Integration of MFC reduces CH₄, N₂O and NH₃ emissions in batch-fed wetland systems

The combination of microbial fuel cells (MFCs) with constructed wetlands (CWs) for enhancing water purification efficiency and generating bioelectricity has attracted extensive attention. However, the other benefits of MFC-CWs are seldom reported, especially the potential for controlling gaseous emissions. In this study, we have quantitatively compared the pollutant removal efficiency and the emission of multiple gases between MFC-CWs and batch-fed wetland systems (BF CWs). MFC-CWs exhibited significantly (p < 0.01) higher COD, NH₄⁺-N, TN, and TP removal efficiencies and significantly (p < 0.01) lower global warming potential (GWP) than BF CWs. The integration of MFC decreased GWP by 23.88% due to the reduction of CH₄ and N₂O fluxes, whereas the CO₂ fluxes were slightly promoted. The quantitative PCR results indicate that the reduced N₂O fluxes in MFC-CWs were driven by the reduced transcription of the nosZ gene and enhanced the ratio of nosZ/(nirS + nirK); the reduced CH₄ fluxes were related to pomA and mcrA. Additionally, the NH₃ fluxes were reduced by 52.20% in MFC-CWs compared to BF CWs. The integration of MFC promoted the diversity of microbial community, especially Anaerolineaceae, Saprospiraceae and Clostridiacea. This study highlights a further benefit of MFC-CWs and provides a new strategy for simultaneously removing pollutants and abating multiple gas emissions in BF CWs.