Bioremoval of arsenic and antimony from wastewater by a mixed culture of sulfate-reducing bacteria using lactate and ethanol as carbon sources

We investigated the remediation of wastewater containing As and Sb through the application of a mixed culture of sulfate-reducing bacteria (SRB). The effect of Fe(II) and different carbon sources on the removal of As and Sb was evaluated. The wastewater initially contained 5 mg L-1 of both As(V) and Sb(V), and the treatment was conducted over a 12-d period. The produced precipitates were characterized by TEM and XRD to elucidate the metalloid removal mechanism. In the absence of Fe(II), Sb was efficiently removed (97.6% and 97.8% with lactate and ethanol as carbon sources, respectively, hereinafter the same), whereas only a relatively small fraction (27.8% and 26.4%) of As was removed. The addition of 200 mg L-1 Fe(II) greatly improved the removal of As (78% and 98.2%) and further increased the removal of Sb (98.8% and 99.4%). We hypothesized that As was removed through sorption/co-precipitation by FeS instead of the formation of As2S3\. The use of ethanol as a carbon source generated a relatively lower yield of sulfide compared to the use of lactate, but it resulted in a higher removal of As and Sb. This may be attributed to the low production of sulfide, which possibly resulted in the slow precipitation of FeS that enhanced the sorption/co-precipitation of ions. This work demonstrates the high application potential of ethanol as a carbon source and the addition of Fe(II) in the bioremoval of As and Sb from wastewater by SRB.