Effect of applied voltage on simultaneous pyrene degradation and nitrate reduction in a dual-chamber microbial electrolysis cell

초록

This study investigates the long-term effect of applied voltage on simultaneous pyrene degradation and nitrate reduction in dual-chamber microbial electrolysis cells (MECs). Reactors were operated at applied voltages of 0.3-1.2 V, alongside direct-circuit (0 Omega) and open-circuit as controls, with 10 mgL(-1) pyrene and 50 mgL(-1) NO3--N. Reactor performance, biofilm morphology, gas composition, and microbial community structure were systematically evaluated. The 0.5 V system exhibited the most stable and efficient performance, achieving 93.2 +/- 2.1% pyrene removal and 95.6 +/- 1.8% nitrate reduction with complete acetate utilization, while minimizing N2O emissions. Higher voltages (>= 1.0 V) induced biofilm disruption, elevated N2O production, and reduced electrochemical efficiency. Microbial analyses revealed selective enrichment of electroactive and PAH-degrading genera at 0.5 V, whereas stress-tolerant fermentative and methanogenic taxa dominated at higher voltages. Multivariate analysis, functional guild clustering, and correlation mapping confirmed strong microbe-function-performance coupling under moderate electrochemical stimulation. Overall, the results show that, under controlled synthetic wastewater conditions, a moderate applied voltage (similar to 0.5 V) provides favorable electro-microbial coupling for simultaneous pyrene degradation and nitrate reduction, indicating potential applicability of MEC systems for treatment of complex contaminated wastewaters.

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