Backwash

• US 8,268,176 B2
• Filed: 08/27/2004
• Issued: 09/18/2012
• Est. Priority Date: 08/29/2003
• Status: Active Grant

• Current Assignee: Evoqua Water Technologies LLC
• Original Assignee: Siemens Industry Incorporated (Siemens AG)
• Inventors: Johnson, Warren Thomas, Beck, Thomas William, Zha, Fufang, Lazaredes, Huw Alexander, Cao, Zhiyi
• Primary Examiner(s): Griffin, Walter D
• Assistant Examiner(s): Anderson, Denise R
• Application Number:
  US10/569,565
• Publication Number:
  US 20070007205A1
• Time in Patent Office: 2,944 Days
• Field of Search: 210/636, 210/650, 210/741, 210/637
• US Class Current: 210/636
• CPC Class Codes: B01D 2321/185 Aeration
• CPC Class Codes: B01D 61/14 Ultrafiltration; Microfiltration
• CPC Class Codes: B01D 63/02 Hollow fibre modules
• CPC Class Codes: B01D 65/08 Prevention of membrane fouling or of concentration polarisation

Abstract

A method of backwashing a membrane filtration module (4), said module (4) including one or more membranes (5) located in a feed-containing vessel (3), the membranes (5) having a permeable wall which is subjected to a filtration operation wherein feed containing contaminant matter is applied to one side of the membrane wall and filtrate is withdrawn from the other side of the membrane wall, the method including: removing liquid from the feed-containing vessel (3) until the level of liquid in the feed-containing vessel (3) falls to a first level (L2) below an upper level of the membranes; suspending the filtration operation; performing a liquid backwash of the membrane wall until liquid level within the feed-containing vessel (3) rises to a second predetermined level (L1) above said first level; aerating the membrane surface with gas bubbles to dislodge fouling materials therefrom; performing a sweep or drain down of the feed-containing vessel (3) to remove the liquid containing the dislodged contaminant matter; and recommencing the filtration operation.

Claims

1. A method of backwashing one or more membranes in a vessel, the method comprising:

removing liquid to be treated from the vessel until a level of the liquid falls to a first level within the vessel below an upper level of the one or more membranes, wherein the removal of liquid to be treated is at least partially accomplished by a filtration operation;

suspending the removal of the liquid to be treated from the vessel when the level of the liquid to be treated falls to the first level;

performing a liquid backwash of the one or more membranes when the first level is reached by the removal of the liquid to be treated from the vessel until the level of the liquid collected in the vessel comprising backwashed liquid is at a predetermined level above said first level;

aerating a membrane surface of the one or more membranes; and

removing liquid containing fouling materials dislodged from the membrane surface from the vessel;

wherein the predetermined level provides sufficient liquid in the vessel to immerse an upper header of the one or more membranes during the aerating of the membrane surface.

2. The method according to claim 1, wherein the step of aerating the membrane surface comprises aerating the one or more membranes until a level of liquid comprising backwashed liquid within the vessel rises to at least the upper level of the one or more membranes.

3. The method according to claim 1, further comprising a step of suspending a flow of the liquid to be treated into the vessel prior to performing the step of removing liquid to be treated.

4. The method according to claim 1, wherein the step of aerating the membrane surface is commenced before performing the step of removing liquid to be treated, and is performed until the step of removing liquid containing fouling materials is performed.

5. The method according to claim 1, further comprising a step of applying a pressurized gas to the liquid to be treated during the filtration operation.

6. The method according to claim 1, wherein the step of removing liquid to be treated comprises draining the liquid from the vessel.

7. The method according to claim 1, wherein the step of removing liquid to be treated comprises pumping the liquid from the vessel.

8. The method according to claim 1, further comprising a step of returning liquid to be treated that was removed from the vessel back into the vessel.

9. The method according to claim 1, further comprising a step of introducing into the vessel liquid to be treated which has been removed from a second vessel.

10. The method according to claim 1, wherein the step of removing liquid to be treated comprises maintaining a substantially constant transmembrane pressure across the one or more membranes.

11. The method according to claim 10, wherein the transmembrane pressure is maintained at or below a predetermined value.

12. The method according to claim 1, further comprising a step of monitoring the transmembrane pressure across said one or more membranes.

13. The method according to claim 12, wherein the step of monitoring the transmembrane pressure is performed while performing the step of removing liquid to be treated.

14. The method according to claim 12, further comprising a step of determining the level of liquid in the vessel.

15. The method of claim 1, wherein the predetermined level is the same as a level of liquid in the vessel prior to removing liquid to be treated.

16. The method of claim 1, wherein aeration of the membrane surface is commenced while performing the liquid backwash.

17. The method of claim 1, wherein the membranes are non-vertically oriented.

18. The method of claim 1, wherein the predetermined level is below the upper level of the one or more membranes.

19. A method of backwashing a membrane filtration module in a vessel, said module including one or more membranes, the method comprising:

removing liquid from the vessel until a level of the liquid falls to a first level within the vessel below an upper level of the one or more membranes, wherein the removal of liquid from the vessel is at least partially accomplished by a filtration operation;

suspending the removal of the liquid from the vessel when the level of the liquid falls to the first level;

performing a liquid backwash of the one or more membranes, after removing the liquid from the vessel, until the level of liquid in the vessel rises to a predetermined level above the first level;

initiating aeration of the membrane surfaces of the one or more membranes after the liquid backwash is completed; and

removing liquid containing fouling materials dislodged from the membrane surfaces from the vessel, after aerating of the membrane surfaces is completed;

wherein the acts of removing liquid from the vessel, performing a liquid backwash, aerating membrane surfaces, and removing liquid containing fouling materials are performed within a single cycle, and wherein the predetermined level provides sufficient liquid in the vessel to immerse an upper header of the membrane filtration module during the aeration of the membrane surfaces.

20. The method of claim 19, wherein the first level is located above a lower header of the membrane module and below an upper header of the membrane module.

21. The method of claim 19, wherein the predetermined level is below the upper level of the one or more membranes.

22. The method of claim 19, wherein the step of performing a liquid backwash introduces less fluid into the vessel than the step of removing liquid from the vessel removes.

23. A method of treating water, comprising:

introducing water to be treated into a vessel;

filtering the water to be treated through membranes immersed in the water;

reducing a level of the water to be treated to a first level within the vessel below an upper level of the membranes, wherein the reduction of the level of the water to be treated is at least partially accomplished by a filtration operation;

commencing a backwash of the membranes when the first level is reached by the reduction of the level of water to be treated, the backwash continuing until a level of a water solution comprising backwashed liquid in the vessel rises to a second predetermined level above the first level; and

aerating the membranes;

wherein the second predetermined level provides sufficient liquid in the vessel to immerse an upper header of the membranes during the aeration of the membranes.

24. The method according to claim 23, further comprising a step of removing the water solution in the vessel after aerating the membranes.