Tetracycline inhibition and transformation in microbial fuel cell systems: Performance, transformation intermediates, and microbial community structure

Tetracycline (TC) transformation in the anode of an air cathode microbial fuel cell (MFC) and in the cathode of an MFC-Fenton system was investigated. TC at 10 mg/L in the anolyte was removed by 43–74% in 14-d cycles, mainly attributed to adsorption. The electrochemical activity, COD and acetate consumption of the anodic biofilm were inhibited by TC; inhibition was reversed when TC addition was stopped. Over 84 d of MFC operation with TC, Geobacter and Mycobacterium in the anode biofilm decreased, while Janthinobacterium and Comamonas increased. Over 99% of TC at 10–40 mg/L was removed within 8 h in the MFC-Fenton cathode. O2−•/HO2• and •OH were responsible for the cathodic TC degradation. The maximum current was 0.93 mA (at 250 Ω) and increased by 36.3% by the MFC-Fenton reaction. Cathodic MFC-Fenton is an efficient and energy-saving process for TC removal, compared to slow and problematic anodic TC bio-oxidation.