Enhanced denitrification at biocathode facilitated with biohydrogen production in a three-chambered bioelectrochemical system (BES) reactor

- Denitrification was apparently enhanced in three-chambered BES reactor.
- Hydrogen content produced in CHBC reached the highest.
- Electrochemical performances were bettered in CHBC than HC and BC.
- Most abundant denitrifiers got enriched in CHBC.

Three groups of bioelectrochemical system (BES), including BC, HBC and CHBC, were investigated for denitrification at biohydrogen production facilitated biocathode. It was found nitrate removal efficiency reached 95% during 6 days for the three-chambered CHBC reactor, while 8 and 12 days were required for HBC and BC, respectively. Besides, highest hydrogen content of 52.49% could be obtained at the biohydrogen cathode in CHBC. In addition, power density and coulombic efficiency (CE) of CHBC reached 118.43 mW m3 and 79.1 ± 0.2%, respectively, which were better than the other two groups. Resistance indicating electron transfer of CHBC also showed to be the lowest among the three systems. Through Illumina MiSeq high-throughput sequencing, it was found that 5 core genus promoting denitrification got enriched in CHBC, including Simplicispira, Thauera, Thermomonas, Azoarcus and Ottowia, while only 1 core genus was enriched in HBC and BC, respectively, which suggested that the three-chambered BES structure could affect the microbial diversity as well as the community compositions, and then promoted the nitrate reduction. Moreover, as hydrogen consumers featured for nitrate reduction were found to be the most abundant at CHBC biocathode, hydrogenotrophic denitrification at biocathode could be enhanced in the three-chambered BES reactor.