METHOD AND EQUIPMENT FOR PRODUCING WATER

摘要

PROBLEM TO BE SOLVED: To provide a method and equipment for producing water capable of achieving a higher recovery rate with a NF(nano-filtration) membrane having a suitable desalination performance when treating a seawater in a membrane process to obtain a permeated water. SOLUTION: A seawater is supplied to a NF membrane module using a nano filtration membrane (NF membrane) whose sulphate ion extraction coefficient is at least 90%, its NF membrane module is so operated as to allow calcium extraction coefficient to be 35% or less and the calcium ion concentration in a concentrated water to be 965 mg/L or less, and a permeated water is pressurized and is treated with a reverse osmosis membrane module to obtain a desalinated water.