Bioremediation of Arsenic from Contaminated Water

Abstract

Presently, over 100 million people worldwide are exposed to arsenic contaminated groundwater making it one of the largest environmental catastrophes. Arsenic originates from the earth’s crust which finds its way into groundwater as a result of various geological, biological and even anthropological processes. Toxicity effects of arsenic have been reported in plants, animals and most vividly in humans. WHO has recently brought down the permissible limit of arsenic in drinking water to 10 μg/L. Various physicochemical and biological arsenic remediation methods have been reported and applied to render groundwater potable for human use. Microbial remediation of arsenic from aquatic environments presents an interesting option because of its high efficiency, low cost and most importantly its ecofriendly nature. Microbial bioremediation of arsenic occurs through various processes. Microbially mediated arsenic redox reactions are one of the most important phenomena for arsenic remediation. We have reported Microbacterium lacticum, a unique bacterium that can tolerate up to 3,000 mg/L arsenite and oxidizes it rapidly to arsenate almost totally and applied this organism for arsenic bioremediation in field level operations in the arsenic affected areas. Besides microbial oxidation, biosorption and methylation are other options that have been tried with limited success. Thus many options are available for microbial bioremediation of arsenic from aqueous environments; these can be effectively used with or without other physicochemical methods. Our article will take an in-depth review of the fundamental processes involved as well as various laboratory scale, pilot scale and field scale technologies developed.