Enhanced pollutants removal and contributions analysis of near-natural floating bed coupling with microbial fuel cell

Urban water bodies are increasingly threatened by pollution due to rapid urbanization and insufficient wastewater management. In this study, a near-natural ecological floating bed coupled microbial fuel cell was constructed to enhance the remediation of overlying water bodies contaminated with carbon, nitrogen, and phosphorus. Three systems-ECOFB (ecological floating bed), ECOFB-OMFC (open circuit), and ECOFB-CMFC (closed circuit)-were comparatively evaluated in laboratory-scale reactors. The results revealed that ECOFB-CMFC achieved superior removal efficiencies for total organic carbon (85.3 %), total nitrogen (80.1 %), and total phosphorus (83.4 %), surpassing the other systems by up to 2.5-fold. The microbial electrochemical systems (MFC) formed an "electronic bridge" in the ecological floating bed that facilitated sediment organic matter oxidation and nitrate reduction, promoted biofilm diversity and electroactivity, and alleviated plant stress. Functional gene analysis showed significantly upregulated genes related to nitrification, denitrification, and nitrogen fixation in the ECOFB-CMFC system. Microbial community analysis indicated increased abundance of electroactive, denitrifying, and polyphosphate-accumulating bacteria. Mass balance analysis confirmed the synergistic roles of plants, microorganisms, and MFC in pollutant removal. This study unveils the mechanistic contributions of system components, providing scientific evidence for the scalable application of ECOFB-CMFC in urban water pollution remediation.