METHOD OF CLEANING MEMBRANES

• US 20110056522A1
• Filed: 06/11/2010
• Published: 03/10/2011
• Est. Priority Date: 06/11/2009
• Status: Active Grant

• Current Assignee: Evoqua Water Technologies LLC
• Original Assignee: Evoqua Water Technologies LLC
• Inventors: Zauner, Peter, Zha, Fufang
• Granted Patent: US 8,956,464 B2
• Time in Patent Office: Days
• US Class Current: 134/27
• CPC Class Codes: B01D 2321/168 Use of other chemical agents
• CPC Class Codes: B01D 65/02 Membrane cleaning or sterilisation ; Membrane regeneration

Abstract

Methods for cleaning polymeric microfiltration or ultrafiltration membranes. The membrane may be contacted with a first cleaning solution including at least one oxidising agent. A second cleaning solution including at least one reducing agent may then be introduced to the membrane and first cleaning solution. The oxidising and reducing agents may undergo a neutralisation reaction to form an oxidation-neutral mixed cleaning solution. The membrane may be simultaneously cleaned during the neutralisation reaction.

Claims

1. A method for cleaning a porous polymeric membrane, comprising:

introducing a first cleaning solution including an oxidising agent to a tank containing the membrane;

contacting at least a portion of the membrane with the first cleaning solution for a first time period;

introducing a second cleaning solution including a reducing agent to the tank containing the membrane and the first cleaning solution after the first time period has elapsed to neutralize an oxidizing residual of the first cleaning solution and to form a mixed cleaning solution containing an acid species;

contacting at least a portion of the membrane with the mixed cleaning solution containing the acid species for a second time period; and

discharging the mixed cleaning solution from the tank after the second time period has elapsed.

2. The method according to claim 1, wherein said membrane is a hollow-fibre membrane.

3. The method according to claim 1, wherein said oxidising agent is a chlorine-based oxidising agent selected from the group consisting of chlorine, hypochlorites, chlorites, chlorates, perchlorates, chlorine dioxide and chloramines.

4. The method according to claim 3, wherein said oxidising agent is sodium hypochlorite, chlorine dioxide or monochloramine.

5. The method according to claim 1, wherein said reducing agent is selected to neutralise the oxidising residual from said oxidising agent.

6. The method according to claim 5, wherein said reducing agent is selected from the group consisting of bisulphites, metabisulfites, sulphites and thiosulfates.

7. The method according to claim 6, wherein said reducing agent is sodium metabisulfite, sodium thiosulphate, or sodium bisulfite.

8. The method according to claim 1, wherein said second cleaning solution further includes an enhancing agent.

9. The method according to claim 8, wherein said enhancing agent is a surfactant or a chelating agent selected from the group consisting of polycarboxylic acids and salts thereof.

10. The method according to claim 8, wherein said enhancing agent is citric acid or a salt thereof, ethylenediaminetetraacetic acid (EDTA) or a salt thereof, or oxalic acid or a salt thereof.

11. The method according to claim 1, wherein a concentration of said oxidising agent in said first cleaning solution is between 0.01 wt % and 2 wt %.

12. The method according to claim 11, wherein the concentration of said oxidising agent in said first cleaning solution is approximately 0.1 wt %.

13. The method according to claim 11, wherein a concentration of said reducing agent is between 0.01 wt % and 2 wt %.

14. The method according to claim 13, wherein the concentration of said reducing agent is approximately 0.15 wt %.

15. The method according to any claim 8, wherein a concentration of said enhancing agent is between 0.01 wt % and 1.0 wt %.

16. The method according to claim 15, wherein the concentration of said enhancing agent is 0.5 wt %.

17. The method according to claim 1, wherein the first time period is at least about three hours, and wherein the second time period is at least about two hours.

18. The method according to claim 1, wherein said membrane is cleaned at ambient temperature and pressure.

19. The method according to claim 1, further comprising recirculating at least one of the first cleaning solution and the mixed cleaning solution in the tank.

20. The method according to claim 1, further comprising filtering at least one of the first cleaning solution and the mixed cleaning solution through the membrane.

21. The method according to claim 1, further comprising soaking the membrane in at least one of the first cleaning solution and the mixed cleaning solution.

22. The method according to claim 1, further comprising air scouring the membrane while contacting the membrane with at least one of the first cleaning solution and the mixed cleaning solution.

23. The method according to claim 1, wherein the second solution is introduced while backwashing the membrane.

24. The method according to claim 1, further comprising adjusting a pH level of the discharged mixed cleaning solution.

25. The method according to claim 1, wherein the first cleaning solution targets organic membrane foulants, and wherein the mixed cleaning solution containing the acidic species targets inorganic membrane foulants.

26. A method of facilitating cleaning of a porous polymeric membrane in place, comprising:

providing a first cleaning solution including at least one oxidising agent and a second cleaning solution including at least one reducing agent; and

providing instructions to;

contact at least a portion of the membrane with the first cleaning solution for a first time period to target organic membrane foulants;

introduce the second cleaning solution to the first cleaning solution after the first time period has elapsed to form a mixed cleaning solution containing an acid species; and

contact at least a portion of the membrane with the mixed cleaning solution containing the acid species for a second time period to target inorganic membrane foulants.

27. The method of claim 26, further comprising providing instructions to discharge the mixed cleaning solution after the second time period has elapsed.

28. The method of claim 27, further comprising providing instructions to adjust a pH level of the discharged mixed cleaning solution.