Isobaric Energy-Recovery Devices: Past, Present, and Future

In the last 25 years, the energy required to desalinate seawater has been reduced by a factor of two. Energy recovery devices (ERDs) are responsible for more than half this reduction. Among commercially available ERDs, pressure-equalizing or isobaric ERDs have demonstrated energy savings of 10–30 percent greater than turbine-based devices or reverse-running pumps. Isobaric ERDs transfer energy from the membrane reject stream directly to the membrane feedstream, thereby reducing the duty of high-pressure pumps. Despite the success, modern isobaric ERDs can experience expensive energy losses over the life of a seawater reverse osmosis plant. This article explores performance of modern isobaric ERDs and potential implications of their improvement, as well as estimated life-cycle costs for investment, maintenance, and optimization.