The use of interstage turbines as an energy recovery device and osmotic pressure control valve has been successfully demonstrated for use in a brackish water desalting facility in Florida. The interstage turbine has been shown to provide a method for hydraulically balancing a two-stage membrane process. Salt passage has been reduced by this configuration, as the turbine provides a pressure boost to the second stage that normally has a concentrated osmotic pressure gradient and reduced hydraulic flow. An incrase in osmotic pressure above the available feed pressure in a second stage membrane configuration can result in salt permeation and reduced permeate flow. This traditional design burden can be overcome via the use of an interstage turbine. The turbine responds to variations in first stage concentrate concentration, and its response can be shown to vary as a function of osmotic pressure. For a constant feed water concentration, an increase in osmotic pressure will result in an increase in the permeate concentration; consequently, a pressure boost will overcome salt passage as more water will be permeated through the membrane under the higher driving pressure force and dilute salt mass transfer. Membrane processes that treat variable brackish water supplies should consider the use of an interstage turbine as a means to balance water production between process stages and save money on pumping costs. Includes 5 references, table.