Membrane bioreactor, process and aerator

• US 20040108268A1
• Filed: 12/05/2002
• Published: 06/10/2004
• Est. Priority Date: 12/05/2002
• Status: Active Grant

• Current Assignee: Zenon Technology Partnership
• Original Assignee: Zenon Environmental Incorporated (Veolia Environnement SA)
• Inventors: Cote, Pierre, Liu, Minggang, Husain, Hidayat, Pottinger, Ian
• Granted Patent: US 6,863,817 B2
• Time in Patent Office: Days
• US Class Current: 210/605
• CPC Class Codes: B01D 2311/2642 Aggregation, sedimentation, flocculation, precipitation or coagulation
• CPC Class Codes: B01D 2313/26 Specific gas distributors or gas intakes
• CPC Class Codes: B01D 2315/06 Submerged-type; Immersion type
• CPC Class Codes: B01D 2321/04 Backflushing
• CPC Class Codes: B01D 2321/16 Use of chemical agents
• CPC Class Codes: B01D 2321/185 Aeration
• CPC Class Codes: B01D 2321/40 Automatic control of cleaning processes
• CPC Class Codes: B01D 61/22 Controlling or regulating
• CPC Class Codes: B01D 65/02 Membrane cleaning or sterilisation ; Membrane regeneration
• CPC Class Codes: B01D 65/08 Prevention of membrane fouling or of concentration polarisation
• CPC Class Codes: C02F 2103/002 Grey water, e.g. from clothes washers, showers or dishwashers
• CPC Class Codes: C02F 2103/005 Black water originating from toilets
• CPC Class Codes: C02F 2209/42 Liquid level
• CPC Class Codes: C02F 3/1215 Combinations of activated sludge treatment with precipitation, flocculation, coagulation and separation of phosphates
• CPC Class Codes: C02F 3/1268 Membrane bioreactor systems
• 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

Abstract

A reactor has an aerobic tank, an anoxic tank and a sealed membrane tank with conduits for circulating mixed liquor between them. Permeation starts when the mixed liquor reaches a high level and stops when the mixed liquor reaches a low level. A sensor, for detecting the mixed liquor level, may stop and start permeation. Pressure builds in the membrane tank when membrane air is on. Transmembrane pressure is also provided by gravity flow or siphon. Membrane air generates an air lift which drives the mixed liquor circulation. The total amount of air provided by an air source is divided and varied in time between the membrane aerator and the process aerator. The process aerator acts as a screening inlet to the conduit to the membrane tank. Chemical maintenance cleaning is provided by gravity flow.

Claims

1. An apparatus comprising,

a) an aerobic tank or zone;

b) an anoxic tank or zone;

c) an immersed membrane tank or zone;

d) a conduit or passage for mixed liquor to flow from the membrane tank or zone to the anoxic tank or zone;

e) a conduit or passage for mixed liquor to flow from the anoxic tank or zone to the aerobic tank or zone;

f) a conduit or passage for mixed liquor to flow from the aerobic tank or zone to the membrane tank or zone;

g) an inlet for feed to enter into the anoxic tank or zone; and

,

h) an outlet for permeate to exit the membrane tank or zone.

19. The apparatus of claim 1 having a quiescent zone in the anoxic tank or zone to allow solids to settle and to store the settled solids until they are removed.

2. A process comprising the steps of,

a) providing an aerobic tank or zone;

b) providing an anoxic tank or zone;

c) providing an immersed membrane tank or zone;

d) flowing mixed liquor from the membrane tank or zone to the anoxic tank or zone;

e) flowing mixed liquor from the anoxic tank or zone to the aerobic tank or zone;

f) flowing mixed liquor from the aerobic tank or zone to the membrane tank or zone;

g) flowing feed into the anoxic tank or zone; and

,

h) removing permeate from the membrane tank or zone.

3. The process of claim 2 wherein operated such that the permeate has lower concentrations of organic carbon, ammonia and total nitrogen than the feed.

