Advancements and Challenges in Bioelectrochemical Systems for Sustainable Nitrogen Removal from Wastewater

Bioelectrochemical systems (BESs) for nitrogen removal, which integrate electrochemical processes with biological nitrogen removal technologies, is a sustainable and energy-efficient alternative to conventional biological nitrogen removal methods. However, the practical application of BESs for nitrogen removal remains limited due to technical challenges, and existing reviews have not provided an integrated analysis that systematically links mechanistic understanding, operational optimization, and engineering-scale challenges across multiple BES configurations. Therefore, the mechanisms and performance of main nitrogen removal pathways in BESs are critically summarized and compared within a unified framework. Low nitrogen removal rate and long-term instability are identified as the main challenges. Furthermore, the links between nitrogen removing performance and the key operational parameters, including substrate concentration, applied voltage, electrode materials and microbial interactions are systematically analyzed to reveal their influences and optimization opportunities. Finally, based on this integrated analysis, alternatives are proposed to improve the nitrogen removal rates and stability of BESs for nitrogen removal.