Pilot Scale\nDemonstration of Low-Salt-Rejection Reverse\nOsmosis (LSRRO) Desalination of High Salinity Brines

Low-salt-rejection\nreverse osmosis (LSRRO) is a novel RO process\nconfiguration capable of treating hypersaline brines that conventional\nseawater reverse osmosis (SWRO) cannot. LSRRO can operate under hydraulic\npressures similar to those of SWRO, thereby having lower specific\nenergy consumption than thermal desalination. This study presents\na unique demonstration of LSRRO. Five feed streams, from simple NaCl\nsolutions (70 g/L total dissolved solids (TDS)) to oil and gas produced\nwater (133 g/L TDS) were used to assess the performance of a pilot\nLSRRO system, using water recovery and stream compositions as performance\nmetrics. The results confirm the capability of LSRRO to achieve water\nrecoveries greater than 60% while generating brines with TDS concentrations\nhigher than 200 g/L, far exceeding conventional SWRO performance,\nwhile limiting hydraulic pressure to 1,100 psi (75.8 bar). Water flux\nthrough the nine unique LSRRO membranes was also evaluated, and the\nresults will help fine-tune salt and water permeabilities for future\nmembrane fabrication. Overall, the rejection of select ions was more\nthan 99% across all experiments, producing high-quality permeate with\nTDS concentrations ranging from a low of 31 mg/L to a high of 333\nmg/L. Membrane integrity testing revealed a lack of damage or scaling\nafter the experiments.