Apparatus and method for cleaning membrane filtration modules

• US 6,641,733 B2
• Filed: 11/21/2002
• Issued: 11/04/2003
• Est. Priority Date: 09/25/1998
• Status: Expired due to Fees

• Current Assignee: Evoqua Water Technologies LLC
• Original Assignee: US Filter Wastewater Group Incorporated (Siemens AG)
• Inventors: Zha, Fufang, Jordan, Edward John
• Primary Examiner(s): DRODGE, JOSEPH W
• Application Number:
  US10/303,447
• Publication Number:
  US 20030075504A1
• Time in Patent Office: 348 Days
• Field of Search: 210/150, 210/151, 210/274, 210/275, 210/321.65, 210/321.69, 210/605, 210/615, 210/617, 210/631, 210/636, 210/637, 210/650, 210/651, 210/791, 210/797, 210/620
• US Class Current: 210/615
• 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 63/02 Hollow fibre modules
• CPC Class Codes: B01D 63/024 with a single potted end
• CPC Class Codes: B01D 63/031 Two or more types of hollow fibres within one bundle or within one potting or tube-sheet
• 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 3/1273 Submerged membrane bioreactors
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage

Abstract

A method and apparatus for cleaning a membrane module, the membrane module having a plurality of porous membranes, the membranes being arranged in close proximity to one another and mounted to prevent excessive movement therebetween and means for providing, from within the module, by means other than gas passing through the pores of the membranes, gas bubbles entrained in a liquid flow such that, in use, the liquid and bubbles entrained therein move past the surfaces of the membranes to dislodge fouling materials therefrom, the gas bubbles being entrained in the liquid by flowing the liquid past a source of gas to draw the gas into the liquid flow. The gas bubbles are preferably entrained into the liquid using a venturi type device. The membranes are preferably partitioned into discrete groups to assist cleaning while maintaining high packing density.

Claims

1. A method of scrubbing a membrane surface using a liquid medium with a plurality of gas bubbles entrained therein, including the steps of:

entraining a plurality of gas bubbles into a liquid medium by flow of the liquid medium and a gas into a junction, wherein the liquid medium comprises a cleaning chemical; and

flowing the gas bubbles and liquid medium along a membrane surface to dislodge fouling materials therefrom.

2. The method according to claim 1, wherein the junction is selected from the group consisting of a venturi tube, a jet, a nozzle, an ejector, an eductor, and an injector.

3. The method according to claim 1, wherein the gas bubbles are entrained or injected into the liquid medium by at least one device which forcibly mixes a gas into the liquid medium to produce a mixture of liquid and gas bubbles.

4. The method according to claim 1, wherein the gas comprises a gas selected from the group consisting of air, oxygen, gaseous chlorine, and ozone.

5. A membrane module comprising a plurality of porous membranes, the membranes having a plurality of pores, the membranes being arranged in close proximity to one another and mounted to prevent excessive movement therebetween, and a junction connected to a header, a source of gas, and a source of a cleaning chemical for providing, from within the module, a plurality of gas bubbles entrained in a liquid flow, the liquid flow comprising the cleaning chemical, such that, in use, the liquid flow and bubbles entrained therein move past outer surfaces of the membranes to dislodge fouling materials therefrom.

6. The membrane module according to claim 5, further comprising an aerobic basin.

7. The membrane module according to claim 6, wherein the membrane module is at least partially immersed in the aerobic basin.

8. The membrane module according to claim 6, further comprising a tank separate from the aerobic basin, wherein the membrane module is at least partially immersed in the tank.

