Roles of external circuit and rhizosphere location in CH4 emission control in sequencing batch flow constructed wetland-microbial fuel cell

Abstract

Connecting external circuits can effectively inhibit the CH4 emissions from constructed wetlands (CW). In this study, the effect of external circuits, plant roots position and external resistance value on the electrical, CH4 emission and pollutant removing performance of sequencing batch constructed wetland-microbial fuel cell (CW-MFC) was investigated for the first time. After connecting external circuit, the CH4 emission from rhizosphere-anode-closed (RAC) constructed wetland-microbial fuel cell (CW-MFC) and rhizosphere-cathode-closed (RCC) CW-MFC was significantly reduced by 49.39% and 74.19%, respectively. When the external resistance was 1000, the highest power density was observed in RAC CW-MFC with a number of 73.32 mW m−3. In comparison, CW-MFC with rhizosphere at cathode emitted less CH4, while CW-MFC with rhizosphere at anode had a better electrical performance. Based on the high-throughput sequencing analysis, dynamic community structure of bacteria and archaea and the related microbial processes in the anode and cathode of CW-MFC were studied. Proteobacteria, Bacteroidetes and Methanosaeta were observed to be dominant in CW-MFCs, and the circuit conditions, external resistance and rhizosphere location all played important roles in the microbial community structure of CW-MFCs.