Effect of Organic Substrate on the Microbial Community Structure in Pilot-Scale Sulfate-Reducing Biochemical Reactors Treating Mine Drainage

摘要

Passive biological systems such as sulfate-reducing biochemical reactors have shown promise for treatment ofnmine drainage because of their low cost, minimal maintenance, and constructability in remote locations.nHowever, few criteria exist for their design and operation. In particular, the impact of the choice of carbonnsubstrate is poorly understood. This study represents the first to directly compare the effect of simple andncomplex organic substrate on microbial communities present in pilot-scale biochemical reactors treating minendrainage. Three organic substrates were evaluated: ethanol (ETOH), hay and pine wood chips (HYWD), andncorn stover and pine wood chips (CSWD). Microbial community compositions were characterized by cloningnand sequencing of 16S rRNA and apsA genes corresponding to the sulfur cycle. Quantitative polymerase chainnreaction was applied to quantify Desulfovibrio-Desulfomicrobium spp. and methanogens. Results revealed dif-nferences in microbial compositions and relative quantities of total and sulfate-reducing bacteria among reactors.nNotably, the greatest proportion of sulfate-reducing bacteria was observed in the ETOH reactors. HYWD andnCSWD reactors contained similar bacterial communities, which were highly complex in composition relative tonthe ETOH reactors. Methanogens were found to be present in all reactors at low levels and were highest in thenlignocellulose-based reactors. Interestingly, higher proportions of aerobic Thiobacillus spp. were detected in twonreactors that experienced an oxygen exposure during operation. This study demonstrates that both substrate andnenvironmental stress influence both microbial community composition and diversity in biochemical reactorsntreating mine drainage. While there were no significant differences in performance observed over the time scalenof this study, potential long-term implications of the differing microbial communities on performance arendiscussed.