Constructed wetland-microbial fuel cell (CW-MFC) has excellent effect and potential in wastewater treatment based on many factors, such as fillers, hydraulic retention time (HRT), influent chemical oxygen demand (COD) concentration, and plants. This study explored the influence of fillers, influent COD concentrations, and HRT on the performance of CW-MFC systems to optimize the operation. Two CW-MFCs with pyrite and activated carbon as anode materials (PCW-MFC and ACW-MFC) were set up, respectively. The results showed that prolonging HRT of the systems could improve the nutrients’ removal efficiency and voltage output. The influent COD concentration had a positive import on the removal efficiency of COD, nitrate-nitrogen (NO ₃ ⁻ -N), and total phosphorus (TP) in CW-MFCs. On the contrary, the removal efficiency of ammonia-nitrogen (NH ₄ ⁺ -N) decreased and the voltage change showed a trend of increasing first and then decreasing with the increase of COD concentration. The optimal operating conditions of CW-MFCs were COD of 200 mg/L and HRT of 24 h. Moreover, it found that the overall performance of PCW-MFC was better than that of ACW-MFC. Microbial community analysis evaluated that the abundance of autotrophic denitrifying bacteria Thiobacillus , Dechloromonas , and Pseudomonas in the cathode layer of PCW-MFC was higher than that of ACW-MFC, indicating that pyrite could effectively promote the bacterial reproduction of nitrogen and phosphorus removal and electrogenesis.

Under the background of carbon neutrality, the constructed wetland-microbial fuel cell coupled system (CW-MFC) has attracted more and more attention in wastewater treatment. This study, the CW-MFC was developed for promoting nutrients removal in wastewater and electricity generation. The results showed that the average removal efficiencies of COD, NH₄⁺-N and TP in CW-MFC were 85.20%, 75.99% and 59.20%, respectively. While the average removal efficiencies of COD, NH₄⁺-N and TP in CW were 78.05%, 70.88% and 50.80%, which were all lower than those in CW-MFC. In addition, the maximum output voltage of 331 mV was achieved in CW-MFC, which could be used for the running of wastewater treatment plant in turn and further reduce the consumption of fossil fuel. Accordingly, the maximum power density of the CW-MFC system reached to 107.54 mW m^-3.