Microbial fuel cells (MFCs) in integration with anaerobic treatment processes (AnTPs) and membrane bioreactors (MBRs) for simultaneous efficient wastewater/sludge treatment and energy recovery -A state-of-the-art review

The promising and challenging approach of microbial fuel cell (MFC) is a novel concept in wastewater treatment facilities which utilizes microbial metabolism to produce direct electricity while treating wastewater/sludge. Despite potential advantages of MFCs and encouraging results obtained at laboratory-scale, low power density and high costs of initial investment and operation have limited their commercial application. Therefore, in order to promote MFCs utilization in a sustainable manner, the synergistic effect of MFCs integrated to other wastewater treatment processes seems efficacious. Among the proposed MFC hybrid systems, the integration of anaerobic treatment processes (AnTPs) and membrane bioreactors (MBRs) with MFCs have been adopted due to the practical implementation potential and the highly positive synergetic effect on energy recovery, power output and treatment efficiency. In AnTP-MFC coupled system, efficient handling of high COD-loaded influents and significant organic load reduction along with improved energy conversion efficiency and energy recovery is accomplished. In MFC-MBR hybrid system, the MBR improves the effluent quality to a high level, while the energy consumption and membrane fouling of MBR are alleviated by MFC. The hybrid processes benefit from MFCs as an online low cost efficient biosensor as well. Current trends, purposes and progresses in respect of these two cardinal hybrid processes are discussed and tables comprised of a wide range of researches within the scope of the integrations are provided in full details to gather a comprehensive literature. Finally, a multilateral evaluation plan, required to make integrated MFC processes competitive against the practically implemented ones, is proposed.