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.

This study investigates alternative treatments of car wash effluents. The car wash wastewater was treated by settling, filtration, and membrane filtration processes. During settling, total solid concentration decreased rapidly within the first two hours and then remained constant. Chemical oxygen demand (COD) and conductivity were decreased by 10% and 4%, respectively. After settling, wastewater was filtered throughout a 100 μm filter. It was found that filtration had a negligible effect on COD removal. Finally, wastewater was filtered by four ultrafiltration membranes of varying molecular weight cutoff (MWCO) (1, 5, 10 and 50 kDa) and one nanofiltration membrane (NF270, MWCO = 200–400 Da). The permeate COD concentrations varied between 64.5 ± 3.2 and 85.5 ± 4.3 mg L⁻¹ depending on UF pore size. When the NF270 nanofiltration membrane was used, the permeate COD concentration was 8.1 ± 0.4 mg L⁻¹ corresponding to 97% removal. FeCl₃ precipitation and activated carbon adsorption techniques were also applied to the retentate and 60–76% COD removals were obtained for activated carbon adsorption and FeCl₃ precipitation, respectively.