Patent ID: 7244357

Claim:
A membrane filtration system comprising: a first piston, said first piston separating a feed chamber from a retentate chamber; a membrane filtration element; and a differential pressure activated (DPA) valve which controls retentate discharge, said DPA valve disposed downstream of said membrane filtration element and said retentate chamber with respect to a flow of retentate, said DPA valve comprising: a single housing comprising a port in fluid connection with an inlet to said filtration element, an inlet port for receiving retentate from said filtration element, and a retentate discharge port; and a single second piston slideably disposed within said single housing, said second piston positively sealing said inlet port when a feed pressure on a first face of said second piston exceeds a retentate pressure on a second face of said second piston; wherein pressure recovery is provided by a pressure difference between the feed chamber and the retentate chamber acting on said first piston.