| 摘要 |
PURPOSE:To perform the effective regeneration treatment of a reverse osmosis membrane even when a precipitate caused by polysilicate is precipitated, in preforming desalting treatment after the treatment of soft water, by washing the reverse osmosis membrane with washing water having pH higher than that at the time of desalting before the ratio of a transmitted water amount reaches a specific value or less. CONSTITUTION:Raw water A containing silicate and hardness components is passed through a hard water softening apparatus 1 to remove hardness components. Subsequently, an NaOH solution is added to soft water from an NaH tank 3 to adjust the pH thereof to 8 or more and pH controlled water is introduced into a reverse osmosis membrane apparatus 8 under pressure by a high pressure pump 7 while desalted transmitted water B and untransmitted water C enhanced in the concn. of salts are collected. After desalting treatment is continued until the ratio of a transmitted water amount reaches 0.8 or less, said treatment is interrupted to perform regeneration treatment. A pump 10 is driven to supply transmitted water in a transmitted water tank 9 to the reverse osmosis membrane apparatus 8 as washing water while an NaOH solution is added thereto and the pH of washing water is made higher than that at the time of desalting. Waste washing water is discharged through an untransmitted water line. The polysilicate adhered to the surface of the membrane is dissolved and the ratio of a transmitted water amount is restored to the original state.
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