PROCESS TO IMPROVE THE EFFICIENCY OF A MEMBRANE FILTER ACTIVATED SLUDGE SYSTEM

• US 20070235386A1
• Filed: 04/11/2006
• Published: 10/11/2007
• Est. Priority Date: 04/11/2006
• Status: Active Grant

• Current Assignee: Evoqua Water Technologies LLC
• Original Assignee: Siemen Water Technologies Corporation (Siemens AG)
• Inventors: Barnes, Dennis
• Granted Patent: US 7,481,933 B2
• Time in Patent Office: Days
• US Class Current: 210/605
• CPC Class Codes: C02F 3/1268 Membrane bioreactor systems
• CPC Class Codes: C02F 3/308 Biological phosphorus removal
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage
• CPC Class Codes: Y10S 210/903 Nitrogenous
• CPC Class Codes: Y10S 210/906 Phosphorus containing

Abstract

A process for treating BOD, nitrogen and phosphorus containing wastewater, wherein the process includes providing wastewater influent into an anaerobic zone having activated sludge and mixing the wastewater influent with the activated sludge in the anaerobic zone to form a mixed liquor. The process further includes providing the mixed liquor into an oxygen-deficit aeration zone and recycling denitrified mixed liquor from the oxygen-deficit aeration zone to the anaerobic zone for mixing therein with wastewater. In addition, the process includes transferring the mixed liquor from the oxygen-deficit aeration zone to an oxygen-surplus aeration zone and transferring a portion of the mixed liquor from the oxygen-surplus aeration zone to a membrane filter wherein a filtrate is separated from sludge. The process also includes recycling at least a portion of the sludge to the oxygen-deficit aeration zone as recycled activated sludge.

Claims

1. A process for treating BOD, nitrogen and phosphorus containing wastewater, the process comprising:

providing wastewater influent into an anaerobic zone having activated sludge;

mixing the wastewater influent with the activated sludge in the anaerobic zone to form a mixed liquor;

providing the mixed liquor into an oxygen-deficit aeration zone;

recycling denitrified mixed liquor from the oxygen-deficit aeration zone to the anaerobic zone for mixing therein with wastewater;

transferring the mixed liquor from the oxygen-deficit aeration zone to an oxygen-surplus aeration zone;

transferring a portion of the mixed liquor from the oxygen-surplus aeration zone to a membrane filter wherein a filtrate is separated from sludge; and

recycling at least a portion of the sludge to the oxygen-deficit aeration zone as recycled activated sludge.

2. The process according to claim 1, wherein oxygen deficit in the oxygen-deficit aeration zone is maintained by controlling aeration so that oxygen supply is less than oxygen consumption by microorganisms therein.

3. The process according to claim 1, wherein the portion of sludge recycled to the oxygen-deficit aeration zone includes dissolved oxygen.

4. The process according to claim 3 wherein the dissolved oxygen content of the recycled flow is less than 8 mg/L.

5. The process according to claim 3 wherein the dissolved oxygen content of the recycled flow is about 4 mg/L to about 8 mg/L.

6. The process according to claim 3, wherein the dissolved oxygen is provided by the membrane filter.

7. The process according to claim 1, wherein an aerator device in the oxygen-deficit aeration zone provides at least some of the oxygen-containing gas and mixing energy to keep the mixed liquor in suspension.

8. The process according to claim 1, wherein the oxygen-surplus aeration zone has a dissolved oxygen concentration of at least about 0.5 mg/L.

9. The process according to claim 1, wherein in the oxygen-deficit aeration zone promotes simultaneous nitrification and denitrification.

10. The process according to claim 1, further comprising recycling a portion of mixed liquor from the oxygen-surplus aeration zone to the oxygen-deficit aeration zone for mixing therein with the wastewater and the recycled activated sludge.

11. A process for treating BOD, nitrogen and phosphorus containing wastewater, the process comprising:

providing wastewater influent into an anaerobic zone having activated sludge;

mixing the wastewater influent with the activated sludge to form a mixed liquor;

providing the mixed liquor into a first aeration zone maintained under conditions which produce a complete mix reaction and provide insufficient oxygen to meet the biological oxygen demand of the resulting mixed liquor;

recycling denitrified-mixed liquor from the first aeration zone to the anaerobic zone for mixing therein with wastewater;

transferring the mixed liquor to a subsequent aeration zone under conditions which produce a complete mix reaction and provide sufficient oxygen to product an overall dissolved oxygen content of at least 0.5 mg/L;

transferring the mixed liquor from the subsequent aeration zone to a membrane filter wherein filtrate is separated from sludge; and

recycling at least a portion of the sludge to the first aeration zone as recycled activated sludge.

12. The process of claim 11 further comprising recycling a portion of the mixed liquor from the subsequent aeration zone to the first aeration zone for mixing therein the wastewater and the recycled activated sludge.

13. The process according to claim 11, wherein the portion of sludge recycled to the oxygen-deficit aeration zone includes dissolved oxygen.

14. The process according to claim 13 wherein the dissolved oxygen content of the recycled flow is less than 8 mg/L.

15. The process according to claim 13 wherein the dissolved oxygen content of the recycled flow is about 4 mg/L to about 8 mg/L.

16. The process according to claim 11, wherein the dissolved oxygen is provided by the membrane filter.

17. A process for treating BOD, nitrogen and phosphorus containing wastewater, the process comprising:

providing wastewater influent into an anaerobic zone having activated sludge;

mixing the wastewater influent with the activated sludge in the anaerobic zone to form a mixed liquor;

providing the mixed liquor into an oxygen-deficit aeration zone;

recycling denitrified mixed liquor from the oxygen-deficit aeration zone to the anaerobic zone for mixing therein with wastewater;

transferring the mixed liquor from the oxygen-deficit aeration zone to an oxygen-surplus aeration zone;

transferring the mixed liquor from the oxygen-surplus aeration zone to an anoxic zone;

transferring a portion of the mixed liquor from the anoxic zone to a membrane filter wherein a filtrate is separated from sludge; and

recycling at least a portion of the sludge to the oxygen-deficit aeration zone as recycled activated sludge.

18. A process according to claim 17 including the step of providing a source of carbon to the anoxic zone to assist denitrification.