Method and apparatus to control a salt stream to be treated in an electrodialytic water splitter

The present invention is a method and apparatus of controlling a raw salt stream to be treated in an electrodialytical water splitter. An aqueous salt feed stream is fed to an electrodialysis water splitter and a dilute salt stream is withdrawn from the water splitter. The dilute salt stream is fed to an electrodialysis unit comprising a concentration compartment and a diluting compartment, at least part of the dilute salt stream being fed to the concentration compartment. An electrodialysis product stream is withdrawn from the concentration compartment. The product stream and the raw salt stream are controllably combined to form the aqueous feed stream. In accordance with the method of the present invention the salt concentration of the product stream can be maintained below the salt concentration of the raw salt stream. The pH of aqueous salt feed stream can be controlled based on the pH of electrodialysis unit product stream.