Enhanced organic matter degradation by a sediment microbial fuel cell system using hexavalent chromium as an electron acceptor

Abstract

In this study, a sediment microbial fuel cell (SMFC) system for the simultaneous biodegradation of organic matter and detoxification of hexavalent chromium Cr (VI) was investigated. The total organic carbon (TOC) removal rate of the SMFC with Cr (VI) was 30.07%, which was significantly higher than that in a SMFC without Cr (VI) (13.74%). In the SMFC with Cr (VI), the maximum values of open-circuit voltage (OCV) and power density were 408 mV and 4.8 mW/m 2 , respectively. During the long-term operation of the SMFC with Cr (VI), 25 mg/L of Cr (VI) were completely reduced from all four consecutive batches over 48 days. MiSeq sequencing revealed that the biofilm microbial community of the anode comprised of Bacteroidetes (42.9%), Proteobacteria (33.6%), Chloroflexi (7.5%), and Euryarchaeota (7.5%) as the predominant phyla. Compared with that of the sediment, certain families were enriched; they included Pseudomonadaceae (46.88-fold), Flavobacteriaceae (5.05-fold), and Syntrophaceae (4.48-fold), which are organic matter-degrading bacteria. These results suggest that SMFCs are useful for TOC removal and detoxification of heavy metals in remediation of contaminated lakes.