Effect of drained-flooded time ratio on ammonia nitrogen removal in a constructed wetland-microbial fuel cell system by tidal flow operation

A novel constructed wetland-microbial fuel cell system by tidal flow operation (TFCW-MFC) was constructed to intensify ammonia nitrogen removal. The nitrogen removal performance of the TFCW-MFC with different ratios of drained and flooded time (D/F ratios) was investigated to determine the optimal operating strategy. The highest TN removal efficiency of 52.89 ± 3.16% was obtained at the D/F ratio of 1:5 (C/N ratio: 5). The bacterial communities in the anode (granular activated carbon and graphite felt, referred to as TF_a1 and TF_a2, respectively) and the cathode (graphite felt, referred to as TF_c) collected from the TFCW-MFC were characterized using 16S rRNA gene high-throughput sequencing technology. The high abundance of Nitrospira predominant in the anode indicated that the tidal flow operation strengthened the system's reoxygenation ability, thus improving the overall nitrification efficiency of the system. Besides, Acinetobacter (21.67%) in the cathode could play an important role in the heterotrophic aerobic denitrification process.