Bioelectrochemical systems for nitrogen removal and recovery from wastewater

Nitrogen is an essential element for life. It is applied in reactive form (NH3 or NO3−) as a fertilizer on soils for growth of agricultural crops. The accumulation of reactive nitrogen in the environment causes environmental problems such as eutrophication and acidification. To decrease the accumulation of nitrogen in the environment, it needs to be removed from wastewaters before discharge into receiving water bodies. Classically, this is done using a combined aerobic and anaerobic treatment process in wastewater treatment plants (WWTPs). This process requires energy for aeration, which can constitute up to 60% of the total energy consumption of a WWTP, while nitrogen is lost. This review gives an overview of the innovative nitrogen removal and recovery technologies based on bioelectrochemical systems (BESs). We show that BESs enable energy-efficient nitrogen removal and even recovery of useful nitrogen (ammonia) from wastewaters