Arsenic reduction and precipitation by shewanella sp.: Batch and column tests

Abstract

The effect of bio-geochemical processes on speciation, fate, and transport of arsenic was investigated through the laboratory tests. Shewanella sp., iron-reducing bacteria, was used for batch and column tests. In contrast to the control batch test, the bio-active batch test indicated that Shewanella sp. reduced As(V) to As(III) with concurrent oxidation of lactate to acetate and the decrease of Eh. As time went, a significant amount of the precipitates were formed, and the removal of arsenic species from the solution was attributed to precipitates. SEM-EDX and chemical analyses of the precipitates suggested that As(III) and As(V) were precipitated with sulfides. The reduction and subsequent precipitation of arsenic species were also observed in the column tests. The batch and column tests suggest that in natural groundwater system, Shewanella sp. participates in the reduction of As(V) and sulfate, and sulfides produced by the microbial activity precipitate As(V) and As(III).