| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress the flow rate reduction of a permeate while suppressing the water quality deterioration of the permeate, in a water treatment method that purifies raw water containing silica and hardness components using a reverse osmosis membrane device. <P>SOLUTION: While adding a scale dispersant containing polycarboxylic acid and phosphonic acid from a second adding device 130, the raw water is supplied to the reverse osmosis membrane device 210 through a supply path 10 to separate the raw water into a permeate and a concentrate by the reverse osmosis membrane module 211. The permeate is sent from a treated water passage 220 to a refiner such as an ion trapping device or a reverse osmosis membrane device to perform refining for removing residual ions, and then used for required purposes, and the concentrate flows to a drain passage 230. The pH of the concentrate is adjusted by a pH adjuster, which is added from a first adding device 120 to the raw water, to control the Langelier index equal to or more than 0 and equal to or less than 0.3. The recovery rate of the permeate in the reverse osmosis membrane module 211 is controlled to maintain the concentration of silica equal to or less than 150 mgSiO<SB POS="POST">2</SB>/L. <P>COPYRIGHT: (C)2012,JPO&INPIT |
