Patent ID: 6893568

Claim:
A process of filtering water comprising the steps of, (a) providing one or more modules of filtering membranes immersed in water in a tank open to the atmosphere; (b) providing a retentate outlet from an upper portion of the tank enclosing a volume of water directly above the one or more modules; and, (c) in repeated cycles, (i) permeating filtered water by (i) adding a selected volume of feed water to the tank, in addition to water already in the tank, and (ii) withdrawing a volume of water through the one or more modules as permeate, the volume of the permeate being substantially the same as the selected volume; and, (ii) after step (i), performing a deconcentration step further comprising the steps of, (A) stopping permeation; (B) providing scouring bubbles from below the modules; (c) at least one of (I) backwashing or (II) providing a flow of feed water into the tank from below the modules or both (I) and (II); and, (D) flowing excess water containing retained solids upwards through the modules and out of the retentate outlet.