Microbial fuel cell hybrid systems for wastewater treatment and bioenergy production: Synergistic effects, mechanisms and challenges

The microbial fuel cell (MFC) technology relies on electroactive bacteria to degrade organic molecules for bioelectricity production. MFC is a potentially useful approach for wastewater treatment with concomitant energy production. The main advantages of MFC for treating wastewater include energy saving, sludge volume reduction and bioenergy generation. In the past two decades, tremendous advances have been made in improving MFC performances. However, MFCs still face significant hurdles for practical deployments due to their low power densities and high costs. Further improvements are becoming harder to achieve for standalone MFC devices. In recent years, MFCs have been integrated with physical, chemical and biological processes for wastewater treatment, bioelectricity production, chemical production and desalination. The hybrid systems are more promising compared with standalone MFCs. This comprehensive and state-of-the-art review discusses different systems coupled with MFCs using different working principles, reactor designs, operating parameters and their effects on system performances. These systems include bioelectro-Fenton-MFC, microbial desalination cell, MFC-electrosorption cell, microbial solar cell, microbial reverse-electrodialysis cell, plant-MFC and constructed wetland-MFC. Synergistic effects and mechanisms of process coupling as well as the challenges for practical applications of each hybrid system are assessed. Although MFC-hybrid systems are more promising than standalone MFCs, much more research is needed to overcome significant hurdles for practical deployment.