The synergistic effect of electrode spacing and aeration intensity on the performance of pyrite based constructed wetland-microbial fuel cells

• The optimal configuration of electrode spacing and aeration intensity was studied. • PCW-MFC-1 showed a higher denitrification capacity under a lower aeration rate. • Higher aeration rate enhanced denitrification and power generation in PCW-MFC-2. • PCW-MFC with smaller electrode spacing was conducive to phosphorus removal. • PCW-MFC with larger electrode spacing benefitted electroactive bacterial function. The electrode spacing and aeration intensity are the major factors influencing the electricity generation and pollutant removal performance of constructed wetland-microbial fuel cells (CW-MFCs) and there is a contradiction between them. It is important to match the two factors in system configuration but few studies have explored their synergistic effects. In the study, two CW-MFCs with pyrite as anode filler (PCW-MFC) were constructed and made up of different electrode spacing (PCW-MFC-1 of 10 cm and PCW-MFC-2 of 18 cm). In PCW-MFC-1, the removal efficiency of total nitrogen was 81.4 %–85.1 %, which was significantly higher than that of PCW-MFC-2 when the aeration rate was 0.2 L/min. Besides, it presented a better performance in electricity generation with a maximum output voltage of 626 mV. The increase in aeration rate weakened the advantage of PCW-MFC-1. However, it enhanced the denitrification ability and power generation of PCW-MFC-2, which achieved 90.8 % of total nitrogen removal efficiency and 685 mV of the maximum output voltage due to the significant contribution of Thiothrix , Candidatus-Competibacter , and norank_Bacteroidetes_vadinHA17 . The phosphorus removal performance of systems was significantly influenced by electrode spacing, with smaller spacing promoting the chemical precipitation of Fe ions and phosphate. In conclusion, the study proposed optimal configurations of electrode spacing and aeration intensity to perform well in pollutant removal and energy recovery.