Arsenic Removal from Drinking Water by Electrocoagulation

Abstract

Arsenic is a toxic element which occurs in water due to mineral dissolution. Arsenic occurs in water mainly in the form of arsenite [As(III)] and arsenate [As(V)]. Maximum allowable limit for arsenic in drinking water is 0.01 mg/I as per WHO guidelines. In India the most severe outbreak of arsenic poisoning have been associated with ground water in the Bengal Delta including Bangladesh and West Bengal (Eastern India) where an estimated total of 120 million people (80 million in Bangladesh, 40 million in India) are at risk. The purpose of this study was to investigate the effects of the operating parameters, such as pH, treatment time, current density, and inter-electrode spacing on arsenic removal from drinking water in the batch electro-coagulation (EC) process. pH 7 was found to be appropriate for treating the drinking water for arsenic removal by EC. Also, the effect of pH on arsenic removal was not significant and remained in the permissible limit for initial pH range of 6 to7. The removal of arsenic increased with decreasing inter-electrode spacing. However, for inter-electrode spacing less than 1 cm, there was no further improvement in the arsenic removal. Better removal of arsenic was observed with increasing current density. It was found that for current density equal to 6.57 mA/cm2 (with 2.5 A current) with four electrodes gave better result as compared to 3.94 and 5.25 mA/cm2. It was possible to bring the residual arsenic content in the treated water within the permissible limit (10 ppb) in 40 minutes of electrolysis time.