FIELD: food-processing industry, in particular, milk industry. SUBSTANCE: method involves subjecting sweet whey to electric deionization in apparatus comprising dilution chamber containing layer of ion-exchange resin positioned between cation-permeable and anion-permeable membranes, anion and cation concentration chambers, respectively, and electrodes for creating electric field; passing substrate through layer of ion-exchange resin placed in dilution chamber. Electric field created by electrodes directs cations from dilution chamber through cation permeable membrane into cation concentration chamber and directs anions from dilution chamber through anion permeable membrane into anion concentration chamber. Method further involves passing washing solution into and through anion and cation concentration chambers for removal of anions and cations from concentration chambers; collecting treated product from dilution chamber; passing sweet whey through resin layer in dilution chamber comprising high cation-exchange resin; maintaining pH of washing solution so that acidity of solution in anion and cation concentration chambers be less than 5. Washing solution may be additionally passed through layer of resin in each chamber having high cation-exchange resin for maintaining acidity of solution in each chamber at the level below 5. Washing solution used may be acid for maintaining its acidity at required level. Sweet whey may be further treated to provide for acidity of sweet whey supplied to resin layer at the level of 7.5-8. Other method differs from above mentioned method in that sweet whey is passed through dilution chamber comprising resin layer containing cation-exchange resin and low anion-exchange resin. Weight ratio of high cation-exchange resin and low anion-exchange resin is 30-40 wt.% of cation-exchange resin and 60-70 wt.% of anion-exchange resin. Washing solution comprises hydrochloric acid. EFFECT: increased efficiency and intensified sweet whey demineralization process. 17 cl, 1 dwg, 4 tbl