9. A method of removing fouling materials from the surface of a plurality of porous hollow fiber membranes, the method comprising:

providing a membrane module comprising a plurality of porous hollow fiber membranes, the membranes mounted and extending longitudinally in an array to form a membrane module, the membranes having a plurality of pores, the membranes being arranged in close proximity to one another and mounted to prevent excessive movement therebetween; and

providing, from within the array, a plurality of gas bubbles entrained in a substantially uniform distribution in a liquid flow, the liquid flow comprising a cleaning chemical, the gas bubbles being entrained in the liquid flow by flowing a gas and a liquid comprising a cleaning chemical into a junction connected to a header so as to cause the gas to be mixed into the liquid, the distribution being such that the gas bubbles pass substantially uniformly between each membrane in the array to, in combination with the liquid flow, scour outer surfaces of the membranes and remove accumulated solids from within the membrane module.

10. The method according to claim 9, wherein the junction is selected from the group consisting of a venturi tube, a jet, a nozzle, an ejector, an eductor, and an injector.

11. The method according to claim 9, wherein the membranes comprise porous hollow fibers, the fibers being fixed at a first end in a first header and at a second end in a second header, at least one header having one or more holes formed therein through which a gas flow or a gas and liquid flow is introduced.

12. A membrane module, the membrane module comprising:

a source of a cleaning liquid, the cleaning liquid comprising a cleaning chemical;

a source of a gas;

a first header, the first header having one or more holes formed therein through which the gas and the liquid are introduced;

a second header;

a plurality of porous hollow fiber membranes, the porous hollow fiber membranes being arranged in close proximity and mounted to prevent excessive movement therebetween, the porous hollow fiber membranes being fixed at a first end in the first header and at a second end in the second header; and

a junction, wherein the junction is connected to the first header, the source of the gas, and the source of the cleaning liquid.

13. The module according to claim 12, further comprising a partition, wherein the partition extends between the porous hollow fiber membranes, thereby partitioning the porous hollow fiber membranes into groups.

14. The module according to claim 12, wherein the partition is formed by a spacing between fiber groups.

15. The module according to claim 13, wherein the porous hollow fiber membranes are arranged in a cylindrical array and a plurality of partitions extend radially from a center of the array or are positioned concentrically within the cylindrical array.

16. A membrane module comprising a plurality of porous hollow fiber membranes and a junction connected to a first header and a source of a cleaning liquid, the cleaning liquid comprising a cleaning chemical, the fiber membranes being arranged in close proximity to one another to form a bundle and mounted to prevent excessive movement therebetween, the fiber membranes being fixed at a first end in the first header and at a second end in a second header, the first header having one or more holes formed therein through which a gas and the cleaning liquid are introduced, and the bundle having a central longitudinal passage extending a length of the bundle between the headers.

17. A membrane module comprising a plurality of porous hollow membrane fibers mounted at a first end to a first potting head and at a second end to a second potting head and extending longitudinally between the potting heads, the membranes having a plurality of pores, the membrane fibers being arranged in close proximity to one another and mounted to prevent excessive movement therebetween, the fibers being partitioned into one or more bundles at least at or adjacent to one of the potting heads so as to form a space therebetween, at least one of the potting heads having an array and a connection to a junction, wherein the junction is connected to a gas source and a source of a liquid comprising a cleaning chemical, the junction providing within the module, through a plurality of aeration openings formed in the array, a plurality of gas bubbles entrained within the liquid, such that, in use, the gas bubbles move past outer surfaces of the membrane fibers to dislodge fouling materials therefrom.

18. The membrane module according to claim 17, wherein the aeration openings are positioned to coincide with the spaces formed between the bundles.

19. The membrane module according to claim 18, wherein at least one aeration opening comprises a slot or a row comprising a plurality of holes, and wherein a bundle is located in at least one of the potting heads adjacent to the slot or row.

20. The membrane module according to claims 19, comprising at least two aeration openings, wherein a bundle is situated between the aeration openings.

21. The membrane module according to claim 19, comprising at least two bundles, wherein the slot or row is situated between the bundles.

22. The membrane module according to claim 19, wherein the holes have a diameter or an equivalent diameter averaging between about 1 mm and about 40 mm.

23. The membrane module according to claim 22, wherein the holes have a diameter or an equivalent diameter averaging between about 1.5 mm and about 25 mm.

