and arsenate.Oxidation o f arsenite to arsenate is not needed for arsenic removal, nor i s adjustment o f pH required before or after treatment. The READ-F is ethylene-vinyl alcohol copolymer-borne hydrous cerium oxide inwhich hydrous cerium oxide (Ce02.nH20) i s the adsorbent. Laboratory tests at the BUET and field testing o f the materials at several sites under the supervision o f the BAMWSP showed that the adsorbent i s highly efficient in removing arsenic from groundwater (Shin N h o n Salt Co. Ltd. 2000). One household treatment unit and one community treatment unitbased on the READ-Fadsorbentare being promoted in Bangladesh. The units need iron removal by sand filtration to avoid clogging o f the resin bed by iron flocs. In the household unit both the sand and resin beds have been arranged in one container while in the c o m u n i t y unit sand and resin beds are placed in separate containers. READ-F can be regenerated by adding sodium hydroxide and then sodium hypochloride and finally washing with water. The regenerated READ-F needs neutralization byhydrochloric acid and washing with water for reuse. The SAFI filter is a household-level candle filter developed and used in Bangladesh. The candle is made o f composite porous materials such as kaolinite and iron oxide on which hydrated ferric oxide is deposited by sequential chemical andheat treatment. The filter works on the principle o f adsorption filtration on the chemically treated active porous composite materials o f the candle. The ion exchange process is similar to that o f activated alumina; however, the mediumi s a synthetic resin of greater ion exchange capacity. The synthetic resin is based on a cross-linked polymer skeleton called the matrix. The charged functional groups are attached to the matrix through covalent bonding and fall into strongly acidic, weakly acidic, strongly basic, and weakly basic groups (Clifford 1999). The resins are normally used for removal of specific undesirable cations or anions from water. The strongly basic resins can be pretreated with anions such as Cl-' and used for the removal o f a wide range o f negatively charged species, including arsenate. Clifford (1999) reports the relative affinities o f some anions for strong- base anion resins as: C r 0 ~ 2 ~ ~ S e 0 ~ 2 ~ ~ S 0 ~ 2 ~ ~ H S O ~ 1 ~ N O ~ ~ 1 ~ B ~ ~ 1 ~ H A s O ~ 2 ~ S ~ O The arsenic removal capacity i s dependent on sulfate and nitrate contents o f raw water, as sulfate and nitrate are exchanged before arsenic. The ion exchange process is less dependent on the pH o f water. Arsenite, being uncharged, is not removed by ion exchange. Hence, preoxidation o f As(II1) to As(V) is required for removal o f arsenite using the ion exchange process. The excess oxidant often needs to be removed before the ion exchange in order to avoid damage of the Figure 10. Tetrahedron Arsenic Removal sensitive resins. Development o f ion- Technology (Drawn by b e d , 2003) specific resin for exclusive removal o f I arsenic can make the process very attractive. Chlorinesource Tetrahedron (United States) promoted Sieve stabilizer Columnhead tap technology in Bangladesh (figure lo). ion exchange-based arsenic removal Stone chips I About 150 units were installed at various locations in Bangladesh under the supervision of the BAMWSP. The technology proved its arsenic removal efficiency even at high flow rates. I t consists o f a stabilizer and an ion exchanger (resin column) with facilities - 151- Arsenic Contaminationof Groundwater inSouth andEast Asian Countries:Volume I1-Paper 3 -Arsenic Mitigation Technologiesin South andEastAsia for chlorination usingchlorine tablets. Tubewell water is pumped or poured into the stabilizer through a sieve containing the chlorine tablet. The water mixed with chlorine is stored inthe stabilizer and subsequently flows through the resin column when the tap is opened for collection o f water. Chlorine from the tablet dissolved inthe water kills bacteria and oxidizes arsenic and iron. Water System International (WSI) Indiahas developed and patented an ion exchange process for arsenic removal from tubewell water. The so-called bucket o f resin unit is encased in a rectangular container placed adjacent to the tubewell. There are three cylinders inside the container. Water in the first cylinder is mixed with an oxidizing agent to oxidize As(II1) to As(V) while As(V) is removed in the second cylinder, which is filled with WSI-patented processed resin. The treated water is then allowed to flow through a bed o f activated alumina to firther reduce residual arsenic from water. Ion Exchange (India) Ltd. has also developed andmarketed an arsenic removal community-levelplantbased on ion exchange resin. 2.4 MembraneTechniques Synthetic membranes can remove many contaminants from water including bacteria, viruses, salts, and various metal ions. They are o f two main types: low-pressure membranes, used in microfiltration and ultrafiltration; and high-pressure membranes, used in nonofiltration and reverse osmosis. The latter havepore sizes appropriate to the removal o f arsenic. Inrecent years, new-generation membranes for nonofiltrationandreverse osmosis havebeen developed that operate at lower pressure and are less expensive. Arsenic removal by membrane filtration is independent o f pH and the presence o f other solutes but is adversely affected by the presence o f colloidal matters. Iron and manganese can also lead to scaling and membrane fouling. Once fouled by impurities inwater, the membrane cannot be backwashed. Water containing high levels o f suspended solids requires pretreatment for arsenic removal using membrane techniques. Most membranes, however, cannot withstand oxidizing agents. EPA (2002) reported that nonofiltration was capable o f over 90% removal o f arsenic, while reverse osmosis provided removal efficiencies of greater that 95% when at ideal pressure. Water rejection (about 2625% o f the influent) may be an issue inwater-scarce regions (EPA 2002). A few reverse osmosis and nonofiltration units have been successfully used in Bangladesh on an experimentalbasis. 2.5 ComparisonofArsenic RemovalTechnologies Remarkable technological developments inarsenic removal from rural water supply based on conventional arsenic removal processes have taken place during the last five years. The relative advantages and disadvantages o f different arsenic removal processes are compared in table 1. Competition between arsenic removal technologies i s based on a number o f factors. Cost appears to be a major determinant inthe selection o f treatment option by users. The available costs o f some o f the arsenic removaltechnologies have been summarized intable 2. The costs o f similar technologies inIndiaare also compared intable 3. - 152- Arsenic Contamination o f Groundwater in South and East Asian Countries: Volume I1-Paper 3 -Arsenic Mitigation Technologies in South and East Asia Table 1.Comparison of MainArsenic RemovalTechnologies ~ ~~~~ Technology Advantages Disadvantages Oxidation and sedimentation: Relatively simple, low cost, but Processesremove only some of air oxidation, chemical slow process (air) the arsenic oxidation Relatively simple and rapid Used as pretreatment for other process (chemical) processes Oxidizes other impurities and k i l l s microbes Coagulation and filtration: alum Relatively low capital cost Not ideal for anion-rich water coagulation, iron coagulation Relativelv simule in oueration treatment (e.g. containing phosphates) < I Common chemicals available Produces toxic sludge Low removal of As(II1) Preoxidation i s required Efficiencies may be inadequate to meet strict standards Sorption techniques: activated Relatively well known and Not ideal for anion-rich water alumina, iron-coated sand, ion commercially available treatment (e.g. containing exchange resin, other sorbents Well-defined technique phosphates) Many possibilities and scope Produces arsenic-rich liquid and for development solid wastes 0 Replacementhegeneration is required High-tech operation and maintenance Relativelyhighcost Membrane techniques: Well-defined and highremoval Highcapital andrunningcosts nanofiltration, reverse osmosis efficiency High-tech operation and No toxic solidwastes produced maintenance Capable o f removal o f other Arsenic-rich rejectedwater i s contaminants produced - 153 - Arsenic Contamination of Groundwaterin South and East Asian Countries: Volume I1- Paper 3 - Arsenic MitigationTechnologies in South and East Asia TabIe 2. Comparisono fArsenic Removal Mechanisms and CostsinBangladesh Type of unit Removal mechanism Type Capital Operation and costhnit maintenance Sono 45-25 Adsorptionby oxidized iron Household 13 0.5-1.5 chips and sand Shapla filter Adsorption of iron-coated ,Household 4 11 brick chips SAFI filter Adsorption Household 40 6 Buckettreatment Oxidation and coagulation- Household 6-8 25 unit sedimentation-filtration Fillanddraw Oxidation and coagulation- Community 250 15 sedimentation-filtration (15 households) Arsenic removal Aeration, sedimentation, Urban water supply 240,000 1-1.5 unitfor urban rapid filtration (6,000 households) water supply Sidko Adsorption by granular Community 4,250 10 WOW3 (75 households) Adsorption by A1-Mn Community Taka O.Ol/L/lOOppb arsenic oxides (Aqua-BindTM) (65 households) concentration inwater Iron-arsenic Aeration, sedimentation, Community 200 1 removalplant rapid filtration (10 households) - 154 - Arsenic Contaminationof Groundwaterin South andEastAsian Countries:Volume I1- Paper 3 - Arsenic Mitigation TechnologiesinSouthand EastAsia Table 3. Comparisonof Costs o fDifferent Arsenic Treatment Technologies inIndia Technology Treatmentprocess Type Capacity cost (US$) (manufacturer) AMAL (Oxide India Adsorptionby Household 7,OOC- 8,000 L 50 CatalystPvt. Ltd., WB) activated alumina Community 1,500,000 Licycle 1,250; 400icharge RPMMarketingPvt. Activatedalumina+ Community 200,000icycle 1,200; 500icharge Ltd. AAFS-50 (patented) All IndiaInstitute of Oxidationfollowed Household 30 L/d 5 Hygiene & Public by coprecipitation- Health filtration Community 12,000 Lid 1,000 Public Health Adsorptiononred Community 600-1,000 Lih 1,000 Engineering hematite, sand, and Department, India activatedalumina PalTrocher Ltd., Adsorptionby ferric Household 20 L/d 8 India hydroxide Community 900,000 Licycle 2,000; 625icharge Chemicon& Adsorptionby ferric Community 2,000,000 Licycle 4,500; 400icharge Associates oxide IonExchange(India) Adsorptionby ion Community 30,000 Licycle 2,000 Ltd. exchangeresin - 155 - Arsenic Contaminationof Groundwaterin South andEast Asian Countries:Volume I1- Paper 3 - Arsenic MitigationTechnologies in SouthandEast Asia 3. Laboratoryand FieldMethodsof Arsenic Analysis Analysis o f groundwater for arsenic has become a routine procedure inthe assessment o f the quality o f water for the development o f groundwater-based water supply. The need for stringent water quality standards and guidelines has given rise to demand for analysis o f arsenic at trace levels. Laboratory analytical methods are relatively more accurate than field testing but involve considerable measurement skills and costs. The extent and nature o f contamination in many countries demands large-scale measurements o f arsenic for screening as well as monitoring and surveillance o f water points. Developing countries with limited laboratory capacity have adopted low-cost semiquantitative arsenic measurement by field test kits to accomplish the huge task o f screening and monitoring. This section provides a short overview o f laboratory and field methods o f analysis o f arsenic inwater. 3.1 Laboratory Methods A variety of analytical methods for laboratory determination o f arsenic has been described in has literature but many o f them essentially employ similar principles. The most common methods prescribed for use after proper validation by international and national standard methods include atomic absorption spectrometry (AAS), inductively coupled plasma (ICP), anodic stripping voltammetry (ASV), and silver diethyldithiocarbamate (SDDC) spectrometric method. A A S is a sensitive single-element technique with known and controllable interference. Both hydride generation (HG) and graphite b a c e (GF) A A S methods are widely used for analysis o f arsenic inwater. ICP atomic emission spectrometry ( A E S ) and mass spectrometry (MS) are multielement techniques, also with known and controllable interference. ASV is a useful technique for analysis o f dissolved arsenic and arsenic speciation but needs special precautions for accuracy. The SDDC spectrometric method has been widely used for its simplicity and low cost but suffers fiom interference and reproducibility. A summary o f laboratory analytical techniques, with important features, is presentedintable 4 (RasmussenandAnderson 2002; Khaliquzzaman andKhan2003). 3.2 Field Test Kit Laboratory methods o f arsenic measurement are costly and laboratories with arsenic measurement capabilities do not have the capacity to meet present needs. Fieldtest kits have been developed for detection and measurement o f arsenic by different institutions and agencies in Bangladesh and in other countries. The detection and semiquantative measurement o f arsenic by all field test kits is based on the Gutzeit procedure, which involves the conversion of all arsenic inwater into As(II1) by reduction, and then formation o f arsine gas by hrther reduction using nascent hydrogen in an acid solution in a Gutzeit generator. The technique i s also known as the mercuric bromide stain method (APHA-AWWA-WEA 1985). Presently available arsenic test kits have been developed adopting various modifications o f the method. The arsine, thus liberated, produces a yellow to brown stain on a vertical paper strip impregnated with mercuric bromide. The amount o f arsenic present inthe water is directly related to the intensity o f the color. The color developed on mercuric bromide-soaked paper is compared either with a standard color chart or measured by a photometer to determine the arsenic concentration o f the water sample. Insome field test kits the generated arsine is passed through a column containing a roll o f cotton moistened with lead acetate solution to absorb hydrogen sulfide gas, if any is present in the gas stream. The important features o f some arsenic field test kits are summarized intable 5. A number of researchers and organizations have evaluated the performance of arsenic field test kits. The National Environmental Engineering Research Institute, Nagpur, India, evaluated the Asian Arsenic Network (AAN)kit (0.02-0.70 m g L-'),the National Institute o f Preventive and Social Medicine (NIPSOM) kit, the Merck kit (0.10-3.0 mgL'),the Aqua kit, and the AIIH&PH kit (NEERI-WHO 1998). The S h a m Institute for Industrial Research, India, studied the performance o f five different arsenic field test kits used in India (SIIR 1998). NGO Forum for Drinking Water Supply and Sanitation, Bangladesh, in collaboration - 156- Arsenic Contamination o f Groundwater in South and East Asian Countries: Volume I1- Paper 3 -Arsenic Mitigation Technologies in South and East Asia with the School of Environmental Studies, Jadavpur University, Calcutta, West Bengal, India, evaluatedthe NIPSOM kit, the GeneralPharmaceuticalLtd. (GPL) kit, the Merckkit (0.025- 3.0 mg L-I),and the Arsenator (NGO Forum-JU 1999). In Bangladesh the performance of some arsenic test kits was evaluated as a requirementfor the procurement of field test kits by the BangladeshArsenic Mitigation Water Supply Project (BAMWSP 2001). Table 4. LaboratoryAnalysis Methods for Arsenic Techniquesa Method Sample System cost Comments Methods detection size (ml) (thousands limit (mg US$) L-l) HG-AAS 0.05-2 50 20-100 Single element I S 0 11969(1990) S M 3114BC (1998) EPA 1632 (1996) A S T M 2972-93B (1998) GF-AAS 1-5 1-2 30-100 Single element ISO/CD 15586 (2000) S M 3113B (1998) EPA 200.9 (1994) ASTM 2972-93C (1998) ICP-AES 35-50 10-20 60-200 Multielement S M 3120B (1998) EPA 200.7 (1994) ICP-MS 0.02-1 10-20 150400 Multielement S M 3125B (1998) EPA 200.8 (1994) ASV 0.1-2 25-50 5-20 Only free EPA 7063 (1996) dissolved arsenic SDDC 1-10 100 2-10 Single element I S 0 6595 (1982) SM3500(1998) a. Abbreviations used: ASV anodic stripping voltammetry GF-AAS graphite furnace-atomic absorption spectrometry HG-AAS hydride generation-atomic absorption spectrometry ICP-AES inductively coupled plasma-atomic emission spectrometry ICP-MS inductively coupled plasma-mass spectrometry SDDC silver diethyldithiocarbamate b.Abbreviations usedreferences: ASTM American Society for Testing and Materials (ASTM 1998) C D Committee Draft EPA Environmental ProtectionAgency, United States I S 0 Intemational Organization for Standardization (IS0 1982, 1996, 2000) S M Standard Method - 157- Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1- Paper 3 -Arsenic MitigationTechnologies in South and East Asia Table 5. Comparison o fArsenic FieldTest Kits Kittype Manufacturer Range (pg L-') Cost (US$) Comments E-Mark kit MISE-Mark, Germany 100-3,000 (old) 50-100 Colors matchwith 5-500 (new) ranges of arsenic concentration. HACH kit HACH Company, USA 10-500 (50 ml sample) One-time use for 350-4,OOO (9.6 ml sample) 100-300 tests Econo QuickTM IndustrialTest Systems 10-1,000 Inc., USA AIIH&PH kit All India Institute of Yesmo type at 50 pgL-' 40-60 Produces color if Hygiene andPublic concentration Health(AIIH&PH) exceeds 50 pg L-I. One-time use Aqua kit Aqua Consortium YedNo type at 50 pgL-' (India) ~~~ AAN-Hironaka kit Dr.Hironaka, Fukuoka 20-700 Not on sale Colors matchwith City Inst. For Hygiene range of arsenic & Environment, Japan concentration. One-time use for NIPSOMkit NIPSOM, with 10-700 40-80 100tests technical assistance from AAN-Hironaka GPL kit General 10-2,500 PharmaceuticalsLtd., Dhaka BUETkit BUET, Dhaka 10-700 Not on sale Digital Arsenator Wagtech International 40-500 1,250 Quantitative values obtained Recently, several arsenic field test kits were tested for their efficacy under the EPA's Environmental Technology Verification Program. The performances o f the field test kits were evaluated for accuracy, precision, linearity, method detection limit, matrix interference effects, operator bias, and rate o f false positives or false negatives. The EPA issued verification reports and verification statements for these arsenic field test kits (Abbgy and others 2002; EPA 2003) The accuracy o f arsenic measurement using the mercuric bromide stain method depends on many factors. The first consideration is the method's ability to eliminate the effects of interfering substances such as sulfide. The second consideration i s the generation o f arsine gas, which can be achieved in several ways. Most kits use zinc, which may contain arsenic as an impurity and interfere with the process. The advantage o f using the chemicals in tablet form can be availed in the case o f arsine generation using sodium tetrahydroborate (NaBH,) and aminosulfonic acid. An excess amount o f the reducing agent is required in this case to produce sufficient hydrogen gas to strip the arsine gas out o f the solution and transfer it to mercuric bromide paper. The passing o f arsine gas through mercuric bromide paper gives more reliable results at low concentrations than passing it over the surface o f a small strip o f mercuric bromide paper inserted into the reactor. The third consideration is that quantification o f the arsenic concentration by visual comparison is subjective and varies from person to person. The faint yellow color is not discemible to the average human eye. Again, for better - 158 - Arsenic Contaminationof Groundwater in South and East Asian Countries:Volume I1- Paper 3 - Arsenic Mitigation Technologies inSouthandEast Asia results, the color comparison should be made as soon as possible as the light-sensitive stain changes color rapidly. The results obtained by arsenic field test kits are, therefore, very much dependent on the type and quality o f chemicals, preparation, the preservation and age o f the chemicals, the quality o f water, the quality o f equipment, the operator's skill, and the procedure o fmeasurement (Jalil and Ahmed2003). The costs o f equipment for arsenic measurement are shown in tables 4 and 5. The equipment costs o f most laboratory methods are very high. Operation and maintenance costs are also veryhigh.Further, the service facilities o f laboratory equipmentmanufacturers are not always available in developing countries. Semiquantitative measurement using arsenic field test kits can be done at low cost, making them affordable in developing countries, though the level o f accuracy is lower thanwith laboratory tests. - 159- Arsenic Contamination o f Groundwater in South and East Asian Countries: Volume I1- Paper 3 - Arsenic Mitigation Technologies in South and East Asia 4. Alternative Water Supply Options The shallow tubewell technology in alluvial aquifers o f recent origin in the South Asia Region, which provided drinking water at low cost, has been