Method for treating wastewater in a membrane bioreactor to produce a low phosphorus effluent

• US 20050045557A1
• Filed: 09/02/2003
• Published: 03/03/2005
• Est. Priority Date: 09/02/2003
• Status: Active Grant

• Current Assignee: CH2M Hill Incorporated (CH2M Hill Companies Limited)
• Original Assignee: CH2M Hill Incorporated (CH2M Hill Companies Limited)
• Inventors: Daigger, Glen T., Wollmann, Albert M., Fleischer, Edwin J.
• Granted Patent: US 6,946,073 B2
• Time in Patent Office: Days
• US Class Current: 210/605
• CPC Class Codes: C02F 3/1215 Combinations of activated sludge treatment with precipitation, flocculation, coagulation and separation of phosphates
• 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 210/906 Phosphorus containing

Abstract

Removal of biological nutrients from a wastewater yielding a low phosphorous (e.g., less than 0.25 mg/L) output includes providing a serial multistage bioreactor containing activated sludge having in hydraulic series an anaerobic zone and a downstream aerobic zone, with each zone having an upstream inlet and a downstream outlet. The wastewater is provided to the anaerobic zone inlet. A quantity of chemical sufficient to precipitate soluble and particulate phosphorous is added to the downstream aerobic zone in an amount sufficient to yield a low phosphorous output. Treated water is separated from the activated sludge and precipitated phosphorous and a return activated sludge separated from the treated water is recycled to the anaerobic zone.

Claims

1. A method for removal of biological nutrients from a wastewater yielding a low phosphorous output comprising:

a) providing a serial multistage bioreactor containing activated sludge having in hydraulic series an anaerobic zone and a downstream aerobic zone, each zone having an upstream inlet and a downstream outlet;

b) providing a wastewater to the anaerobic zone inlet;

c) adding a quantity of chemical to precipitate soluble and particulate phosphorous to the downstream aerobic zone in an amount sufficient to yield a low phosphorous output;

d) separating treated water from the activated sludge and precipitated phosphorous; and

e) recycling return activated sludge separated by the immersed membrane filter from treated water to the anaerobic zone.

2. The method of claim 1 wherein step a) further comprises providing a multistage bioreactor having an anoxic zone in hydraulic series intermediate the anaerobic and downstream aerobic zone.

3. The method of claim 1 wherein the separating of step c) is performed by filtering through an immersed membrane filter operatively associated with the downstream aerobic zone.

4. The method of claim 1 wherein step a) further comprises providing a multistage bioreactor having an upstream anoxic zone, an upstream aerobic zone and a downstream anoxic zone in hydraulic series between the anaerobic zone and the downstream aerobic zone.

5. The method of claim 2 wherein in step d) the return activated sludge is first recycled to near an inlet to the anoxic zone and is then recycled from near an outlet of the anoxic zone to the anaerobic zone.

6. The method of claim 3 wherein in step d) the return activated sludge is recycled to near an inlet to the upstream anoxic zone and is then recycled from near an outlet of the upstream anoxic zone to the anaerobic zone.

7. The method of claim 6 wherein in step d) the return activated sludge is first recycled to near an inlet of the upstream aerobic zone and then recycled from near the outlet to the upstream aerobic zone to near the inlet of the upstream anoxic zone and from near the outlet of the upstream anoxic zone to the aerobic zone.

8. The method of claim 1 wherein in step c) the low phosphorous output is less than 0.25 mg/L.

9. The method of claim 1 wherein in step c) the low phosphorous output is less than 0.1 mg/L.