Simultaneous nutrient-energy recovery from source-separated urine based on bioelectrically enhanced bipolar membrane-driven in-situ alkali production coupling with gas-permeable membrane system

Source-separated urine has attracted widespread attention recently because it was rich in nutrients and can be recycled for reuse. In this work, the bioelectrically enhanced bipolar membrane-driven in-situ alkali production coupling with gas-permeable membrane system (BBGS) was innovatively proposed to treat urine for organic matter removal, ammonia nitrogen (AN), and value-added product hydrogen recovery, which provided a novel way for nutrient-energy recovery from urine. Urea was hydrolyzed quickly by microorganisms, and ions were migrated and enriched under the driving action of an electric field. In-situ alkali production by the bipolar membrane (BPM) created a high pH environment for the absorption of AN and promoted the formation of gaseous ammonia. Meanwhile, the AN was absorbed by the acid through the gas-permeable membrane (GPM) and thus recovered. Urea with a concentration of 1717 mg L-1 can be 100% removed, while a high AN of 202.94 +/- 11.23 mg L-1 is obtained with an AN recovery of 90.39 +/- 5.00% in the absorption bottle. With initial COD of 880 + 10 mg L-1 in influent, the effluent COD was 110.50 +/- 10.56 mg L-1 with COD removal of 87.36 +/- 1.32%. In addition, the average nitrogen recovery rate was 0.56 + 0.03 mg h(-1), the average hydrogen production rate was 0.46 +/- 0.01 m(3) m(-3) d(-1), and the average coulombic efficiency (CE) was 69.53 +/- 3.04%. The active recovery of nutrients from urine was beneficial for reducing the high energy consumption in the terminal wastewater treatment plant, solving the sanitary storage problem of urine, and effectively utilizing high-quality nutrition sources for recycling and reuse. The BBGS was of great significance for the treatment and resource utilization of urine.