32. The process of claim 2 further comprising the step of adding a coagulant for chemical precipitation of phosphorus.

33. The process of claim 32 wherein the coagulant is provided in batched when permeation starts.

34. The process of claim 32 wherein the coagulant is added continuously during permeation.

4. A process comprising the steps of,

a) providing one or more process tanks or zones for one or more of aerobic digestion, nitrification or denitrification;

b) providing an immersed membrane tank or zone;

c) flowing mixed liquor from the membrane tank or zone to the one or more process tanks or zones;

d) flowing mixed liquor from the one or more process tanks or zones to the membrane tank or zone;

e) flowing feed into one or more of the tanks or zones; and

,

f) removing permeate from the membrane tank or zone

wherein the step of removing permeate begins when the level of mixed liquor in the one or more tanks or zones reaches a selected maximum mixed liquor level and stops when the level of mixed liquor in the one or more tanks or zones reaches a selected minimum mixed liquor level.

5. An apparatus comprising,

a) one or more process tanks or zones for one or more of aerobic digestion, nitrification or denitrification;

b) an immersed membrane tank or zone;

c) a conduit or passage for mixed liquor to flow from the membrane tank or zone to the one or more process tanks or zones;

d) a conduit or passage for mixed liquor to flow from the one or more process tanks or zones to the membrane tank or zone;

e) an inlet for feed to enter into one or more of the tanks or zones;

f) an outlet for permeate to exit the membrane tank or zone; and

,

g) a level sensor for detecting a selected maximum mixed liquor level and a selected minimum mixed liquor level in one of the one or more process tanks or zones.

6. The apparatus of claim 5 wherein the level sensor is operatively connected to devices for one or more of (a) stopping and starting permeation, (b) increasing and decreasing the total air supply provided by an air supply or (c) altering a regime of cyclic aeration.

7. A apparatus comprising,

a) one or more membrane or membrane modules located in a membrane tank or zone;

b) an aerator for aerating the one or more membranes or membrane modules at least from time to time;

c) a conduit for withdrawing permeate from the one or more membranes or membrane modules;

d) an inlet to the membrane tank or zone;

e) an outlet from the membrane tank or zone; and

f) a path between the inlet and outlet

wherein the membrane tank or zone is sealed but for the inlet and outlet.

8. The apparatus of claim 7 wherein the outlet is a gravity flow outlet or siphon.

9. A process comprising the steps of,

a) providing an apparatus having,

i) one or more membrane or membrane modules located in a membrane tank or zone;

ii) an aerator for aerating the one or more membranes or membrane modules at least from time to time;

iii) a conduit for withdrawing permeate from the one or more membranes or membrane modules;

iv) an inlet to the membrane tank or zone;

v) an outlet from the membrane tank or zone; and

vi) a path between the inlet and outlet; and

,

b) operating the aerator to produce an air lift which causes mixed liquor to circulate between the outlet and the inlet.

10. The process of claim 9 wherein the membrane tank or zone is sealed but for the inlet and outlet.

11. An apparatus comprising,

a) one or more process tanks or zones for one or more of aerobic digestion, nitrification or denitrification;

b) an immersed membrane tank or zone;

c) a conduit or passage for mixed liquor to flow from the membrane tank or zone to the one or more process tanks or zones;

d) a conduit or passage for mixed liquor to flow from the one or more process tanks or zones to the membrane tank or zone;

e) an inlet for feed to enter into one or more of the tanks or zones;

f) an outlet for permeate to exit the membrane tank or zone, and,

g) one or more membrane aerators for producing bubbles in the membrane tank or zone;

h) an air source connected to the one or more membrane aerators,

wherein mixed liquor flows from the membrane tank or zone to one of the one or more process tanks or zones during at least a part of the time when air is provided to the one or more membrane aerators.

12. An apparatus according to claim 11 wherein the membrane tank is sealed but for being open to the conduits.

13. An apparatus comprising,

a) one or more process tanks or zones for one or more of aerobic digestion, nitrification or denitrification;

b) an immersed membrane tank or zone;

c) a conduit or passage for mixed liquor to flow from the membrane tank or zone to the one or more process tanks or zones;

d) a conduit or passage for mixed liquor to flow from the one or more process tanks or zones to the membrane tank or zone;

e) an inlet for feed to enter into one or more of the tanks or zones;

f) an outlet for permeate to exit the membrane tank or zone; and

,

g) one or more membrane aerators for producing bubbles in the membrane tank or zone;

h) one or more process aerators for producing bubbles in one of the one or more process tanks or zones; and

,

i) an air source connected to the one or more membrane aerators,

wherein the air source is connected to the one or more process aerators and the one or more membrane aerators and total amount of air provided by the air source is divided between the one or more membrane aerators and the one or more process aerators.

