Micro-electricity utilization performance and microbial mechanism in microbial fuel cell powered electro-Fenton system for azo dye treatment

A microbial fuel cell powered electro-Fenton system (MFCⓅEFs) with low consumption of power source and high efficiency of degrading refractory pollutants was constructed to treat textile wastewater. The bioelectricity generated from the degradation of sewage sludge and was used by the microbial fuel cell to generate H2O2 in situ to stimulate methylene blue (MB) degradation. On pH 3, external resistance 100 Ω and air flow rate 400 mL/min, Coulombic efficiency, Faraday efficiency, H2O2 production, and the degradation rates of total chemical oxygen demand (TCOD) and MB were 1.26 %, 74.25 %, 20.18 mg/L, 31.58 % and 93.50 %, respectively. For the MFCⓅEFs, open circuit voltage and power density have been improved to 0.96 V and 1.99 W/m3 (0.81 V and 1.31 W/m3 of control group) respectively, higher electric double layer capacitance indicating faster electron transfer performance. The system’s degradation of MB mainly relied on the oxidation of hydroxyl radical (·OH). After the·OH in the system was quenched, the degradation rate of MB decreased by 45.19 %. CAZy, KEGG, and COG were characterized to annotate the functional genes of the MFCⓅEFs, which has a great significance to explore the mechanism of advanced treatment of dying wastewater by microbial electrochemical system.