Patent ID: 7347942

Claim:
A process for cleaning or inhibiting the fouling of membranes immersed in water at ambient pressure in a tank with outsides of the membranes in contact with the water, the method comprising the steps of, providing a flow of a gas which produces bubbles in the water at ambient pressure outside of the membranes, which bubbles rise and contact the outsides of the membranes, under an aeration regime effective to clean or inhibit fouling of the membranes, wherein the flow of gas is alternated in repeated cycles of more than 10 seconds in duration but not more than 120 seconds in duration between a higher flow rate and a lower flow rate, the lower flow rate being in a range from and including a condition in which bubbles are not produced to, but less than, one half of the higher flow rate, and wherein, during the step of providing a flow of gas, permeate is withdrawn from the membranes by a partial vacuum applied to insides of the membranes.