Enhanced activated sludge treatment
OwnerMichael T. Ungerinventor
Life of this patent
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Abstract
An enhanced activated sludge wastewater treatment method increases volumetric pollutant loading, hydraulic loading capacity and nutrient removal efficiency at a conventional activated sludge wastewater treatment plant. The method describes the control of return activated sludge rates, and the operation of partitioned aeration and reaeration zones according to measured properties of the mixed liquor to achieve the claimed benefits. Operating an existing treatment plant according to the enhanced treatment method provides a more consistent treatment process that is resistant to shock loading and increases plant capacity without the need for costly construction and operation of additional reactors and clarifiers.
Claims3
An activated sludge wastewater treatment apparatus for use in a wastewater treatment facility including an aeration vessel having a plurality of aeration zones, a settling vessel, and a digestion vessel, said apparatus comprising:
- said aeration vessel having approximately 20 percent to 45 percent of its total volume comprising one or more reaeration zones;
- a sludge return line to transport activated sludge from said settling vessel to said one or more reaeration zones;
- the return activated sludge flow rate being less than 60 percent of the wastewater influent flow rate;
- a supernatant return line for adding supernatant from said digestion vessel to said one or more reaeration zones;
- and
- wherein the concentration of mixed liquor suspended solids in said aeration vessel is maintained so that the ratio of MLSS between said reaeration zones and the other aeration zones is greater than 1:1;
- and
- wherein the average influent volumetric loading capacity is greater than approximately 3.2 kg BOD5/m3day.
An activated sludge wastewater treatment facility having an aeration vessel with a plurality of aeration zones, a settling vessel and a digestion vessel, said facility comprising:
- said aeration vessel having approximately 20 percent to 45 percent of its volume comprising one or more reaeration zones;
- a supernatant return line adding a portion of the supernatant from said digestion vessel to said one or more reaeration zones;
- a sludge return line for returning activated sludge from said settling vessel to a portion of the reaeration zones;
- the return activated sludge flow rate being less than 60 percent of the wastewater influent flow rate to the aeration vessel;
- and
- wherein the concentration of dissolved oxygen in said aeration vessel is controlled so that the typical concentration of dissolved oxygen at the downstream end of said portion of said reaeration zones is generally at least three times the concentration of dissolved oxygen at the downstream end of the other of said reaeration zones;
- wherein the concentration of mixed liquor suspended solids in said aeration vessel is controlled so that the ratio of MLSS between said reaeration zones and the other aeration zones is greater than 1:1;
- and
- wherein the average influent volumetric loading capacity of said facility is greater than approximately 3.2 kg BOD5/m3day and said facility has an average nutrient removal rate greater than 0.005 lbs nitrogen per lb volatile suspended solids.
An apparatus for the treatment of wastewater comprising:
- means for combining an influent wastewater stream and an activated sludge in a primary aeration reactor thereby creating an aerated mixed liquor;
- means for transferring said aerated mixed liquor to a settling basin and withdrawing from said settling basin an effluent stream and an activated sludge stream;
- means for transferring a portion of said activated sludge stream to a first reaeration reactor thereby generating a first reaeration liquor which is returned to said primary aeration reactor;
- means for transferring a portion of said activated sludge stream to a second reaeration reactor thereby generating a second reaeration liquor which is returned to said primary aeration reactor;
- means for transferring a portion of said activated sludge stream to said primary aeration reactor;
- means for transferring a portion of said activated sludge stream to a digestion phase;
- and
- means for transferring a portion of the contents from said digestion phase to said second reaeration reactor;
- wherein the flow rate of said activated sludge stream is between 20 percent and about 60 percent of the flow rate of said influent wastewater stream.
Dependencies are inferred from the claim text.