Microbial fuel cells (MFC) have recently received increasing attention due to their promising potential in sustainable wastewater treatment and contaminant removal. In general, contaminants can be removed either as an electron donor via microbial catalyzed oxidization at the anode or removed at the cathode as electron acceptors through reduction. Some contaminants can also function as electron mediators at the anode or cathode. While previous studies have done a thorough assessment of electron donors, cathodic electron acceptors and mediators have not been as well described. Oxygen is widely used as an electron acceptor due to its high oxidation potential and ready availability. Recent studies, however, have begun to assess the use of different electron acceptors because of the (1) diversity of redox potential, (2) needs of alternative and more efficient cathode reaction, and (3) expanding of MFC based technologies in different areas. The aim of this review was to evaluate the performance and applicability of various electron acceptors and mediators used in MFCs. This review also evaluated the corresponding performance, advantages and disadvantages, and future potential applications of select electron acceptors (e.g., nitrate, iron, copper, perchlorate) and mediators.

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Carcinogenic bromate (BrO3−) can be present in drinking water as a result of its formation from bromide (Br−) during ozonation. A fixed bed column reactor filled with elementel sulfur and limestone was operated for about six months under autotrophic and mixotrophic (autotrophic + heterotrophic) conditions at 30°C. The reactor was operated at the hydraulic retention time (HRT) ranging from 16.5 to 10.1 h at autotrophic conditions. Under mixotrophic conditions, 45 mg/L NO3‐N was removed completely at C/N ratio (mg CH3OH/mg NO3‐N) between 0.55 and 1.66 at HRT of 10.1 h. The average effluent pH was 7.8 and the sulfate concentration was lower than the Environmental Protection Agency limits at the mixotrophic stages. Efficient simultaneous BrO3− and nitrate removal was achieved at feed concentrations of 100–500 µg/L BrO3− and 45 mg/L nitrate under autotrophic and mixotrophic conditions. Effluent Br− measurements indicated that BrO3− was completely reduced without accumulation of by‐products.