Efficient biodegradation of trimethoprim and transformation mechanism using the photoelectrocatalytic system

In this study, the coupling of a three-electrode photocatalytic microbial fuel cell system (PMFC) was established for trimethoprim (TMP) degradation, to achieve efficient degradation and electrical energy production simultaneously. The photocatalytic bioanode, degradation performance, electrochemical characteristics and microbial structure were analyzed to explore the degradation of TMP in PMFC. The results showed that rapid degradation and enhanced mineralization of TMP were obtained in the PMFC, which were 1.7 and 1.4 times higher than those of traditional microbial fuel cells (MFCs), respectively. Intermediates in the degradation process were identified in both systems, and three degradation pathways were inferred in the PMFC. The electricity characteristics were investigated and superior electrical production and higher electron transfer efficiency were observed in the PMFC, resulting in a maximum power density of 75.1 mW/m² and a maximum voltage of 0.225 V. Additionally, the cyclic voltammetry test and electrochemical impedance spectra were used for electrochemical performance characterization, and the results showed the stronger oxidation ability of PMFC with half the charge transfer resistance of MFCs. The microbial community structure demonstrated that the dominant species were enriched and coexisted, involving degradation bacteria, exoelectrogens, and hydrocarbon removal bacterial. Furthermore, canonical correspondence analysis (CCA) revealed a mutual promotion of TMP degradation and electricity production with the involvement of these active genera. In conclusion, this novel technology is an excellent alternative in practical applications for the treatment of wastewater containing antibiotics.