Operation of immersed membrane using cross flow

Abstract

A method of operating an immersed membrane filtration system includes a step of providing a liquid flow, for example a recirculation flow, past the surface of the membranes to clean, or help clean, the membrane surface. Since immersed outside-in membranes are effectively filtering out clean water from the effluent, they are also dewatering the effluent. To avoid solids concentration, most immersed membrane systems require that a certain amount of effluent liquid is recirculated back to an area upstream of the membranes. This is called a recirculation flow in general and is, for example, associated with the flow of return activated sludge (RAS) in a membrane bioreactor (MBR). In systems and methods described herein, we control a recirculating flow to have enough energy to scour the surface of the membranes, thus combining its use of providing liquid to the membranes and scouring their surfaces.

Dependencies are inferred from the claim text.