Reverse osmosis is a membrane separation process in which pure water passes from the high pressure seawater side of a semi permeable membrane to the low pressure permeate side of the membrane. To overcome the natural osmotic process, the seawater side of the system has to be pressurized to create a sufficiently high net driving pressure across the membrane. In practice, the seawater can be pressurized to pressures as high as 70 to 80 bars. The remaining feed water
continues through the pressurized side of the unit as brine. No heating or phase change takes place