FIELD: water treatment. SUBSTANCE: invention relates to reverse osmosis-based seawater sweetening process that can be used in power engineering, chemical, food, and other industries. Power consumption is reduced by performing osmotic mass transfer through semipermeable diaphragm, feeding countercurrently different-concentration salt solutions on the both sides of diaphragm. High-concentration salt solution is concentrate obtained in reverse- osmosis salt water sweetening process and low-concentration salt water is initial water. Spent solution is withdrawn under pressure equal to half osmotic pressure gradient. EFFECT: reduced power consumption and reduced negative environmental effect of waste water. 2 cl, 1 dwg
