Aerated immersed membrane system

• US 20010027951A1
• Filed: 05/03/2001
• Published: 10/11/2001
• Est. Priority Date: 10/09/1998
• Status: Active Grant

• Current Assignee: Zenon Technology Partnership
• Original Assignee: Zenon Environmental Incorporated
• Inventors: Gungerich, Christian, Cote, Pierre Lucien, Guibert, Denis, Rabie, Hamid, Langerak, Robert
• Granted Patent: US 6,656,356 B2
• Time in Patent Office: Days
• US Class Current: 210/636
• CPC Class Codes: B01D 2313/025 Specific membrane holders
• CPC Class Codes: B01D 2313/21 Specific headers, end caps
• 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 2321/2058 by vibration of the membrane, e.g. with an actuator
• CPC Class Codes: B01D 61/18 Apparatus therefor
• 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 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: C02F 1/444 by ultrafiltration or microfiltration
• CPC Class Codes: C02F 1/74 with air aeration of stretches of water C02F7/00

Abstract

An element of immersed, suction driven, filtering membranes has a plurality of hollow fiber membranes suspended between upper and lower headers. The lower header is movable between a first position in which the fibers are substantially elongated and second position in which the two headers are closer to each other by between 1 and 4% of the un-potted length of the membranes. The weight of the lower header is sufficient to keep the lower header in the first position in substantially quiescent water while allowing the lower header to rise to the second position in upwardly flowing water. Aerators are mounted generally below the elements and supply scouring bubbles to each element at a higher rate and then at a rate less than one half of the higher rate in repeated cycles. The cycles are preferably between 10 seconds and 60 seconds in duration. The lower header rises to the second position when bubbles are supplied at the higher rate and falls to the first position when bubbles are supplied at the lower rate.

Claims

1. An element of filtering hollow fibre membranes comprising;

(a) a fixed upper header;

(b) a lower header;

(c) a plurality of hollow fibre membranes attached to and suspended between the headers, the hollow fibre membranes having each at least one open end and having each an outer surface, the outer surface of the open ends of the membranes connected to at least one header with a water impermeable connection; and

,

(d) one or more permeate channels in at least one of the headers in fluid communication with the interior of the hollow fibre membranes for collecting permeate,

wherein,

(e) the lower header is movable between a first position in which the fibres are substantially elongated and second position in which the headers are a selected distance closer together; and

,

(f) the weight of the lower header is sufficient to keep the lower header in the first position in substantially quiescent water while allowing the lower header to rise to the second position in upwardly flowing water or water and bubbles.

2. The element of

claim 1

wherein the selected distance is 0.1% to 5% of the un-potted length of the hollow fibres.

5. The modules or elements of any of claims 1 through 4 inclusive further comprising aerators mounted below the elements and operable to supply scouring bubbles to each element at a higher rate and then at a rate less than one half of the higher rate in repeated cycles.

6. The invention of

claim 5

wherein the cycles are between 10 seconds and 60 seconds in duration.

3. A module of filtering hollow fibre membranes comprising;

(a) one or more elements, each element having,

(i) an upper header;

(ii) a lower header;

(iii) a plurality of hollow fibre membranes attached to and suspended between the headers, the hollow fibre membranes having each at least one open end and having each an outer surface, the outer surface of the open ends of the membranes connected to at least one header with a water impermeable connection; and

,

(iv) one or more permeate channels in at least one of the headers in fluid communication with the interior of the hollow fibre membranes for collecting permeate;

and,

(b) a frame for,

(i) fixedly securing the upper header;

(ii) restraining the lower header within a selected range of movement between a first position in which the fibres are substantially elongated and second position in which the headers are a selected distance closer together,

wherein,

(c) the weight of the lower header is sufficient to keep the lower header in the first position in substantially quiescent water while allowing the lower header to rise to the second position in upwardly flowing water or water and bubbles.

4. The module of

claim 3

wherein the selected distance is 0.1% to 5% of un-potted length of the hollow fibre membranes.

17. The module of

claim 3

having a plurality of elements placed side by side but horizontally spaced apart by at least one third of the width of the headers measured in the direction of the horizontal spacing.

18. The invention of

claim 17

wherein the horizontal spacing is variable.

19. The module of

claim 3

having a plurality of elements placed side by side but spaced apart and having the lower headers of the elements fixed together so that they move upwards or downwards together and may not rotate relative to each other.

7. A process for treating water with filtering hollow fibre membranes comprising;

(a) providing a plurality of elements of filtering hollow fibre membranes each having,

(i) an upper header;

(ii) a lower header;

(iii) a plurality of hollow fibre membranes attached to and suspended between the headers, the hollow fibre membranes having each at least one open end and having each an outer surface, the outer surface of the open ends of the membranes connected to at least one header with a water impermeable connection; and

,

(iv) one or more permeate channels in at least one of the headers in fluid communication with the interior of the hollow fibre membranes for collecting permeate,

wherein (v) each element is a rectangular skein of hollow fibres between 18 and 40 mm thick and (vi) adjacent elements are horizontally spaced apart by at least one third of the width of the headers measured in the direction of the horizontal spacing;

(b) applying suction to the interior of the hollow fibre membranes to withdraw a filtered permeate;

(c) providing a supply of scouring bubbles from below the elements while applying suction to the interior of the hollow fibre membranes; and

,

(d) varying the supply of scouring bubbles form a higher rate to a rate less than one half of the higher rate in repeated cycles.

8. The process of

claim 7

wherein the distance between the headers is between 95% and 99.9% of the un-potted length of the hollow fibre membranes for at least a substantial part of the time during which bubbles are supplied at the higher rate.

9. The process of claims 7 or 8 wherein the cycles are between 10 seconds and 60 seconds in duration.

10. The process of

claim 9

wherein the higher flow rate has a superficial velocity of between 0.013 m/s and 0.15 m/s.

11. A process for treating water with filtering hollow fibre membranes comprising;

(a) providing one or more elements of filtering hollow fibre membranes each having,

(i) an upper header;

(ii) a lower header;

(iii) a plurality of hollow fibre membranes attached to and suspended between the headers, the hollow fibre membranes having each at least one open end and having each an outer surface, the outer surface of the open ends of the membranes connected to at least one header with a water impermeable connection; and

,

(iv) one or more permeate channels in at least one of the headers in fluid communication with the interior of the hollow fibre membranes for collecting permeate;

(b) applying suction to the interior of the hollow fibre membranes to withdraw a filtered permeate;

(c) providing a supply of scouring bubbles from below the elements while applying suction to the interior of the hollow fibre membranes; and

,

(d) moving at least one header while applying suction to the interior of the hollow fibre membranes between a first position in which the fibres are substantially elongated and a second position in which the headers are a selected distance closer together.

12. The process of

claim 11

wherein 4 the selected distance is 0.1% to 5% of fibre length.

13. The process of claims 11 or 12 wherein the bubbles are supplied at a higher rate and then at a rate less than one half of the higher rate in repeated cycles.

14. The process of

claim 13

wherein the cycles are between 10 seconds and 60 seconds in duration.

15. The process of

claim 14

wherein the lower header moves upwards when bubbles are supplied at the higher rate and moves downwards when bubbles are supplied at the lower rate.

16. The process of

claim 13

wherein the higher flow rate has a superficial velocity of between 0.013 m/s and 0.15 m/s.