portions of a feed liquid are passed through respective condensers and liquid - liquid heat exchangers . the feed liquid is then heated and injected into a first feed - liquid containment chamber , where vapor from the feed is passed through a first gas - permeable membrane and directed into a first condenser , where the vapor is cooled by the feed liquid passing through the first condenser and condenses as it cools to produce a first liquid permeate . the first liquid permeate is passed through the first liquid - liquid heat exchanger where the first liquid permeate is cooled by the feed liquid passing therethrough . after the vapor is removed from the feed liquid in the first feed - liquid containment chamber , the remaining feed liquid from the first feed - liquid containment chamber is injected into a second feed - liquid containment chamber , where the process is repeated . the first liquid permeate from the first liquid liquid - liquid heat exchanger is combined with the second liquid permeate from the second condenser to form a combined liquid permeate ; and the combined liquid permeate is passed through the second liquid - liquid heat exchanger where the combined liquid permeate is cooled by the feed liquid passing therethrough .