Abstract: A method of cleaning filtering membranes involves scouring the membranes with bubbles while the lumens of the membranes contain a gas at pressure below the bubble point of the membranes. The method may be combined with an integrity test or chemical cleaning process also involving adding a gas to the lumens of the membranes. A tank containing the membranes may be full, draining, refilling, or at a lowered water surface level during the air scouring process. The membranes may be horizontally oriented and assume a concave downward shape during the scouring process.