Cyclic aeration system for submerged membrane modules

• US 6,706,189 B2
• Filed: 02/21/2003
• Issued: 03/16/2004
• Est. Priority Date: 10/09/1998
• Status: Expired due to Term

• Current Assignee: Zenon Technology Partnership
• Original Assignee: Zenon Environmental Incorporated
• Inventors: Janson, Arnold, Singh, Manwinder, Rabie, Hamid, Côté, Pierre
• Primary Examiner(s): BUSHEY, CHARLES S
• Application Number:
  US10/369,699
• Publication Number:
  US 20030127389A1
• Time in Patent Office: 389 Days
• Field of Search: 261/23.1, 261/28, 261/43, 261/59, 261/64.1, 261/122.1, 261/124, 261/122.2, 210/636, 210/641, 210/644, 210/649, 210/650, 210/651, 210/652, 210/138, 210/142, 210/321.75, 210/321.78, 210/321.79, 210/321.84, 210/321.88
• US Class Current: 210/636
• CPC Class Codes: B01D 2315/06 Submerged-type; Immersion type
• CPC Class Codes: B01D 2321/04 Backflushing
• CPC Class Codes: B01D 2321/185 Aeration
• CPC Class Codes: B01D 2321/2083 By reversing the flow
• CPC Class Codes: B01D 61/18 Apparatus therefor
• CPC Class Codes: B01D 63/02 Hollow fibre modules
• CPC Class Codes: B01D 63/024 with a single potted end
• CPC Class Codes: B01D 63/026 Wafer type modules or flat-surface type modules
• CPC Class Codes: B01D 63/043 with separate tube sheets
• 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: B01F 23/23105 Arrangement or manipulation of the gas bubbling devices
• CPC Class Codes: B01F 23/23121 having injection means, e.g. nozzles with circumferential outlet
• CPC Class Codes: B01F 23/231231 the outlets being in the form of perforations
• CPC Class Codes: B01F 23/231242 in the form of slits or cut-out openings
• CPC Class Codes: B01F 23/231265 being tubes, tubular elements, cylindrical elements or set of tubes
• CPC Class Codes: B01F 23/2319 Methods of introducing gases into liquid media
• CPC Class Codes: B01F 33/4062 with means for modifying the gas pressure or for supplying gas at different pressures or in different volumes at different parts of the bottom
• CPC Class Codes: B01F 35/145 Washing or cleaning mixers not provided for in other groups in this subclass; Inhibiting build-up of material on machine parts using other means
• CPC Class Codes: B08B 3/10 with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
• CPC Class Codes: C02F 1/444 : by ultrafiltration or microfiltration
• CPC Class Codes: C02F 1/74 : with air aeration of stretches of water C02F7/00
• CPC Class Codes: C02F 3/1273 : Submerged membrane bioreactors
• CPC Class Codes: C02F 3/201 : Perforated, resilient plastic diffusers, e.g. membranes, sheets, foils, tubes, hoses
• CPC Class Codes: Y02W 10/10 : Biological treatment of water, waste water, or sewage

Abstract

An aeration system for a submerged membrane module has a set of aerators connected to an air blower, valves and a controller adapted to alternately provide a higher rate or air flow and a lower rate of air flow in repeated cycles. In an embodiment, the air blower, valves and controller, simultaneously provide the alternating air flow to two or more sets of aerators such that the total air flow is constant, allowing the blower to be operated at a constant speed. In another embodiment, the repeated cycles are of short duration. Transient flow conditions result in the tank water which helps avoid dead spaces and assists in agitating the membranes.

Claims

1. A method of cleaning or inhibiting the fouling of membranes immersed with outsides of the membranes in contact with a water to be filtered or treated, the method comprising the steps of,

a) producing bubbles which flow upwards past the membranes, wherein,

b) the rate at which the bubbles are produced is varied in repeated cycles between (i) a higher rate and (ii) a lower rate which is in the range between a condition in which bubbles are not produced and less than one half of the higher rate;

and,

c) the cycles are between about 20 seconds and about 120 seconds in duration.

2. The method of claim 1 wherein the rate at which the bubbles are produced is varied abruptly in repeated cycles between the higher and lower rates.

