Bio-electrochemical enhancement of anaerobic reduction of nitrobenzene and its effects on microbial community

• MEC assisted anaerobic reactor (R1) improved NB removal, AN production, and COD removal.
• Raising voltage from 0.5 to 1.2 V improved the conversion of NB to AN.
• The cathode of R1 presented higher value of NB reduction rate constant (k).
• The abundances of bacteria and methanogens were higher than that of reference reactor.
• More NB reduction – related bacteria was enriched in R1.

Nitrobenzene (NB) is listed as a priority pollutant in many countries due to its high toxicity and environmental risk. In this study, a microbial electrolysis cell (MEC) combined anaerobic reactor with a pair of Fe – carbon electrodes (R1) was designed to reduce NB to less-toxic and biodegradable aniline (AN). Applying a voltage of 0.5 V in R1 enhanced the NB reduction, AN production, and COD removal comparing to the reference reactors. Raising voltage from 0.5 to 1.2 V improved the conversion of NB to AN. The assistance of MEC intensified Fe2+ leaching and accelerated the process of sludge granulation. As compared with abiotic electrode, the cathode of R1 presented higher value of NB reduction rate constant (k). Real-time PCR and cloning sequencing analysis showed that the abundances of bacteria and methanogens were significantly higher than that of reference reactor, in which some species capable of reducing NB were dominant in R1.