water, desalination, energy, efficiency, membranes
Seawater reverse osmosis is an advanced desalination process used to filter water in which seawater is forced through a semi-permeable membrane, producing pure water on one side and concentrated brine on the other. The process, however, is energy-intensive because of the high pressures that must be attained for it to work effectively. Recent technological advances, including the development of energy recovery devices, have dramatically improved the energy efficiency and reduced cost. Early energy recovery devices were only 50% to 75% efficient but newer ones can recover up to 98% of the energy from the high-pressure concentrate stream. This paper describes seawater reverse osmosis processes and identifies the chief energy consumption points in the process. The author reviews the technologies used to minimize energy consumption and contrasts their efficacy. The author also provides cases studies from a variety of seawater desalination plants and presents data quantifying specific energy saving attained from the deployment of energy recovery devices. The paper concludes with an examination of the role of energy recovery devices in improving the energy efficiency of high pressure water application beyond desalination, such as the mining and food production industries.