found to be contaminated with arsenic in many places. This unexpected calamity has exposed millions o f people in contaminated areas to unsafe water. The problem has been magnified by the existence o f hotspots where the percentage o f contaminated tubewells i s high, givingusers few altemative options for safe dnnking water. In the absence o f an altemative source, people in such hotspots often have an unfortunate choice between continuing to drink arsenic-contaminated water or using unprotected surface water and exposing themselves to the risk o f waterborne diseases. Arsenic toxicity has no known effective treatment, but drinking arsenic-free water can greatly reduce the symptoms. Apart from treatment o f arsenic-contaminated water, potential altemative water sources for arsenic-safe water supplies include: 0 Deep tubewell 0 Dug or ringwell 0 Rainwater harvesting Treatment o f surface water 0 Piped water supply 4.1 Deep Tubewell Aquifers are water-containing rocks that have beenlaid down duringdifferent geological time periods. Deeper aquifers are often separated from those above by relatively impermeable strata that keep them free o f the arsenic contamination o f shallower aquifers'. A study in Bangladesh by the British Geological Survey (BGS) and the DPHE has shown that o f tubewells with a depth greater than 150 m, only about 1%have levels o f arsenic above 50 p g L-',and 5% have arsenic levels above 1OpgL1(BGS-DPHE 2001). As such, deep aquifers separated from shallow contaminated aquifers by impermeable layers can be a dependable source o f arsenic-safe water. The presence o f a relatively impermeable layer separating a deep uncontaminated aquifer from a shallow contaminated aquifer Figure 11*Deep Tubewell with claySeal i s a Drereauisite for installation o f a deeD (Ahmed, 2004) tubewell for arsenic-safe water. The annular spaces o f the boreholes o f the deep tubewells must be sealed, at least at the level of the impermeable strata, to avoid percolation of arsenic-contaminated water (figure 11). It i s very difficult to seal a small-bore tubewell but technological refinement using clay as a sealant is ongoing. A protocol for the installation o f deep tubewells for arsenic mitigation has been developed inBangladesh (Government o f Bangladesh 2004). In the coastal area o f Bangladesh proven arsenic-safe deep aquifers protected by overlying thick clay layers are available for the development o f safe water supplies. In other areas, arsenic-safe aquifers separated 'In some areas, e.g. China, the deeper aquifers may be arsenic-affected. See paper 1. - 160- Arsenic Contaminationof Groundwater in South andEast Asian Countries:Volume I1- Paper 3 -Arsenic Mitigation TechnologiesinSouth andEast Asia from arsenic-contaminated shallow aquifers are available but extensive and very costly hydrogeological investigations are required to delineate those aquifers. In the meantime, installation o f deep tubewells following a deep tubewell protocol will continue through examination o f water quality and soil strata intest boreholes inthe prospective deep tubewell areas. However, there are many areas where separating impermeable layers are absent and aquifers are formed by stratified layers o f silt and medium sand. The deep tubewells in those areas may yield arsenic-safe water initially but are likely to experience an increase in the arsenic content o f water over time due to mixing of contaminated and uncontaminated waters. However, recharge o f deep aquifers by infiltration through coarse media and replenishment by the horizontal movement of water are likely to keep such aquifers arsenic free even after prolonged water abstraction. Information about the configuration o f an aquifer and its recharge mechanismi s critical for the installation o fdeep tubewells. Experience in the design and installation o f tubewells shows that reddish sand produces the best-quality water in terms o f dissolved iron and arsenic. The reddish color o f sand is produced by oxidation o f iron on sand grains in a ferric form that will not release arsenic or iron in groundwater. On the contrary, ferric iron-coated sand will adsorb arsenic from groundwater. This mechanismis probably responsible for the relative freedom from arsenic o f the Dhaka water supply, in contrast to the arsenic contamination that occurs in surrounding areas. Hence, installation o f tubewells in reddish sand, if available, should be safe from arsenic contamination. 4.2 Dugor RingWell Dugwells are the oldest method o f groundwater withdrawal for water supply.The water from dug wells has been found to be relatively free from dissolved arsenic and iron, even in locations where tubewells are contaminated. The reasons for this are not fully known, but possible explanations include: The oxidation o f dug well water due to its exposure to open air and agitation duringwater withdrawal can causeprecipitation o f dissolved arsenic and iron. Dugwells accumulate groundwater from the top layer ofawater table, which is replenished each year by arsenic-safe rain andpercolation o f surface waters through the aerated zone o fthe soil. The fresh recharges also dilute contaminated groundwater. A study in an acute arsenic problem area shows that frequent withdrawal of water initiates ingress o f arsenic-contaminated water into dug wells and reduces the subsequent in situ oxidation that, under normal operating conditions, increases the oxygen content o f water and the reduction o f arsenic. Since the upper layer o f soil contains organic debris, dug well water i s often characterized by bad odor, high turbidity and color, and high ammonia content. Dug wells are also susceptible to bacterial contamination. Percolation o f contaminated surface water is the most common cause o f well water pollution. Satisfactory protection against bacteriological contamination i s possible by sealing the well top with a watertight concrete slab, lining the well, and constructing a proper apron around the well. Water may be withdrawn through the installation o f a manually operated handpump.Completely closed dug wells have good sanitary protectionbut the absence o f oxygen can adversely affect the quality o fthe water. Construction and operational difficulties have been encountered insilty and loose to medium- dense sandy soils. Sand boiling interferes with the digging, and sometimes leads to collapse of dug wells. Constructed dug wells are also gradually filled up during operation by sand boiling. Water in the well needs chlorination for disinfection after construction. Application o f lime also improves the quality o f dug well water. Disinfection o f well water should be continued -161 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1-Paper 3 -Arsenic Mitigation Technologies in South and East Asia for open dug wells during operation by pot chlorination, but controlling the chlorine dose in dugwell water is difficult. 4.3 Surface Water Treatment A prospectiveoption for the development of a surface water-based water supply system is the construction of community slow sand filters, commonly known as pond sand filters in Bangladesh, where they were originally designed for the filtration o f pond water. This is a package-type slow sand filter unit developed to treat surface waters, usually low-saline pond water, for domestic water supply incoastal areas. The water from the pond or river is pumped by a manually operated tubewell to feed the filter bed, which is raisedfrom the ground (figure 12). The treated water is collected through a tap. Tests have found that treated water from a pond sand filter i s normally bacteriologically safe or within tolerable limits. The sand in the filter bed usually needs to be cleaned and replaced every two months. The operating conditions for slow sandfilters include: Low turbidity, not exceeding 30 nephelometric turbidity units (NTU) Figure 12. Pond SandFilterfor Treatment of Surface Water (Ahmedand Others, 2002) system Raw water from pond - Low bacterial count No algal bloom, absenceo fcynobacter Free from bad smell and color A protected surface water source is ideal for slow sand filtration. The problems encountered when the above operating conditions are not maintained include low discharge, the need for frequent washing, and poor effluent quality. Since these are small units, community involvement in their operation and maintenance is absolutely essential in order to keep the system operational. By June 2000, the DPHE had installed 3,710 pond sand filter units, a significant proportion o f which remain out o f operation due to poor maintenance, drying o f the source, or excessive contamination o fthe water source. The package-type slow sand filter is a low-cost technology with very high efficiency in turbidity and bacterial removal. It has received preference as an alternative water supply system for medium-size settlements inarsenic-affected areas. Although pond sandfilters have a very high bacterial removal efficiency they may not reduce bacterial count to acceptable - 162- Arsenic Contamination o f Groundwater in South and East Asian Countries: Volume I1-Paper 3 -Arsenic Mitigation Technologies in South and East Asia levels in cases o f heavily contaminated surface water. In such cases, the treated water may require chlorination to meet dnnking water standards. A combined filter consisting o f roughing filters and a slow sand filter is needed when the turbidity o f water exceeds 30 NTU.The roughing filters remove turbidity and color to levels acceptable for efficient operation o f the slow sand filter. Small-scale conventional surface water treatment plants involving coagulation-sedimentation-filtration and disinfection can be constructed to cope with variable raw water quality for community water supplies but the cost will be relatively high. 4.4 Rainwater Harvesting Rainwater harvesting can be an alternative source o f drinking water in arsenic-contaminated South Asian countries. The relative advantages and disadvantages o f rainwater harvesting are shown in table 6. A rainwater-based water supply system requires a determination o f the storage tank capacity and the catchment area for rainwater collection inrelation to the water requirement, rainfall intensity, and distribution. The availability o f rainwater is limited by the rainfall intensity and availability o f a suitable catchment area. The unequal distribution o f rainwater over the year in Asian countries requires a larger storage tank for uninterrupted water supply throughout the year. This storage tank constitutes the main cost o f the system. Table 6. Advantages and Disadvantages ofRainwater Collection System Advantages Disadvantages The quality o f rainwater is comparatively The initial cost may prevent a family from good installinga rainwater harvesting system The system i s independent and therefore Water availability is limited by the rainfall suitable for scattered settlements intensity and available roof area Local materials and craftsmanship can be Mineral-free rainwater has a flat taste, which used in construction o f rainwater system may not be likedby many No energy costs are incurred inrunning the Mineral-free water may cause nutrition system deficiencies inpeople who are onmineral- Ease o f maintenance by the ownerluser deficient diets The system can be located very close to the The poorer segment ofthe population maynot consumption point have a roof suitable for rainwater harvesting May not last through the entire dry season. - 163 - Arsenic Contamination of Groundwater inSouth and East Asian Countries: Volume I1- Paper 3 -Arsenic Mitigation Technologes in South and East Asia The catchment area for rainwater collection is usually the roof, which is connected to the storage tank by a gutter system. Rainwater can be collected from any type o f roof but concrete, tiles, and metal roofs give clean water. The corrugated iron sheet roofs commonly used in Bangladesh and India perform well as catchment areas. The poorer segments o f the population are in a disadvantageous position in respect to the utilization o f rainwater as a source o f water supply. These people have smaller thatched roofs or no roof at all to be used as a catchment for rainwater collection. A thatched roof can be used as a catchment area by covering it with polyethylene but it requires good skills to guide water to the storage tank. In coastal areas o f Bangladesh, cloths fxed at four corners with a pitcher underneath are used during rainfall for rainwater collection. A plastic sheet, as shown infigure 13, has been tried as a catchment for rainwater harvesting for people who do not have a roof suitable for rainwater collection. The use o f land surface as a catchment area and underground gravel or sand-packed reservoirs as storage tanks can be an alternative system o f rainwater collection and storage. Inthis case, the water has to be channeled towards the reservoir and allowed to pass through a sand bed before entering underground reservoirs. This process is analogous to recharge o f underground aquifers by rainwater during the rainy season for utilization in the dry season. The quality o f rainwater i s relatively good but it i s not free o f all impurities. Analysis o f stored rainwater has shown some bacteriological contamination. Cleanliness o f the roof and storage tank i s critical to maintaining the good quality o f rainwater. The first runoff from the roof should be discarded to prevent entry o f impurities from the roof. If the storage tank is clean, the bacteria or parasites carried with the flowing rainwater will tend to die off. Some devices and good practices have been suggested to store or divert the first foul flush away from the storage tank. In case o f difficulties inthe rejection o f first flow, cleaning o f the roof and gutter at the beginning o f the rainy season and their regular maintenance are very important to ensure better quality o f the rainwater. The storage tank requires cleaning and disinfection when the tank i s empty or at least once ina year. Rainwater is essentially lacking in minerals, the presence of which is considered essential in appropriate proportions. The mineral salts innatural ground andsurface waters sometimes impart apleasingtaste to water. 4.5 PipedWater Supply Piped water supply is the ultimate goal o f safe water supply to the consumer because: Figure 13. Plastic Sheet Catchment (AhmedandOthers. 2002) Water can be delivered to close proximity o fthe consumers. Pipedwater is protected from extemal contamination. Better quality control through monitoring i s possible. Institutional arrangements for operation and maintenance are feasible. Water o f required quantity canbe collected with ease. In terms of convenience in collection and use, only pipedwater can compete with the existing system o f tubewells for water supply. It can be a feasible option for clustered rural settlements andurbanfringes. Water canbe made available through house connection, yard connection, or standpost, depending on the affordability o f - 164 - Arsenic Contaminationof Groundwater in South andEast Asian Countries:Volume I1- Paper 3 -Arsenic Mitigation Technologiesin SouthandEast Asia each option to the consumer. The water can be produced, according to demand, by sinking deep tubewells into an arsenic-safe aquifer or by treatment o f surface water or even arsenic- contaminated tubewell water by community-level treatment plants. Rural piped water supply has received priority for arsenic mitigation inBangladesh and a large numbero fpilot schemes by different organizations are under implementation. It appears that piped water supply will be a suitable option for populations living in clustered settlements, but it will be a difficult andcostly option for scatteredpopulations. 4.6 Cost ComparisonofAlternativeWater Supply Options As has been discussed in this chapter, a variety o f altemative technological options is available for water supply inarsenic-affected areas. The cost o f arsenic mitigationwill depend on the type of technology adopted. The costs o f installation and operation o f some major technological options available from various organizations involved in arsenic mitigation are summarized intable 7. The quality and quantity o f water, reliability, cost, and convenience o f collection o f water vary widely for the various options. Deep tubewells can provide water at nominal operation and maintenance costs but they are not feasible, nor able to provide arsenic-free water, at all locations. Dug or ring wells can provide water at moderate installation andnominal operation and maintenance costs. It is not yet fully known whether the quality o f water can be maintained at desired levels. Bacteriological quality i s likely to remain at safe levels under conditions o f proper sanitary protection. Piped water supply can be provided at a higher cost and with relatively higher operation and maintenance costs but the convenience and health benefits are much greater because water of adequate quantity and relatively superior quality for all domestic purposes, including sanitation, becomes available at or near residences. Increasingthe number o fhouseholds connected reduces average costs. Available data suggest that the average cost o f piped water supply becomes lower than other options when the number o f households exceeds 500 (see paper 4). The relative cost o f installation for a rainwater harvestingsystem at household level with only about 50% reliability is very high. Installation o f community rainwater harvesting systems may be cheaper, but management o f such systems may be difficult. Table 7. Costs o fAlternative Technological Options inArsenic-Affected Areas Alternative No. of Unit cost Operationand Comments Technologicaloptions (US$> maintenance per unit costdyear(US$) Rainwaterharvesting 1 200 5 Low reliability Dugor ringwell 25 800 3 Depthabout 8 m Deeptubewell 50 900 4 Depthabout 300 m Pondsandfilters 50 800 10-20 Slow sandfilter process Surfacewater 1,000 15,000 3,000 Conventionalprocess treatment Pipedwater supply 1,000 40,000 800 Systems are basedon arsenic-safe groundwater Source: Govemment of Bangladesh2002. - 165 - Arsenic Contaminationof Groundwater in South andEast Asian Countries:Volume I1- Paper 3 - Arsenic Mitigation Technologies inSouthandEast Asia 5. Operational Issues The presence o f arsenic in low concentration and the need to reduce it to levels associated with desired health benefits have given rise to many operational difficulties. Measurement o f arsenic at low concentration i s difficult, as i s the monitoring o f treatment system performance. Validation o f the claims o f proponents Concerning the performance o f treatment technologies and arsenic measurement devices i s an important requirement. Safe disposal o f toxic sludge and spent media is an environmental concern. The technologies based on patented media or processes and imported components may face operational difficulties due to lack of availability and supplyo fmaterials and components. Operational issues are very important for small-scale water treatment facilities at the household and community levels. It is not possible to make an institutional arrangement for operation, repair, and maintenance o f small water supply systems. People's participation and capacity building at the local level are considered vital for keeping the system operational. There are many examples o f failure o f small water supply systems in the absence o f initiatives, commitment, and ownership o f the system. Inmany cases, the small systemmay bemore costly due to scaling down o f a conventional system for water treatment. 5.1 Technology Verification and Validation Quite a lot o f development o f arsenic treatment and measurement technologies has taken place over the last five years inresponse to demand. Verification and validation o f the claims o f these technologies are needed to help buyers select the right technology. The EPA has developed protocols for validation o f arsenic treatment technologies and arsenic field test kits under its Environmental Technology Verification Program. The protocols have been developed in collaboration with the Environmental Technology Verification Program in Canada and Bettle Laboratories, United States (EPA 2003). The WHO has developed generic protocols for adoption inSouth-East Asia Region countries (WHO 2003). A systematic evaluation of arsenic mitigation technologies is being conducted under the Environmental Technology Verification-Arsenic Mitigation Program by the Bangladesh Council o f Scientific and Industrial Research in collaboration with the Ontario Centre for Environmental Technology Advancement, Canada. Generic and technology-specific test protocols consistent with environmental and operative conditions in Bangladesh have been developed for this verification program. The program has thus far completed verification o f five arsenic removaltechnologies inPhaseI(BCSIR 2003). An additional 14technologies are pending for verification inPhase I1o f the program. Verification o f some technologies in Bangladesh shows that their performance is very much dependent on pH, and the presence o f phosphate and silica in natural groundwater. Most o f the technologies do not meet the claims o f the proponents concerning treatment capacity. A reduction in the rated capacity will further increase the cost o f treatment per unit volume o f water. 