14. An apparatus according to claim 13 wherein the amount of air provided by the air source to the one or more process aerators varies in time and the amount of air provided by the air source to the one or more membrane aerators varies in time.

15. An apparatus according to claim 14 wherein the total amount of air provided by the air source is substantially constant over a period of time during which the amount of air provided by the air source to the one or more process aerators varies in time and the amount of air provided by the air source to the one or more membrane aerators varies in time.

24. The apparatus of claim 13 combined with the aeration system of claim 20.

30. A process comprising the steps of providing an apparatus according to claim 13 and changing the distribution of air in quantity or time between process air and membrane air to maintain acceptable process oxygen concentrations in the one or more process tanks or zones.

16. An aerator comprising,

a) an aerator body with holes for releasing bubbles from the aerator body or for allowing mixed liquor surrounding the aerator to enter the aerator body;

b) an inlet for air to enter the aerator body; and

,

c) an outlet for mixed liquor to exit the aerator body.

17. The apparatus of claim 16 wherein the outlet is connected to a mixed liquor conduit for removing mixed liquor from a tank or zone containing the aerator.

18. The apparatus of claim 17 wherein the inlet is connected to an aeration system which provides an airflow sufficient to create bubbles from at least some of the holes at some times and which allows mixed liquor to flow into the holes during at least some times.

20. An aeration system comprising,

a) one or more process aerators,

b) one or more membrane aerators;

c) an air supply;

d) a process air line which provides a path for air from the air supply to the one or more process aerators;

e) a membrane air line which provides a path for air from the air supply to the pone or more membrane aerators;

f) a valve in one of the process air line or the membrane air line, the valve having a first position in which it is fully or partially open and a second position in which it is fully or partially closed,

wherein when the valve is in the first position, at least a major portion of the air provided by the air supply flows to the one or more aerator serviced by the air line having the valve, and when the valve is closed, at least a major portion of the air provided by the air supply flows to the other one or more aerators.

21. The apparatus of claim 20 wherein the one or more aerators serviced by the air line having the valve are located to a lesser depth in water compared to the other one or more aerators.

22. The apparatus of claim 20 wherein the valve is controlled by a valve controller which changes the valve from the first position to the second position and back to the first position in repeated cycles.

23. The apparatus of claim 22 wherein the repeated cycles are between 10 and 40 seconds long.

25. An apparatus comprising,

a) one or more process tanks or zones for one or more of aerobic digestion, nitrification or denitrification;

b) an immersed membrane tank;

c) a conduit or passage for mixed liquor to flow from the membrane tank to the one or more process tanks or zones;

d) a conduit or passage for mixed liquor to flow from the one or more process tanks or zones to the membrane tank;

e) an inlet for feed to enter into one or more of the process tanks or zones;

f) an outlet for permeate to exit the membrane tank; and

,

g) isolation valves in the conduits or passages to permit the membrane tank to be removed from the one or more process tanks or zones.

26. An aeration system comprising,

a) one or more process aerators;

b) one or more membrane aerators;

c) an air supply;

d) a process air line which provides a path for air from the air supply to the one or more process aerators;

e) a membrane air line which provides a path for air from the air supply to the one or more membrane aerators;

wherein the air supply is adapted to provide at least a higher flow rate of air and a lower flow rate of air.

27. The aeration system of claim 26 combined with the apparatus of claim 5 wherein the level sensor is operatively connected to the air supply to control when air is provided at the higher rate of flow and the lower rate of flow.

28. The aeration system of claim 27 wherein air is provided at the higher rate of flow whenever the level of mixed liquor is above a high level, the high level related to the need for the higher rate of flow to meet process air requirements.

29. The aeration system of claim 27 wherein air is provided at the higher rate of flow from the time that the mixed liquor reaches a maximum mixed liquor level to the time when the mixed liquor reaches a minimum mixed liquor level.

31. The aeration system of claim 26 wherein the process aerator is a fine bubble aerator and the membrane aerator is a coarse bubble aerator.

35. A process of chemical cleaning comprising the step of providing a backwashing flow of a chemical cleaning solution followed by a period in which permeate is not withdrawn.