Chemical clean for membrane filter

• US 9,675,938 B2
• Filed: 04/28/2006
• Issued: 06/13/2017
• Est. Priority Date: 04/29/2005
• Status: Active Grant

• Current Assignee: Evoqua Water Technologies LLC
• Original Assignee: Evoqua Water Technologies LLC
• Inventors: Zha, Fufang, Cao, Zhiyi
• Primary Examiner(s): Menon, Krishnan S
• Application Number:
  US11/912,859
• Publication Number:
  US 20080203017A1
• Time in Patent Office: 4,064 Days
• Field of Search: 210321, 210636, 210749, 210106
• CPC Class Codes: B01D 2321/04 Backflushing
• CPC Class Codes: B01D 2321/16 Use of chemical agents
• CPC Class Codes: B01D 61/22 Controlling or regulating
• CPC Class Codes: B01D 65/02 Membrane cleaning or sterilisation ; Membrane regeneration
• CPC Class Codes: C02F 1/444 by ultrafiltration or microfiltration
• CPC Class Codes: C02F 2303/16 Regeneration of sorbents, filters

Abstract

A method of cleaning a porous polymeric membrane having a feed side and a permeate side including the steps of introducing a fluid containing a cleaning agent to the permeate side of a membrane allowing the cleaning agent to contact the permeate side of the membrane for a predetermined time, and contact the pores of the membrane, or introducing a fluid containing a cleaning agent to the feed side of a membrane; applying a transmembrane pressure to force the fluid containing the cleaning agent from the feed side to the permeate side of the membrane; allowing the cleaning agent to contact the permeate side of the membrane for a predetermined time, and contact the pores of the membrane. Preferably a concentration gradient between the feed side fluid and the lumen side fluid containing the cleaning agent causes cleaning agent to diffuse into the feed side fluid. Pressure may be applied to the fluid containing a cleaning agent to dislodge, where present, dissolved and undissolved solid from the membrane pores. The pressure may be applied in a pulsed fashion, and can be by way of compressed air at a pressure not more than the membrane'"'"'s bubble point. The methods of the present invention may be preceded by, or followed with a backwash.

Claims

1. A method of cleaning a porous polymeric membrane having a feed side and a permeate side comprising:

providing a liquid on the feed side of the membrane;

reducing a feed side volume of the liquid by filtration;

suspending the filtration and the reduction of the feed side volume when the feed side volume is less than half of a feed side liquid holding volume and a level of the liquid is above a lower potting of the membrane;

introducing a fluid containing a cleaning agent to the permeate side of the membrane subsequent to the suspension of the filtration and the reduction of the feed side volume;

contacting the permeate side and pores of the membrane with the fluid containing the cleaning agent under static head pressure for a predetermined time of at least 30 seconds;

removing the fluid containing the cleaning agent from the permeate side of the membrane; and

resuming filtration.

3. The method of claim 1, further including applying pressure to the fluid containing the cleaning agent on the permeate side of the membrane.

4. The method of claim 3, wherein the pressure is applied in a pulsed fashion.

5. The method of claim 3, wherein the membrane has a bubble point and wherein applying pressure to the fluid containing the cleaning agent comprises applying compressed air at a pressure not more than the membrane'"'"'s bubble point to the fluid containing the cleaning agent.

6. The method of claim 1, further comprising backwashing the membrane after the suspending of the filtration and the reduction of the feed side volume and before introducing the fluid containing the cleaning agent to the permeate side of the membrane.

7. The method of claim 1, further comprising backwashing the membrane subsequent to removing the fluid containing the cleaning agent and prior to the resumption of filtration.

8. The method of claim 1, wherein the introduction of the fluid containing the cleaning agent to the permeate side of the membrane subsequent to the suspension of the filtration and the reduction of the feed side volume, the contacting of the permeate side and the pores of the membrane with the fluid containing the cleaning agent under static pressure for a predetermined time, and the removal of the fluid containing the cleaning agent from the permeate side of the membrane are repeated in cycles prior to the recommencement of filtration.

9. The method of claim 1, wherein the porous polymeric membrane is part of one of a pressurized membrane filtration and an immersed membrane filtration system.

10. The method of claim 1, wherein the membrane is selected from a microfiltration, ultrafiltration, or nanofiltration membrane.

11. The method of claim 1, wherein the membrane is a flatsheet membrane.

12. The method of claim 1, wherein the membrane is a hollow fiber membrane having a lumen side, the lumen side being the permeate side, and a module or shell side, the module or shell side being the feed side.

13. The method of claim 12, performed upon a plurality of hollow fiber membranes housed inside a module housing.

14. The method of claim 13, wherein the plurality of the membranes is arranged in aligned bundles, creating a plurality of lumen spaces inside the hollow fibers and a contiguous space on the outer or shell side of the hollow fibers and wherein the lumens are arranged so that filtered fluid accumulates therein and is passed from the plurality of lumens into a combined filtration stream.

15. The method of claim 1, wherein the fluid is water.

16. The method of claim 14, wherein the fluid containing the cleaning agent is introduced to the lumens of the hollow fiber membranes.

17. The method of claim 1, wherein the fluid containing the cleaning agent is retained in the permeate side of the membrane without applied pressure.

18. The method of claim 1, wherein the fluid containing the cleaning agent is retained in the permeate side of the membrane with pressure approximately equal to a static head pressure.

19. The method of claim 1, wherein the cleaning agent comprises one of a dissolved oxidative agent and a dissolved reductive agent.

20. The method of claim 1, wherein the predetermined time is sufficient for the cleaning agent to diffuse into the reduced feed side volume of the liquid.

21. The method of claim 20, further comprising pushing the cleaning agent diffused into the reduced feed side volume of the liquid back into the permeate side of the membrane.

22. The method of claim 1, wherein the predetermined time is between 30 seconds and 20 minutes.

23. The method of claim 12, further comprising venting the lumen side of the membrane during the act of contacting the permeate side and pores of the membrane with the fluid containing the cleaning agent.

2. A method of cleaning a hollow fiber porous polymeric membrane having a feed side and a permeate side comprising:

providing a feed side fluid in contact with the feed side of the membrane;

introducing a fluid containing a cleaning agent to the permeate side of the membrane;

contacting the permeate side and the pores of the membrane with the cleaning agent;

providing for the cleaning agent to diffuse into and through the membrane pores to the feed side fluid, the diffusion of the cleaning agent driven only by a concentration gradient; and

discharging the fluid containing the cleaning agent.