Patent ID: 8721887
Filing Date: 2014-05-13
Classification: C02F

Abstract:
1. A method for treating wastewater comprising: biologically treating the wastewater in an anaerobic zone with a suspended mixed liquor to reduce biodegradable organic materials contained within the wastewater; after treatment in the anaerobic zone, biologically treating the wastewater in an anoxic zone with the suspended mixed liquor to oxidize reduced sulfur compounds contained within the wastewater, wherein the anoxic zone has a solids retention time of at least three days; after treatment in the anoxic zone, biologically treating the wastewater in an aerobic zone with the suspended mixed liquor to oxidize ammonia contained within the wastewater and to remove phosphorus contained within the wastewater; and circulating at least a portion of the wastewater treated in the aerobic zone to the anoxic zone to maintain a concentration of nitrates within the anoxic zone at least at 0.7 mg nitrate-N/mg H