Manganese-mediated anaerobic methane oxidation coupled with constructed wetland-microbial fuel cell for enhanced methane mitigation: Performance and microbial mechanisms
In recent years, as research has progressed, two pathways for methane emission reduction have been identified: CW-MFC (constructed wetlands-microbial fuel cells) and AOM (anaerobic oxidation of methane). However, the methane emission reduction effects, microbial ecological networks, and electron transfer mechanisms of CW-MFC, AOM, and CW-MFC coupled with AOM remain unclear. Therefore, this study established four CWs (constructed wetlands) using quartz sand and manganese sand as substrates, namely CW-QS, CW-MFC-QS, CW-Mn and CW-MFC-Mn. Studies have shown that the COD removal efficiencies of both CW-Mn and CW-MFC-Mn exceeded 90%. CW-MFC-Mn enriched ANME-2d archaea and key genes associated with cyt c (cytochrome c), which enhanced AOM and EET (extracellular electron transfer) and reduced methane emissions by 3037%. However, the enriched Geobacter in CW-Mn competed with ANME-2d for electron acceptors, inhibited the ANME-2d archaea. High influent COD conditions can significantly promote the enrichment of Geobacter, facilitating the establishment of interspecies electron transfer pathways with methanogens, thus hindering methane emission reduction. In summary, this study reveals the effects and mechanisms of CW-MFC, AOM, and their coupled system on methane emissions. It is expected to provide data support and theoretical basis for methane reduction, thereby laying a solid foundation for future research.