Bioremediation of acid mine drainage using Fischer-Tropsch waste water as a feedstock for dissimilatory sulfate reduction

Abstract The treatment of acid mine drainage (AMD) using dissimilatory sulfate reduction (DSR) utilises the ability of sulfate reducing bacteria (SRB) to reduce sulfate to sulfide using organic compounds as electron donors. Given that AMD contains relatively low levels of organic matter, the electron donors need to be supplied externally to facilitate the bioremediation process. In this research we recognise Fischer Tropsch waste water (FTWW) as a potential organic source because of its richness in organic acids and alcohols. The FTWW was combined with synthetic AMD at an initial COD/SO42− ratio of 1.8 and was maintained in batch mode for 800 h before being turned to a fed batch mode, with an aerobic reactor receiving the sulfide rich effluent from the sulfate reducing reactor. The purpose of the aerobic reactor was to remove hydrogen sulfide through biological oxidation. The influent oxygen was regulated to avoid complete conversion of hydrogen sulfide to sulfate. We obtained up to 92.63 % sulfate removal, and almost 100 % COD removal in the anaerobic sulfate reducing reactor. The pH in the anaerobic reactor was raised from approximately 2 to above neutral. The subsequent aerobic sulfur oxidising reactor was able to convert up to 96.82 % of the sulfide produced in the anaerobic sulfate reducing reactor to sulfur.