3. The method of claim 2 wherein the lower rate is less than about 10% of the higher flow rate.

4. The method of claim 3 wherein the lower rate is less than about 5% of the higher flow rate.

5. The method of claim 1 wherein the time taken for the variations between the rates at which bubbles are produced is about 6 seconds or less.

6. The method of claim 1 wherein the time taken for the variations between the rates at which bubbles are produced is about 3 seconds or less.

7. The method of claim 1 wherein the rate at which the bubbles are produced is varied abruptly in repeated cycles between (i) a higher rate and (ii) a condition in which bubbles are not produced.

8. The method of claim 7 wherein the time taken for the variations between the higher rate at which bubbles are produced and the condition in which bubbles are not produced is about 6 seconds or less.

9. The method of claim 8 wherein the time taken for the variations between the higher rate at which bubbles are produced and the condition in which bubbles are not produced is about 3 seconds or less.

10. The method of claim 1 wherein the cycles are 20 seconds or more in duration.

11. The method of claim 10 wherein the cycles are not more than 60 seconds in duration.

12. The method of claim 1 wherein bubbles are produced at the higher rate for about one half of each cycle.

13. The method of claim 1 wherein the membranes are assembled into modules immersed in a tank and the bubbles flow past all of the modules at generally the same rate at the same time.

14. The method of claim 1 further comprising producing a flow of water past the membranes which accelerates and decelerates in each cycle.

15. The method of claim 14 wherein the flow of water past the membranes is rarely in a steady state.

16. The method of claim 1 wherein the higher rate corresponds to a superficial velocity of gas provided in the bubbles of between 0.013 m/s and 0.15 m/s.

17. A method of cleaning or inhibiting the fouling of membranes immersed with outsides of the membranes in contact with a water to be filtered or treated and used to withdraw a permeate from the membranes, the method comprising the steps of,

a) producing bubbles which flow upwards past the membranes, wherein,

i) the rate at which the bubbles are produced is varied in repeated cycles between a higher rate and a lower rate which is in the range between a condition in which bubbles are not produced and less than one half of the higher rate;

and,

ii) the cycles are greater than about 10 seconds and less than about 120 seconds in duration; and

,

b) producing a transient flow of water past the membranes, wherein the cycles are repeated generally continuously while withdrawing permeate from the membranes.

18. The method of claim 17 wherein the flow of water past the membranes is rarely in a steady state.

19. The method of claim 18 wherein the rate at which the bubbles are produced is varied abruptly in repeated cycles between the higher and lower rates.

20. The method of claim 17 wherein the lower rate is less than about 10% of the higher flow rate.

21. The method of claim 20 wherein the lower rate is less than about 5% of the higher flow rate.

22. The method of claim 17 wherein the time taken for the variations between the rates at which bubbles are produced is about 6 seconds or less.

23. The method of claim 22 wherein the time taken for the variations between the rates at which bubbles are produced is about 3 seconds or less.

24. The method of claim 17 wherein the rate at which the bubbles are produced is varied abruptly in repeated cycles between (i) a higher rate and (ii) a condition in which bubbles are not produced.

25. The method of claim 24 wherein the time taken for the variations between the higher rate at which bubbles are produced and the condition in which bubbles are not produced is about 6 seconds or less.

26. The method of claim 25 wherein the time taken for the variations between the higher rate at which bubbles are produced and the condition in which bubbles are not produced is about 3 seconds or less.

27. The method of claim 17 wherein the cycles are 20 seconds or more in duration.

28. The method of claim 27 wherein the cycles are not more than 60 seconds in duration.

29. The method of claim 17 wherein bubbles are produced at the higher rate for about one half of each cycle.

30. The method of claim 17 wherein the membranes are assembled into modules immersed in a tank and the bubbles flow past all of the modules at generally the same rate at the same time.

31. A method of cleaning or inhibiting the fouling of membranes immersed with outsides of the membranes in contact with a water to be filtered or treated, the method comprising the steps of,

a) providing air at a generally constant rate to a plurality of sets of the membranes for producing bubbles which flow upwards past the membranes;

and,

b) varying the rate at which the bubbles are produced below a set of the membranes in repeated cycles between a higher rate and a lower rate which is in the range between a condition in which bubbles are not produced and less than one half of the higher rate,

wherein

the cycles are greater than about 10 seconds and less than about 120 seconds in duration.