Hybrid osmotically assisted reverse osmosis and reverse osmosis (OARO-RO) process for minimal liquid discharge of high strength nitrogenous wastewater and enrichment of ammoniacal nitrogen.

• NH 4 +-N was enriched via osmotically-assisted reverse osmosis-reverse osmosis (OARO-RO). • The influence of different operational parameters during OARO-RO was investigated. • Hybrid OARO-RO successfully enriched NH 4 +-N in industrial wastewater. • Specific energy consumption of the OARO-RO process was determined to be 8.8kWh/m3. • OARO-RO is feasible for minimal liquid discharge and enrichment of wastewater. Ammoniacal nitrogen (NH 4 N) is a ubiquitous nitrogen pollutant found in wastewater, which could cause eutrophication and severe environmental stress. It is therefore necessary to manage NH 4 N by enrichment and recovery for potential reuse, as well as to regulate the amount of environmental discharge. Hybridization of membrane-based processes is an attractive option for further enhancing water and nutrient reclamation from waste streams; thus, in this present work, a hybrid osmotically assisted reverse osmosis (OARO) and reverse osmosis (RO) process was demonstrated for subsequent ammoniacal nitrogen enrichment and wastewater discharge management. Using a commercially-available cellulose triacetate membrane module, model and real wastewater containing approximately 4,000ppm NH 4 N were effectively dewatered and enriched to a final NH 4 N content of 40,300ppm. This corresponds to enrichment of around 10 times and approximately 90% pure water recovery. The effective combination of both processes resulted in high efficiency, as well as economical and energy-saving benefits, as shown by the process performance and our preliminary techno-economic analysis. The specific energy consumption of the hybrid process projected to operate at a capacity of 2,000 m3 h −1 was determined to be 8.8kWh m −3, or 0.56kWh kg−1 NH 4 Cl removed/recovered for an initial feed solution containing around 15,300ppm NH 4 Cl. Hybrid OARO and RO operation was able to achieve satisfactory enrichment by the OARO process and obtaining clean water by the RO process. The hybrid OARO-RO process has shown great potential as a suitable end-stage membrane-based process for wastewater dewatering and NH 4 N enrichment and recovery toward a circular economy and environmental management, as well as clean water recovery. [Display omitted] [ABSTRACT FROM AUTHOR]