METHOD FOR HEATING FEED WATER IN REVERSE OSMOSIS PROCESS

PURPOSE:To improve production efficiency of permeating water and reduce operation cost, by heating feed water with concentrated water or permeating water before being pressurized to raise the temperature of the feed water without using a special heat source. CONSTITUTION:Before being pressurized, feed water is introduced into a heat exchanger 16 by a high pressure pump 10 to be heated by concentrated water and permeating water, in which the quantity of concentrated water and permeating water which is released respectively by a relief valve 18 and 20 is controlled so that the quantity of the concentrated water and permeating water fed to the heat exchanger 16 is controlled. As a result, heating rate for the feed water at the heat exchanger 16 is controlled to keep the temperature of the feed water nearly constant. The feed water leaving the heat exchanger 16 is pressurized by the high pressure pump 10 to be sent to a reverse osmosis module 12, where said water is separated into concentrated water and permeated water. Being pressurized, the temperature of the feed water rises; as a result, the temperature of the concentrated water and permeating water after reverse osmosis treatment is higher than that of the feed water before pressurization; therefore, it is possible to raise the temperature of the feed water by utilizing the heat of concentrated water and/or permeating water.