Batch-mixed iron treatment of high arsenic waters

This paper develops batch-mixed treatment with zero-valent iron as a point- of-use technology, appropriate for arsenic removal from water stored within rural homes in Bangladesh and West Bengal, India, where arsenic poisoning has affected an estimated 20 million people, Batch tests with iron yielded the following results: (1) High arsenic removal (> 93%) was achieved from h ighly arsenated waters (2000 mug/L) over short contact times (0.5-3 h) with iron filings added at doses ranging from 2500 to 625 mg/L; (2) Most rapid arsenic removal was observed in head-space free systems with sulphates pres ent in solution, while phosphate buffers were observed to inhibit arsenic r emoval by iron; (3) The arsenic removed from water was found to be strongly bound to the elemental iron filings, such that the treated water could be decanted and iron could be reused at least 100 times; (4) Some iron dissolv ed into water over the contact period, at concentrations ranging from 100 t o 300 mug/L, which are within safe drinking water limits. These results ind icate that, with appropriate assessment of water chemistry in the affected region, treatment with metallic iron followed by simple decantation can be used as a practical, in-home, point-of-use technique for reducing human exp osure to arsenic in drinking water. (C) 2001 Elsevier Science Ltd. All righ ts reserved.