| 摘要 |
PURPOSE:To subject water to be treated to reverse osmosis membrane treatment at a high recovery rate while the deposition of silica is prevented in case the water to be treated including hard components and silica is subjected to the reverse osmosis membrane treatment to separate it into permeated water and a concentrate by keeping pH of the concentrate not more than a specified value to perform the treatment. CONSTITUTION:In a reverse osmosis membrane treating method, water to be treated including at least hard components and silica is subjected to reverse osmosis membrane treatment to separate it into permeated water and a concentrate. In this case, pH of the concentrate is kept >=6 to perform reverse osmosis treatment. For example, after city water flowing in from an inflow pipe 1 is passed through an active carbon filter 2, it is introduced into a water to be treated tank 3. The water to be treated is introduced into a reverse osmosis membrane module 6 by a high pressure pump 5 and permeates through a reverse osmosis membrane 7 to separate it into permeated water where silica, etc., are reduced and a concentrate other than the permeated water. Further, the permeated water is taken out from a take-out pipe 8, and the concentrate is circulated from a circulating pipe 9 to the water to be treated tank 3. A chemical injecting pump 14 is controlled by a pH sensor 13 and hydrochloric acid, etc., are added so that pH of the concentrate may be specified.
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