Patent ID: 7850851

Claim:
A process for treating waste water to remove phosphorous and nitrogen in a treatment system including an anaerobic zone including an anaerobic mixed liquor having organisms which release phosphorous; an anoxic zone including an anoxic mixed liquor having denitrifying phosphorous accumulating organisms which uptake phosphorous and an aerobic zone including an aerobic mixed liquor having organisms which further uptake phosphorous; the process comprising the steps of: (a) providing wastewater to be treated into the anaerobic zone; (b) communicating anaerobic mixed liquor from the anaerobic zone to the anoxic zone; (c) communicating anoxic mixed liquor from the anoxic zone to the anaerobic zone; (d) communicating anoxic mixed liquor from the anoxic zone to the aerobic zone; (e) applying aerobic mixed liquor to a feed side of a membrane filter; (f) producing a treated effluent from a filtrate side of the membrane filter; (g) flowing oxygen-containing gas bubbles past the feed side of said membrane filter to remove accumulated solids; (h) communicating at least some of the material rejected by the membrane filter to a degassing device to remove some or all of any dissolved oxygen contained in said rejected material; and (i) communicating said degassed material to the anoxic zone.