Microbial fuel cells for municipal wastewater treatment: From technology fundamentals to full-scale development

Microbial fuel cells (MFCs) in municipal wastewater treatment plants (M-WWTPs) have garnered increasing interest in terms of attaining energy self-sufficiency due to their theoretical superiority to conventional M-WWTP processes. Despite being widely studied, pertaining literature primarily focuses on the fundamentals and configurations of the MFCs while overlooking their targeted application niche. Therefore, the adoption of MFCs in many niches (i.e., M-WWTPs) has not been adequately reviewed yet. This study aims to critically review the adoption of MFCs for carbon handling in the liquid stream of M-WWTPs with an emphasis on MFC's scalability, use of municipal wastewater (M-WW) as the substrate, and MFC's capital cost. The review includes the scaled-up results and other efforts to engineer MFCs. Three key challenges stymie MFC's adoption in M-WWTPs: low power generation, wide range of reported carbon removal efficiencies, and high capital cost. Accordingly, MFCs should be adopted in M-WWTPs with the goal of energy neutrality, not extra electricity production. To meet the effluent discharge standards, MFCs should be preceded by primary treatment, followed by an anaerobic fluidized bed membrane bioreactor. However, breakthroughs are still required to make this technology cost-efficient and energy-efficient. These efforts should take into consideration the multivariate nature of the MFCs. Additionally, the development of bioelectrochemically assisted anaerobic technologies has shown great prominence as an alternative technology that can be integrated into M-WWTPs. However, validation based on larger-scale applications, cost, and energy estimations is still needed.