Primary insight into the cathode strengthened electrons transport and nitrous oxide reduction during hydrogenotrophic denitrification in bioelectrochemical system (BES)

Abstract

Long time for acclimating biocathode and low efficiency of electrons transport owing to the high cathodic over-potentials were the main challenges for hydrogenotrophic denitrification in bioelectrochemical system (BES). The current study was aimed to reveal the mechanism of polarity reversal and porous polypyrrole (PPy) modification on facilitating the electrons transfer from hydrogen to nitrate reduction chain and nitrous oxide reduction. The results showed the highest accumulated NADH concentration was achieved in the group of combination, which was 7.5%, 18.2% and 48.5% higher compared with the PPy group, reversal group and control group, respectively. Moreover, significant increases of nitrous oxide reductase (Nos) concentrations were detected in the groups of cathode strengthening compared with the control group. In addition, specific microorganisms related with electrons transport and nitrous oxide reduction were enriched by polarity reversal and PPy modification. Overall, the cathode strengthening strategies could both improve electrons transport and nitrous oxide reduction in hydrogenotrophic denitrification process.