WASHING METHOD OF MEMBRANE SEPARATOR, AND MEMBRANE SEPARATOR

PROBLEM TO BE SOLVED: To enable to inhibit that the supply pressure applied to washing liquid rises rapidly and become overpressure status when washing liquid is supplied to a membrane separator with a pump.SOLUTION: In the membrane separator in which two or more membrane separation modules 52 are arranged in a treatment tank 51, and which discharges membrane permeation liquid which has permeated a separation membrane of each of the membrane separation modules 52, passing through a membrane permeation liquid piping 53 which arranges a chamber 56 on the way; the membrane permeation liquid piping 53 is plugged/closed in the downstream side position from the chamber 56 to form a closed pipe line region; and washing liquid is supplied to each of the membrane separation modules 52 by a liquid chemical pump apparatus 66 through the closed pipe line region by the status of forming a gas phase space which has confined the required quantity of pressure buffer gas inside the chamber 56.