Effect of organic substrate composition on microbial community structure of pilot-scale biochemical reactors treating mining influenced water

Abstract

Mining-influenced water (MIW) is acidic, metal rich water formed when sulfide minerals react with oxygen and water. There are various options for the treatment of MIW; however, passive biological systems such as biochemical reactors (BCRs) have shown promise because of their low cost and maintenance requirements. The purpose of this study was to explore the effect of organic substrate on microbial communities present in pilot-scale BCRs treating MIW in order to understand how substrate-microbe interactions drive performance. Three organic substrates were evaluated: ethanol (ETOH); and two lignocellulose-based mixtures: hay and wood chips (HYWD), and corn stover and wood chips (CSWD). The microbial community compositions were characterized by cloning of 16S rRNA genes and apsA genes associated with sulfate reduction. Quantitative polymerase chain reaction (Q-PCR) was applied to quantify Desulfovibrio-Desulfomicrobium spp. and methanogens. Results revealed distinct differences in microbial compositions and relative quantities of total and sulfate-reducing bacteria (SRB) among the BCRs. In particular, the greatest proportion of SRBs were observed in the ETOH BCRs, but the total number of bacteria was low. The HYWD and CSWD BCRs had highly similar bacterial communities, which were complex in composition in comparison to the ETOH BCRs. Methanogens were found to be present in all BCRs at low levels and were the highest in the lignocellulose-based BCRs. This study demonstrates that substrate influences microbial community composition and diversity, which may play an important role in performance and reliability.