Heterogeneous ion exchange membranes consisted of ion exchange resin particles finely dispersed in polypropylene matrix, have good electrical and mechanical properties and excellent resistance against high temperature and chemicals.Any foulant adhered on membranes can be completely removed by high concentration acid and/or alkali cleaning.The Electrodialyser using these membranes have been developed and it can resist up to 3 kg/cm2G against inner pressure. The Electrodialyser has been applied to the desalination of the river water of Shatt Al Arab in Iraq since July, 1976.Though it is quickly fouled by organic matter and others in raw water, it has been confirmed that capability had been completely recovered by cleaning using 3ξ caustic soda and dilute acid, and continuous operation around 6,000 hr without desassembling had been successfully carried on.Evaluating the above, desalination plant for boiler feed water of fertilizer plant of Iraq Government is being under construction and will start on April 1978.This plant is consisted of two trains, each train has capacity of 208 m3/hr and can be automatically cleaned within 3 hours.Simulated dynamics by digital computer are shown.