TREATMENT SYSTEM HAVING SPIRAL MEMBRANE ELEMENT AND METHOD FOR OPERATING THE TREATMENT SYSTEM

摘要

At the time of back washing of a treatment system, filtrate 2 is reverse-osmosis-filtrated by a reverse osmosis membrane separation device 51 so as to be separated into permeate 3 and concentrate 4. The concentrate 4 obtained from the reverse osmosis membrane separation device 51 is supplied as washing water into a spiral membrane element 10 through pipes 21 and 21a. On this occasion, the concentrate 4 is pressurized by a supply pump 104, so that a separation membrane is back-washed under a back pressure higher than 0.05 MPa but not higher than 0.3 MPa.