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 omega, 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/m(3). 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.

Automated summary

Constructed wetland-microbial fuel cell system (CW-MFC) is an effective technology for domestic wastewater treatment and bioelectricity generation. This study investigated the influence of influent COD concentration, HRT, and external resistance on system performance and found the optimal operating conditions. The results showed that CW-MFC outperformed traditional CW system in terms of pollutant removal efficiency and bioelectricity production. The analysis of microbial community indicated that the enrichment of electroactive bacteria and denitrifying bacteria might contribute to the performance improvement of CW-MFC system.