Water treatment equipment and its operation method

Abstract

The water treatment apparatus 1 includes: a pretreated water tank 2 for storing pretreated water W; a high-pressure pump 3 for conveying the pretreated water W; a first reverse osmosis membrane 4; a concentration tank 5 for storing concentrated water W1 from the first reverse osmosis membrane 4; a high-pressure pump 6; and a second reverse osmosis membrane 7 for treating the concentrated water W1 from the first reverse osmosis membrane 4. The apparatus is configured to return the permeate water W2 from the second reverse osmosis membrane 7 to the pretreated water tank 2 and discharge the concentrated water from the second reverse osmosis membrane 7. The permeate flow rates of the first reverse osmosis membrane 4 and the second reverse osmosis membrane 7 are 0.5 m / day or more and 1.0 m / day or less when the effective membrane pressure is 2 MPa (water temperature 25°C, pure water), or 0.5 m / day or more and 1.0 m / day or less when the effective membrane pressure is 1.5 MPa (water temperature 25°C, pure water). This water treatment apparatus can efficiently concentrate difficult-to-remove substances and discharge them outside the system without deteriorating the quality of the permeate water from the first reverse osmosis membrane.

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