Pilot-scale evaluation and optimization of osmotically assisted reverse osmosis (OARO) for concentrating real SWRO brine

The sustainable management of seawater reverse osmosis (SWRO) brines remains a critical issue for desalination processes and acquires increasing significance at larger scale. In addition to disposal challenges, these brines offer opportunities for resource recovery and circular economy implementation. Increasing brine concentration can facilitate both volume reduction and the extraction of valuable components. This study evaluates, at pilot scale, an integrated brine concentration process combining osmotically assisted reverse osmosis (OARO) technology with a conventional RO pre-concentrator stage, using real seawater RO (SWRO) brine pre-treated by nanofiltration. System performance, energy efficiency and operational behaviour were assessed to identify feasible operating ranges and optimal conditions. Final brine concentrations of up to 245 g/L were achieved, while overall water recoveries varied between 72 and 85%. Specific energy consumption ranged from 7 to 14 kWh/m 3 of permeate production and 18–56 kWh/m 3 of concentrated brine. Optimal performance was identified at target concentrations of 210–230 g/L, providing a balance between recovery, energy demand and process stability. Membrane temperature limitations (≤40 °C) defined the practical operating range and were identified as a key factor influencing system performance. The results confirm that OARO is an energy-efficient and scalable technology for SWRO brine concentration. This experimental validation under unique real conditions supports the integration of OARO in advanced brine management and resource recovery strategies. • Pilot-scale evaluation of OARO technology for real SWRO brine concentration. • Integrated RO–OARO system (28–59 m 3 feed/d) achieved up to 245 g/L brine salinity. • Overall water recovery between 72 and 85% with stable operation. • SEC values of 7–14 kWh/m 3 of permeate and 18–56 kWh/m 3 of brine. • OARO enables energy-efficient and scalable SWRO brine concentration.