BIOLOGICAL PROCESS FOR REMOVING PHOSHPORUS INVOLVING A MEMBRANE FILTER

• US 20020185435A1
• Filed: 04/30/2002
• Published: 12/12/2002
• Est. Priority Date: 07/20/1999
• Status: Active Grant

• Current Assignee: Zenon Environmental Incorporated
• Original Assignee: Zenon Environmental Incorporated
• Inventors: Phagoo, Deonarine, Husain, Hidayat, Koch, Frederic
• Granted Patent: US 6,485,645 B1
• Time in Patent Office: Days
• US Class Current: 210/605
• CPC Class Codes: C02F 3/1268 Membrane bioreactor systems
• CPC Class Codes: C02F 3/1273 Submerged membrane bioreactors
• CPC Class Codes: C02F 3/30 Aerobic and anaerobic processes
• CPC Class Codes: C02F 3/308 Biological phosphorus removal
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage

Abstract

A waste water treatment process for biologically removing phosphates incorporates a membrane filter. The process includes three zones, an anaerobic zone, an anoxic zone and an aerobic zone containing an anaerobic, anoxic and aerobic mixed liquor. Water to be treated flows first into the anaerobic zone. Anaerobic mixed liquor flows to the anoxic zone. Anoxic mixed liquor flows both back to the anaerobic zone and to the aerobic zone. The aerobic mixed liquor flows to the anoxic zone and also contacts the feed side of a membrane filter. The membrane filter treats the aerobic mixed liquor to produce a treated effluent lean in phosphorous, nitrogen, BOD OR COD, suspended solids and organisms at a permeate side of the membrane filter and a liquid rich in rejected solids and organisms. Some or all of the material rejected by the membrane filter is removed from the process either directly or by returning the material rejected by the membrane filter to the anoxic or aerobic zones and wasting aerobic sludge. In a first optional side stream process, phosphorous is precipitated from a liquid lean in solids extracted from the anaerobic mixed liquor. In a second optional side stream process, anaerobic mixed liquor is treated to form insoluble phosphates which are removed in a hydrocyclone.

Claims

1. A process for treating water to remove phosphorous and nitrogen comprising the steps of:

(a) providing an anaerobic zone having an anaerobic mixed liquor having organisms which release phosphorous into the anaerobic mixed liquor and store volatile fatty acids from the anaerobic mixed liquor;

(b) providing an anoxic zone having an anoxic mixed liquor having organisms which metabolize stored volatile fatty acids, uptake phosphorous and denitrify the anoxic mixed liquor;

(c) providing an aerobic zone having an aerobic mixed liquor having organisms which metabolize stored volatile fatty acids, uptake phosphorous and nitrify the aerobic mixed liquor;

(d) flowing water to be treated into the anaerobic zone;

(e) flowing anaerobic mixed liquor to the anoxic zone;

(f) flowing anoxic mixed liquor to the anaerobic zone;

(g) flowing anoxic mixed liquor to the aerobic zone;

(h) flowing aerobic mixed liquor to the anoxic zone;

(i) contacting aerobic mixed liquor against the feed side of a membrane filter;

(j) producing a treated effluent lean in phosphorous, nitrogen, BOD OR COD, suspended solids and organisms from a permeate side of the membrane filter; and

,

(g) removing some or all of the material rejected by the membrane filter from the process,

wherein the steps above are performed substantially continuously and substantially simultaneously and wherein the MLSS is between 3 and 30 g/L.

2. The process of claim 1 wherein the MLSS is between 5 and 15 g/L.

3. The process of claim 1 wherein material rejected by the membrane filter is also mixed with the aerobic mixed liquor.

4. The process of claim 3 wherein the step of removing material rejected by the membrane filter from the process is accomplished by removing aerobic mixed liquor containing material rejected by the membrane filter.

5. The process of claim 1 wherein material rejected by the membrane filter is also mixed with the anoxic mixed liquor.

6. The process of claim 1 wherein the net hydraulic retention time for the anaerobic, anoxic and aerobic zones combined is between 2 and 12 hours.

7. The process of claim 1 wherein the net hydraulic retention time for the anaerobic, anoxic and aerobic zones combined is between 2 and 9 hours.

