Sediment microbial fuel cells for bioremediation of pollutants and power generation: a review

Worldwide pollution of almost all natural media by toxic compounds is a major public health issue requiring the development of advanced remediation techniques such as sediment microbial fuel cells that can treat contaminants in aquatic sediments. The principle of these fuel cells relies on an electrical connection between the anaerobic sediment and the aerobic overlying water column, an inexhaustible terminal electron acceptor. As a consequence, this technique is particularly adapted to power generation and to the remediation of persistent organic pollutants that are trapped within sediments. Here we review sediment microbial fuel cells with focus on principles of this technique, influencing parameters, applications, and challenges. We discuss sediment redox properties, electrodes, anode reduction pathways, microbial communities, exoelectrogens, and microbial electron transfer. Influencing parameters include pH, temperature, internal resistance, and the substrate nature. Applications to power generation, and water and sediment remediation are presented. Challenges are related to modelling, monitoring, electromicrobiology, sediment properties, the overlying water, scaling up, and economic aspects. We found that sediment microbial fuel cells best operate at a pH 6-9. Optimal temperatures vary widely and depend on the microbial community, with good performance reported from 10 & DEG;C to around 45 & DEG;C. A lower internal resistance generally improves the performance of the system by favouring electron transfer. Biofilm characteristics and water salinity influence the internal resistance of the system, with marine microbial fuel cells exhibiting generally lower internal resistance than freshwater systems. High contaminant concentration evolves the sediment microbial consortium towards generalist degraders, rather than electrochemically active microbes that can enhance the pollutants biodegradation rates.