Apparatus for withdrawing permeate using an immersed vertical skein of hollow fibre membranes

• US 20030141248A1
• Filed: 06/25/2002
• Published: 07/31/2003
• Est. Priority Date: 08/11/1995
• Status: Active Grant

• Current Assignee: Zenon Technology Partnership
• Original Assignee: Henry Behmann, Mailvaganam Mahendran, Steven Pedersen, Wayne Henshaw
• Inventors: Behmann, Henry, Mahendran, Mailvaganam, Pedersen, Steven, Henshaw, Wayne
• Granted Patent: US 6,682,652 B2
• Time in Patent Office: Days
• 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 2321/12 Use of permeate
• CPC Class Codes: B01D 2321/185 Aeration
• CPC Class Codes: B01D 2321/2066 Pulsated flow
• CPC Class Codes: B01D 61/18 Apparatus therefor
• CPC Class Codes: B01D 61/20 Accessories; Auxiliary operations
• CPC Class Codes: B01D 63/02 Hollow fibre modules
• CPC Class Codes: B01D 63/021 Manufacturing thereof
• CPC Class Codes: B01D 63/022 Encapsulating hollow fibres
• CPC Class Codes: B01D 63/0222 using centrifugal forces
• CPC Class Codes: B01D 63/023 Encapsulating materials
• CPC Class Codes: B01D 63/0231 using supporting structures, e.g. filaments for weaving mats
• CPC Class Codes: B01D 63/026 Wafer type modules or flat-surface type modules
• CPC Class Codes: B01D 63/027 Twinned or braided type modules
• CPC Class Codes: B01D 63/04 comprising multiple hollow fibre assemblies
• 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: C02F 1/444 by ultrafiltration or microfiltration
• CPC Class Codes: C02F 3/1273 : Submerged membrane bioreactors
• CPC Class Codes: Y02W 10/10 : Biological treatment of water, waste water, or sewage
• CPC Class Codes: Y10S 264/48 : Processes of making filters

Abstract

An apparatus is described for withdrawing filtered permeate from a substrate contained in a reservoir at ambient pressure. The apparatus includes a plurality of membrane assemblies. Each assembly has a plurality of hollow fiber filtering membranes, immersed in the reservoir, at least one permeating header with the membranes sealingly secured therein, and a permeate collector to collect the permeate sealingly connected to the at least one permeating header and in fluid communication with lumens of the membranes. The membranes of each assembly extend generally vertically upwards from a first header during permeation. One or more sources of suction are provided in fluid communication with the lumens of the membranes of each assembly through the permeate collectors and apply sufficient suction to withdraw permeate from the lumens of the membranes. An aeration system for discharging bubbles assists in keeping the membranes clean. In other aspects, a method of removing fouling materials from the surface of a plurality of porous membranes includes providing, from within a membrane module, gas bubbles in a uniform distribution relative to the membranes. The bubbles move past the surfaces of the membranes to dislodge fouling materials from them. The membranes are arranged in close proximity to one another and mounted to prevent excessive movement.

Claims

1. An apparatus for withdrawing filtered permeate from a substrate, including

a reservoir containing substrate at ambient pressure;

a plurality of membrane assemblies, each assembly having,

a plurality of hollow fiber filtering membranes, immersed in the reservoir;

at least one permeating header having the membranes sealingly secured therin; and

,

a permeate collector to collect the permeate, sealingly connected to the at least one permeating header and in fluid communication with lumens of the membranes;

one or more sources of suction in fluid communication with the lumens of the membranes of each assembly through the permeate collectors of each assembly and operable to apply sufficient suction to withdraw permeate from the lumens of the membranes; and

an aeration system for discharging bubbles to assist in keeping the membranes clean, the aeration system including a pipe with holes for discharging bubbles which contact the membranes, pipe oriented generally verically above the first header and located within the plurality of membranes,

wherein the membranes of each assembly extend generally vertically upwards from a first header during permeation.

2. The apparatus of claim 1 wherein the first header is a permeating header.

3. The apparatus of claim 1 wherein the pipe is embedded in the first permeating header and the membranes are secured in the first permeating header around the pipe.

4. The apparatus of claim 1 wherein the holes in the pipe include holes spaced around the circumference of the pipe and holes spaced along the length of the pipe.

5. The apparatus of claim 1 wherein the first header is circular in plan view and the pipe is located on a vertical line through the center of the first header.

6. An apparatus for withdrawing filtered permeate from a substrate, including

a reservoir containing substrate at ambient pressure;

a plurality of membrane assemblies, each assembly having,

a plurality of hollow fiber filtering membranes immersed in the reservoir;

at least one permeating header having the membranes sealingly secured therein; and

,

a permeate collector to collect the permeate, sealingly connected to the at least one permeating header and in fluid communication with lumens of the membranes;

one or more sources of suction in fluid communication with the lumens of the membranes of each assembly through the permeate collectors of each assembly and operable to apply sufficient suction to withdraw permeate from the lumens of the membranes; and

,

an aeration system having openings of air passages at first ends of through-passages, the openings located to discharge bubbles which contact the membranes, the through-passages passing through the first header,

wherein the membranes of each assembly extend generally vertically upwards from a first header during permeation;

7. The apparatus of claim 6 wherein second ends of the through-passages are in communication with a source of pressurized air.

