Mitigation and Remedy of Groundwater Arsenic Menace in India

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Mitigation and Remedy of Groundwater Arsenic Menace in India : A Vision Document(ii)(iii)(iv)(v)Fluctuation: Some of the major issues for fluctuation are high level of arsenicfluctuation in raw water in subsequent weeks, fine silvery colloidal sand, pollution due tounstabilised sub-surface condition and old under-used tube-wells. They have createdmany initial problems for the technology park programme and are a common scenario inmost of the sites in lower deltaic region. Operation and maintenance have, thus, becomequite a difficult task for obvious reasons. Erratic behaviour of arsenic, in raw water, isquite baffling as observed in each week and even on daily fixed time study. Thefluctuation ranges from 11% to 35.6%, as observed. Some units tend to increase the pHand conductivity in the filtered water. Some units also show increase in hardness in thefiltered water. All are capable of lowering Iron to permissible level. Backwashing isquite a regular feature for all the units. The suppliers of devices shall have to take noteof the high level of arsenic fluctuation and in situ sub-soil condition for future devicemaking as they seem to affect and alter the performance of media in both short term andlong term interest.As (III) & As (V) speciation: Although it is generally felt that As (V) is betterremoved in the adsorption approach, for which in the design concept of most of theARPs a primary oxidizing-interface for converting As(III) species to pentavalent statusis ensured. The speciation studies have observed that all the As (III) species, present inthe raw water, get converted or removed through the media interface. This may not beessentially true for the removal or adsorption in the process for As (V). In fact,whatever Arsenic remains after filtration is of As (V) species. Besides, it is to be noted,with interest, that this phenomenon is also repeated with even non-oxidant interface likethe units with only Activated Alumina. One of such units has been installed by OxideIndia.Sludge: Apparently sludge disposal, management and detoxification have not receiveddue priority in the plan of actions, initiated along with the device installation by the ARPmanufacturers. Even no discernible programme is seen for the backwash whichcontains high level of As in media-washed water. It needs high priority in the installationprogrammes. Both the raw water, pumped out for ordinary use, and back washedwater; require to be passing through a soak pit type of arrangement, to avoid surfacecontamination.Operation & Maintenance: The maintenance of the systems requires doubleattention for the ARPs and the tube wells. Majority of the operation and maintenanceissues are related to tube wells, that have nothing to do with the ARP or its chemicalmedia. In the resultant scenario, whole programme of operation and maintenance shallcontinue to suffer till design changes are ensured for the lift pumps. This can be done byreleasing the back pressure through an outlet before it can exert cumulative pressure onthe inlet valve.NIH & CGWB 119
A Critical Appraisal- Future Risk, Scope to Remediate, Technological Competence, etc.In fact, without adequate in-built maintenance arrangements apparently, the performanceof all the devices would suffer. Proper training and mobilization of the user community,in the operation and maintenance aspect, would be an essential task before any futureinstallation programme can be envisaged. This aspect holds good for the bestperforming devices too.(vi)(vii)People's Participation: In a scenario, rural community has come to believe thatgetting free water is their fundamental right and getting pipe supply water at the doorstep is a matter of priority expectations. This poses serious concerns to planners ofcommunity based systems in maintenance and fund mobilization for the upkeep of thefacilities at the time of media replacement. A fundamental change in communityperception can only ensure the success of these endeavors. Although it will continue tosuffer but the chances of getting free water from governmental agencies are still quitebright. By executing the programme of establishing the Technology Park andevaluating the critical performance parameters, it was understood that beyondfund mobilization through motivation, the community participation, in a programmeof high technical na ture, requires continuous physical involvement of manufacturers' representative at site, otherwise quality of filtered water cannot be ensured.This matter needs to be appreciated in reality.Sludge Treatment : Treatment of the slurry, obtained from arsenic removal process(from groundwater), is essential to make the slurry arsenic free so that it can bedisposed without any hazard of the arsenic re-entering the aquifer system. The slurrymay be transferred to plastic tanks and clear water from top drained off, further slurryadded and top clear water drained off. In this way a large amount of slurry is obtained inconcentrated form for treatment.The slurry can be dissolved in hydrochloric and/or sulphuric acid. Then it can be treatedwith metal scraps and/or other suitable reducing agents to convert arsenic of the slurrysolution into arsine gas, which can be allowed to escape in the atmosphere (as a primarytentative measure). As a future research, depending on the total amount of arsenic to betreated and availability of fund, the arsenic generated may be absorbed in oxidativealkaline medium to produce sodium arsenate or calcium arsenate. The compounds maybe consumed by glass industries.6.5 Alternate approach for ensuring supply of arsenic-free waterIt is important to note that in most of the areas, the arsenic contaminated zone is at theshallow/intermediate depth ranged largely between 20m and 50m. The groundwater in deeperaquifer ≥ 100 m has been reported arsenic-free, and has potential prospect of tapping. Thoughour studies at School of Fundamental Research in Nadia district showed tube wells up to 250120NIH & CGWB
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ACKNOWLEDGEMENTThe Government of In
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nearly 33 villages in 4 districts i
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(iii) Whether ex-situ removal techn
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6.4 Experiences during Arsenic Remo
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List of FiguresFigure no. Figure ca
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List of TablesTable no. Table Capti
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Mitigation and Remedy of Groundwate
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Mitigation and Remedy of Groundwater Arsenic Menace in India

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