Performance optimization and microbial community evaluation for domestic wastewater treatment in a constructed wetland-microbial fuel cell

Constructed wetland-microbial fuel cell system (CW-MFC), an attractive technology still under study, has shown to improve domestic wastewater treatment efficiency and generate bioelectricity. This work investigated the effect of multiple factors on the performance optimization for the pollutants removal and bioelectricity production compared to a traditional CW, including influent chemical oxygen demand (COD) concentration, hydraulic retention time (HRT) and external resistance. The results showed that the optimal operating conditions of COD concentration, HRT and external resistance for CW-MFC were 200 mg/L, 24 h and 1000 Ω, respectively. The average COD, NH₄⁺-N, NO₃^--N and TP removal efficiencies were 6.06%, 3.85%, 3.68% and 3.68% higher than these in CW system, respectively. Meanwhile, the maximum output voltage and power density of CW-MFC were 388 ± 12 mV and 107.54 mW/m³. In addition, the microbial community analysis indicated that the pollution removal and bioelectricity generation might benefit from the gradual enrichment of electroactive bacteria (Tolumonas) and denitrifying bacteria (Denitratisoma, Methylotenera and Sulfuritales). The findings can provide the optimum operation parameters and mechanism insight for the performance of CW-MFC systems.