Patent ID: 6861000

Claim:
A method of running a spiral wound membrane element, comprising an envelope separation membrane wound on the outer peripheral surface of a perforated hollow pipe and allowing back wash reverse filtration with a back pressure higher than 0.05 MPa and not more than 0.3 MPa, comprising steps of: feeding a raw liquid from an end of said spiral wound membrane element and taking out a permeated liquid from at least one opening end of said perforated hollow pipe in running; introducing a washing liquid from at least one opening end of said perforated hollow pipe and discharging the washing liquid from at least one end of said spiral wound membrane element thereby performing back wash reverse filtration on said separation membrane with a back pressure higher than 0.05 MPa and not more than 0.3 MPa in washing; and setting the ratio of the amount of the permeated liquid permeated through said separation membrane in a running period to the amount of the washing liquid permeated through said separation membrane in a washing period to not more than 600.