Abstract: In a membrane filtration system and process, retentate exiting a filtration element is maintained inside a loop and redirected back to the inlet of a pump. The pump may produce a generally constant velocity in the loop. Water is concentrated inside the loop until discharged in batches. Feed water enters the loop automatically. The flux through the filtration element is maintained by a controlled valve or pump in communication with a permeate outlet. A filtration element has one or more rigid inserts in a housing. The inserts are covered with membranes. The element is configured to provide open feed channels beside the inserts. The membranes and inserts are potted at an edge, which may be their only attachment to the housing. Permeate flows between the membrane and the insert to the potted edge. The filtration element may be used in the system and process described herein or in others.