Patent ID: 7087173

Claim:
A method of withdrawing a permeate from a substrate using a membrane immersed in the substrate comprising the steps of: (a) providing a reservoir containing a substrate at ambient pressure; (b) providing an assembly having a solid body, a hollow fiber membrane disposed generally vertically and attached to the solid body and a permeate collection means in communication with the inside of the membrane; (c) a structure having an upper portion, a wall or walls surrounding a space below the upper portion, and passages through the upper portion in communication with the space; (d) applying a suction to the permeate collection means to withdraw permeate from the substrate through the membrane; and, (e) while applying the suction, directing a gas to flow continuously or intermittently into the space so as to form a pocket of the gas at least temporarily in the space, the pocket of the gas having an interface with the substrate below the upper portion, such that at least a portion of the gas flows through the openings to provide bubbles which contact the membranes during the step of applying the suction.