| 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 filters 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 23, the raw water is supplied to the reverse osmosis membrane device 20 through a supply path 10 to separate the raw water into a permeate and a concentrate by the reverse osmosis membrane module 24. The permeate flows through a treated water passage 30 to be used for required purposes, and the concentrate flows to a drain passage 40. The pH of the concentrate is adjusted by a pH adjuster, which is added from a first adding device 22 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 24 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 |
