Recovery of reactive nitrogen from wastewater using bioelectrochemical systems

As a key component of biosynthesis and an essential nutrient for biogeochemical cycles, nitrogen is also one of the key contaminants and nutrients in diverse wastewater. Almost all wastewater treatment plants prefer to remove reactive nitrogen from wastewater, which not only consumes a lot of resources and energy, but also loses bio-available nitrogen from our eco-system. Thus, the recovery of reactive nitrogen is more ecologically and economically beneficial than its removal. Bioelectrochemical systems (BESs) is a promising strategy to recover reactive nitrogen from wastewater. The reactive nitrogen is concentrated by an electric field driven by the BESs to form N-enriched streams, which can be directly used as a product or further recovered by stripping and transmembrane chemisorption. However, the engineering application of BESs is still in its infancy, and there are still some theoretical knowledge gaps and technical challenges to be overcome. Therefore, in this review, the principles and various corresponding technologies for reactive nitrogen recovery via BESs are comprehensively presented, and the impact of pH, nitrogen loading, the composition of wastewater, etc. on the efficiency of nitrogen recovery by BESs are analyzed. The energy balance, environmental impact and limitations of BESs are further discussed for better engineering application. This review provides future research priorities for the recovery of reactive nitrogen by BESs, including scale-up applications of BESs and the trade-off between nitrogen recovery efficiency and energy consumption.