A Cost-Effective Technology for Arsenic Removal: Case Study of Zerovalent Iron-Based IIT Bombay Arsenic Filter in West Bengal

Abstract

Arsenic is present in groundwater in some parts of India. Despite the fact that a variety of treatment methods are available, the efficiency of these methods is not fully known. With the revision of Indian standards for permissible levels of arsenic in drinking water to 10 μg/L or lower, it is necessary to develop a treatment method, which meets drinking water standards of 10 μg/L. Iron based adsorbents have been reported to have high affinity for arsenic. Many researchers have also shown that the corrosion of Zero Valent Iron (ZVI) forms Hydrous Ferric Oxide (HFO) which can act as an adsorbent for arsenic. And the oxidation of Fe to Fe has also been reported to oxidize As(III) to As(V). Using this information a ZVI based Arsenic Filter has been developed by Indian Institute of Technology, Bombay. Test units of the IITB-Arsenic Filter have been installed in the field in four villages in West Bengal. From the results, it is clear that the filter is able to consistently achieve arsenic levels around 10 μg/L for initial arsenic concentrations ranging from 0.06 to 0.4 mg/L. The flowrate of the filtered water is aprox. 600 L/hr. Thereby the IITB-Arsenic Filter is able to consistently provide drinking water for about 200 families on a daily basis. The IITB-Arsenic Filter does not require frequent backwashing/cleaning (cleaning frequency is once in 3 months, and is done by the villagers) and therefore has low operation and maintenance costs. Moreover, it does not require monitoring of flow parameters and is easy-to-operate by unskilled personnel. The Fe/As ratio used in the filter is around 20. Low Fe/As ratios mean lesser sludge generation. Thus it is felt that the IITB Arsenic filter is a suitable technology for rural India.