DEVICE FOR DESALINATION OF SALT WATER AND WATER PRODUCING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a water producing method which ensures a constant amount of treated water and quality of treated water without depending on a salt concentration of raw water, temperature of raw water, desalination performance of a first stage reverse osmosis module and the like in a device for desalination of salt water which obtains fresh water from salt water such as sea water or brackish water using reverse osmosis membrane module.SOLUTION: A device for desalination of salt water includes: a supply pump 1 for pressurizing salt water; a first stage reverse osmosis module 2 for supplying the pressurized salt water; a second stage reverse osmosis module 3 for supplying the first fresh water; a line 9 for supplying the first salt water; a line 10 for supplying the second salt water; a water quality meter 7 for measuring a salt concentration of the first fresh water or a physical quantity which can be added to the salt concentration; a line 13 for discharging the first concentrated water; a line 14 for discharging treated water; a line 15 for discharging the second concentrated water; a bypass line 16; and a control unit 8 for the bypass line to control a switching unit of the bypass line based on the water quality data obtained by the water quality meter 7.