Method and apparatus for generating fresh water, and method and apparatus for desalinating sea water

摘要

An object is to provide a sea water desalinating method that is capable of efficiently producing purified water, such as fresh water, from unpurified water, such as sea water. Provided is a fresh water generating method for generating fresh water by way of reverse osmosis membrane filtration, which includes filtering low salt concentration water having a salt concentration lower than sea water by way of reverse osmosis and mixing it with sea water to produce mixed water. The mixed water prepared by the above mixing is subjected to reverse osmosis membrane filtration, thereby generating fresh water. The salt concentration of the low salt concentration wastewater is measured and used for controlling the amount of permeate produced by both reverse osmosis filtration stages.