Limits of High Recovery Inland Desalination: Closed-Circuit Reverse Osmosis – a Viable Option?

Cost-efficient operation of inland brackish water reverse osmosis (BWRO) demands a high recovery. As recovery of BWRO is often limited to scaling, antiscalants (AS) are applied, whose environmental impact is disputed. In this paper, different systems (conventional single- and two-stage plug flow RO (PFRO) and closed-circuit RO (CCRO)) were simulated in various configurations (AS dosing, ion exchange (IEX) pretreatment, elements per vessel) to determine the recovery limiting factor for a hard feed. The novel proposed IEX-CCRO reached the highest recovery without AS dosing. PFRO configurations had lower recoveries, mainly due to hydraulic limitations. Utilizing RO brine reduced both the water demand and salts necessary for IEX regeneration.