Insights into the mechanism, performance and electrode modification of BES-AD combined systems for refractory wastewater treatment: A review

Abstract Using conventional anaerobic digestion to treat refractory wastewater has several drawbacks such as long start-up period, temperature sensitivity, volatile fatty acids (VFAs) accumulation and so on. The coupling of the bioelectrochemical systems with anaerobic digestion (BES-AD) has been proposed to enhance the degradation of refractory pollutants. In this review, the mechanism of BES-AD is firstly discussed. Then, the performance of BES-AD is evaluated with respect to different types of wastewater, anaerobic reactors, electrode materials and microbial communities associated with different systems. The embedding of BES addresses the accumulation of VFA and accelerates the start-up period, thus, allows for the growth of various microbial communities in the system. Novel electrodes with high biocompatibility and large specific surface area can be fabricated by the bioelectrodes-based modification and used for synergistic reinforcement of the system by combining macroscopic effects with microscopic biological mechanisms. However, the modification of BES electrodes is deemed to be the key for further improving BES performance.