5.2 Sludge Disposal Since arsenic cannot be destroyed all arsenic treatment technologies ultimately concentrate arsenic in sorption media, sludge, or liquid media. A variety o f arsenic-rich solids and semisolids, such as arsenic-saturated hydrous ferric or aluminium oxides and other filter media, are generated fiom arsenic removal processes. Regeneration o f activated alumina and ion exchange resins results invarious liquidwastes that may be acidic, caustic, saline, and too arsenic rich for simple disposal. Hence, environmentally safe disposal o f sludge, saturated media, and liquidwastes rich inarsenic is a concern. The EPA has developed a toxic characteristic leaching procedure (TCLP) test to identify wastes likely to leach toxic chemicals into groundwater. The permissible level for TCLP - 166 - Arsenic Contaminationof Groundwaterin SouthandEast Asian Countries:Volume I1- Paper 3 -Arsenic Mitigation TechnologiesinSouthandEast Asia leachate is generally 100 times higher thanthe maximumcontaminant level indrinking water, for example 5,000 pg L-'for leached arsenic when the acceptable level indnnkingwater is 50 pgL-'.Sludge leachingmore that 5,000 pg L-'o f arsenic would be considered hazardous and would require disposal ina special hazardous waste landfill. The TCLP test was conducted on different types o f wastes collected fiom arsenic treatment units and materials in Bangladesh (Eriksen-Hamel and Zinia 2001; Ali and others 2003). It has been observed that in almost all cases arsenic leaching was very minor. Arsenic leaching tests were conducted at the BUET using different extraction fluids. For all extractants arsenic concentration in the column effluents was initially very high, but then dropped sharply (Ali and others 2003). Several researchers also conducted TCLP tests on sludge resulting from arsenic removal with aluminium and ferric salts and found arsenic in leachate in the range o f 9-1,500 p g L-' (Brewster 1992; Chen and others 1999). These arsenic levels in leachate are well below the level required for classification as hazardous wastes. I t appearsthat most sludge would not be considered hazardous even if the WHO guideline value o f 10 p g L' for arsenic in drinking water were considered. Hazardous wastes are often blended into stable waste or engineering materials such as glass, brick, concrete, or cement block. There is a possibility o f air pollution or water pollution downstream o f kilns buming brick containing arsenic-contaminated sludge due to volatilization o f arsenic during burning at high temperatures. InHungary experiments showed that some 30% o f arsenic in the coagulated sludge was lost to atmosphere in this way (Johnston, Heijnen, and Wurzel 2000). Sludge or spent filter media with low arsenic content can be disposed o f on land or in landfills without significant increase in the background concentration o f arsenic. Wastes with highconcentration o f arsenic may need solidification or confinement before final disposal. 5.3 costs The cost o f arsenic removal technology i s an important factor for its adoption and sustainable use inrural areas. The cost o f the technologies depends on many factors such as the materials used for fabrication of components, quantity o f media or chemicals used, and quality o f groundwater. Most o f the technologies have been installedand are being operated under field testing and pilot-scale operations. Hence the costs o f installation, operation, and maintenance o f all the arsenic removal systems are not known or are yet to be standardized based on modifications to suit the local conditions. The available costs and system capacities o f some arsenic removal technologies are presented in tables 2 and 3. The costs o f alternative water supply systems arepresented intable 7. The unit costs o f water produced by different water supply systems to meet present service levels have been calculated on the basis o f annualized capital recovery using an annual interest rate o f 12% (table 8). It has been assumed that the arsenic-safe water requiredper family for d d i n g and cooking is 45 L/day. However, the water production capacity o fmost alternative water supply systems is much higher than this and can serve additional users, or provide existing users with more water for all householdpurposes. Ifthe full water production capacities o fthese systems are utilized the cost per unit volume o f water is greatly reduced. - 167 - Arsenic Contamination o f Groundwater inSouth and East Asian Countries: Volume I1-Paper 3 - Arsenic Mitigation Technologies in South and East Asia Table 8. Cost ofWater Supply Options for Arsenic Mitigation Technology Tech life Annualized Operation & Water output Unitcost (years) capital recovery maintenance (m3) (us$/m3) (US$)a cost'year (US$) Alternative water supply: Rainwater harvesting 15 30 5 16.4 2.134 Deep tubewell 20 120 4 820 0.151 4,500 0.028b Pond sand filter 15 117 15 820 0.161 2,000 0.066b Dugor ringwell 25 102 3 410 0.256 1,456 0.072b Conventional treatment 20 2,008 3,000 16,400 0.305 Piped water 20 5,872 800 16,400 0.375 73,000 0.084b Arsenic treatment (households) based on: Coagulation-filtration 3 3 25 16.4 1.70 Iron-coated sandibrick dust 6 0.9 11 16.4 0.73 Iron filings 5 3 1 16.4 0.24 Synthetic media 5 1.2 29 16.4 1.84 Activated alumina 4 3.2 36 16.4 2.39 Arsenic treatment (community) based on: Coagulation-filtration 10 44 250 246 1.21 Granulated ferric 10-15 500-600 450-500 820-900 1.20 hydroxide/oxide Activated alumina 10-15 30-125 500-5 20 164200 3.20 Ion exchange 10 50 35 25 3.40 Reverse osmosis 10 440 780 328 3.72 As-Fe removal (air 20 32,000 7,500 730,000 0.054 oxidation-filtration) a. The capital recoveryiamortization factor has been calculated usingthe formula: (1 + i)N where i = interest rate and N = number o f years. \ / ((1 + $'-I) / i b. Development of full potential ofthe system. - 168 - Arsenic Contaminationof Groundwater in SouthandEastAsian Countries: Volume I1- Paper 3 - Arsenic Mitigation TechnologiesinSouthandEastAsia 6. Conclusions The problem o f treatment o f arsenic-contaminated water arises fiom the requirement for its removal to very low levels to meet the stringent drinking water quality standards and guideline values for arsenic. Arsenic removal technologies have improved significantly over the last few years but many o f the technologies do not work satisfactorily for natural groundwater. Reliable, cost-effective, and sustainable treatment technologies are yet to be identified and further developed. All the technologies have their strengths and weaknesses and are being refined to accommodate rural conditions. Modifications based on pilot-scale implementation o fthe technologies are inprogress with the objectives of: 0 Improving efficiency o f arsenic removal Reducing capital and operation cost o f the systems 0 Makingthe technology user friendly 0 Overcoming maintenance problems 0 Resolving sludge and arsenic concentrates management problems. Because o f the cost and operational complexity o f arsenic removal technologies, altemative water supply options we often given preference in arsenic mitigation. Surface water of desirable quality is not always available for low-cost water supply, while the cost o f treatment o f surface water using conventional coagulation-sedimentation-filtration and disinfection processes is very high. Rainwater harvesting as a household option is also costly. Dug wells do not produce or maintain water o f desirable quality in all locations and are difficult to construct insome areas. The technologies are site specific and there are various considerations for selection o f a particular technology in any given locality. Some o f the important considerations for the development o f sustainable water supply options for purposes o f arsenic mitigation are: 0 The profile o fthe beneficiaries and settlement pattern Present water supply system and level o f arsenic inthe drlnkingwater 0 Possible altemative sources o f water for water supply 0 Relative risk and cost o f development o f water supply system The level o f technical andmanagerial capacity buildingneeded 0 Affordability and willingness to pay. A lot o f effort has been spent developing the performance o f arsenic field test kits. Although the accuracy o f arsenic detection andmeasurement by field test kits is not filly satisfactory, it i s a convenient tool for testing water inrural areas. Field test kits are being widely used and will continue to be used in the near future until a network o f in-country laboratories is established for testing arsenic at a reasonable cost. It is therefore essential to improve the performance o f the field test kits and implement quality assurance programs for field-based measurement with back-up support from available in-country laboratories to meet the present need. - 169- Arsenic Contaminationof Groundwaterin South andEast Asian Countries:Volume I1- Paper 3 -Arsenic Mitigation Technologesin SouthandEast Asia References Abbgy, A,, T. Kelly, C. Lawrie, and K.Riggs. 2002. Environmental Technology Verijication Report: QuickTMArsenic TestKit. EPA Environmental Technology Verification Program. Ahmed, M. F. 2003. "Treatment of Arsenic Contaminated Water." In:M. F. Ahmed, ed., Arsenic Contamination: Bangladesh Perspective 354-403. Dhaka, Bangladesh: ITN-Bangladesh. Ahmed, M. F., M.A. Ali, and Z. Adeel, eds. 2001. 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Jekel, M.R. 1994. "Removal of Arsenic inDrinking Water Treatment." In: J. 0.Nriagu, ed., Arsenic in the Environment, Part I:Cycling and Characterization. New York: John Wiley & Sons, Inc. Johnston, R.,H.Heijnen, and P. Wurzel. 2000. Safe Water Technology. www.who.int/water~sanitation~health/arseniclArsenic~Rep7 .htm. Joshi, A. and M. Chaudhuri. 1996. "Removal of Arsenic from Groundwater by Iron-Oxide-Coated Sand." ASCEJ. Environmental Engineering 122(8):769-771. Kartinen, E. 0. and C. J. Martin. 1995. "An Overview of Arsenic Removal Processes." J. Desalination 103:79-88. Khaliquzzaman, M.and A. H.Khan. 2003. "Analysis of Water for Arsenic inBangladesh." In:M.F. Ahmed, ed., Arsenic Contamination: Bangladesh Perspective. Dhaka, Bangladesh:ITN-Bangladesh. - 171 - Arsenic Contamination of Groundwater in South and East Asian Countries: Volume I1-Paper 3 -Arsenic MitigationTechnologies in South and East Asia Khan, A. H., S. B. Rasul, A. K. M.Munir, M.Alauddin, M. Habibuddowlah, and A. Hussam. 2000. "On Two Simple Arsenic Removal Methods for Groundwater of Bangladesh." In: M. F. Ahmed, ed., Bangladesh Environment 2000 151-173. BangladeshPoribeshAndolon. Manning, B. and S. Goldberg. 1996. "Modelling Competitive Adsorption of Arsenate with Phosphate and Molybdate on Oxide Minerals." Soil ScienceSociety ofAmerica Journal 60:121-133. McNeill,L.S. and M.Edward. 1997."Arsenic Removal during Precipitative Softening." Journal of Environmental Engineering 123:453-460. Meng, X. G., S. B. Bang, and G. P. Korfiatis. 2000. "Effects of Silicate, Sulfate, and Carbonate on Arsenic Removal by Ferric Chloride." Water Research 34:1255-1261. Meng, X. G. and G. P. Korfiatis. 2001. "Removal of Arsenic from Bangladesh Well Water Using Household Filtration System." In: Ahmed, M. F., M. A. Ali, and Z. Adeel, eds., Technologies for Arsenic Removal from Drinking Water 121-130. Bangladesh University of Engineering & Technology andUnitedNations University. Munir, A. K.M., S. B.Rasul, M.Habibuddowlah,M.Alauddin, A. Hussam, and A. H.Khan. 2001. "Evaluation of Performance of Sono 3-Kolshi Filter for Arsenic Removal from Groundwater Using Zero Valent Iron through Laboratory and Field Studies." In:Ahmed, M.F., M. A. Ali, and Z. Adeel, eds., Technologies for Arsenic Removal @om Drinking Water 171-189. Bangladesh University of Engineering& Technology and UnitedNations University. Murcott, S. 2000. A Comprehensive Review of Low-Cost Well-Water Treatment Technologies for Arsenic Removal. phys4.harvard.edu/-wilsont murcott2.html. NEEM-WHO (National Environmental Engineering Research Institute and World Health Organization). 1998.Assessment of Arsenic Field Testing Kits. FinalReport. NGO Forum-JU (Jadavpur University). 1999. Report on Evaluation of Field Kits Usedfor Arsenic Detection in Groundwater. NGO Forum and Jadavpur University School of Environmental Studies, Calcutta, West Bengal. Nikolaidis, N. P. and J. Lackovic. 1998. Arsenic Remediation Technology-AsRT. Presented at International Conference on Arsenic Pollution of Ground Water in Bangladesh: Causes, Effects and Remedies, Dhaka, 8-12 February 1998. Pal, B. N. 2001. "Granular Ferric Hydroxide for Elimination of Arsenic from Drinking Water." In: Ahmed, M.F., M.A. Ali, and Z. Adeel, eds., Technologiesfor Arsenic Removalfrom Drinking Water 59-68. BangladeshUniversity of Engineering& Technology and UnitedNations University. Pierce, M. L. and C. B. Moore. 1982. "Adsorption of Arsenite and Arsenate on Amorphous Iron Hydroxide." Water Resources 16:1247-1253. Pontius, F. W., ed. 1990. Water Quality and Treatment: A Handbook of Community Water Supplies. American Water Works Association.New York: McGraw-Hill. Rasmussen, L. and K. J. Andersen. 2002. Environmental Health and Human Exposure. www.who.int/water~sanitation~health/arsenic/ArsenicUNRep2 .htm. Shen, Y. S. 1973. "Study of Arsenic Removal from Drinking Water." J. American Water Works Association 65(8):543-548. ShinNihonSalt CO.Ltd. 2000. Report on Perfonnance of Read-F Arsenic Removal Unit (ARU). SIIR (Shriram Institute for Industrial Research). 1998. Assessment of Arsenic Testing Kits. Final Report. Sorg, T. J. and G. S. Logsdon. 1978. "Treatment Technology to Meet the Interim Primary Drinking Water Regulationsfor Inorganics: Part2." J.American Water WorksAssociation 70(7):379-393. Wegelin, M., D. Gechter, S. Hug, A. Mahmud, and A. Motaleb. 2000. SORAS - A Simple Arsenic Removal Process. phys4.harvard.edu/-wilson/mitigation/ SORAS- Paper.html. - 172- Arsenic Contaminationof Groundwater inSouth andEast Asian Countries:Volume I1-Paper 3 -Arsenic MitigationTechnologies in South andEastAsia WHO (World Health Organization). 2003. Verification of Arsenic Mitigation Technologies and Field TestMethods. Report on Intercountry Consultation, Kolkata, India, 9-12 December 2002. New Delhi: WHO RegionalOffice for South-EastAsia. Young, E. 1996. "Cleaning UpArsenic and Old Waste." New Scientist 14 December 1996. - 173 - Paper 4 The Economics of Arsenic Mitigation T h i s paper was prepared by Dr. Phoebe Koundouri of Reading University and University College London, acting in her capacity as a private consultant. University of Reading and University College London are not responsible for the contents of this document. Additional contributions were made by Karin Kemper, Amal Talbi, and Mona Sur. Arsenic Contaminationof Groundwater in SouthandEast Asian Countries: Volume I1- Paper4 The Economics o fArsenic Mitigation - Summary T h i s paper introduces an approach that provides a quick and readily applicable method for performing a cost-benefit analysis o f different arsenic mitigation policies. In particular, our suggested approach estimates benefits o f mitigation activities as the sum o f forgone medical costs and saved output productivity achieved by reducing arsenic exposure. The present value o f these benefits is then compared with the present value o f costs o f various mitigation measures in order to investigate when and which mitigationpolicies pass a cost-benefit analysis (that is, produce a positive change insocial welfare). The paper applies this approach in order to provide some estimate o f costs and benefits o f arsenic mitigation in one case study country: Bangladesh. This case study serves as an applied example o f such rapid socioeconomic evaluation and is also used as a basis for discussing trade-offs in decisionmaking with respect to the allocation o f financial resources. Our approach i s applicable to both cases: (a) the risk that arsenic might be found in an area where a project is planned; and (b) approaches inregardto risk mitigationoptions where a project aims at arsenic mitigation per se. Our case study showed that for the case of Bangladesh the cost-benefit ratios for many relevant mitigation techniques and policies are positive under varying levels o f success in terms o f their effectiveness. These results indicate the imminentneed for facing the arsenic crisis inBangladesh, but also the clarity with which our approach can answer the difficult question on the balance o f relevant costs andbenefits o f various mitigation options andpolicies. - 175 - Arsenic Contaminationof Groundwater in SouthandEast Asian Countries: Volume I1 Paper4 "he Economics of Arsenic Mitigation - - 1. The Issue 1.1 Aims of This Paper 1. This paper reviews existing studies and data on arsenic mitigation inthose countries where it has been undertaken, and the costs o f achieving such mitigation. Then these costs are compared with relevant benefits, while taking into consideration the limited knowledge base regarding the epidemiology o f arsenic in the region. Discussion o f the different limits for arsenic in drinking water in different countries and simulation o f cost implications from implementing each limit, as well as the trade-offs between different water sources (ground or surface water, for example) in a range of socioeconomic circumstances, i s central to the paper. 2. All decisions imply a money value of benefits, while policies can only be accepted or rejected. Ifa policy costs $X, accepting and implementing it implies that benefits exceed $X. Rejecting the policy implies that benefits are less than $X. Hence, there is no escape from monetary valuation. This paper provides a general introduction to the way o f thinking about costs and benefits o f mitigating (natural) pollutants, including considerations o f trade-offs in decisionmaking with respect to the allocation o f financial resources in a budget-constrained environment. 3. Inparticular, a methodology is suggestedfor analyzing options inorder to choose between different approaches indealing with (a) the risk that arsenic mightbe found inan area where a project is planned; and (b) approaches to risk mitigation options where a project's goal is arsenic mitigationper se. 4. The paper also provides decisionmakers and project managers with an efficient and readily applicable methodology for rapid assessment o f the socioeconomic desirability o f different arsenic mitigation policies under various scenarios. The proper way o f deciding whether to implement a particular mitigation policy involves conducting a cost-benefit analysis (CBA), which in turn involves (a) consideration o f several different policy options to test costs and benefits o f each; (b) a general equilibrium approach to the costs of a policy; (c) behavioral studies o f water user responses to different levels o f mitigation; and (d) behavioral studies o f user responses to nonavailability o f contaminated water, especially substitution with other sources o f water. The true compliance cost o f any arsenic mitigation policy i s unknown but some estimated figures canbe used. However, we do not know the full behavioral reactions to different possiblemitigation policies. 5. An alternative, equally ideal model on which decisionmaking could be based involves (a) estimation o f changes inlevels o f exposure; (b) exposure-response functions linking levels to human mortality, human morbidity, and ecosystems and species; (c) willingness to pay for measures that avoid impacts identified in exposure-response relationships; and (d) allocation o fbenefits and costs to time periods (years). Such a procedure for estimating healthbenefits i s more tractable than a CBA, but remains very difficult due to the absence o f (a) a behavioral model o f the economic sectors that use arsenic-contaminated water; (b) knowledge o f change in exposure; (c) knowledge of exposure-response functions; and (d) intemalization assumptions for occupational effects. 6. Inthe absence of a full study (because of missing information and prevailing uncertainties) and given the millions o f people around the world who are currently menaced by arsenic poisoning, health policymakers need to devise policies capable o f counteracting this threat based on an "nth best" approach. One method o f analysis would be a cohort study, selecting control (no intervention) and intervention villages (with implementation o f mitigation methods) and tracking the effects o f the disease on people's health and livelihood, including coping mechanisms, over some period o f time. Any study method using real populations would, however, only provide results after long periods, which limits t h s method's applicability to the immediate public health concern. In addition, it is questionable whether long-term cohort follow-up would be achieved in a country where tracking o f individuals is - 176- Arsenic Contamination of Groundwaterin Southand EastAsian Countries: Volume I1- Paper4 The Economics ofArsenic Mitigation - limited. Finally, ethical considerations would preclude such studies as soon as it becomes apparent that mitigation methods do work andproviderelief. 