Removal of arsenic from arsenic rich sludge by volatilization using anaerobic microorganisms treated with cow dung

Abstract

The microbial mediated volatilization of arsenic by anaerobic digestion method was studied using cultures of methanogenic bacteria. Cow dung was utilized as the major substrate for the bacterial growth during arsenic volatilization. Effect of contact time showed that arsenic volatilization followed a linear kinetics lip to 40 days and thereafter the kinetics was negligible. Arsenic volatilization was fitted to 1st order plot and the reaction rate constant "k" calculated to be 0.0282 mg/L/day. The regeneration time of the bacteria was found to be 53.3 hour. The effect of substrate (covi, dung) was studied to measure the arsenic volatilization and it was observed that substrate concentration of 25 g/L could volatilize about 35% of arsenic. However, higher substrate concentration decreased arsenic volatilization rate, which may be due to formation of methane that inhibits higher doses of arsenic and led to the formation of non-volatile compounds. The maximum uptake was found to be 1.08 mg of As(V)/g of substrate. The effects of different organic acids on arsenic mobilization have been discussed.