8. The apparatus of claim 6 wherein the openings are located to discharge bubbles directly into the substrate between the membranes.

9. The apparatus of claim 6 wherein the first header is a permeating header.

10. An apparatus for withdrawing filtered permeate from a substrate, including

a reservoir containing substrate at ambient pressure;

a plurality of membrane assemblies, each assembly having,

a plurality of hollow fiber filtering membranes, immersed in the reservoir;

at least one permeating header having the membranes sealingly secured therein; and

,

a permeate collector to collect the permeate, sealingly connected to the at least one permeating header and in fluid communication with lumens of the membranes;

one or more sources of suction in fluid communication with the lumens of the membranes of each assembly through the permeate collectors of each assembly and operable to apply sufficient suction to withdraw permeate from the lumens of the membranes; and

, an aeration system for discharging lines of bubbles from openings near the first headers, the lines of bubbles separated by 30 fibres or less,

wherein each assembly has at least a first header and the membranes extend generally vertically upwards from the first header during permeation.

11. An apparatus for withdrawing filtered permeate from a substrate, including a reservoir containing substrate at ambient pressure;

a plurality of membrane assemblies, each assembly having,

a plurality of hollow fiber filtering membranes, immersed in the reservoir;

at least one permeating header having the membranes sealingly secured therein; and

,

a permeate collector to collect the permeate, sealingly connected to the at least one permeating header and in fluid communication with lumens of the membranes; and

,

one or more sources of suction in fluid communication with the lumens of the membranes of each assembly through the permeate collectors of each assembly and operable to apply sufficient suction to withdraw permeate from the lumens of the membranes,

each assembly having at least a first header which is elongated in plan view, the membranes extending generally vertically upwards from the first header during permeation, the first headers of the assemblies being located in a spaced side by side relationship; and

,

an aeration system having through-passages for discharging lines of bubbles between and at the sides of the elements from openings located near the first headers and, there being n+1 lines of bubbles for n elements.

12. The apparatus of claim 11 wherein, the lines of bubbles are separated by 30 fibres or less.

13. An apparatus for withdrawing filtered permeate from a substrate, comprising:

a header having a first face and a second face;

a receptacle for collecting permeate, the receptacle being in fluid communication with the second face of the header and having a permeate outlet;

a plurality of hollow fibre membranes, the hollow fibre membranes sealingly secured in the header and protruding from the first face of the header, and having ends open to the receptacle for collecting permeate such that a portion of the substrate drawn into the lumens of the fibres as permeate may flow into the receptacle; and

,

a pipe with holes for discharging bubbles, the holes located near the first face of the header, the pipe protruding from the first face of the header from a location within or adjacent to the plurality of membranes.

14. The apparatus of claim 13 wherein the pipe protrudes from the first face of the header from a location within the plurality of membranes.

15. The apparatus of claim 13 wherein the pipe is located axially within a plurality of membranes that surround the pipe.

16. The apparatus of claim 13 wherein the membranes are generally parallel to each other and the pipe is generally parallel to the membranes.

17. The apparatus of claim 13 wherein the holes are located at various locations around the circumference of the pipe.

18. The apparatus of claim 13 wherein the pipe has holes for discharging bubbles at a plurality of locations along the length of the pipe.

19. The apparatus of claim 13 wherein the holes are located in arms extending outwards from the pipe.

20. The apparatus of claim 16 wherein the first face of the header is circular and the pipe protrudes from the center of the first face of the header.

21. The apparatus of claim 20 wherein the pipe is secured in and extends through the header.

22. The apparatus of claim 16 wherein the membranes and pipe protrude perpendicular to the first face.

23. A system for withdrawing filtered permeate from a substrate, comprising:

a reservoir containing a substrate at ambient pressure;

an apparatus of claim 13 immersed in the substrate such that the first face of the header is generally horizontal and the membranes extend generally vertically upwards from the first face of the header;

a source of suction in fluid communication with the permeate outlet and operable to apply sufficient suction to withdraw permeate from the lumens of the membranes; and

,

an aeration system for supplying a pressurized gas to the pipe.

24. The use of an apparatus according to claim 13 to filter permeate from a substrate at ambient pressure.

25. The use according to claim 24 wherein the membranes extend along their entire length generally vertically, and bubbles discharged from said holes scrub the generally vertical membranes.

26. A process for withdrawing filtered permeate from a substrate comprising the steps of:

providing a reservoir containing a substrate at ambient pressure;

providing an apparatus according to claim 13;

placing the apparatus in the substrate such that the first face of the header is generally horizontal and the membranes extend generally vertically upwards from the first face of the header;

applying suction to the permeate outlet to withdraw permeate from the lumens of the membranes; and

,

supplying a pressurized gas to the pipe.

27. A method of removing fouling materials from the surface of a plurality of porous membranes arranged in a membrane module by providing, from within the module, by means other than gas passing through the pores of said membranes, gas bubbles in a uniform distribution relative to the porous membrane array such that said bubbles move past the surfaces of said membranes to dislodge fouling materials therefrom, said membranes being arranged in close proximity to one another and mounted to prevent excessive movement therebetween.

