Exploring the effect of voltage on biogas production performance and the methanogenic pathway of microbial electrosynthesis

Microbial electrosynthesis (MES) has great potential for energy and resource recovery in wastewater treatment and has therefore gradually become a popular research topic. In this study, MES with an applied voltage (0.6 V, 0.8 V and 1.0 V) significantly improved biogas production (36.0 %, 52.3 %, and 59.1 %, respectively) compared with the control (without electrodes). Analysis of microbial community structure revealed that Clostridium and Methanosaeta had the highest relative abundance in all reactors. The abundances of Acetivibrio and Geobacter dominated the bioanode, and methane production was mainly mediated by the acetoclastic methanogenic pathway. On the biocathode, the abundances of Methanolinea and Methanothermobacter were higher than those of other microbes, and methane was produced primarily through the hydrogenotrophic methanogenic pathway. When the acetoclastic methanogenic pathway in the biocathode was inhibited, MES could efficiently produce methane through other pathways. In addition, MES was more tolerant to the effects of high NH4+-N concentrations than anaerobic digestion (AD). These results suggest that applying voltage to the bioanode and biocathode could better improve the efficiency of methane production.