7. Our suggestedapproach attempts to estimate the medical costs and forgone productivity from specific diseases or health end states. The paper applies this approach in order to provide some estimate o f costs and benefits o f arsenic mitigation in one case study country, namely Bangladesh. O f the regions o fthe world with groundwater arsenic problems Bangladesh i s the worst case that has been identified, with some 35 million people thought to be dnnking groundwater containing arsenic at concentrations greater than 50pg L-'and around 57 million drinking water with more than 1Opg L-'(see, Paper 1 o f this report). The large scale o f the problem reflects the large area of affected aquifers, the high dependence o f Bangladeshis on groundwater for potable supply, and the large population accumulated in the fertile lowlands o f the Bengal Basin. Today, there are an estimated 11 million tubewells in Bangladesh serving a population o f around 130 million people. The scale o f arsenic contamination in Bangladesh means that it has received by far the greatest attention in terms o f groundwater testing and more is known about the arsenic distribution in the aquifers than in any other country inAsia (as well as most o f the developed world). However, much more testing is still required. Our Bangladeshi case study serves as an applied example o f such a rapid socioeconomic evaluation and will also be used as a basis for discussing trade-offs in decisionmaking with respect to the allocation o f financial resources. 1.2 SituationalAnalysis 8. Groundwater is a significant source o f drinlung water in many parts o f the world. Well- protected groundwater is safer in terms o f microbiological quality than water from open dug wells and ponds. However, groundwater is notoriously prone to chemical and other types o f contamination from natural sources or anthropogenic activities. One o f these i s contamination caused by high concentration levels o f arsenic in water. Arsenic is a chemical that is widely distributed innature andprincipally occurs inthe form o f inorganic or organic compounds. 9. The available treatment technologies for arsenic removal provide varying results depending on the concentration o f arsenic inthe water, the chemical composition o f the water (including interfering particles), and the amount o f water to be treated. Another important consideration i s the feasibility and cost of the treatment process. The most commonly used biophysical methods are coagulation, softening, iron and manganese oxidation, anion exchange, activated alumina membrane processes, and electrodialysis. The frequently prohbitive cost of these technologies inrural contexts has prompted the search for alternative sources o f arsenic-free water, such as rainwater harvesting. 10. Reliable data on exposure and health effects are rarely available, but it is clear that there are many countries in the world where arsenic in drinking water has been detected at concentrations greater than the WHO guideline value o f 10 pg L-',or the prevailing national standard. These include Argentina, Chile, Japan, Mexico, New Zealand, the Philippines, the United States o f America, and some countries in South and East Asia, as described indetail in Paper 1. - 177- Arsenic Contaminationof Groundwater in South andEastAsian Countries: Volume I1 Paper4 The EconomicsofArsenic Mitigation - - 2 An IdealApproach to Evaluationof Arsenic Mitigation Measures 11. Inorder to show what is necessaryfor a proper evaluation of arsenic mitigationmeasuresthis chapter lays out an "ideal" approach - one based on a conceptually sound model, but which as a function o f its assumptions has certain limitations. This permits us to judge the gap between what should be done and what canbe done inpractice. 2.1 Uncertaintyand the IdealApproach 12. One misconception needs to be dispelled at the outset. One o f the criticisms o f economic (cost-benefit) approaches to policy evaluation is that they add to the uncertainty associated with evaluation. As such, it is argued, the approaches are best not adopted in the first place. There are indeed uncertainties, and often significant uncertainties, in cost-benefit appraisal. The problem i s that the uncertainty i s not reduced through nonadoption o f cost-benefit analysis (CBA). Invariably, uncertainty i s actually increased when CBA is not used. There are manyreasonsfor this conclusion, buttwo will suffice. 13. First, what CBA does is to compare benefits and costs in the same units (money).' This permits a decision o f whether or not to adopt the policy at all. Adoption follows if benefits exceed costs and not otherwise. Failure to monetize benefits means that the choice context is one o f cost-effectiveness in which costs are in money unitsbut effectiveness is in a different unit, for example some notion of risk reduction (such as lives saved). However, cost- effectiveness can only rank alternative policies; it cannot say whether anything should be done. We may, for example, choose policy A over B because A secures more risk reduction per dollar than B.Nevertheless, bothA and B could still fail cost-benefit tests, indicating that neither should be undertaken. Thus, a failure to adopt CBA increasesrisk because a new risk emerges, namely that incorrect policies are adopted. 14. Second, the risk reduction in question will show up invarious ways. On the simplest level it may manifest itself in reduced mortality and reduced morbidity. Cost-effectiveness analysis cannot now be conducted unless we have some idea o f the relative importance o f reducing one form o f risk over another form o f risk. Relative importance is measured by a set o f weights, such that the ratio o f the weights on any two forms o f risk reduction reflects the relative importance o f reducing one risk compared to another. Ifweights are not adopted, it i s not possible to make any comparison between options, and rational decisionmaking is not possible. All decision analysis involves one means or another o f selecting weights: by implied political preference, overt expert judgments, or, in the case o f CBA, individuals' willingness to pay for one change compared to another. Inshort, CBA's weights are prices. Compared to a situation in which there is no knowledge o f weights at all, CBA reduces uncertainty and does not increase it. I t then becomes an issue o f which set o f weights is preferable. One advantage o f CBA weights (prices) i s that they reflect the preferences o f those exposed to risk, andare hencemore democratic thanexpert weights.' This simple observation also explainswhy one cannot logically avoid monetization.First, all policies have costs. Ifthey did not have costs, there would be no needto consider whether or notthey are "good" policies. Hencethe acceptance of apolicy implies thatbenefits must exceedcosts, which sets a lower boundonthe scale of monetary benefits. Ifthe policy is rejected, the reverse applies. Second, costsare measuredinmonetaryterms andfew peoplehave difficulty inagreeingthatthis i s the correctway to measure costs. But costs are simply negativebenefits, since all costs are properlymeasuredby the forgonebenefitsof spendingmoneyonthe chosenprojectratherthan on something else. So, positive moneycostsare the samething as negativemoney benefits.Itfollows that benefits must also be expressible inmonetaryunits. 'It couldbe arguedthat political weights are best of all since politicians are electedto make such decisions. Unfortunately,the political model underlyingthis view is nai've, andassumes politicians always act inthe best interests ofvoters. Moreover,techniques such as CBA are designedas checks onpolitical decisionmaking; this i s the purposeofpolicy analysis. - 178 - Arsenic ContaminationofGroundwater inSouthandEast Asian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - 2.2 An IdealModel 15. The ideal approach to measuring the social benefits and costs o f arsenic mitigation would be as follows. 16. First, some assessment would need to be made of the extent to which the selected mitigation strategy will reduce human and environmental exposure to arsenic contamination. Refer to this change as AX where X refers to exposure. This stage of the analysis would therefore produce the policy effect on exposure. 17. Second, we need an exposure-responserelationship. Two effects can be identified. The first is the effect on humanhealth, call this AH. Again, there will be many different health effects, ranging from reduced premature mortality to changesin, for example, hospital admissions and days away from work. Therefore, A H is a vector. It is helpful to divide human health effects into reduced occupational risks (AHo) and reduced public health risks (AHp). This i s because there may be differences in the way the two effects are to be valued in monetary terms. The second effect is the environmental impact on ecosystems and biodiversity. Call this AE. Then, the sum o fthe effects is AHo +AHp+AE = A I where Iis overall impact. 18. Third, we need economic values for each impact since it is implicit inthe equation for A I that the effects are expressed in the same units. We refer to these as the shadow prices because they are the prices that would be attachedto the reducedriskifthere were an overt market for riskreduction. These shadow prices reflect individuals' willingness to pay for avoiding the ill health or negative environmental impact associated with arsenic. Again there will be a whole set o f shadow prices covering all o f the impacts. We refer to these shadow prices as P and they are formally equivalent to the weights discussed insection 2.1. 19. Fourth, we need to know when in time the changes in exposure will occur. This is because future changes in exposure will be valued less than near-term changes in exposure. The economic concept that reflects the different weights attached to time is known as a discount factor. The process o f attaching weights to time i s known as discounting. The discount factor (DF) is linked to the discount rate(s) (expressed as an interest rate; that is, in percentage terms) as shown inequation 1: Equation1.Discount Factor DF=- 1 (1 s)` + Where t =time (years from the pre~ent).~ 20. Timing is important, however; not all mitigation measures can predict the exact timing o f exposure reduction. For example the regulator or policymaker, ina situation where a village's groundwater resources are contaminated, can decide to introduce piped arsenic-free water supply. Exposure to arsenic will be reduced at the moment piped water supply is introduced, ifthe regulator can effectively monitor that the inhabitants of the village do not continue to use other contaminated groundwater sources. Monitoring o f abstraction activities i s difficult, time consuming, and hence expensive, especially when areas are heavily populated. As a result monitoring will have to be coupled with an attempt to increase social awareness o f the adverse effects o f using contaminated water (for example through an educational campaign). An educational campaign, however, will be costly and a medium-term measure. Overall, even for mitigation measures as drastic as introducing another source o f water, the timing o f reduction exposure is not as evident as mightbe imagined. Space precludes further discussion of discounting. It should be noted that it i s not possible to avoid discounting.Not discountingis formally equivalent to discounting at 0%. Unfortunately, zero discountinghas logical implications that make it undesirable, however reasonable it may at first appear (Koundouri and others 2002). - 179- Arsenic Contamination of Groundwater in SouthandEast Asian Countries: Volume I1 Paper 4 The Economics ofArsenic Mitigation - - 21. Moreover, if a regulator is interested inrestricting groundwater abstraction in order to reduce the possible anthropogenic impacts o f pumpingon groundwater contamination, then the exact timing o f the contribution o f this measure to exposure reduction (and possibly the timing o f reintroducing groundwater as a water source) becomes even more difficult to identify. The significant impacts o fpumpingon groundwater flow may result inmedium-term or long-term changes inthe aquifer systems (see Paper 1o f this report). Not only is it difficult to quantify these impacts, both with regards to their time and space dimension, but it is also necessary to be aware o f the various dimensions o f the potential human influences. These include the impacts o f pumping-induced flow on transport o f arsenic both within and between aquifers, impact o f pollutants such as organic carbon and phosphate on aquifer redox and sorption or desorption, and impact o f seasonal waterlogging o f soils for rice production on subsurface redox conditions. 22. Fifth, we need to know where the exposure changes occur. For example, if they occur in heavily populated areas the benefits o f risk reductions will be higher. Environmental effects are even more location specific. 23. The ideal model can now be summarized as follows. The benefits that ensue from arsenic mitigation are givenby equation 2.4 Equation2. Ideal Model ofBenefits Ensuingfrom Arsenic Mitigation PV(B)= j,' (1 s)' + Where: i =the individual impacts PV(B) = the present value o f benefits from arsenic mitigation and is the value that would be compared to the present value o f costs. 24. A particular mitigation option would pass a cost-benefit test if PV(B) > PV(C) (present value o f costs), as shown inequation 3. Equation3. MitigationOptionPassinga Cost-Benefit Test c Mi,' (a' 1 PV(B-C) = (1+S)' -PV(Costs) 2 0 25. Notice that the situation in equation 3 could be met overall in a country but a particular mitigation option could fail in any one region o f the country. Similarly, a mitigation policy could fail a cost-benefit test at the country level, but pass it ina given region. 2.3 Problemswith the IdealModel 26. Models o f the kind shown in equation 3 have been used fairly extensively for such air pollutants as sulfur and nitrogen oxides, particulate matter, and volatile organic compounds (Olsthoorn and others 1999; Krewitt and others 1999). These models make use o f long- established emission-diffusion-deposition models (such as RAINS Euro e), w h c h also contain measurable ecosystem impacts based on notions o f critical loads. They also have P Equation 2 ignores location for convenience o f exposition, but it will be appreciated that benefits and costs vary by location. A critical load is the maximum level of deposition o f airborne pollutants that produces no discernible change in the receiving ecosystem. Above this level, some form of ecological damage occurs. Note that critical loads relate solely to ecosystems and not to health effects. A critical level would be that ambient concentration that producedno discernible change in, for example, human health, materials corrosion, or crop loss. - 180- Arsenic Contaminationof Groundwater in South andEast Asian Countries: Volume I1 Paper4 The Economicsof Arsenic Mitigation - - established exposure-responserelationships for humanhealth. The policies that are simulated also have known, or reasonably known, time schedules over which the pollutants are reduced. Finally, they utilize economic values per effect based on longstanding work under the ExtemE program of DGXII inthe European Commission. 27. The contrast with what is known about arsenic pollution i s a stark one. Inorder to be able to provide an overall policy-level model that will be able to measure the social benefits and costs of arsenic mitigation one would need to know the following (andunfortunately we do not): 0 The effects of mitigationactivities on exposure (AX), since this is dependent onthe behavioral reaction o fproducers, users, and regulators to (a) the changes ininformation generatedby arsenic mitigation efforts andrelevant educational campaigns; and (b) the costs o fregulation. Put another way, we have no economic model o f the relevant economy - includingall users-with which to simulate the effects o f any policy change. The health and environmental exposure-responsefunctions (AI(AX)) for arsenic pollution, o f which, inany event, there are many thousands. 0 The locations at which risks will change. 0 The split between occupational andpublic health effects. 0 The time schedule o fAX, although some assumption could be made about this. 28. We do have some economic values for health end states, but valuation o f environmental effects would not be possible since we have no idea o f the end states o f the changes in, for example, groundwater flows (both interms o f quantityand quality). 29. We conclude that it is not possible to approximate the ideal model in the case o f arsenic mitigation. The information is simply not available. After recognizing that we have to move away from the first-best world o f full information and certainty, in the next section we develop a so-called nth best model, which allows approximation o f the costs and benefits o f arsenic mitigation, but does not claim to be an exact representation (model) o f the actual situation. The reasonsfor the need to have an approximate rather than an accurate model have been explained in this section and need to be taken very seriously by any policymaker who would choose to make use o f this paper. This paper should be thought o f as providing guidance on the methodological approach that one should use when contemplating the economic costs and benefits o f different arsenic mitigation policies. However, the empirical application of the suggested methodological approach should be treated with great caution and results should be read as case study specific, derived under conditions of severe information scarcity and pervasive uncertainty, with regards both to the human and physical reactions to implementable mitigationpolicies. 30. The merit o f our methodological approach (presented insection 2.4) compared to an approach attempting to implement the first-best (ideal) model, i s that it explicitly accepts, identifies, and characterizes the heroic assumptions made in the evaluation process. We hope that this feature o f the proposed nth best model will act as a constant reminder o f the pervasive uncertainties and incomplete informationthat prevail inarsenic mitigation policies. 2.4 The NthBest Model 31. Giventhe circumstances, we have to proceedina far more ad hoc way. 32. The first thing to do is to invert equation 3 and find out just how large the benefits need to be for a particular arsenic mitigation policy to pass a cost-benefit test. We do ths for health effects only since we cannot estimate environmental effects. This procedure gives us a benchmark. If health benefits exceed this level then we know that the particular policy comfortably passes a cost-benefit test. We also have a minimum estimate of benefits since environmental effects are not calculated andthese unknownbenefits would needto be added. - 181- Arsenic Contamination of Groundwater in SouthandEastAsian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - 33. Second, we need some crude ways in which benefits can be estimated given certain assumptions. Water intended for human consumption should be both safe and wholesome. This has been defined as water that i s free from pathogenic agents, free from hannful chemical substances, pleasant to taste, free from color and odor, and usable for domestic purposes (Park 1997). Without ample safe drinking water, communities cannot be healthy. 34. Cvjetanovic (1986) reviews the various mechanisms by which the provision o f safe water supply is transformed into health benefits. His conceptual framework shows that an investment in water supply and sanitation results in an improvement in the quantity and/or quality of water available to the household. This yields direct healthbenefits resultingfrom improved nutrition, personal hygiene, and the interruption o f water-related disease. Moreover, the health benefits from reducing water-related disease can in some circumstances translate into greater work capacity, which may contribute to increased production and hence to overall economic development. According to Becker (1971, 1981), the household uses time, labor, and purchased goods to create commodities for the household. The household attempts to produce safe water for consumption, which is dependent on time and resource constraints. Safe water for household use is dependent on the time and labor used in the collection o f water, the time and resources used to boil or sterilize the water, and managing water within the household. Households may not have access to safe water suppliesbecausethe financial, labor, or time and energy costs o f collection and management are too high, either at a given point intime or perpetually. 