Acid mine drainage bioremediation using bacteria enriched from the confluence zone between its flow and treated sewage

Abstract

Sediments from the confluence zone between an acid mine drainage stream and a water stream receiving the effluent from a municipal wastewater treatment plant were inoculated in a Postgate B medium base having methanol, glycerol, or ethanol as carbon source/electron donor, over a pH range between 2.00 and 6.00, aiming to obtain native cultures enriched in acidophilic/acid-tolerant sulfate-reducing bacteria. The most effective sulfate reduction observed in acidic conditions was in the enrichment cultures with methanol. Thus, the microbial consortium enriched in these conditions was further used in acid mine drainage bioremediation experiments at an initial pH of 4.50 and using different doses of nutrients medium base and methanol as carbon source/electron donor. The most promising results, with more than 99% removal of metals, were obtained in the mixture of 20% Postgate B medium base plus 80% acid mine drainage (v/v), which corresponds to 0.115% basal salts and 0.02% yeast extract (w/v). Metataxonomic analysis based on 16S rRNA gene sequences showed the presence of Desulfosporosinus spp. in all enrichment cultures, with the highest relative abundance in cultures at pH 4.00 with methanol. Furthermore, metataxonomic analysis in the acid mine drainage remediation tests revealed the presence of Desulfosporosinus spp. in all tested conditions. In addition, the study also revealed Clostridium members in all tests. Plus, their relative abundances were related to the dose of nutrient medium base and in balance with the abundances of Desulfosporosinus spp.