Patent ID: 6054044
Filing Date: 2000-04-25
Classification: C02F,Y02W

Abstract:
An apparatus for treating wastewater, comprising:a supply of wastewater;means downstream from said supply of wastewater for separating large suspended solids from said wastewater to produce a wastewater fraction for treatment and a solids fraction;at least one anoxic biological culture downstream from said separating means;at least one anaerobic biological culture downstream from said at least one anoxic culture to remove organic material from said wastewater in the absence of exogenous oxygen;at least one aerobic biological culture downstream from said at least one anaerobic culture to remove organic material from said wastewater in the presence of exogenous oxygen;at least one means for supplying exogenous oxygen to said at least one aerobic culture;means for determining the level of oxygen in said at least one aerobic culture;means for turning off said means for supplying exogenous oxygen when said oxygen level achieves a pre-set level for a pre-set period of time;means for turning on said means for supplying exogenous oxygen when said oxygen level achieves a different pre-set level, wherein said wastewater in said at least one aerobic culture cycles from aerobic conditions to anoxic conditions and from anoxic conditions to aerobic conditions;means for recycling at least a portion of said wastewater from at least one of said at least one aerobic culture to at least one of said at least one anoxic culturemeans downstream from said at least one aerobic culture for clarifying said wastewater from said at least one aerobic culture to produce clarified wastewater; wherein said clarifying means comprises at least one anoxic sub-zone; andmeans for recycling at least a portion of said clarified wastewater to said supply of wastewater.