Patent ID: 8070953

Claim:
A sea water desalinating method for desalinating sea water by way of filtration using a reverse osmosis membrane device, comprising carrying out a mixing step of mixing, as diluent water, biologically treated water produced by biologically treating organic wastewater into sea water to produce mixed water, a mixed water processing step of feeding the mixed water produced by the mixing step to the reverse osmosis membrane device, at which the mixed water is filtered, thereby desalinating the sea water, and a wastewater treatment step of producing biologically treated water by biologically treating organic wastewater, producing permeate by filtering the biologically treated water by using a clarifier that has at least one of a microfiltration membrane, an ultrafiltration membrane and a sand filtration means, and producing permeate that is purified water and concentrated water by filtering the permeate using a reverse osmosis membrane device, wherein the biologically treated water used as the diluent water in the mixing step is the concentrated water.