Patent ID: 6547968
Filing Date: 2003-04-15
Classification: B01D,C02F,Y02W

Abstract:
A method for cleaning filtering membranes, each membrane having a permeate side, normally immersed in tank water rich in solids in a tank of an industrial or municipal reactor between 1 m and 10 m deep and used to permeate a water lean in solids, in one or more cleaning events, each cleaning event comprising the steps of:(a) stopping permeation; (b) draining the tank water from the tank to below the level of the membranes; and, (c) while the tank water is below the level of the membranes and permeation is stopped, flowing a chemical cleaner in pulses in which the chemical cleaner is delivered to the permeate sides of the membranes in a direction opposite to the direction in which water lean in solids normally permeates through the membranes separated by a time between pulses in which the chemical cleaner is not delivered to the membranes; (d) refilling the tank; and (e) resuming permeation, wherein the pulses have a pressure which substantially reduces the relative size of local pressure variations inside membranes or portions of membranes at different elevations so as to provide a more even distribution of flux of cleaning chemical throughout the membranes.