Electro-assisted autohydrogenotrophic reduction of perchlorate and microbial community in a dual-chamber biofilm-electrode reactor

Abstract

The electro-assisted autohydrogenotrophic reduction of perchlorate (ClO4−) was investigated in a dual-chamber biofilm-electrode reactor (BER), in which the microbial community was inoculated from natural sediments. To avoid the effect of extreme pH and direct electron transfer on perchlorate reduction, a novel cathode configuration was designed. The pH of the cathode compartment was successfully controlled in the range of 7.2–8.4 during whole experiment. The effective biological autohydrogenotrophic reduction of perchlorate was achieved using hydrogen generated in-situ on the electrode surface, and the removal rate of 10 mg L−1 perchlorate reached 98.16% at HRT of 48 h. The highest perchlorate removal flux reached to 1498.420 mg m−2·d−1 with a 0.410 kW·h g-perchlorate−1 energy consumption. The microbial community evolution in the BER was determined by high-throughput sequencing and the results indicated that the Firmicutes and Bacteroidetes were dominant at phylum level when perchlorate concentration was 10 mg L−1 or lower. And the Proteobacteria became ascendant at the perchlorate concentration of 20 mg L−1. The functional populations for perchlorate reduction were successfully enriched including Nitrosomonas (30%), Thermomonas (9%), Comamonas (8%) and Hydrogenophaga (3%). Meanwhile, the proportion of functional population in biofilm linked to perchlorate concentration. With the increase of influent perchlorate concentration, the perchlorate-reducing bacteria (PRB) were enriched successfully and became ascendant.