35. The provision o f a local safe water supply source i s likely to considerably reduce the burden o f producing safe water for the household. The labor cost o f collecting water is bome largely by women and girls, who are responsible for domestic chores inmost developing countries. It has been found inKenyathat carrying water may account for up to 85% o f total daily energy intake o f females (Dufaut 1990). While this is not currently the case everywhere inSouth and East Asia, ifarsenic mitigation activities implyswitching wells to a safe well, which mightbe located at a significant distance from the house, then it may mean that even inthese countries women have to walk long distances for water. A number o fphysical ailments may result from carrying heavy loads, including head, neck, and spinal problems (Dufaut 1990). Clearly there i s considerable health benefit to be gained from decreasing women's weight-bearing responsibilities. In addition, Krishna (1990) points to the indirect health benefits that may be gained from mothers having greater time to spend on childcare. The extent o f benefit is relatedto service level (proximity to point o f use) andto reliability. 36. All o f these health benefits should be seriously considered in a CBA o f various potential mitigation measures, especially when mitigation measures are likely to deprive women o f these health benefits. That is, due consideration should be paid to the incentives that various mitigation measurescreate for the people, which will to a large extent define the acceptability and effectiveness o f the measures. Ifa mitigation measure is too costly in terms o f time and adverse health effects then implementation will be difficult and monitoring very expensive, if it is possible at all. 37. Access to safe water will also depend on nonmaterial factors, such as basic hygiene knowledge, social position, and water quality. Basic hygiene knowledge and high water quality facilitate access to safe water. It is said that these factors alter the efficiency o f the household as a safe water producer. Social factors affecting access to water supply sources will also determine the ability o f the household to produce safe water. Lower-caste households may not have access to high-quality water supply sources due to cultural norms, whch embrace principles o f social exclusion. Conversely, higher-caste households may be unwilling to share high-quality water supply sources with lower-caste households, which instead may choose alternative sources o f lower-quality water. In other social contexts, the effects on higher castes may be adverse, for example if they are socially excluded from water sourcesused by lower castes. - 182- Arsenic Contamination ofGroundwater in South andEastAsian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - 38. A model for calculating these benefits is developed in chapter 4. Our model, however, takes into account only some o f the identified health benefits and occupational benefits. Other social benefits, such as those outlined in the last three paragraphs o f this section, are not included in the application o f our model due to the lack o f relevant information. Inthe case that such relevant estimates exist, our model i s flexible enough to accommodate such benefits. 2.5 I s Passing a Cost-Benefit Test Sufficient? 39. The requirement that benefits be greater than costs is not sufficient for a policymaker to sanction investment in a particular project. We can say that a cost-benefit ratio >1 is a necessary condition for approval o f a project, but is not a sufficient condition for its approval. This i s because every government invariably faces a limited budget and cannot undertake all projects where social benefits exceed social costs. We therefore require a procedure to rank different projects. It is tempting simply to rank them using the net present value o f benefits, butthis is actually amistake. This is easily demonstratedbytable 1. Table 1.Ranking of Projects Project P V P V N P V P V (benefits) (costs)a (benefits) (benefits)b / PV (costs) X 100 200 100 2.0 Y 50 110 60 2.2 Z 50 120 70 2.4 a. P V = present value. b.NPV =netpresent value. 40. This shows three projects, X, Y, and Z, with the present value (PV) o f their benefits, costs, and net benefits. Suppose the budget constraint is 100 units. Then a ranking by NPV (benefits) would suggest X, Z, Y and we would undertake X only with a cost o f 100. The gain to society would be NPV(X) = 100. But casual inspection shows that we could afford Y and Z, andthe NPV would beNPV(Y) +NPV(Z) = 60 + 70 = 130. Clearly, rankingbyNPV does not give us the right answer. This is given by a ranking o f P V (benefits) divided by PV (costs), or the so-called benefit-cost ratio. 41. The above discussion points to an additional consideration: that one should try to develop a clear picture o f how arsenic mitigation interventions figure inthe overall water and sanitation sector and inthe broader economy o f a country. For example, interventions in sanitation that would drastically reduce diarrhea and infant mortality rates might be another way o f achieving significant social benefits in a developing country such as Bangladesh. Alternatively, perhaps investing in education and transport infrastructure or investing inother sectors o f the economy would produce higher social net present value. Given the different potential social welfare-increasing projects, the policymaker should rank them according to the cost-benefit ratios associatedwith each one, as discussed above. 42. It shouldbe noted, however, that the ability to performsuch arankingexercise depends on the availability o f CBAs for all potential investments, which is an expensive endeavor. Developing countries will not have the means to accommodate such an expensive and holistic exercise; however, they should implement this exercise for policies when possible to prioritize projects. Prioritization will reflect ethical judgments within the country, or binding constraints imposed by the national or international political andpolicy arena. 43. Another point to note, and one which was touched upon in section 2.2 o f t h s paper, is that when embarking on such CBA one should be aware o f the long-run effects o f proposed projects and mitigation measures. Inthe calculation o f present values o f costs and benefits o f - 183 - Arsenic Contamination of Groundwater in South andEast Asian Countries: Volume I1 Paper 4 - The Economics ofArsenic Mitigation - public sector projects and policies, future values are multiplied by a discount factor that is calculated from the social discount rate (social time preference rate). However, at even a modest rate, the practice o f discounting reduces the value o f costs or benefits for longperiods o f time (many years) and hence almost to zero. This disenfranchizes future generations from consideration in today's decisions. Recent work on discounting over the long term has now made it clear that constant rate discounting has only a limited justification, and that it is possible to make recommendations for better practice (Koundouri and others 2002; Pearce and others 2003). The recent literature argues that discount rates vary with time and that, in general, they decline as the time horizonincreases.6The effects o f declining discount rates on the appraisal o f relatively long-term government policies, programs, and projects can be summarized as follows: I s small over a short (for example 30-year) period, but large over a very longperiod Caninfluence the choice of apolicy or project Does not always support the option perceived as best for the environment Can affect financial planning, inbothpublic andprivate sectors 0 May result inreevaluation o f hurdle cost-benefit ratios or budgets inthe public sector 44. Finally, one should keep in mindthat economic poIicy is about making comparisons o f the economic situation, which requires knowledge about the desirability o f the change that an action seeks to bring about. In the real world, choices lead to gains by some and losses by others. To avoid making value judgments in t h s context, a number o f compensation tests have beendevised inan effort to find a basis to compare states that i s founded on effi~iency.~ However, attempts to devise a criterion based solely on efficiency, and without resort to ethical judgments, are simply not available and economists' policy recommendations are controversial. There are several strands to the arguments infavor of declininglong-run interestrates.The first set of argumentsderives from empirical observations ofhow people actually discount the future. There is some evidencethat individuals' time preferenceratesare not constant over time, but decreasewith time. Individuals are observedto discount values inthe near future at ahigherratethan values inthe distant future. While some evidencestill supports time-constantdiscountrates, the balanceofthe empirical literaturesuggests that discount ratesdecline inahyperbolicfashionwith time. The secondset of argumentsinfavor oftime-varying discount ratesderives from uncertaintyabout economic magnitudes. Two parametershave been selectedfor the main focus ofthis approach.The first isthe discountrateitself. The argumenti sthat uncertaintyabout the social weight to be attachedto future costsandbenefits-the discount factor -producesa certainty-equivalent discount rate, which will generallydeclineover time. The seconduncertainparameter is the future state ofthe economy as embodiedinuncertaintyabout future consumptionlevels.Under certain assumptions, this form of uncertaintyalso producesa time-declining discountrate.The third set of argumentsfor time-declining discount ratesdoesnot derive from empirical observationor from uncertainty.Instead, this approach-the "social choice" approach- directly addressesthe concernsof manythat constant-ratediscountingshifts unfair burdens of social cost onto future generations.It adopts specific assumptions (axioms) about what areasonableandfair balanceof interestswould be betweencurrent and futuregenerations, andthen shows that this balancecanbe broughtabout by atime-declining discount rate.Any one, or all, ofthese three lines of arguments supportsthe hypothesisthat the socialtime preferenceratedeclinewith time. Moreover,there have beenanumber of attemptsto construct models to quantify the shape of this decline and, insome cases, to test them empirically. An excellent discussionof compensationtests canbe found in Chipmanand Moore 1978. - 184- Arsenic Contamination of Groundwater inSouth andEast Asian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - 3. The CostofArsenic MitigationMeasures: Review of PossibleActions 45. As indicated in chapter 2, the CBA undertaken inthis paper will only take into account some of the health-related costs o f arsenic contamination and resulting occupational hazards.These costs will translate into benefits if avoided through the implementation o f effective mitigation measures. Hence, in order to derive the cost-benefit ratio o f the different mitigation measures these benefits should be compared with the costs o f the relevant mitigation measures. These costs andbenefits are described inthis chapter. 3.1 HealthEffects ofArsenic inDrinkingWater 46. The World Health Organization (WHO) recommendations on the acceptability and safety o f levels o f arsenic indnnking water have dropped twentyfold from a concentration o f 200 pg L-' in 1958to 10pgL-'inits 1993 Drinking Water Guidelines. However, somecountries are still using the former WHO standard o f 50 pg L'. For example, the Bangladesh Standards for TestingInstitution sets the maximumpermissible limit for arsenic at this former level. 47. Differences in standards derive partly from the fact that there i s no widely accepted complete definition o f what constitutes arsenicosis. Inorganic arsenic i s a classified carcinogen (IARC 1980) that also has a multitude o f noncancer effects. The widespread effects o f arsenic are perhaps responsible in part for the lack o f a widely accepted care definition for arsenicosis. Furthermore, some symptoms o f arsenicosis (such as shortness o f breath) may be observationally indistinguishable from the health effects o f other illnesses. A comprehensive review o f the health effects o f arsenic contamination o f dnnkmgwater is undertaken in Paper 2 o f this report. The purpose o f this section is to highlight some o f the main findings o f the literature on health effects, especially with respect to predictive use o f the available information. In addition, arsenic poisoning may be acute or chronic. In the context o f community drinking water supply, only chronic exposure i s relevant. Acute poisoning is therefore not discussed further. 48. According to the United StatesNational Research Council report (NRC 1999, p. 89), the most widely noted noncancer effect o f chronic arsenic consumption is skin lesions. Over time, arsenic exposure i s associated with keratoses on the hands and feet. The time from exposure to manifestation is debated inthe literature, while the youngest age reported for patients with hyperpigmentation and keratosis i s two years o f age (Rosenberg 1974). InBangladesh, Guha Mazumder and others (1998) suggest a minimum time gap o f five years between first exposure and initialmanifestations. 3.1.1 Cancer Health Effects' 49. Hutchinson (1887) identified arsenic as a carcinogen because o f the high number o f skin cancers occurring in patients treated with arsenicals. The International Agency for Research on Cancer (IARC 1980) classified inorganic arsenic compounds as skin and lung (via inhalation) carcinogens. Inthe period following this classification, concerns have grown over the possibility o f arsenic indrinkingwater causing a number o f other cancers. 50. An early study by Tseng and others (1968) found evidence o f a dose-response relationship between concentration o f arsenic in drinlung water and prevalence o f skin cancer. The International Program on Chemical Safety (IPCS 1981) estimated skin cancer risk from lifetime exposure to arsenic in drinking water at 5% for 200 pg L', based on the findings o f Tseng (1977). Based on the increased incidence o f skin cancer observed in the population in Taiwan, China, the United States Environmental Protection Agency (EPA 1988) has used a Arsenic i s also associated with peripheral vascular disease, which i s a condition that results in gangrene inthe extremities and usually occurs in conjunction with skin lesions. Other cardiovascular problems such as hypertension (Chen and others 1995) and ischemic heart disease have also been found to be associated with arsenic (Tsuda and others 1995). Moreover, Guha Mazumder and others (1998) found evidence o f liver enlargement and restrictive lung disease. In terms o f hematologcal effects, anemia is commonly cited (NRC 1999). Another widely suggestedhealth effect is diabetes mellitus. - 185- Arsenic Contaminationof Groundwater in Southand East Asian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - multistage model that is both linear and quadratic in dose to estimate the lifetime skin cancer risk associated with the ingestion of arsenic in drinking water. With this model and data on males, the concentrations o f arsenic in drinking water associated with estimated excess lifetime skin cancer risks o f IO4, and are 1.7, 0.17, and 0.017 p g L-'respectively. Considering other data and the fact that the concentration o f arsenic in drinkingwater at an estimated skin cancer risk o f IO-' is below the practical quantification limit o f 10 pg L', the provisional guideline value o f 10 pgL-'is recommended (WHO 1996). The guideline value is associated with an excess lifetime risk for skin cancer of 6 x (that is, six persons in 10,000). 51. Highlevels o f arsenic indrinking water are also associatedwith a number o f internal cancers. However, it is difficult to quantitatively establish risk inmany o f the studies, due to problems in measuring exposure to arsenic. Chen and others (1985) calculated standardized mortality ratios for a number o f cancers in 84 villages in Taiwan. Mortality for the period 1968-1986 was compared with age and sex-adjusted expected mortality. Significantly, increased mortality was observed among both males and females for bladder, hdney, lung, liver, and colon cancers. However, the authors were not able to directlyestimate arsenic concentrations in well water. Chen and Wang (1990) were able to use data on arsenic concentrations in 83,656 wells in 314 precincts and townships collected from 1974 to 1976 in Taiwan. The authors used a multiple regression approach to control for socioeconomic confounding factors, and compared age-adjusted mortality rates with average arsenic concentrations in each township. They found a significant relationship between arsenic concentration and mortality from cancers o f the liver, nasal cavity, lung, bladder, and kidney for both sexes. 52. The above-mentioned studies all used an ecological design and are thus susceptible to bias from confounding factors. However, the bladder and lung cancer results o f these studies are also confirmed by cohort studies, which may be less susceptible to this form o f bias. These studies are also useful in providing data on the latency period o f internal cancers. Cuzick, Sasieni, and Evans (1992) studied a cohort o f patients treated with Fowler's solution (potassium arsenite) in England from 1945 to 1969. The authors found evidence that the period between first exposure and death from bladder cancer varied from 10 years to over 20 years. 53. To conclude, the results from studies o f cancer indicate strong evidence that exposure to arsenic i s related to skin, lung, and bladder cancer. It i s likely that arsenic causes a number o f other cancers, but thus far epidemiological evidence has not been consistent for other sites in the body. 3.1.2 Treatment of Arsenicosis Sufferers 54. Guha Mazumder (1996) suggestedthat the first stage intreating those with arsenicosis should be the immediate cessation of consumption o f arsenic-contaminated water. Once this has been achieved, the emphasis should be on the provision o f a diet highinprotein and vitamins. The chelating agents DMPS (dimercaptopropane sulphonate) and DMSA (dimercaptosuccinic acid) are recommended as treatment drugs (Angle 1995). However, Guha Mazumder (1996) notes that these drugs are very expensive. Palliative care may be the only affordable treatment in rural areas of developing counties, where expensive drugs and protein-rich diets are unlikely to be available to the vast majority o f people. Inthe case o f keratosis, application o f ointment containing salicylic acid canhelp to soften the skin and ease the patient's pain. 3.2 Mitigation of Arsenic inDrinkingWater 55. This section will analyze the technologies that can be used to provide safe drinkingwater in rural Bangladesh, which serves as an example for most relevant mitigation options. The available options for safe water can be classified by source: groundwater, surface water, and rainwater. Recent years have seen increasing acceptance o f strategies for incremental improvement inenvironment and healthingeneral and o f demand-dnven approaches to water supply and sanitation in particular. It is inappropriate therefore to pursue a single overall - 186 - Arsenic Contamination o f Groundwater in South and East Asian Countries: Volume I1 Paper 4 The Economics ofArsenic Mitigation - - technological solution but rather to inform communities and individuals o f alternatives and their characteristics inorder to facilitate choice o f the most appropriate options. 3.2.1 Groundwater 56. The simplest and most immediately achievable option is the sharing o f tubewells that are currently either free from arsenic or contain very low levels. Wells containing arsenic may still be used safely for such activities as washing laundry, and a simple color coding (using, for example, "traffic light" colors) may have a significant impact on community arsenic exposure if carefully and continuously backed up by awareness raising and education. However, inthe most highly contaminated areas not enough tubewells will contain safe levels o f arsenic. Furthermore, color coding would have to be monitored carefully over time, as tubewells with previously safe test results may be later found to contain increased levels o f arsenic. The principal costs o f such an approach relate to the ongoing testing and labeling o f wells and o f continuous awareness raising and education. These costs may be borne by the community or by an outside agency. Inpractice, the household burden o f water collection is likely to increase (because a greater average distance will be traveled in order to collect the same volume o f water). 