Enhanced biosorption of wastewater organics using dissolved air flotation with solids recycle

Patent metadata

Field	Value
Publication number	US-10131550-B2
Application number	US-201414890628-A
Country	US
Kind code	B2
Filing date	May 1, 2014
Priority date	May 6, 2013
Publication date	Nov 20, 2018
Grant date	Nov 20, 2018

Abstract

Systems and methods for treating wastewater including a dissolved air flotation operation performed upon a portion of a mixed liquor output from a contact tank prior to the mixed liquor entering a biological treatment tank.

First claim

What is claimed is:

1. A method of facilitating increased operating efficiency of a wastewater treatment system, the method comprising:
configuring a dissolved air flotation (DAF) unit in a wastewater treatment system in fluid communication between a contact tank and a biological treatment unit to remove solids from a portion of a first mixed liquor output from the contact tank prior to the portion of the first mixed liquor entering the biological treatment unit and to recycle at least a portion of the solids to the contact tank, the recycle of the at least a portion of the solids to the contact tank reducing an amount of biological oxygen demand to be treated in the biological treatment unit as compared to the wastewater treatment system operating in the absence of recycling the at least a portion of the solids to the contact tank.

2. The method of claim 1 , wherein greater than 50% of the solids are recycled from the DAF unit to the contact tank.

3. The method of claim 1 , comprising recycling solids from the DAF unit to the contact tank in an amount sufficient to increase biogas production of an anaerobic digester of the wastewater treatment system having an inlet in fluid communication with an outlet of the DAF unit, at least a second portion of the solids removed in the DAF unit being directed into the anaerobic digester.

4. The method of claim 1 , comprising recycling solids from the DAF unit to the contact tank in an amount sufficient to reduce the energy consumption of the wastewater treatment system.

5. A wastewater treatment system comprising:
a contact tank having a first inlet configured to receive wastewater to be treated, a second inlet, and an outlet, the contact tank configured to mix the wastewater to be treated with activated sludge to form a first mixed liquor;
a dissolved air flotation (DAF) unit having an inlet in fluid communication with the outlet of the contact tank, a solids outlet, a DAF unit effluent outlet, and a gas inlet, the gas inlet configured to introduce gas into the dissolved air flotation unit to facilitate the flotation of suspended matter from the first mixed liquor and the removal of the suspended matter from the DAF unit, the solids outlet in fluid communication with the first inlet of the contact tank and configured to transfer at least a portion of the suspended matter from the DAF unit to the first inlet of the contact tank;
a biological treatment unit having a first inlet in fluid communication with the outlet of the contact tank, a second inlet, a third inlet in fluid communication with the DAF unit effluent outlet, and an outlet, the biological treatment unit configured to biologically break down organic components of the first mixed liquor and of an effluent from the DAF unit to form a second mixed liquor; and
a clarifier having an inlet in fluid communication with the outlet of the biological treatment unit, an effluent outlet, and a return activated sludge outlet in fluid communication with the second inlet of the contact tank and with the second inlet of the biological treatment unit, the clarifier configured to output a clarified effluent through the effluent outlet and a return activated sludge though the return activated sludge outlet.

6. The system of claim 5 , where the biological treatment unit includes:
an aerated anoxic region having a first inlet in fluid communication with the outlet of the contact tank, a second inlet, and an outlet; and
an aerobic region having a first inlet in fluid communication with the outlet of the aerated anoxic region, a second inlet in fluid communication with the DAF unit effluent outlet, and an outlet.

7. The system of claim 6 , wherein the aerated anoxic region and the aerobic region are included in a same treatment tank.

8. The system of claim 7 , wherein the aerated anoxic region and the aerobic region are separated by a partition.

9. The system of claim 6 , wherein the aerated anoxic region is included in a first treatment tank and the aerobic region is included in a second treatment tank distinct from the first treatment tank.

10. The system of claim 6 , comprising a first sub-system including the contact tank and the DAF unit which is physically separated from a second sub-system including the biological treatment unit and the clarifier.

11. The system of claim 6 , wherein the contact tank and the aerated anoxic region are included in a same tank.

12. The system of claim 5 , further comprising an anaerobic digester having an inlet in fluid communication with the second outlet of the DAF unit and an outlet.

13. The system of claim 12 , wherein the outlet of the anaerobic digester is in fluid communication with at least one of the contact tank and the biological treatment unit.

14. The system of claim 13 , further comprising a primary clarifier having an inlet in fluid communication with a source of the wastewater to be treated and a solids-lean outlet in fluid communication with the contact tank.

15. The system of claim 14 , further comprising a thickener having an inlet in fluid communication with a solids-rich outlet of the primary clarifier and an outlet in fluid communication with the anaerobic digester.

16. The system of claim 14 , wherein the primary clarifier further comprises a solids-rich outlet in fluid communication with the DAF unit.

17. A method of treating wastewater comprising:
introducing the wastewater into a contact tank including an activated sludge;
mixing the wastewater with activated sludge in the contact tank to form a mixed liquor;
directing a first portion of the mixed liquor to a DAF unit;
separating the first portion of the mixed liquor in the DAF unit to form a DAF unit effluent and separated biosolids;
directing at least a portion of the separated biosolids from the DAF unit to the contact tank;
directing a second portion of the mixed liquor to a biological treatment unit;
directing the DAF unit effluent to the biological treatment unit;
biologically treating the mixed liquor and the DAF unit effluent in the biological treatment unit to form a biologically treated mixed liquor;
directing the biologically treated mixed liquor to a clarifier;
separating the biologically treated mixed liquor in the clarifier to form a clarified effluent and a return activated sludge;
recycling a first portion of the return activated sludge to the contact tank;
recycling a second portion of the return activated sludge to the biological treatment unit; and
directing the clarified effluent to a treated wastewater outlet.

18. The method of claim 17 , wherein the biological treatment unit includes an aerated anoxic treatment unit and an aerobic treatment unit, and the method further comprises:
directing the second portion of the mixed liquor to the aerated anoxic treatment unit;
treating the second portion of the mixed liquor in the aerated anoxic treatment unit to form an anoxic mixed liquor;
directing the anoxic mixed liquor to the aerobic treatment unit;
directing the DAF unit effluent to the aerobic treatment unit;
treating the anoxic mixed liquor and the DAF unit effluent in the aerobic treatment tank to form an aerobic mixed liquor;
directing the aerobic mixed liquor to the clarifier;
separating the aerobic mixed liquor in the clarifier to form the clarified effluent and the return activated sludge; and

recycling the second portion of the return activated sludge to the aerated anoxic treatment unit.

19. The method of claim 18 , wherein the first portion of the return activated sludge and the secon

Assignees

• Erdogan Argun O
• Doyle michael l
• Evoqua Water Tech Llc

Inventors

• Erdogan Argun Olcayto
• Doyle michael l

Classifications

• C02F2209/40

  Liquid flow rate · CPC title

• B03D1/1431

  Dissolved air flotation machines · CPC title

• C02F1/5245

  using basic salts, e.g. of aluminium and iron · CPC title

• C02F3/302

  Nitrification and denitrification treatment (C02F3/308 takes precedence) · CPC title

• C02F2209/03

  Pressure · CPC title