Mitigation and Remedy of Groundwater Arsenic Menace in India

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nearly 33 villages in 4 districts in West Bengal, up till 2008; 9 districts covering 3417 villagesin 111 blocks in West Bengal, 15 districts covering 57 blocks in Bihar, 3 districts covering 69villages in 7 blocks in Uttar Pradesh, 1 district covering 68 villages in 3 blocks in Jharkhand, 3districts covering 9 blocks in Assam, 4 districts in Manipur, and 1 district covering 4 villages in1 block in Chhattisgarh have been detected for groundwater arsenic contamination. The areaand population of these states are 529674 km 2 & approx. 360 million respectively, in which88688 km 2 and approximately 50 million people have been projected vulnerable togroundwater arsenic contamination. People in these affected states are chronically exposed toarsenic drinking arsenic contaminated hand tube-wells water. With every new survey, newarsenic affected villages and people suffering from arsenic related diseases are being reportedand the problem resolving issues are getting complicated by a number of unknown factors.Further to those, Arsenic groundwater contamination has far-reaching consequences includingits ingestion through food chain, which are in the form of social disorders, health hazards andsocioeconomic dissolution besides its sprawling with movement, and exploitation ofgroundwater. Whether the knowledgebase, understandings and technological options availableare adequate to resolve the issues or, there are further needs of more investigations and studiesto strengthen understanding of geochemical processes to mitigate and remediate arsenic fromgroundwater, are some of the concerns to be addressed for attaining sustainability in supply ofarsenic safe groundwater to the affected areas.Although the exact sources and mobilization processes of such large scale occurrenceof arsenic in groundwater are yet to be established the cause is understood to be of geogenicorigin released from soil under conditions conducive to dissolution of arsenic from solid phaseon soil grains to liquid phase in water and percolation of fertilizer residues may have played amodifying role in its further exaggeration. There are numbers of hypotheses about the source ofarsenic and probable reasons of its occurrence in groundwater. Among the hypotheses of sources,which have been described, Arsenic is transported : (i) by the River Ganges and its tributariesfrom the Gondwana coal seams in the Rajmahal trap area located at the west of the basin; (ii) bythe north Bengal tributaries of the River Bhagirathi and the River Padma from near theGorubathan base-metal deposits in the eastern Himalayas; and (iii) with the fluvial sedimentsfrom the Himalayas and chemical processes of arsenic in groundwater, the most accepted oneis recognized as transport of arsenic from the Himalayas with the fluvial sediments. Regardingchemical processes of occurrence of arsenic in groundwater, out of two hypotheses, onedescribing oxidation of As-bearing pyrite minerals and the other one recognizing due todissolution of As-rich iron oxyhydroxides (FeOOH), the later case is hypothesized as the mostaccepted one. Whether the reasons of dissolution of arsenic from soil to aqueous phases areexcessive exploitation of groundwater is yet to be established.Over the last 25 years, since the groundwater arsenic contamination first surfaced inthe year 1983, a number of restorative and substituting measures coupled with action plansfocusing mainly towards detailed investigations to understand the physiochemical process andmechanism, alternate arrangement to supply arsenic free water to the affected populace havevii
een initiated mainly in West Bengal. Efforts have also been made in the development ofdevices for arsenic removal and their implementation at the field. While in other States, theyare meager. Despite number of corrective and precautionary measures, the spread over ofarsenic contamination in groundwater continues to grow and more new areas have been addedto the list of contaminated area. The problem resolving issues, thus, seem to be partial andinadequate, that need to be strengthened by strategic scientific backing.Numerous investigations have come out with number of findings, and alternativespropositions, varying from identification of shortfalls to success stories. Undoubtedly, eachresearch study has its own merits and added new information; however, a need arises totranslate all those research outcomes to problem resolving issues through framework ofactivities. The present state of affairs of the arsenic menace in India demands a systematictranslation of success stories of one place/region to another, and overcoming the shortfalls byconceiving R & D studies in areas wherever they are deemed fit. Advancement inunderstanding of geochemical and mobilization processes, devising satisfactory arsenicremoval filters, identification of shortfalls in operation and maintenance of arsenic removaltechniques, delineation of risk free deeper aquifers for groundwater tapping as an alternatesource of groundwater, developing surface water based water supply schemes in many arsenicaffected areas, success stories of community participation in running arsenic removal plants,etc. are some of the important achievements, which could help deriving a comprehensiveframework of activities leading to mitigation and remediation of the issues emerging out ofarsenic menace.Towards the supply of arsenic safe water by treatment of contaminated groundwaterusing arsenic removal filters and devices, a variety of treatment technologies, mainly based onoxidation, co-precipitation, adsorption, ion-exchange and membrane process, have beendeveloped and extended to the field. However, the efficiency and applicability/appropriatenessof the technologies have proved more conflicting than successful mainly because ofdisadvantages associated with them with regard to management of large amounts of toxic sludgeproduce from the devices and O & M difficulties. There is, therefore, a need for furtherrefinement in those treatment devices besides their sustainability in terms of economicviability and social acceptability. To provide arsenic safe groundwater from alternate longdistance sources piped water supply scheme, based on surface sources in feasible locations hasbeen put in place and successfully operating in West Bengal. Tapping of deeper aquifersunderneath the contaminated zones in many locations is proving feasible alternative.Numerous studies highlight different concepts with regard to mobilization processes andsuggested for deriving alternative sources for supply of water to the affected areas, thoseinclude; watershed management, artificial groundwater recharge, tapping of deeper aquifers,etc. However, the concerns are: (i) whether available knowledge, understanding andtechnologies are adequate to achieve sustainable solution of the arsenic remedy for differenthydro geological setups? (ii) As to how to proceed for envisaging alternate feasible solutions?viii
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5.2.2 Co-precipitationMitigation an
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5.8 SummaryMitigation and Remedy of
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Mitigation and Remedy of Groundwater Arsenic Menace in India

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