24. The membrane module according to claim 17, wherein the fibers within the module have a packing density of between about 5 and about 70%.

25. The membrane module according to claim 24, wherein the packing density is between about 8 and about 55%.

26. The membrane module according to claim 17, wherein an inner diameter of the fibers averages between about 0.1 mm and about 5 mm.

27. The membrane module according to claim 26, wherein the inner diameter averages between about 0.25 mm and about 2 mm.

28. The membrane module according to claim 17, wherein a wall thickness of the fibers averages between about 0.05 and about 2 mm.

29. The membrane module according to claim 28, wherein the wall thickness averages between about 0.1 mm and about 1 mm.

30. A membrane bioreactor comprising:

a source of a cleaning liquid comprising a cleaning chemical;

a source of a gas;

a membrane module, the membrane module comprising a first header, the first header having one or more holes formed therein through which the gas and the liquid are introduced;

a second header; and

a plurality of porous hollow fiber membranes, the porous hollow fiber membranes being arranged in close proximity and mounted to prevent excessive movement therebetween, the porous hollow fiber membranes being fixed at a first end in the first header and at a second end in the second header, the membrane module provided with means for withdrawing a filtrate from at least one end of the fiber membranes;

a junction, wherein the junction is connected to the first header of the membrane module, the source of the gas, and the source of the cleaning liquid;

a tank having means for introducing the cleaning liquid, wherein the membrane module is positioned within the tank so as to be immersed in an activated sludge; and

means for forming the activated sludge within the tank.

31. A method of operating a membrane bioreactor, the method comprising the steps of:

providing a membrane module comprising a plurality of porous hollow membrane fibers mounted at a first end to a first potting head and at a second end to a second potting head and extending longitudinally between the potting heads, the membranes having a plurality of pores, the membrane fibers being arranged in close proximity to one another and mounted to prevent excessive movement therebetween, the fibers being partitioned into one or more bundles at least at or adjacent to one of the potting heads so as to form a space therebetween, at least one of the potting heads having an array and a connection to a junction, wherein the junction is connected to a gas source and a source of a liquid comprising a cleaning chemical, the junction providing within the module, through a plurality of aeration openings formed in the array, a plurality of gas bubbles entrained within the liquid, such that, in use, the gas bubbles move past outer surfaces of the membrane fibers to dislodge fouling materials therefrom;

providing a tank, wherein the membrane module is at least partially immersed in the tank;

introducing a feed to the tank; and

applying a vacuum to the fibers to withdraw a filtrate therefrom while periodically or continuously supplying a plurality of gas bubbles through the aeration openings to within the module such that, in use, the gas bubbles move past the outer surfaces of the membrane fibers to dislodge fouling materials therefrom.

32. The method according to claim 31, wherein the gas bubbles are entrained or mixed with a liquid flow when fed through the aeration openings.

33. The membrane bioreactor according to claim 31, wherein the membrane module is suspended vertically within the tank and a further source of aeration is provided beneath the suspended module.

34. The membrane bioreactor according to claim 33, wherein the further source of aeration comprises a group of air permeable tubes or gas distributors.

35. A membrane bioreactor comprising:

a tank having a feed inlet;

a source of oxygen for forming an activated sludge within the tank;

a source of a gas; and

a membrane module, the membrane module comprising a first header, the first header having one or more holes formed therein through which the gas and the liquid are introduced;

a second header; and

a plurality of porous hollow fiber membranes, the porous hollow fiber membranes being arranged in close proximity and mounted to prevent excessive movement therebetween, the porous hollow fiber membranes being fixed at a first end in the first header and at a second end in the second header;

a junction, wherein the junction is connected to the first header, the source of the gas, and the source of the cleaning liquid;

the membrane module positioned within the tank so as to be immersed in the sludge, and the membrane module provided with a pump for withdrawing a filtrate from at least one end of the fiber membranes.