57. For some countries, such as Bangladesh and Nepal, the other altemative for groundwater supply is the development of deep tubewells. The principal costs of such anapproach relate to the costs of developing the deep tubewells. These include the costs oftraining and equipping dnlling teams as well as the direct costs of drilling itself, including a proportion o f unsuccessful bores. These costs may be bome by the community or an outside agency. If contaminated wells remain in use for other purposes such as laundering ongoing awareness raising and education will be essential. Ifnew wells are appropriately sited then the household burden o fwater collection may be constant or even decrease. Deep tubewells have beeninuse for years in coastal areas because o f high salinity in shallow aquifers. However, it is not possible to exploit this technology in all areas because rock formations may make drilling infeasible. 58. The Danish Agency for International Development (Danida) has conducted research in Noakhali in Bangladesh since November 1998 on the removal o f arsenic using a mix o f 200 pg L-'alum and 1.5 pg L-'KMn04introduced into a large bucket (18 liters), o f which the supernatant is drained off after 1-1.5 hours into a bucket standing beneath it. Cost o f chemicals for an average family is Tk 10/US$0.2 a month. Lab tests show a reduction in arsenic levels o f 1,100 pgL' to 16 p g L'. Inthe field tests arsenic ranging from 120-450 pg L" was reduced to 20-40 pg L-'consistently. Though well within the Bangladesh standard, the removal efficiency was considerably less than in the laboratory. Stirring (time, mixing efficiency -paddle stick instead o f cane stick) is believed to make a difference and Danida is currently verifying this in a field test. Danida has also designed a two-bucket column (total investment cost for the set is Tk 300/US$6), which circumvents the resuspension o f the settled solids. Danida reports that 50-80% o f the two-bucket systems deliver water within Bangladesh standards (Danida 2000). 59. Coprecipitation is a well-known phenomenon and has been the subject o f a small study by WaterAid in East Madaripur near Chittagong. Iron ranges from 0 to 10 p g L'. In the first phase o f the study it seemedthat removal rates were very good. However, upon further study it was found that some wells showed very low removal rates. It seems that salinity has a detrimental effect on removal. Hardness may possibly have an effect as well. 60. The Danida and WaterAid studies also examined the sustainability o f methods at the household level. Apart from initial acceptance o f a suitable method, households will also have to apply the technique consistently and properly to continue to avail themselves o f the benefits o farsenic avoidance. - 187 - Arsenic Contamination of Groundwater in SouthandEast Asian Countries: Volume I1 Paper 4 The Economics of Arsenic Mitigation - - 61. The PanAmerican Center for Sanitary Engineering and Environmental Sciences (CEPIS)' in Peruhas developed a technology called ALUFLOC for arsenic removal at the household level and it has been tested in Argentina. ALUFLOC is a sachet containing chemicals that are added to a bucket o f arsenic-contaminated tubewell water. After about an hour the treatment process i s complete and the water is safe for consumption. Preliminary field test results suggest that ALUFLOC is effective inreducing arsenic content to safe levels. However, it is necessary to optimize the product for treating tubewell water with a concentration o f arsenic greater than 1,000 pg L-'.The cost o f the technology is estimated at US$O.lS per bucket treated, given the assumption o f production at an industrial level. The cost o f such an approach relates to the ongoing need for awareness raising and education; the cost o f treatment materials (including manufacture and distribution); and the costs o f additional household expenditure on equipment(such as additional buckets) and interms o f time. It may however be deployed rapidly and costs may be borne by the community or an outside agency, or may be subsidized. 3.2.2 SurfaceWater 62. Surface water (including rainwater, rivers, lakes) i s typically low in arsenic and therefore a potentially attractive source o f drinking water in arsenic-rich areas. However, surface waters are frequently contaminated with human and animal fecal matter and other material and are unsafe for this reason. This risk initially led to the preference for groundwater sources in Bangladesh and other developing countries worldwide. The critical issues in arsenic-rich areas therefore concern whether treating surface water for fecal contamination can be reliably achieved at a lower overall cost than securing groundwater from low-arsenic sources or through treatment to remove arsenic from groundwater. 3.2.2.1 Surface WaterTreatment 63. Treatment o f surface water can be achieved by several means. Slow sand filtration, for example, is a typical method o f treatment for rural areas and small towns. The water passes slowly through a large tank filled with sand and gravel. There i s some reservation about the sustainability o f this method inBangladesh. The reasons for t h s include the need for careful maintenance and the risk o f bacteriological infection if the system is not operated properly. However, pond sand filters are still useful as an option in Bangladesh, especially in the coastal beltwhere there are few alternatives. 64. The key elements in the decisionmaking process leading to the selection o f technology using surface water rather than groundwater concern the costs o f capital investment ininfrastructure andthe cost o fmaintenance, includingsupervisory support. Ifwells containing arsenic remain in use, ongoing awareness raising and education will be required. The household burden of water collection i s likely to increase (as the number o f available sources i s likely to decrease) unless the opportunity i s taken to make capital investments to develop pipeddistribution. 3.2.2.2 Rainwater 65. Rainwater harvesting i s a recognized water technology in use in many developing countries around the world (WHO-IRC 1997). The United Nations Children's Fund (UNICEF) has promoted dissemination o f the technology since 1994 in Bangladesh. The rainwater i s collected using either a sheet material rooftop and guttering or a plastic sheet and is then diverted to a storage container. 66. Rainwater harvesting is capital intensive and the costs (and availability) o f suitable roofing, materials for guttering, and storage tanks are important factors. Rainwater use has proven to be successful inTaiwan, Sri Lanka, and Thailand. 67. In some circumstances there is the possibility o f chemical contamination o f the collected water, particularly where air pollution is a major problem and where bacteriological CEPIS is part ofthe PanAmericanHealthOrganization(PAHO), the WHO RegionalOffice for the Americas. - 188 - Arsenic Contaminationof Groundwater in South andEastAsian Countries: Volume I1- Paper4 The Economicsof Arsenic Mitigation - contaminationmay be causedby birddroppings. There is also the possibility o f contamination (for example intrusion o f insects), particularly when the water is stored for long periods. Health inspections are needed regularly to ensure that the water is o f good quality. However, these reservations mightbe less problematic as rainwater quality inmany circumstances is at least as good as the pipedwater distributedinmanytowns inBangladesh. 68. The above are only examples o f technologies that might be considered as alternatives to groundwater abstraction. Other low-cost technologies that mightbe considered include use o f springs andinfiltration galleries. 69. In our empirical application we consider eight alternative technologies designed to provide arsenic-free water: dug wells, roof rainwater combined with dug wells for the dry season, deep tubewells, arsenic removal in existing shallow tubewells, pond sand filters, deep production wells (piped scheme), impoundment-engineered pond (piped scheme), and surface water infiltration (pipedscheme). 3.2.3 TechnologyChoice 70. The following analysis is based on Bangladesh data and naturally it will vary in different countries, due mainly to the population density, the severity o f the arsenic problem, and the geographic distribution o f the population. Moreover, we take into account only the mal population o f Bangladesh. The technology options considered can all be applied in Bangladesh, but some o f them may not be applicable inother countries. For example, in some countries deep tubewells may not be usefbl because the aquifer structure i s such that deep tubewells may alsobe contaminated (see Paper 1). 71. The choice between these technologies should take into account their cost-effectiveness in providing arsenic-free and microbiologically safe drinkingwater. Differentoptions may have very different balances o f cost between, for example, capital and recurrent costs and may impact differently on the household costs o f water management. However, the criteria o f sustainability and acceptanceby rural users must be incorporated into the calculation o f cost- effectiveness in order to aid the decisionmaking process concerning which mitigation method(s) to implement. Table 2 indicates the mitigation options for which cost evaluation is conducted. Table 2. Arsenic Mitigation Technology Options Optionno. Technology A Dugwells B1 Roofrainwaterharvestinghousehold(60 m2)+ dugwell for dry season B2 Roofrainwaterharvestinghousehold(60 m2)+ deeptubewell for dry season C Deeptubewell D Existing shallow tubewellwith householdarsenic removal E l Pondsand filter E2 Pondsand filter (30 householdsipondsand filter) F Pipedscheme deepproductionwell G Pipedscheme impoundment-engineeredpond H Pipedscheme surface water infiltrationgallery 72. The aforementioned technology options are evaluated for three kinds o f villages: small (100 households), medium (500 households), and large (1,000 households). We further assume that - 189- Arsenic Contamination of Groundwater in Southand East Asian Countries: Volume I1 Paper4 The Economics ofArsenic Mitigation - - each household consists o f an average 5.5 members and that the distribution o f income is as follows: 10% have high income, 20% have medium income, and 70% have low income. The level o f service provided to each household depends on the income o f the household. The high-income people will be provided water by multiple taps (one for each household), the medium-income people will have a single yard tap per two or three households, while a communal standpost will be provided per 10 households o f low income. The distribution o f income as well as the level o f service i s necessaryfor the most accurate cost estimation. 73. Table 3 shows the capital costs and operation and maintenance annual costs applied to a small village o f 100households." The most expensive technology interms o f capital costs i s option B (both B1andB2), which combines rainwater harvestingwith the construction of dug wells or deep tubewells. In terms of operation and maintenance expenses option D is the most expensive, due to the costs o f the arsenic removal techniques. The level o f service provided for a small village by each o f the techniques is summarized intable 4. 74. In the same mode, for a mediumvillage o f 500 households, table 5 shows the capital costs andannual operation andmaintenance costs, while table 6 shows the level o fservice. 75. For a large village o f 1,000 households, table 7 shows the capital costs and annual operation andmaintenancecosts, while table 8 shows the level o f service. lo A detaileddescriptionofthe costs involvedineachtechnology for avillage of 500 householdsis givenin annex 1. - 190- Arsenic ContaminationofGroundwaterinSouthand EastAsianCountries: Volume I1 Paper4 -The Economicsof Arsenic Mitigation - Table3. Small Village: Capital andOperationandMaintenance Costs Technology Capitalcosts (US$)" Operation& maintenance costs (US$)" ~ A Dugwells 17,750 2,968 B1 Rainwater harvesting+ dugwell 33,913 3,523 B2 Rainwater harvesting+ deeptubewell 35,335 2,819 C Deeptubewell 21,561 1,083 D Shallowtubewellwith arsenic removal 7,966 4,237 El Pondsandfilter 25,719 2,242 E2 Pondsandfilter (30 households/unit) 3,810 332 F Deepproductionwell, piped 19,432 3,05 1 G Impoundment, piped 19,432 3,390 H River abstraction,piped 17,653 3,051 a. Costs are for a smallvillage of 100households. Table4. Small Village: Technology-Specific Levelof Service Technology No. ofhouseholdsper unit by income Total for 100 households High Medium Low (10%)" (20%)b (70%)' A Dugwells 1 3 10 24 B1/2 Rainwater+ dugwell/tubewell 1 1 1 100 C Deeptubewell 1 3 10 24 D Shallowtubewell/arsenicremoval 1 1 1 100 El Pondsandfilter 1 2 10 27 E2 Pondsandfilter (30 householdsiunit) 30 30 30 4 F Deepproductionwell, piped 1 2 10 27 G Impoundment, piped 1 2 10 27 H River abstraction, piped 1 2 10 27 Type of service: a. multiple taps; b. single yardtap; c. communalstandposts. - 191- Arsenic Contamination o f Groundwater in South andEast Asian Countries: Volume I1- Paper4 The Economics ofArsenic Mitigation - Table 5. MediumVillage: Capital andOperation andMaintenance Costs Technology Capitalcosts (US$)" Operation& maintenance costs (US$)* A Dugwells 88,750 14,842 B1 Rainwater harvesting+ dugwell 169,566 17,616 B2 Rainwaterharvesting +deeptubewell 176,677 14,097 C Deeptubewell 107,803 5,415 D Shallowtubewellwith arsenic removal 39,831 21,186 E l Pondsandfilter 128,593 11,212 E2 Pondsandfilter (30 households/unit) 16,193 1,412 F Deepproductionwell, piped 47,093 6,780 G Impoundment,piped 48,246 7,627 H River abstraction, piped 44,534 6,780 a. Costsare for amediumvillage of 500 households. Table 6. MediumVillage: Technology-Specific Level of Service Technology No. ofhouseholdsper unit by income Total for 500 households High Medium Low (20%)b (70%)' A Dugwells 1 3 10 118 B1/2 Rainwater+ dugwellitubewell 1 3 10 118 C Deeptubewell 1 3 10 118 D Shallowtubewell/arsenicremoval 1 1 1 500 E l Pondsand filter 1 2 10 135 E2 Pondsand filter (30 households/unit) 30 30 30 17 F Deepproductionwell, piped 1 2 10 135 G Impoundment, piped 1 2 10 135 H River abstraction, piped 1 2 10 135 Type of service: a. multiple taps; b.single yardtap; c. communal standposts. - 192- Arsenic Contamination ofGroundwater in SouthandEast Asian Countries: Volume I1- Paper4 The Economicsof Arsenic Mitigation - Table 7. Large Village: Capital and Operation and Maintenance Costs Technology Capitalcosts (US$)a Operation& maintenancecosts (US$)a A Dugwells 177,500 29,684 B1 Rainwaterharvesting+ dugwell 339,131 35,232 B2 Rainwaterharvesting+ deeptubewell 353,355 27,178 C Deeptubewell 215,607 10,831 D Shallowtubewellwith arsenic removal 79,661 42,373 E l Pondsandfilter 257,186 22,424 E2 Pondsandfilter (30 householdshnit) 32,386 2,824 F Deepproductionwell, piped 87,075 9,322 G Impoundment,piped 89,075 10,508 H River abstraction,piped 85,024 9,322 a. Costsare for alargevillage of 1,000 households. Table 8. Large Village: Technology-Specific Level of Service Technology No. ofhouseholdsper unit by income Total for 1.ooo High Medium LOW households (20%)b (70%)' A Dugwells 1 3 10 237 B1/2 Rainwater+ dugwellitubewell 1 3 10 1,000 C Deeptubewell 1 3 10 237 D Shallowtubewell/arsenicremoval 1 1 1 1,000 E l Pondsandfilter 1 2 10 270 E2 Pondsandfilter (30 householdshnit) 30 30 30 34 F Deepproductionwell, piped 1 2 10 270 G Impoundment,piped 1 2 10 270 H River abstraction, piped 1 2 10 270 Type of service: a. multiple taps; b. single yardtap; c. communalstandposts. - 193 - Arsenic Contamination ofGroundwater in Southand East Asian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - 76. We further conducted a present value analysis in order to identify the technology option with the lowest cost for each kind o f village. Our analysis suggests that the most efficient option for small villages is option C, deep tubewells, while for mediumand large villages option H, river abstraction (piped), should be employed. These options guarantee arsenic-free water. However, ifwe disregard the issue o f the level o f service, the most efficient technique i s pond sand filters (30 households per pond sand filter). Special attention should bepaid to avoidance of bacterial contamination o f the water, as percolation o f contaminated surface water is the most common route o f pollution. Disinfection o f the water by pot chlorination should be continued during operation. As regards option F, the deep aquifers in Bangladesh have been found to be relatively free from arsenic contamination. The study by the British Geological Survey and the Department o f Public Health Engineering (BGS and DPHE 2001) has shown that only about 1% o f tubewells having a depth greater than 150 m are contaminated with arsenic at concentrations higher than 50pg L1and 5% o f tubewells have arsenic content above 10 pg L-' (See Paper 1 for a more detailed analysis). The combination o f deep production wells with piped water supply can ensure the provision o f good quality water to people. Details for the present value o f the total costs o f the various techniques for each o f the three sizes o f village are given in tables 9, 10, and 11. The numbers inbold indicate the least costly options. Table 9. Small Villages: Present Value Analysis o fTechnology Costs Technology Costs(millions US$)" D R ~ 10% for DRb10% for DRb15% for 10 years 15 years 20 years A Dugwells 35,989 43,021 36,330 B1 Rainwaterharvesting +dugwell 55,561 63,908 55,966 B2 Rainwater harvesting+ deeptubewell 52,660 59,339 52,984 C Deeptubewell 28,216 30,781 28,340 D Shallowtubewellwith arsenic removal 34,002 44,041 34,489 E l Pond sandfilter 39,497 44,809 39,754 E2 Pondsandfilter (30 householdshnit) 5,851 6,638 5,890 F Deepproductionwell, piped 38,178 45,406 38,528 G Impoundment, piped 40,261 48,292 40,650 H River abstraction, piped 36,399 43,626 36,749 a. Total costs of servingall small villages of 100 households. Figures inboldindicateleast-cost options. b. DR= discount rate. - 194- Arsenic Contamination ofGroundwater in SouthandEastAsian Countries: Volume I1 Paper4 The Economics o fArsenic Mitigation - - Table 10. MediumVillages: PresentValue Analysis ofTechnology Costs Technology Costs (millions US$)a D R ~ 10% for DR~10% for D R ~15% for 10 years 15 years 20 years A Dugwells 179,946 215,107 181,650 B1 Rainwaterharvesting +dugwell 277,807 319,539 279,829 B2 Rainwaterharvesting+ deep tubewell 263,300 296,697 264,9 18 C Deeptubewell 141,078 153,907 141,700 D Shallowtubewellwith arsenic removal 170,012 220,203 172,443 El Pondsandfilter 197,485 224,046 198,772 E2 Pondsandfilter (30 householdsiunit) 24,869 28,213 25,031 F Deepproductionwell, piped 88,751 104,812 89,529 G Impoundment, piped 95,111 113,180 95,986 H River abstraction, piped 86,192 102,253 86,970 a. Total costs of servingall mediumvillages of 500 households.Figuresinbold indicate least-cost options. b. DR= discount rate. Table 11.LargeVillages: PresentValue Analysis ofTechnology Costs Technology Costs(millions US$)a D R ~ 10% for D R ~10%for D R ~ 15% for 10 years 15 years 20 years A Dugwells 359,893 430,213 363,300 B1 Rainwater harvesting + dug well 555,615 639,078 559,658 B2 Rainwaterharvesting+ deeptubewell 520,351 584,736 523,470 C Deeptubewell 282,156 307,814 283,399 D Shallowtubewellwith arsenic removal 340,024 440,405 344,887 E l Pondsandfilter 394,971 448,092 397,544 E2 Pond sandfilter (30 householdsiunit) 49,737 56,426 50,061 F Deepproductionwell, piped 144,354 166,438 145,424 G Impoundment, piped 153,645 178,539 154,851 H River abstraction, piped 142,304 164,387 143,373 a. Total costs of servingall largevillages of 1,000 households.Figuresinboldindicateleast-cost options. b. DR = discount rate. - 195 - Arsenic Contamination of Groundwater in Southand EastAsian Countries: Volume I1- Paper4 - The Economics of Arsenic Mitigation 77. The first column o f tables 9, 10, and 11refers to a discount rate o f 10% for a 10-year period, the second column to a discount rate o f 10% for a 15-year period, and the third column to a discount rate o f 15% for a 20-year period. These figures can be used as the basis for a sensitivity analysis, whose reasoning derives from: (a) 10-15% is the lending rate in Bangladesh; and (b) 10-20 years is a reasonable payout period given the financial market in Bangladesh. 78. In order to assess the total cost o f providing the Bangladesh people with arsenic-free water, we need to make some hrther assumptions. These assumptions, which are listed below, are adopted solely for demonstration purposes and they do not reflect in any way the policy priorities o f the World Bank. Technology is chosen accordingto the geographic population distribution. 0 Deep tubewells are the optimal choice for small villages up to 100households, while river abstraction (piped) is the optimal choice for mediumand large villages o f 500 and 1,000 households. 