PROBLEM TO BE SOLVED: To provide an apparatus in which clogging of a reverse osmosis membrane module due to fouling can be effectively removed, and method of cleaning the reverse osmosis membrane module.;SOLUTION: A fresh water production apparatus includes: permeated water connection piping 10 the one end of which is connected to a first permeated water outlet 17 and the other end of which is connected to a suck-back tank 3; permeated water piping 11 which conveys permeated water discharged from a second permeated water outlet 18; a check valve 5 provided in the permeated water piping; a concentrated water tank 4 which stores concentrated water of a reverse osmosis membrane unit 2; concentrated water connection piping 12 the one end of which is connected to a concentrated water outlet 19 and the other end of which is connected to the concentrated water tank 4; bypass piping 9 which bypasses from piping for supplying water to be treated; and a drain valve 6 which is provided in the bypass piping 9 and drains cleaning drainage water. The reverse osmosis membrane unit 2 is cleaned by supplying concentrated water, which has a thicker salt concentration than the water to bet treated, to a supply water side of the reverse osmosis membrane unit 2, and using the permeated water of a front part of the reverse osmosis membrane unit, which has a low osmotic pressure, for a permeated water side and utilizing a suck-back effect.;COPYRIGHT: (C)2016,JPO&INPIT
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