Desalination method and desalination apparatus
OwnerMasahiro Kihara, Takayuki Nakanishi +1inventors
InventorsMasahiro Kihara, Takayuki Nakanishi, Tamotsu Kitade
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Abstract
A method and apparatus for desalinating water, especially sea water, having a plurality of membrane module units disposed at respective successive stages are disclosed. Permeated water from a first stage membrane module unit is supplied to a second stage membrane module unit to obtain permeated water. The apparatus contains at least first and second membrane module units at respective successive first and second stages for water permeation.
Claims26
A method of desalinating water in a plurality of stages at which respective membrane module units are disposed, wherein permeate water from a first stage membrane module unit is supplied to a second stage membrane module unit to obtain desalinated permeate water therefrom, the method comprising:
- a first step of processing feed water having a total salt concentration of 3.0 to 4.8% by weight and a calcium ion concentration of 200 to 500 mg/l, in which first step at least a proportion of the feed water is treated with the first stage membrane module unit, to obtain the permeate water and which permeate water is optionally mixed with additional feed water, the water thus processed in the first step thereby having a total salt concentration of 55 to 90% of that of the feed water and a calcium ion concentration of 95% or less of that of the feed water;
- and
- a second step of supplying the water processed by the first step to the second stage membrane module unit, thereby obtaining the desalinated water.
A desalination apparatus comprising:
- at least first and second membrane module units at respective successive first and second stages for water permeation, as a said first membrane unit at the first stage, a nanofiltration membrane module unit having a membrane module and an outlet channel for water permeated thereby,
- as a said second membrane unit at the second stage, a reverse osmosis membrane module unit disposed in the outlet channel of the nanofiltration membrane module unit, for permeated water;
- and
- means for diverting a proportion of feed water supplied to the nanofiltration membrane module unit directly to the said outlet channel thereof so as to bypass the membrane module thereof.
Dependencies are inferred from the claim text.