Recent advances in constructed wetland-microbial fuel cells for simultaneous bioelectricity production and wastewater treatment: A review

The coupling of constructed wetlands (CWs) to microbial fuel cells (MFCs) has turned out to be a source of renewable energy for the production of bioelectricity and for the simultaneous wastewater treatment. Both technologies have an aerobic zone in the air-water interface and an anaerobic zone in the lower part, where the anode and the cathode are strategically placed. This hybridization is a promising bioelectrochemical technology that exerts a symbiosis between plant-bacteria in the rhizosphere of an aquatic plant, converting solar energy into bioelectricity through the formation of root exudates as an endogenous substrate and a microbial activity. The difference between CW-MFC and MFC conventional lies in the bioelectricity and substrate production in situ, where exogenous substrates are not required for example wastewater. However, CW-MFC can take organic content present in wastewater, promoting the removal of some pollutants. Different areas that comprise the study of a CW-MFC have been explored, including the structures and their operation. This review aims to provide concise information on the state of the art of CW-MFC systems, where a summary on important aspects of the development of this technology, such as bioelectricity production, configurations, plant species, rhizodeposits, electrode materials, wastewater treatment, and future perspectives, is presented. This system is a promising technology, not only for the production of bioenergy but also to maintain a clean environment, since during its operation, no toxic byproducts were formed.