Aerated anoxic membrane bioreactor

• US 7,713,413 B2
• Filed: 04/11/2006
• Issued: 05/11/2010
• Est. Priority Date: 04/11/2006
• Status: Expired due to Fees

• Current Assignee: Evoqua Water Technologies LLC
• Original Assignee: Siemen Water Technologies Corporation (Siemens AG)
• Inventors: Barnes, Dennis J.
• Primary Examiner(s): PRINCE JR, FREDDIE GARY
• Application Number:
  US11/279,334
• Publication Number:
  US 20070235385A1
• Time in Patent Office: 1,491 Days
• Field of Search: 210/605, 210/621, 210/622, 210/623, 210/629, 210/903, 210/906, 210/908
• US Class Current: 210/605
• CPC Class Codes: C02F 3/1273 Submerged membrane bioreactors
• CPC Class Codes: C02F 3/302 Nitrification and denitrification treatment C02F3/308 takes precedence
• 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
• CPC Class Codes: Y10S 210/908 Organic

Abstract

A process for treating biological oxygen demand (BOD), nitrogen and phosphorus containing wastewater, wherein the process includes providing wastewater influent to an oxygen-deficit aeration zone having activated sludge and mixing the wastewater influent with the activated sludge in the oxygen-deficit aeration zone to form a mixed liquor. The process further 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. In addition, the process 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 to an oxygen-deficit aeration zone having activated sludge;

maintaining an oxygen deficit throughout the oxygen-deficit aeration zone by controlling a rate of oxygen supplied to the oxygen-deficit aeration zone to less than a rate of oxygen consumption by micro-organisms in the oxygen-deficit aeration zone;

mixing the wastewater influent with the activated sludge in the oxygen-deficit aeration zone to form a first mixed liquor;

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

mixing the first mixed liquor with activated sludge in the oxygen-surplus aeration zone to form a second mixed liquor;

recycling a portion of the second mixed liquor to the oxygen-deficit aeration zone;

transferring a second portion of the second mixed liquor from the oxygen-surplus aeration zone to an anoxic reactor tank;

mixing the second portion of the second mixed liquor with activated sludge in the anoxic reactor tank to form a third mixed liquor;

transferring a portion of the third mixed liquor from the anoxic reactor tank to a membrane filter;

filtering the third mixed liquor to form a filtrate and an activated sludge; and

recycling at least a portion of the activated sludge from the membrane filter to the oxygen-deficit aeration zone.

2. The process according to claim 1, wherein the oxygen deficit in the oxygen-deficit aeration zone is maintained by controlling aeration in the oxygen-deficit aeration zone.

3. The process according to claim 1, wherein the recycled activated sludge includes dissolved oxygen.

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

5. The process according to claim 3 wherein the dissolved oxygen content of the recycled activated sludge is in a range of from about 4 mg/L to about 8 mg/L.

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

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

8. The process according to claim 1, wherein the second mixed liquor has a dissolved oxygen concentration of at least about 0.5 mg/L.

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

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

11. The process according to claim 10, wherein recycling a portion of the second mixed liquor to the oxygen-deficit aeration zone comprises recycling a portion of the second mixed liquor directly from an outlet of the oxygen-surplus aeration zone to the oxygen-deficit aeration zone

12. The process according to claim 1, wherein the overall dissolved oxygen content in the mixed liquor in the oxygen-deficit aeration zone does not exceed about 0.5 mg/L.

13. The process according to claim 1 including the step of providing a source of carbon to the anoxic reactor tank to assist denitrification.

14. The process according to claim 1, wherein recycling at least a portion of the activated sludge from the membrane filter to the oxygen-deficit aeration zone comprises recycling at least a portion of the activated sludge directly from the membrane filter to the oxygen-deficit aeration zone.

15. The process according to claim 1, wherein the membrane filter comprises a membrane bioreactor.

16. The process according to claim 1, wherein at least one of the oxygen-deficit aeration zone, the oxygen-surplus aeration zone, and the anoxic reactor tank includes a mechanical mixer.

17. The process according to claim 1, wherein the hydraulic residence time for at least one of the first mixed liquor in the oxygen-deficit aeration zone and the second mixed liquor in the oxygen-surplus aeration zone is between two and twelve hours.