We studied the microbial functional and structural interactions between nitrate (NO 3 -) and perchlorate (ClO 4 -) reductions in the hydrogen (H 2)-based membrane biofilm reactor (MBfR). When H 2 was not limiting, ClO 4 - and NO 3 - reductions were complete, and the MBfR's biofilm was composed mainly of bacteria from the ε- and β-proteobacteria classes, with autotrophic genera Sulfuricurvum, Hydrogenophaga, and Dechloromonas dominating the biofilm. Based on functional-gene and pyrosequencing assays, Dechloromonas played the most important role in ClO 4 - reduction, while Sulfuricurvum and Hydrogenophaga were responsible for NO 3 - reduction. When H 2 delivery was insufficient to completely reduce both electron acceptors, NO 3 - reduction out-competed ClO 4 - reduction for electrons from H 2, and mixotrophs become important in the MBfR biofilm. β-Proteobacteria became the dominant class, and Azonexus replaced Sulfuricurvum as a main genus. The changes suggest that facultative, NO 3 --reducing bacteria had advantages over strict autotrophs when H 2 was limiting, because organic microbial products became important electron donors when H 2 was severely limiting.
ASJC Scopus subject areas
- Environmental Chemistry