Arsenic and iron contamination of groundwater is a serious concern in few parts of India and Bangladesh. Groundwater abstracted by hand pumps through tubewells is the main source of drinking water in rural areas in the region. Arsenic mobilization from iron rich aquifer is primarily due to reducing conditions prevailing in groundwater aquifer. Thereby, arsenic [As(III) and As(V)] and iron (Fe2+) co-occur in groundwater. Though, As(V) has high affinity for Iron compounds, As(III) requires prior oxidation to As(V) for its removal by most of the technologies. Further, Fe2+ oxidation by dissolved oxygen produces oxidizing intermediates which can oxidize As(III) to As (V). Thus efforts were made to develop technologies for arsenic oxidation and removal employing Fe2+ such that need of additional oxidant was eliminated. The domestic electrocoagulation unit is based on dissolution of iron by electric current, co-oxidation of Fe2+ to Fe3+ and As3+ to As5+ in the presence of dissolved oxygen and co-precipitation of arsenic with iron. The results of laboratory and field trials indicate that the technology is economically viable but needs careful operation. The community arsenic removal technology (IITB Arsenic Filter) utilizes ZVI (iron nails) and employs sequential co-precipitation of arsenic with iron in granular media filter. Prevailing ZVI/iron based methods suggest influent Fe/As (w/w) &gt; 250 to achieve arsenic concentration of 10 ppb in treated water, whereas the suggested method is able to achieve 10 ppb at Fe/As (w/w) around 5, which also significantly reduces waste produced. The units have been designed for a flow rate of 600 L/h and more than 45 units are operational in several Indian villages for more than three years. The treated water arsenic concentration is 10 ppb with IITB Arsenic filter.

Arsenic removal technology for drinking water for developing countries

249th National Meeting (2015)

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