Continuous production membrane water treatment plant and method for operating same

A method is provided for the continuous production of treated waters using a staged, tapered array membrane plant (1) by a process of process logic controlled (PLC) (12) stage isolation and washing concurrent with continued operation of all other stages of the plant (1). These are sensors that supply the PLC (12) with data required to identify location and degree of fouling of stages (2), (3), (4); when a stage (2, 3, 4) is fouled the PLC (12) commands initiation of a sequence of automated valve openings (7, 27-32) and closings to a) remove the fouled stage from feed water service, b) flush and wash the stage, and c) return the stage to service. Optionally, a feed water pump (6) produces varying amounts of membrane process permeate during the treatment of fouling.