0 40% o f the population i s assumedto inhabit small villages, while the remainder o f the population is equally dividedbetween medium and large villages. 0 Out o fthe total population (129 million), roughly 29 millionpeoplelive inarsenic- affected areas. Moreover, we concern ourselves here with the rural population, which i s approximately 99 million." 0 The methodology outlined canbe implemented ina range o f cases: for example, for one village, for a specific region, or for the whole region. 79. The rural population, approximately 99 million people, consists o f around 18 million households. Giventhe geographic distribution o f the population, we will assume for analytical purposes that 7,200,000 households live insmall villages (72,000 villages o f 100 households), 5,400,000 households live in medium villages (10,800 villages of 500 households), and 5,400,000 households live in large villages (5,400 villages of 1,000 households). Tables 12, 13, and 14 indicate the costs applicable to each o f the three categories o f village. Table 15 indicates total capital and operation and maintenance costs for the entire rural population. In this mode, total capital costs for the selected technology options range from US$0.6 to $6.4 billion, and total operation and maintenance costs range from $0.05 to $0.8 billion per year (table 15). ''There are very wide differences inthe levels o f exposure to arsenic throughout this rural population. Using data in Maddison, Luque, and Pearce 2004 we calculated an average exposure level for the entire rural population o f 57 pgL-I,which forms the basis o fthe analysis undertaken here. - 196- Arsenic ContaminationofGroundwaterin SouthandEast Asian Countries: Volume I1 Paper4 -The EconomicsofArsenic Mitigation - Table 12. SmallVillages: Total Costs ofMitigationTechnology Options Technology Capitalcosts Operation& (million maintenancecosts (million US$)" A Dugwells 1,278.00 213.72 B1 Rainwaterharvesting+ dugwell 2,441.75 253.67 B2 Rainwaterharvesting + deeptubewell 2,544.15 203.00 C Deeptubewell 1,552.37 77.98 D Shallow tubewellwith arsenic removal 573.56 305.08 E l Pondsand filter 1351.74 161.45 E2 Pondsandfilter (30 householdsiunit) 274.33 23.92 F Deepproductionwell, piped 1,399.12 219.66 G Impoundment,piped 1,399.12 244.07 H River abstraction,piped 1,270.98 219.66 a. Costsare for an estimated72,000 small villages of 100households each= 7,200,000 households. Table 13. MediumVillages: Total Costs ofMitigationTechnology Options Technology Capital costs Operation& (million US$)a maintenance costs (million US$)a A Dugwells 958.50 160.29 B1 Rainwater harvesting + dugwell 1,831.31 190.25 B2 Rainwater harvesting+ deeptubewell 1,908.11 152.25 C Deeptubewell 1,164.28 58.48 D Shallow tubewellwith arsenic removal 430.17 228.81 E l Pondsand filter 1,388.81 121.09 E2 Pondsand filter (30 householdsiunit) 174.89 15.25 F Deepproductionwell, piped 508.61 73.22 G Impoundment,piped 521.05 82.37 H River abstraction, piped 480.97 73.22 a. Costsare for an estimated 10,800 mediumvillages of 500householdseach= 5,400,000 households. - 197- Arsenic Contaminationof Groundwater inSouthandEastAsian Countries: Volume I1 Paper4 -The Economicsof Arsenic Mitigation - Table 14. LargeVillages: Total Costs ofMitigationTechnology Options Technology Capitalcosts Operation& (million US$)" maintenancecosts (million US$)" A Dugwells 958.50 160.29 B1 Rainwater harvesting + dugwell 1,831.31 190.25 B2 Rainwaterharvesting+ deep tubewell 1,908.1 1 146.76 C Deeptubewell 1,164.28 58.48 D Shallowtubewellwith arsenic removal 430.17 228.81 El Pondsand filter 1,388.81 121.09 E2 Pondsand filter (30 householdshnit) 174.89 15.25 F Deepproductionwell, piped 470.20 50.34 G Impoundment,piped 481.OO 56.75 H River abstraction, piped 459.13 50.34 a. Costsare for an estimated5,400 largevillages of 1,000 householdseach = 5,400,000 households. Table 15. All Villages: Total Costs ofMitigationTechnology Options Technology Capitalcosts Operation& (million US$)" maintenancecosts (million US$)" A Dugwells 3,195 .OO 534.31 B1 Rainwaterharvesting dugwell + 6,104.36 634.17 B2 Rainwaterharvesting+ deeptubewell 6,360.38 502.02 C Deep tubewell 3,880.93 194.95 D Shallowtubewell with arsenic removal 1,433.90 762.71 El Pond sandfilter 4,629.36 403.63 E2 Pond sandfilter (30 householdshnit) 624.11 54.41 F Deepproductionwell, piped 2,377.93 343.22 G Impoundment,piped 2,401.18 383.19 H River abstraction, piped 2,211.08 343.22 a. Aggregate costs for all small, medium, andlargevillages (tables 12, 13, and 14). - 198 - Arsenic Contamination ofGroundwater in SouthandEast Asian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - 4. Applying the Model 4.1 Methodologyfor the Model 80. The model developed inthis chapter is a CBA model described by the following equation: PV(B-C)= i J (1 s)' + -PV(Costs) 2 0 We proceedby calculating the presentvalue of costs andthen estimatingthe relevant benefits. 4.2 Data and Estimatesfor the Model 81. Given our analysis o f capital costs and operation and maintenance expenses in the previous chapter, we translate these figures into present values by using a 50-year horizon and a 5%, lo%, and 15% discount rate.I2 Moreover, we disaggregate these costs into costs paid by individuals and costs paid by the government based on the assumption that 20% of capital costs are paid by the individuals who bear the operation and maintenance expenses as well. This disaggregation i s directly related to healthbenefits, as health expenditure i s both private andpublic. As table 16 suggests, the present value oftotal costs is inthe range US$1.6 billion to $15.4 billion for the 5% discount rate. Using the optimal choice, however, this cost drops to $0.5 billion for the government and to $l.lbillion for individuals (total $1.7 billion). The respective figures for the 10%and 15% discount rates are $1.1 billionand $0.9 billion. Table 16. PresentValue o fCosts o fArsenic Mitigation Options for Whole Population Technology Govtcost Presentvalue ofprivate cost Presentvalue oftotal cost 5% 10% 15% 5%o 10% 15% A Dugwells 2,556 10,393 5,937 4,198 12,949 8,493 6,754 B1 Rainwater+dugwell 4,883 12,798 7,509 5,445 17,682 12,392 10,328 B2 Rainwater+ deeptubewell 5,088 10,437 6,249 4,616 15,525 11,338 9,704 C Deeptubewell 3,105 4,335 2,709 2,075 7,440 5,814 5,179 D Shallowtubewelliarsenicremoval 1,147 14,211 7,849 5,367 15, 358 8,996 6,514 El Pondsandfilter 3,703 8,294 4,928 3,614 11,998 8,631 7,318 E2 Pondsandfilter (30 householdsiunit) 499 1,118 664 487 1,618 1,164 987 F Deepproductionwell, piped 1,902 6,741 3,879 2,762 8,664 5,781 4,664 G Impoundment,piped 1,921 7,476 4,279 3,032 9,397 6,200 4,953 H River abstraction, piped 1,769 6,708 3,845 2,728 8,477 5,614 4,497 Combinedoption 1,994 4,178 2,497 1,841 6,172 4,491 3,835 Inthis chapter both costs and benefitsare discountedat 5%, lo%, and 15%. Since healthbenefits shouldbe discountedfor a period of at least 50 years as they spread over a lifetime, we do the same with the costs. The relevant discount rate for benefits spread over the long run(more than 30 years) shouldbe much lower thanthe one used on short-runprojects. This is the reasonthe 5% discountrate is used in additionto the 10% and 15% discountrates. Inthe previous chapter only 10-15% was usedas the focus was only on costs, and (a) 10-15% is the lendingrate in Bangladesh; and (b) 10-20 years is a reasonablepayout period given the financial market in Bangladesh. - 199- Arsenic Contaminationof Groundwater in South andEast Asian Countries: Volume I1- Paper4 The Economics of Arsenic Mitigation - 82. For a mitigation policy to result inapositive present value, the present value o f benefits needs to exceed the present value o f relevant costs, as these costs are calculated in table 16. Inwhat follows we state the technique and basic assumptions made for the calculation o f the relevant benefits. 83. Due to data nonavailability, we take into account only two sources o f arsenic mitigation benefits. The first amounts to direct medical expense savings as reduced arsenic exposure dramatically improves people's health. The second amounts to indirect benefits o f improved productivity and elevated output growth. Due to the lack o f estimates on other social benefits (see section 2.4), these are not included in our model. Our exact technique for calculating these benefits is defined negatively; that is, we estimate the costs the government would bear ifno mitigation policy were undertaken. Hence, benefits are implicitly calculatedas reduced costs and their present value is equal to the discounted cash flow o f benefits for a 50-year horizon. 84. First, output benefits are calculated as foregone output for each person that becomes affected by arsenic-related diseases. Inorder to project the number o fpeople who develop fatal cancer due to arsenic, we associate the level o f arsenic inwater with the risk o f cancer. Specifically, the WHO (1993) set a provisional guideline value o f 10 pg L1for arsenic in drinkingwater, which is associated with a lifetime excess skin cancer o f about 6 per 10,000 persons. The Bangladesh standard o f 50 pg L-' is associated with a higher risk: 30 per 10,000 persons. Using the model developed by the United States Environmental Protection Agency and the distribution o f population exposed to different levels o f arsenic, the estimated total number o f excess skin cancer victims is 375,000 ifthe present arsenic contamination level i s maintained. Ifthe Bangladesh standardis met, this figure drops to 55,000 and, if the WHO standardis met, it further drops to 15,000 (Ahmed 2003). However, skin cancer is not the only disease related to arsenic. Yu, Harvey, and Harvey (2003) estimate the number o f people developing hyperpigmentation to be 1,200,000 and those developing keratosis to be 600,000. We project the number o f people who die or become unable to work in the next 10 years to be approximately 50,000 per year (increasing by that number each year). This figure is derived by dividing the estimated 2.5 million people that are expected to develop arsenic-related diseases in the next 50 years, by 50 years (in order to get a per year estimate o f affected people). 85. From a more detailed survey o f the data currently available in the literature, Maddison, Luque,andPearce (2004) estimate the annualimpact onhealthfrom arsenic inBangladeshas shown intable 17. - 200 - Arsenic Contamination of Groundwater in SouthandEastAsian Countries: Volume I1- Paper4 The Economics of Arsenic Mitigation - Table 17. Bangladesh: EstimatedHealthImpact of Arsenic Contaminationof Tubewells Impact on healthhype o f illness Males Females Combined Cancer cases: Fatal cancers/year 3,809 2,718 6,528 Nonfatal cancerdyear 1,071 1,024 2,095 Total cancer fatalitiesaccumulatedover 50 190,450 135,900 326,400 years Arsenicosiscasesa: Keratoses 277,759 74,473 352,233 Hyperpigmentation 654,718 316,511 971,230 cough 21,823 68,887 90,7 12 Chest sounds 144,831 67,025 211,858 Breathlessness 93,247 176,874 270,122 Weakness 132,927 240,176 373,104 Glucosuria 67,887 63,551 131,439 Highbloodpressure 94,396 88,366 182,762 Total arsenicosis cases ineachyear 1,487,588 1,095,863 2,583,460 a. Figures indicate average number of cases occurring in each year (not number o f new cases). Source: Maddison, Luque, and Pearce 2004, p. 32. - 201 - Arsenic Contamination of Groundwater in South andEast Asian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - 86. Estimates by Maddison, Luque, and Pearce (2004) suggest that 6,500 people die from cancer every year (a total o f 326,000 people in a period o f 50 years), while a maximum13o f 2.5 million people develop some kind o f arsenicosis. In our model, we add to the number o f fatalities from cancer (6,500 people) an additional 1.7% o f the total number o f arsenic- affected people. This 1.7% representsthe number o fpeople that develop nonfatal diseases and become unable to work andproduce. 87. Annual gross domestic product (GDP) is adjusted for the loss in output due to people becoming unable to work or dying. As a starting value for GDP, we take the 2002 GDP estimated at US$239 billion in purchasing power parity terms. We then assume that GDP increases by 4% each year over the next 50 years. The output lost is then calculated as the fraction o f GDP the people becoming illwould have produced. These output benefits amount to present values o f $88.36 billion, $22.89 billion, and $8.77 billion for constant discount rates o f 5%, lo%, and 15% respectively over a 50-year period. 88. Information from the National Institute o f Preventive and Social Medicine (NIPSOM) o f Banglade~h'~indicates that the medical expenditure for treating mild to moderate arsenicosis i s US$4to $5 per month, and the treatment generally lasts from three to six months. As far as arsenicosis cancers are concerned, the medical expenditure ranges from $300 to $1,000 per patient. Usingthe information above, we calculate the direct medical cost o f treating mild to moderate arsenicosis, as well as arsenicosis cancer. Referring back to table 17, 8,623 people (6,500 fatal cancers plus 2,095 nonfatal cancers) are expected to develop cancer per year, while 971,230 to 2,583,460 people will develop some other arsenic-related disease. In our calculations we use this range (971,230 to 2,583,460) as an approximation o f the number o f treatments o f mild to moderate arsenicosis per year. Then, using the upper bound o f the estimates o f medical costs provided by NIPSOM, we find that the total cost o f treating arsenicosis cancer amounts to US$8,623,000'5 and the cost o f treating the rest o f arsenic- related diseases is a number between $29,136,900 (= 971,230 x $30) and $77,503,800 (= 2,583,460 x $30). Usingthe average o f the cost o f treating noncancer arsenic-related diseases, related diseases for a 50-year period at rates o f 5%, lo%, and 15%, we get the present value and discounting the sumo fmedical expenditure onboth cancer and mildto moderate arsenic- o fmedical costs, which amount to $1.14 billion, $0.62 billion, and $0.41 billionrespectively. 89. Before moving to section 4.3, where we calculate the net present value o f different mitigation technologies, it is crucial to note that the calculated health expenditures in the previous paragraph represent lower bounds o f the relevant magnitudes. That is, while these are the current actual expenditures made, they may not be really sufficient for the treatment o f arsenic-related illnesses in Bangladesh. Thus it is likely that these are underestimates o f the optimal level o f the relevant health expenditure. This possibility i s reinforced if one looks at the results of the contingent valuation study conducted by the Water and Sanitation Program, South Asia in December 2002 (Ahmad and others 2002). For rural Bangladesh, this study estimated the willingness to pay for arsenic-free, safe drinkingwater (that is, it estimated the value o f avoiding arsenic-related health risks, which can approximate the value o f avoiding the relevant health expenditure attached to these risks) to be equal to 0.2% to 0.3% o f the average income o f rural households. Although economic theory dictates that in a C B A one l3Individuals sufferingfrom keratosis can also suffer from cough, weakness, etc. Therefore, it is not possibleto translate the sum of the people suffering from different symptoms, as shown in table 17, into a unique figure indicating the total number of people suffering from arsenicosis. The figures in the table, however, can be translatedinto arange of possiblenumbers.This range will vary from 971,230 (assumingthat every personwho develops arsenicosis will have all the symptoms) to 2,592,083 (assuming that each person has a unique symptom, inwhich case the number of peoplewith arsenicosisis the sum of the number of symptoms). l4This i s calculatedas ((6,528 + 2,095) x 1,000). Privatecommunicationwith Dr.Akhtar. - 202 - Arsenic Contaminationof Groundwater in South and EastAsian Countries: Volume I1 Paper4 The Economicsof Arsenic Mitigation - - should use optimal levels o f costs andbenefits, we decided to use the lower bounds calculated inthe previousparagraphinorder to minimizethe risk ofexaggerating the health expenditure cost. Certainly our analysis shows that productivity losses due to illness are the primary component that drives the numbers, while the health expenditures are a secondary component to the net present value results. 4.3 Results for the M o d e l 90. Taken together both output and medical costs generate a present value that ranges from US$9.18 billion to $23.51 billion to $89.50 billion as the discount rate ranges from 15% to 10% to 5%.16 91. The resulting net present value ranges from $8.2-1.1 billion to $22.3-11.1 billion to $71.8- 87.9 billion as the discount rate ranges from 15% to 10% to 5% (while the variation under the same discount rate reflects varying costs o f different technology options). The net present value arising from these calculations can be as large as 11% o f current Bangladesh GDP. However, in estimating the benefits o f the arsenic mitigation program it i s unrealistic to assumethat a mitigationpolicy will be fully (100%) effective inremoving arsenic. 92. For this reason we further proceed in estimating the benefits under two scenarios: (a) effectiveness o f mitigation technology amounts to 70% o f exposure reduction; and (b) effectiveness o f mitigationtechnology amounts to 50% o f exposure reduction. Under scenario (a) the relevant net present value (discounted at 10%) amounts to approximately $9.5 (15 -4) billion, which constitutes around 4% o f Bangladesh GDP. Under scenario (b) the relevant net present value (discounted at 10%) amounts to approximately US$5 ((-0.6) - 10.6) billion, around2% o f Bangladesh GDP. 93. Tables 18, 19, and 20 show analytically our results on the net present value o f various arsenic mitigationpolicies, with different degrees o f effectiveness, and discounted at different interest rates. The effect o f a lower discount rate on the resulting level o f net present value, and consequently the desirability o f a project (section 2.5), is obvious from these tables. 94. With the exception o f the option o f rainwater harvesting (+ dug well) when discounted at a 10% rate, all other considered mitigation technologies are welfare increasing (that is, they pass a CBA) under all three levels o f effectiveness at both 5% and 10% discount rates. However, when discounted at a 15% rate many o f the mitigation technologies do not pass a CBA at lower than 100% level o f effectiveness. Moreover, rainwater harvesting (+ dug well) and rainwater harvesting (+ deep tubewell) are not welfare increasing even at 100% level o f effectiveness. This result indicates that one needs to carefully evaluate what mitigation measures are implemented and that it is not true that any mitigation technology can be applied. Moreover, these results indicate that at the project level, one may want to carry out a least-cost analysis. 