( This is a report evaluating the water and related concerns in 4 states of India – Bihar, Maharashtra, Odisha and Rajasthan. Every week a part of the report will be published.)
Author : Konica Sehgal
3. How the problem is being addressed?
Government has been working hard for improving the situation and various conventional and unconventional techniques are being employed for the same. Alternatives are being searched and developed where technology cannot help. Different contaminants have different chemical configurations and are found at different elevation levels of the aquifers. Therefore, addressing the problem requires a careful study of the ground zero conditions, developing an appropriate technology unique for the area and spreading awareness about it along with the preventive measures community can take at its level.
Arsenic affected areas along the Gangetic plains and the deltaic plains in West Bengal and Bangladesh is marked by multi-level aquifer systems. By extensive exploration of govt. agencies, it is found that arsenic contamination in general is confined up to the depth of 60m and the deep aquifer below the shallow arsenic contaminated aquifer is arsenic free. Therefore, one alternative recognized is tapping of clean potable water from deep aquifers. This alternative is viable since there is no danger of deep aquifer being contaminated with arsenic over time and we can prevent the shallow water from leaking into the deep aquifer through state of the art technologies. Then there are in situ technologies, which make arsenic immobilization possible within the aquifer itself. Introduction of atmospheric oxygen to Iron rich water oxidises iron and arsenic, which enables the adsorption of arsenic by Iron compounds. This chemical reaction has been adopted in various forms across all scales. Ex-situ technologies involve pumping out the water and then treating it for arsenic. Various conventional methods of coagulation, flocculation and sedimentation, precipitation are utilized to neutralize the water. Most economical ex-situ techniques are those, which use precipitation and adsorption techniques. Over all, in-situ techniques are more cost effective than the ex-situ ones as they eliminate the need to build up structures that provide an environment for the processes to take place.
The level of fluoride contamination does not vary with the elevation levels of the aquifers and govt. agencies have found that the level of contamination in both deep and shallow aquifers is the same. Therefore, deep aquifer tapping does not help in fluoride contamination. Treatment of contaminated water or dilution through recharge is an applicable solution. Adsorption and ion exchange, coagulation and precipitation, membrane techniques are used for neutralizing the water for fluoride.
Remedial measures for salinity include distillation, membrane techniques and other technologies like freezing and hybrid facilities.
In addition, many innovative technologies are coming up which can be utilized by the community themselves to clear water of any contamination. Following are some technologies, which are being deployed by households reducing their dependency on government authorities:
Table 6: Various technologies with their specifications