28. A method according to claim 27 including the step of moving said membranes by means of said gas bubbles.

29. A method according to claim 28 including mounting said membranes relative to one another so as to produce a rubbing effect between said membranes when moved.

30. A method according to claim 27 wherein the porous membranes comprise hollow fibre membranes.

31. A method according to claim 27 including the step of providing gas bubbles from within the module by means of gas distribution holes or openings in a pot used to mount the fibre membranes.

32. A method according to claim 27 including the step of providing gas bubbles from within the module by means of at least one porous tube located within the module.

33. A method according to claim 27 including the step of providing gas bubbles from within the module by means of a tube or tubes positioned to output gas within the module.

34. A method according to claim 33 wherein the tubes are in the form of a comb of tubes containing holes which are located within the module.

35. A membrane module comprising a plurality of porous membranes, said 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 said membranes, gas bubbles such that, in use, said bubbles move past the surfaces of said membranes to dislodge fouling materials therefrom.

36. A membrane module according to claim 35 wherein said porous membranes are arranged to be moved by means of said gas bubbles.

37. A membrane module according to claim 36 wherein said porous membranes are mounted relative to one another so as to produce a rubbing effect between said membranes when moved.

38. A membrane module according to claim 35 wherein the porous membranes comprise hollow fibre membranes.

39. A membrane module according to claims 35 wherein the means for providing gas bubbles from within the module includes gas distribution holes or openings in a pot used to mount the membranes.

40. A membrane module according to claim 35 wherein the means for providing gas bubbles from within the module includes at least one porous tube located within the module.

41. A membrane module according to claim 35 wherein the means for providing gas bubbles from within the module includes a tube or tubes positioned to output gas within the module.

42. A membrane module according to claim 41 wherein the tubes are in the form of a comb of tubes containing holes which sit within the module.

43. A membrane module according to any one of claim 35 wherein the membranes comprise porous hollow fibres, the fibres being fixed at each end in a header, a lower header having a plurality of holes formed therein through which gas is introduced to provide the gas bubbles.

44. A membrane module according to claim 43 wherein the fibres are sealed at the lower end and open at their upper end to allow removal of filtrate.

45. A membrane module comprising a plurality of porous hollow membrane fibres extending longitudinally between and mounted at each end to a respective potting head, said membrane fibres being arranged in close proximity to one another and mounted to prevent excessive movement therebetween, one of said potting heads having a distributed array of aeration holes formed therein and said fibres being substantially uniformly mounted in said one potting head relative to said aeration holes.

46. A membrane module according to claim 45 wherein said aeration holes are sized and located such that bubbles, formed by gas passing therethrough when the module is immersed in a liquid, pass substantially uniformly between each membrane.

47. A membrane module according to claim 45 wherein said porous membranes are arranged to be moved by means of said gas bubbles.

48. A membrane module according to claim 47 wherein said porous membranes are mounted relative to one another so as to produce a rubbing effect between said membranes when moved.

54. A filtration system including a membrane module according to claim 45 wherein said membrane module is positioned vertically in a tank containing feed liquid to be filtered, and including means to apply a transmembrane pressure to said fibres in said array to cause filtrate to pass through pores in said fibres and means to supply continually or intermittently a supply of gas to said means for providing gas bubbles such that said gas bubbles move upwardly and uniformly between said fibres to scour the outer surfaces thereof.

55. A filtration system according to claim 54 wherein a backwash is used in conjunction with the scouring process to assist solids removal from the membrane pores and outer surface of the membranes.

49. A method of removing accumulated solids from the surface of a plurality of porous hollow fibre membranes mounted and extending longitudinally in an array to form a membrane module, said membranes being arranged in close proximity to one another and mounted to prevent excessive movement therebetween, the method comprising the steps of providing, from within said array, by means other than gas passing through the pores of said membranes, uniformly distributed gas bubbles, said distribution being such that said bubbles pass substantially uniformly between each membrane in said array to scour the surface of said membranes and remove accumulated solids from within the membrane module.

50. A method according to claim 49 including the step of moving said membranes by means of said gas bubbles.

51. A method according to claim 50 including mounting said membranes relative to one another so as to produce a rubbing effect between said membranes when moved.

52. A method according to claim 49 wherein said membranes are mounted vertically to form said array and said bubbles pass generally parallel to the longitudinal extent of said fibres.

53. A method according to claim 52 wherein said uniformly distributed gas bubbles are provided at the lower end of the array.

56. A method of removing accumulated solids from the outer surface of a plurality of porous hollow fibre membranes mounted and extending longitudinally in an array to form a membrane module, said membranes being arranged in close proximity to one another and mounted to prevent excessive movement therebetween, the method comprising the steps of providing, from within said array, by means other than gas passing through the pores of said membranes, gas bubbles, said gas bubbles generating movement of said membranes by passing therebetween and causing removal of said accumulated solids.

57. A method according to claim 56 including mounting said membranes relative to one another so as to produce a rubbing effect between said membranes when moved.