Patent ID: 8268176

Claim:
A method of backwashing one or more membranes in a vessel, the method comprising: removing liquid to be treated from the vessel until a level of the liquid falls to a first level within the vessel below an upper level of the one or more membranes, wherein the removal of liquid to be treated is at least partially accomplished by a filtration operation; suspending the removal of the liquid to be treated from the vessel when the level of the liquid to be treated falls to the first level; performing a liquid backwash of the one or more membranes when the first level is reached by the removal of the liquid to be treated from the vessel until the level of the liquid collected in the vessel comprising backwashed liquid is at a predetermined level above said first level; aerating a membrane surface of the one or more membranes; and removing liquid containing fouling materials dislodged from the membrane surface from the vessel; wherein the predetermined level provides sufficient liquid in the vessel to immerse an upper header of the one or more membranes during the aerating of the membrane surface.