To facilitate the desalting treatment of waste water by cooling feed raw water (waste water) to a prescribed temp. and thereafter, allowing the raw water to permeate through reverse osmosis membranes.
In this water treatment, a leachate that contains salts and is discharged from a waste disposal site, is introduced into a cooling tower as feed raw water and there, the raw water is cooled to an about ≤35°C temp. at which such water can be treated with conventional reverse osmosis membranes, to prevent the desalting capacity of the reverse osmosis membranes from being adversely affected because of high temp. Then, the cooled raw water is introduced into a reverse osmosis membrane device 1 to subject the raw water to desalting and the resulting concentrated water is introduced into an NF(nanofilter) membrane device 2 and there, salts, particularly divalent or higher negative ions in the form of CaCO3, etc., in the water is filtered off and removed. At this time, the permeant water formed in the NF membrane device 2 is treated with a high pressure reverse osmosis membrane device 3 and then, withdrawn as highly concentrated water from the device 3. Further, the concentrated water formed in the NF membrane device 2 and also, one portion of the highly concentrated water formed in the high pressure reverse osmosis membrane device 3 are supplied to a crystallization vessel 4 to solidify salts and remove them as solid matter and at this time, the supernatant is returned to the NF membrane device 2. Thus, even high temp. raw water can be allowed to permeate through the reverse osmosis membranes without causing any damage to the membranes and the need of using any large adjustment vessel can be eliminated.
SAEKI KAZUMARU
USHIGOE KENICHI
TAJI AKIHIRO
FUKAO YOSHIMITSU
KINOSHITA KIYOSHI
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