Energy efficient bioelectro-concentration and recovery system of nutrients from human urine by integrating forward osmosis

Human urine contains abundant nutrients, while separately collecting urine can significantly alleviate nutrient loads in existing wastewater treatment facilities. Herein,0020a novel forward osmosis integrated bioelectro-concentration and recovery system (OsBCRS) was developed to recover nutrient ions from urine. NH 4 + and PO 4 3– migrated out from urine and enriched in the internal chamber of OsBCRS driven by the self-generated electric field, which were further concentrated by water extraction from the integrated forward osmosis (FO) process, and finally recovered as struvite. The current density of OsBCRS reached 27.3 A m –3 , which in turn drove the migration of NH 4 + -N (93.7 ± 1.6%) and PO 4 3– -P (94.6 ± 0.8%) out from urine, and these separated nutrients were enriched by 9.4–9.5 times in the internal chambers. Subsequently, these enriched nutrients in the catholyte were 3.2-fold concentrated with 68.6% of volume reduction by FO. The system removed up to 83.4% of NH 4 + -N and 88.8% of PO 4 3– -P, most of which were recovered as struvite taking advantage of reverse-fluxed Mg 2+ . The recovered struvite exhibited similar crystal structure and composition to that of standard struvite. The preliminary operating cost analysis of OsBCRS demonstrated that the revenue, including electricity generation and struvite recovery, could offset the operating cost. This study demonstrated highly efficient enrichment and recovery of nutrient ions from human urine by OsBCRS in a cost-effective way, and would encourage further exploration for nutrients recovery from wastes.