Influence of C/N ratio on the efficacy of the continuous flow double-sludge AOA process with double cathode microbial fuel cell

Background

The continuous flow double-sludge anaerobic/aerobic/anoxic process is a good choice for removing nitrogen (N) and phosphorus (P) simultaneously, although these are difficult to remove efficiently. Microbial fuel cells (MFCs) can extract energy from wastewater and use electrons to remove pollutants. This study proposes a novel integration of MFCs with the continuous flow double-sludge AOA process, investigating the system's performance across different carbon (C)/N ratios (2, 3.5, 5 and 6.5) in terms of pollutant removal, electricity generation and microbial community structure.

Result

When the influent C/N ratio was 3.5, the average removal rates of chemical oxygen demand, ammonium (NH₄⁺)-N, and phosphate (PO₄³⁻)-P were 92.01%, 79.68% and 92.91%, respectively, and the average simultaneous nitrification and denitrification (SND) and SND P removal (SNDPR) rates of nitrogen oxide (NO_x⁻)-N were 53.30% and 42.09%, respectively. The diversity and abundance of microbial community were at a good level, and the relative abundance of Dechloromonas, Pseudomonas and Candidatus_Competibacter reached 4.16%, 2.16% and 4.61%, respectively, at C/N = 3.5.

Conclusions

Significant differences in pollutant removal were observed under different C/N conditions, with electron acceptors emerging as the biggest factor affecting power generation. According to the microbiological results, the combination of lower C/N ratios and higher PO₄³⁻-P contributed to the enrichment of key functional microorganisms. © 2025 Society of Chemical Industry (SCI).