A novel single-pass reverse osmosis configuration for high-purity water production and low energy consumption in seawater desalination

Seawater reverse osmosis (SWRO) desalination is required to produce high-quality water to meet stricter water standards, which could be satisfied with single-pass RO through the advancement of reverse osmosis (RO) membranes. In this study, a novel single-pass RO configuration was proposed to further improve permeate quality. Split partial single-pass (SSP) RO is a design in which the permeate from the rear RO element(s) in a pressure vessel is blended with the RO feed. This blending resulted in the dilution of the feed, leading to the production of high-quality permeate with lower energy demand. Modeling of the RO process demonstrates that SSP RO had the highest energy efficiency when the permeate from the 7th element (i.e., the last one in the single pass RO configuration) was circulated back and mixed with the feed. For typical SWRO operating conditions, SSP RO was effectively able to improve permeate quality. In fact, SSP RO produced an approximately 15% purer permeate compared to conventional single-pass RO. SSP RO was also always more energy-efficient than the two-pass RO configurations. The economic feasibility of the design was assessed further and the possibility of its practical application explored.