95. The use o f pond sand filters (30 households per unit), taking account o f the level o f service, turns out to be superior to other technologies. However, even though our analysis concludes that pond sand filters are the most economically efficient option, two real-life caveats make this option less attractive. First, pond sand filters are often very polluted. To take this into account in a CBA one should ideally include in the methodology a risk-weighting factor, which will indicate the increase o f child morbidity and mortality due to water sources. The second caveat refers to the lack o f space in Bangladesh for accommodating so many pond sandfilters. Inearlier years space was not an issue, butnow there is either not enough landin any givenvillage due to the highpopulationdensity, or people actually use the ponds for fish farming, a significant source o f income inrural Bangladesh. This situation makes the shadow l6Usinga different methodology,which relies on the estimationof epidemiologicaldose-responsefunctions, Maddison,Luque, andPearce (2004, p. 34) estimatethe presentvalue of benefitsat US$138.7billion, which is comparableto our total healthbenefit of $162.2 billion. - 203 - Arsenic Contamination of Groundwater inSouthandEast Asian Countries: Volume I1- Paper4 - The Economics of Arsenic Mitigation price involvedinusingthe pondvery high, as it should include the price o fthe landwhere the pond will be situated. It can even be the case that the corresponding landhas to be purchased through an actual money transaction, which makes the relevantprice an explicit one. 96. Overall, no significant discrepancies among technologies are documented. The more dramatic effect on the desirability o f different mitigation technologies emerges by the changes in the choice o f discount rate of the hture flow o f cost and benefits. As expected, as the discount rate increases, the net benefits o f mitigationpolicies are reduced, to the point that, with a 15% discount rate, we encounter negative net present value. This exercise highlights the significance o f the choice o f the discount rate, as 'well as the importance of the ability to predict the degreeo f effectiveness o f a proposed policy. - 204 - Arsenic Contaminationof Groundwaterin SouthandEastAsianCountries:Volume I1 Paper 4 The Economics of Arsenic Mitigation - - Table 18. NPV(inBillionUS$)ofArsenic Mitigation Policies, Discountedat 5% 100% successful A Dugwells 12.9 1.1 88.4 89.5 76.6 B1 Rainwaterharvest+dugwell 17.7 1.1 88.4 89.5 71.8 B2 Rainwaterharvest+ deep tubewell 15.5 1.1 88.4 89.5 74.0 C Deeptubewell 7.4 1.1 88.4 89.5 82.1 D Shallowtubewell / arsenicremoval 15.4 1.1 88.4 89.5 74.1 El Pondsandfilter 12.0 1.1 88.4 89.5 77.5 E2 Pond sand filter (30 householdshnit) 1.6 1.1 88.4 89.5 87.9 F Deepproductionwell, piped 8.6 1.1 88.4 89.5 80.9 G Impoundment,piped 9.4 1.1 88.4 89.5 80.1 H River abstraction, piped 8.5 1.1 88.4 89.5 81.0 50% successful Technology Costs Health Output Benefits NPV (PV) benefits benefits (PV) A Dugwells 12.9 0.6 44.2 44.8 31.8 B1 Rainwaterharvest+dugwell 17.7 0.6 44.2 44.8 27.1 B2 Rainwaterharvest+ deeptubewell 15.5 0.6 44.2 44.8 29.2 C Deeptubewell 7.4 0.6 44.2 44.8 37.3 D Shallowtubewell/ arsenicremoval 15.4 0.6 44.2 44.8 29.4 El Pondsandfilter 12.0 0.6 44.2 44.8 32.8 E2 Pondsandfilter (30 households/unit) 1.6 0.6 44.2 44.8 43.1 F Deepproductionwell, piped 8.6 0.6 44.2 44.8 36.1 G Impoundment,piped 9.4 0.6 44.2 44.8 35.4 H River abstraction, piped 8.5 0.6 44.2 44.8 36.3 70% successful Technology Costs Health Output Benefits NPV (PV) benefits benefits (PV) A Dugwells 12.9 0.8 61.9 62.7 49.7 B1 Rainwaterharvest+ dugwell 17.7 0.8 61.9 62.7 45.0 B2 Rainwaterharvest+ deeptubewell 15.5 0.8 61.9 62.7 47.1 C Deeptubewell 7.4 0.8 61.9 62.7 55.2 D Shallowtubewell/ arsenic removal 15.4 0.8 61.9 62.7 47.3 E l Pondsand filter 12.0 0.8 61.9 62.7 50.7 E2 Pondsand filter (30 households/unit) 1.6 0.8 61.9 62.7 61.0 F Deepproductionwell, piped 8.6 0.8 61.9 62.7 54.0 G Impoundment, piped 9.4 0.8 61.9 62.7 53.3 H River abstraction, piped 8.5 0.8 61.9 62.7 54.2 a. PV =presentvalue. b. NPV = net presentvalue. - 205 - Arsenic Contamination o f Groundwater in Southand East Asian Countries: Volume I1 Paper4 The Economics ofArsenic Mitigation - - Table 19.NPV (inBillionUS$) ofArsenic Mitigation Policies, Discounted at 10% 100% successful A Dugwells 8.5 0.6 22.9 23.5 15.0 B1 Rainwaterharvest+dugwell 12.4 0.6 22.9 23.5 11.1 B2 Rainwaterharvest+deeptubewell 11.3 0.6 22.9 23.5 12.2 C Deeptubewell 5.8 0.6 22.9 23.5 17.7 D Shallowtubewell/ arsenic removal 9.0 0.6 22.9 23.5 14.5 E l Pondsandfilter 8.6 0.6 22.9 23.5 14.9 E2 Pondsand filter (30 householdsiunit) 1.2 0.6 22.9 23.5 22.3 F Deepproductionwell, piped 5.8 0.6 22.9 23.5 17.7 G Impoundment,piped 6.2 0.6 22.9 23.5 17.3 H River abstraction, piped 5.6 0.6 22.9 23.5 17.9 50% successful Technology Costs Health Output Benefits NPV (PV) benefits benefits (PV) A Dugwells 8.5 0.3 11.4 11.8 3.3 B1 Rainwater harvest+dugwell 12.4 0.3 11.4 11.8 -0.6 B2 Rainwater harvest+deep tubewell 11.3 0.3 11.4 11.8 0.4 C Deeptubewell 5.8 0.3 11.4 11.8 5.9 D Shallowtubewell/ arsenic removal 9.0 0.3 11.4 11.8 2.8 E l Pondsandfilter 8.6 0.3 11.4 11.8 3.1 E2 Pondsandfilter (30 households/unit) 1.2 0.3 11.4 11.8 10.6 F Deepproductionwell, piped 5.8 0.3 11.4 11.8 6.0 G Impoundment, piped 6.2 0.3 11.4 11.8 5.6 H River abstraction, piped 5.6 0.3 11.4 11.8 6.1 70% successful Technology Costs Health Output Benefits (PV) benefits benefits (PV) NPV A Dugwells 8.5 0.4 16.0 16.5 8.0 B1 Rainwaterharvest+ dugwell 12.4 0.4 16.0 16.5 4.1 B2 Rainwaterharvest+ deep tubewell 11.3 0.4 16.0 16.5 5.1 C Deeptubewell 5.8 0.4 16.0 16.5 10.6 D Shallowtubewell/ arsenic removal 9.0 0.4 16.0 16.5 7.5 E l Pondsandfilter 8.6 0.4 16.0 16.5 7.8 E2 Pondsandfilter (30 households/unit) 1.2 0.4 16.0 16.5 15.3 F Deep productionwell, piped 5.8 0.4 16.0 16.5 10.7 G Impoundment,piped 6.2 0.4 16.0 16.5 10.3 H hver abstraction,piped 5.6 0.4 16.0 16.5 10.8 a. PV =presentvalue. b. NPV=net presentvalue. - 206 - Arsenic Contamination of Groundwater in SouthandEast Asian Countries: Volume I1 Paper4 - The Economics of Arsenic Mitigation ~ Table 20. NPV (inBillionUS$) of Arsenic MitigationPolicies, Discounted at 15% 100% successful Technology Costs Health Output Benefits NpVb (PV)a benefits benefits (PV)a A Dugwells 6.8 0.4 8.8 9.2 2.4 B1 Rainwaterharvest dugwell + 10.3 0.4 8.8 9.2 -1.1 B2 Rainwaterharvest+ deep tubewell 9.7 0.4 8.8 9.2 -0.5 C Deeptubewell 5.2 0.4 8.8 9.2 4.0 D Shallow tubewell / arsenic removal 6.5 0.4 8.8 9.2 2.7 El Pondsandfilter 7.3 0.4 8.8 9.2 1.9 E2 Pondsandfilter (30 households/unit) 1.o 0.4 8.8 9.2 8.2 F Deepproductionwell, piped 4.7 0.4 8.8 9.2 4.5 G Impoundment,piped 5.0 0.4 8.8 9.2 4.2 H River abstraction, piped 4.5 0.4 8.8 9.2 4.7 50% successful Technology Costs Health Output Benefits (PV) benefits benefits (PV) NPV A Dugwells 6.8 0.2 4.4 4.6 -2.2 B 1 Rainwaterharvest+ dugwell 10.3 0.2 4.4 4.6 -5.7 B2 Rainwaterharvest+deeptubewell 9.7 0.2 4.4 4.6 -5.1 C Deeptubewell 5.2 0.2 4.4 4.6 -0.6 D Shallowtubewell/ arsenic removal 6.5 0.2 4.4 4.6 -1.9 E l Pondsand filter 7.3 0.2 4.4 4.6 -2.7 E2 Pondsandfilter (30 households/unit) 1.o 0.2 4.4 4.6 3.6 F Deepproductionwell, piped 4.7 0.2 4.4 4.6 -0.1 G Impoundment,piped 5.0 0.2 4.4 4.6 -0.4 H River abstraction, piped 4.5 0.2 4.4 4.6 -0.1 70% successful Technology Costs Health Output Benefits NPV (PV) benefits benefits (PV) A Dugwells 6.8 0.3 6.1 6.4 -0.3 B1 Rainwaterharvest+dugwell 10.3 0.3 6.1 6.4 -3.9 B2 Rainwaterharvest +deep tubewell 9.7 0.3 6.1 6.4 -3.3 C Deeptubewell 5.2 0.3 6.1 6.4 1.2 D Shallowtubewell / arsenic removal 6.5 0.3 6.1 6.4 -0.1 El Pondsandfilter 7.3 0.3 6.1 6.4 -0.9 E2 Pondsand filter (30 households/unit) 1.o 0.3 6.1 6.4 5.4 F Deepproductionwell, piped 4.7 0.3 6.1 6.4 1.8 G Impoundment, piped 5.0 0.3 6.1 6.4 1.5 H River abstraction, piped 4.5 0.3 6.1 6.4 1.9 a. PV =presentvalue. b. NPV = net presentvalue. - 207 - Arsenic Contamination of Groundwater in South andEastAsian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - 97. The approach suggested and applied above is applicable to both cases: (a) the risk that arsenic might be found in an area where a project is planned; and (b) approaches regarding risk mitigation options where a project's stated purpose is arsenic mitigation itself. While the relevance o f our approach to case (b) has already been demonstrated inthis paper, below we clarify how the methodology canbe applied to case (a). 98. The methodology can be applied in cases inwhich arsenic contamination i s not as widespread as in Bangladesh and decisions have to be made about what needs to be done inadvance o f a project plannedinan areawith a highrisk of being contaminated. More specifically, insuch a case the policymaker should try to collect information (through hydrogeological surveys) on the existence andextent ofcontaminationinthe areaunder consideration. After acquiring this information, the policymaker should apply the suggested methodology in order to perform a rapid CBA, which will help decide whether it i s affordable to mitigate arsenic and then complete the project under consideration, or whether arsenic mitigation i s too expensive, possibly due to extensive contamination in the area. If the latter is true (that is, mitigation costs are significantly higher than benefits), then the relevant area should not be further developed through the other planned project, as development would attract people to the area, resultinginmorepeoplebeingexposedto arsenic inthe future. 99. At this point it is worth mentioning that in order to establish the extent o f contamination it is necessary to have a well-structured screening methodology and knowledge o f the hydrogeology o f the differentareas ina country. This highlights the importance of investment in a screening program, as well as hydrogeological studies of high-risk areas. Both of these are necessary tools for acquiring knowledge about what i s going on in a certain country, region, or area before mitigation measures or development plans are implemented. Although both o f these tools are quite expensive (for example, the price o f arsenic laboratory analysis is US$9, not taking into account transportation costs, while the price o f a field kit is $0.5 per test) they are a necessaryfirst step o f any decision about project implementation. 100.The logic behind this necessity i s the following. The long-run nature o f project-specific developments means that initial screening costs will be discounted over a long-run horizon; hence, these costs will be relatively small in net present value terms irrespective o f their absolute initial value. On the contrary, the effects o f arsenic contamination could be detrimental to both the economy and health of the inhabitants o f an area over a much shorter horizon. Moreover, it should be kept inmindthat the decision to develop a particular area is irreversible in practical terms. This characteristic o f irreversibility necessitates great caution about the decision to develop or not, hence such decisions should be taken under minimum risk conditions. The combined result of these three effects increases the net potential benefit to society that can be achieved through gathering information regarding the existence and extent o f arsenic contamination prior to any other project-related appraisal. 101.This discussion indicates that an option value underliesthe development o fparticular projects in high-risk areas. Option value is a measure of people's (society's) risk aversion to factors that might affect future access to use o f environmental or biological assets. More precisely, the option value relevant to our discussion is the premiumthat society is willing to pay to avoid having to face the effects o f arsenic contamination in the area where economic and social development is planned. In our case, this premiumi s the money that the society (the government) will spend on screening and hydrological studies in order to gather enough information to allow the choice o f a development area with a minimum risk o f arsenic contamination. T h ~ sallows society to reduce the risk (variance) associated with future welfare. 102.Inconclusion, as long as society is risk averse andthe development horizon is long, screening andhydrological studies that enable such riskreductions are likely to bewelfare increasing. - 208 - Arsenic Contamination of Groundwater in SouthandEast Asian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - 5. Summary and Conclusions 103. This paper reviews existing studies and data on arsenic contamination, related health effects, andthe costsofmitigationinthose countries where it hasbeenundertaken. Then it introduces an approach which provides a quick and readily applicable method for performing a CBA of different arsenic mitigation policies. Inparticular, our suggested approach estimates benefits o f mitigation activities as the sum o f foregone medical costs and saved output productivity achieved through the reduction o f arsenic exposure. The present value o f these benefits is then compared with the present value o f costs o f various mitigation measuresinorder to determine when and which mitigationpolicies pass a CBA (that is, produce a positive change to social welfare). 104.The paper applies this approach in order to provide some estimate of costs and benefits of arsenic mitigation inone case study country, Bangladesh. This case study serves as an applied example of a rapid socioeconomic evaluation and is also used as a basis for discussing trade- offs in decisionmaking with respect to the allocation o f financial resources. Our approach is applicable to the following cases: (a) where there i s riskthat arsenic mightbe found inan area where a project i s planned; and (b) inregard to riskmitigation options where a project's goal i s arsenic mitigationper se. 105.With the exception o f the option o f rainwater harvesting (+ dug well) when discounted at a 10% rate, all other considered mitigation technologies are welfare increasing (that is, they pass a cost-benefit analysis) under all three levels o f effectiveness at both 5% and 10% discount rates. However, when discounted at a 15% rate, many o f the mitigation technologies do not pass a CBA at lower than 100%level o f effectiveness. Moreover, rainwater harvesting (+ dug well) and rainwater harvesting (f deep tubewell) are not welfare increasing even at 100% level o f effectiveness. This result indicates that one needs to carefully evaluate what mitigation measuresare implemented andthat it is not true that any mitigation technology can be applied. Moreover, these results indicate that, at the project level, one may want to carry out a least-cost analysis. 106.It is also worth mentioning that (a) in our calculation we did not take into account the environmental benefits o f mitigation strategies (mainly due to lack o f precise data); and that (b) the health expenditures only represent a lower bound. That is, the calculated net benefits from arsenic mitigation are underestimates o f the true benefits and should be used as a very conservative figure of welfare increases to be derived from implementing the various mitigationpolicies. 107.Finally, these figures indicate the imminent need for facing the arsenic crisis inBangladesh, but also the clarity with which our approach can answer the difficult question on the balance o f relevant costs andbenefits o fvarious mitigationpolicies. - 209 - Arsenic Contamination of Groundwater inSouth andEast Asian Countries: Volume I1 Paper4 The Economics of Arsenic Mitigation - - Annex 1. Detailed Technology Costs The tables below itemize the costs of each technology for a village of 500 households (see section 3.2.3). Average Village Model: 500Households IncomeCategories Nos. High Medium Low Total Homesteads(clusters) 50 Proportion 10% 20% 70% 100% Households @ 10per homestead 500 Households 50 100 350 500 Population@ 5.5 per household 2,750 Population 275 550 1,925 2,750 Option A: DugWells Capital costs Unit Qty Rate (US$) Amt (US$) Excavation: depth 12.5 m m3 10 10 102 Pipe rings supply m 12.5 20 254 Piperings install m 12.5 8 106 Handpumpsupply & install no. 1 68 68 Transport sum 1 85 85 Contingenciesandhandovedtraining sum 1 34 34 Platform +other core componentswork sum 1 102 102 Total 750 Operation& maintenancecosts annual Unit QtY Rate(US$) Amt (US$) Chemical: disinfection kg 15 2 25 Labour h Y S 24 2 41 Sparedparts sum 1 17 17 Water quality monitoring sum 5 8 42 Total 125 Infrastructurerequired Income High Medium Low Total Proportion 10% 20% 70% 100% Households 50 100 350 500 Householdsidugwell 1 3 10 n.a. No. of dugwells 50 33 35 118 Financialcosts Capital 88,750 Annual operation& maintenance 14,842 n.a.Not applicable. - 210 - Arsenic Contamination of Groundwater in South andEast Asian Countries: Volume I1- Paper4 - The Economics of Arsenic Mitigation Option B1: Roof Rainwater Harvest/Household(60 sq m) DugWell + Capitalcosts: roofcatchment Unit Qty Rate (US$) Amt (US$) Roofgutters m 36 3 107 Pipework m 7 5 36 Tank 3.2 m3on platfond3 month storage no. 1 105 105 Handpump supply and install no. 0 n.a. n.a. Transport sum 1 17 17 Contingencies andhandoverhaining sum 1 8 8 Roofrainwater harvest capital cost Total 273 Dugwell capital cost sum 1 750 750 Operation& maintenancecosts annual (roofcatchment) Unit Qty Rate (US$) Amt (US$) Chemical: disinfection kg 0.25 2 0 Labour days 7 2 12 Sparedparts sum 1 3 3 Water quality monitoring sum 1 8 8 Total 24 Dug well months 12 10.45 125 Infrastructurerequired Income High Medium Low Total Proportion 10% 20% 70% 100% Households 50 100 350 500 Households/rainwaterharvest 1 1 1 n.a. No. ofrainwater harvest systems 50 100 350 500 Households/dugwell 3 10 20 n.a. No. of dugwells 17 10 18 44 Financialcosts Capital 169,566 Annual operation & maintenance 17,616 n.a.Not applicable. -211 - Arsenic Contamination ofGroundwater in South andEastAsian Countries: Volume I1- Paper4 - The Economicsof Arsenic Mitigation OptionB2: RoofRainwater Harvest/Household(60 sq m) Deep Tubewell + Capitalcosts: roofcatchment Unit Qty Rate (US$) Amt (US$) Roof gutters m 36 3 107 Pipework m 7 5 36 Tank 3.2 m3on platfond3 month storage no. 1 105 105 Handpumpsupply and install no. 0 n.a. n.a. Transport sum 1 17 17 Contingencies and handovedtraining sum 1 8 8 Roofrainwater harvest capital cost Total 273 Deep tubewell capital cost sum 1 911 911 Operation& maintenancecosts annual (roof catchment) Unit Qty Rate (US$) Amt (US$) Chemical: disinfection k g 0.25 2 0 Labour days 7 2 12 Sparedparts sum 1 3 3 Water quality monitoring sum 1 8 8 Total 24 Deep tubewell months 12 4 46 Infrastructurerequired Income High Medium Low Total Proportion 10% 20% 70% 100% Households 50 100 350 500 Householdsirainwater harvest 1 1 1 n.a. No, of rainwater harvest systems 50 100 350 500 Households/deep tubewell 3 10 20 n.a. No. of deep tubewells 17 10 18 44 Financialcosts Capital 176,677 Annual operation & maintenance 14,097 n.a. Not applicable. - 212 - Arsenic Contaminationof Groundwater in SouthandEastAsianCountries:Volume I1 Paper4 The Economics of Arsenic Mitigation - - Option C: Hand Deep Tubewell Capitalcosts Unit Qty Rate (US$) Amt (US$) Sinking m 250 0.3 64 35 mmpipe supply + stainer m 250 1.7 424 Pipe install m 250 0.8 212 Handpump supply & install no. 1 127.1 127 Transport sum 1 33.9 34 Contingencies and handover sum 1 16.9 17 Platform + othercore components work sum 1 33.9 34 Total 911 Operation& maintenancecosts annual Unit QtY Rate (US$) Amt (US$) Chemical: disinfection kg 0 n.a. n.a. Labour days 12 1.7 20 Sparedparts sum 1 16.9 17 Water quality monitoring sum 1 8.5 8 Total 46 Infrastructurerequired Income High Medium Low Total Proportion 10% 20% 70% 100% Households 50 100 350 500 Households/deep tubewell 1 3 10 n.a. No. of deep tubewells 50 33 35 118 Financialcosts Capital 107,804 Annual operation & maintenance 5,415 n.a. Not applicable. - 213 - Arsenic Contamination of Groundwater in South andEast Asian Countries:Volume I1 Paper4 The Economics of Arsenic Mitigation - - Option D: ExistingShallow Tubewellwith HouseholdArsenic Removal _ _ _ _ _ _ _ _ ~ ~ ~ Capitalcosts Unit Qty Rate (US$) Amt (US$) Arsenic removal supply & install no. 1 50.8 51 Transport sum 1 3.4 3 Contingencies and handoveritraining sum 1 25.4 25 Total 80 Operation& maintenancecosts annual Unit Qty Rate (US$) Amt (US$) Chemical: disinfection k g 0 n.a. n.a. Labour days 0 n.a. n.a. Media/spares/parts sum 1 25.4 25 Water testing (for arsenic) sum 2 8.5 17 Total 42 Infrastructurerequired Income High Medium Low Total Proportion 10% 20% 70% 100% Households 50 100 350 500 Households/arsenic removal unit 1 1 1 n.a. No. of arsenic removal 50 100 350 500 Financialcosts Capital 39,831 Annual operation & maintenance 21,186 n.a. Not applicable. - 214 - Arsenic Contamination of Groundwater in SouthandEastAsian Countries: Volume I1 Paper4 - The Economicsof Arsenic Mitigation - OptionE:Pond Sand Filter Capitalcosts Unit Qty Rate (US$) Amt (US$) Excavation m3 6 3.4 20 Reinforced concrete including formwork m3 4 1.7 7 Block wall m2 48 11.9 569 Handpump supply & install no. 1 67.8 68 Transport sum 1 33.9 34 Contingencies and handovedtraining sum 1 254.2 254 Total 953 Operation& maintenancecosts annual Unit Qty Rate (US$) Amt (US$) Chemical: disinfection kg 15 1.7 25 Labour h Y S 24 1.7 41 Sparedparts sum 1 16.9 17 Total 83 Infrastructurerequired Income High Medium L o w Total Proportion 10% 20% 70% 100% Households 50 100 350 500 Households/pond sand filter 1 2 10 n.a. No. of pond sand filters 50 50 35 135 Financialcosts Capital 128,593 Annual operation & maintenance 11,212 n.a. Not applicable. - 215 - Arsenic Contamination o f Groundwater in SouthandEast Asian Countries: Volume I1 Paper 4 The Economics of Arsenic Mitigation - - Option F:PipedScheme Deep ProductionWell (Domestic) Capital costs Unit Qty Rate (US$) Amt (US$) Production wells sum 3,627 Sinkingidrilling and core samples m 300 3.2 966 Pumping facilities sum 6,356 Masonry/concrete storage tanks sum 8,305 Trunk maidtransmissionmain sum 847 Distribution system sum 18,271 House connections sum 8,720 Capital costs Total 47,093 Operation & maintenance costs annual Total 6,780 Option G: Piped SchemeImpoundment: EngineeredPond Capital costs Unit Qty Rate (US$) Amt (US$) Impoundment sum 4,237 Intake/infiltration gallery sum 1,508 Pumpingfacilities sum 6,356 Masonryiconcretestorage tanks sum 8,305 Trunkmaidtransmissionmain sum 847 Distribution system sum 18,271 House connections sum 8,720 Capital costs Total 48,246 Operation & maintenance costs annual Total 7,627 Option H:Piped Scheme SurfaceWater: RiverAbstractionDnfiltration Gallery Capital costs Unit Qty Rate (US$) Amt (US$) Intakehfiltrationgallery sum 2,034 Pumping facilities sum 6,356 Masonry/concrete storage tanks sum 8,305 Trunk maidtransmission main sum 847 Distribution system sum 18,271 House connections sum 8,720 Capital costs Total 44,534 Operation & maintenance costs annual Total 6,780 - 216 - Arsenic Contamination of Groundwater in SouthandEastAsian Countries: Volume I1 Paper4 The Economicsof Arsenic Mitigation - - References Ahmad, J. 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