8. The process of claim 1 wherein the net hydraulic retention time for the anaerobic, anoxic and aerobic zones combined is between 4.5 and 9 hours.

9. The process of claim 1 wherein the sludge retention time is between 10 and 30 days and a crystalline phosphorous accumulation occurs in the mixed liquor.

10. The process of claim 1 wherein the recycle ratio between the aerobic zone and the anoxic zone is between 2 and 4.

11. A process for treating water to remove phosphorous and nitrogen comprising the steps of:

(a) providing an anaerobic zone having an anaerobic mixed liquor having organisms which release phosphorous into the anaerobic mixed liquor and store volatile fatty acids from the anaerobic mixed liquor;

(b) providing an anoxic zone having an anoxic mixed liquor having organisms which metabolize stored volatile fatty acids, uptake phosphorous and denitrify the anoxic mixed liquor;

(c) providing an aerobic zone having an aerobic mixed liquor having organisms which metabolize stored volatile fatty acids, uptake phosphorous and nitrify the aerobic mixed liquor;

(d) flowing water to be treated into the anaerobic zone;

(e) flowing anaerobic mixed liquor to the anoxic zone;

(f) flowing anoxic mixed liquor to the anaerobic zone;

(g) flowing anoxic mixed liquor to the aerobic zone;

(h) flowing aerobic mixed liquor to the anoxic zone;

(i) contacting aerobic mixed liquor against the feed side of a membrane filter;

(j) producing a treated effluent lean in phosphorous, nitrogen, BOD OR COD, suspended solids and organisms from a permeate side of the membrane filter; and

,

(g) removing some or all of the material rejected by the membrane filter from the process,

(h) extracting a liquid containing phosphorous but lean in solids from the anaerobic mixed liquor;

(i) precipitating phosphorous from the liquid containing phosphorous but lean in solids; and

, (j) producing a phosphorous lean effluent from the liquid containing phosphorous but lean in solids,

wherein the steps above are performed substantially continuously and substantially simultaneously.

12. The process of claim 11 wherein material rejected by the membrane filter is also mixed with the aerobic mixed liquor.

13. The process of claim 12 wherein the step of removing material rejected by the membrane filter from the process is accomplished by removing aerobic mixed liquor containing material rejected by the membrane filter.

14. The process of claim 11 wherein material rejected by the membrane filter is also mixed with the anoxic mixed liquor.

15. The process of claim 11 wherein the phosphorous is precipitated by the addition of between 400 to 800 mg/L of alum.

17. The process of claim 16 wherein the phosphorous is precipitated by the addition of between 400 to 800 mg/L of alum.

16. A process for treating water to remove phosphorous and nitrogen comprising the steps of:

(a) providing an anaerobic zone having an anaerobic mixed liquor having organisms which release phosphorous into the anaerobic mixed liquor and store volatile fatty acids from the anaerobic mixed liquor;

(b) providing an anoxic zone having an anoxic mixed liquor having organisms which metabolize stored volatile fatty acids, uptake phosphorous and denitrify the anoxic mixed liquor;

(c) providing an aerobic zone having an aerobic mixed liquor having organisms which metabolize stored volatile fatty acids, uptake phosphorous and nitrify the aerobic mixed liquor;

(d) flowing water to be treated into the anaerobic zone;

(e) flowing anaerobic mixed liquor to the anoxic zone;

(f) flowing anoxic mixed liquor to the anaerobic zone;

(g) flowing anoxic mixed liquor to the aerobic zone;

(h) flowing aerobic mixed liquor to the anoxic zone;

(i) treating aerobic mixed liquor in a solid-liquid separator to produce a treated effluent lean in phosphorous, nitrogen suspended solids and organisms and a liquid rich in solids rejected by the solid liquid separator;

(j) removing some or all of the liquid rich in solids rejected by the solid-liquid separator;

(k) extracting a phosphorous containing permeate lean in solids from the anaerobic mixed liquor;

(l) precipitating phosphorous from the phosphorous containing permeate lean in solids; and

,

(m) producing a phosphorous lean effluent from the phosphorous containing permeate lean in solids,

wherein the steps above are performed substantially continuously and substantially simultaneously.