CLEANING IN MEMBRANE FILTRATION SYSTEMS

• US 20110114557A2
• Filed: 12/19/2005
• Published: 05/19/2011
• Est. Priority Date: 12/24/2004
• Status: Active Grant

• Current Assignee: Evoqua Water Technologies LLC
• Original Assignee: Evoqua Water Technologies LLC
• Inventors: Johnson, Warren, Yeo, Rebecca, Beck, Thomas
• Granted Patent: US 8,496,828 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 2321/16 Use of chemical agents
• CPC Class Codes: B01D 2321/162 Use of acids
• CPC Class Codes: B01D 2321/164 Use of bases
• CPC Class Codes: B01D 2321/168 Use of other chemical agents
• CPC Class Codes: B01D 63/02 Hollow fibre modules
• CPC Class Codes: B01D 65/02 Membrane cleaning or sterilisation ; Membrane regeneration
• CPC Class Codes: C02F 1/444 by ultrafiltration or microfiltration

Abstract

A method of cleaning permeable, hollow membranes (6) in an arrangement of the type wherein a pressure differential is applied across the walls (15) of the permeable, hollow membranes (6) immersed in a liquid suspension, the liquid suspension being applied to the outer surface of the porous hollow membranes (6) to induce and sustain filtration through the membrane walls (15) wherein some of the liquid suspension passes through the walls (15) of the membranes (6) to be drawn off as clarified liquid or permeate from the hollow membrane lumens (7), and at least some of the solids are retained on or in the hollow membranes (6) or otherwise as suspended solids within the liquid surrounding the membranes (6). The method of cleaning comprises the steps of applying a cleaning solution (14) to one side of the membrane wall (15); applying a pressure differential across the membrane wall (15) to cause flow of the cleaning solution (14) through the wall (15) from the one side of the membrane wall (15) to the other side of the membrane wall (15) and applying a reverse pressure differential across the membrane wall (15) to cause flow of the cleaning solution (14) through the wall (15) from the other side of the membrane wall (15) back to the one side of the membrane wall (15). A method of determining the amount of chemical cleaning solution required is also disclosed.

Claims

1. A method of cleaning a permeable, hollow membrane, the permeable, hollow membrane comprising a wall, a filtrate side, and an outer side, the method comprising:

removing liquid from the filtrate side of the membrane;

removing liquid from the outer side of the membrane;

applying a chemical cleaning solution to the outer side of the membrane;

causing flow of the chemical cleaning solution through the wall from the outer side of the membrane into the filtrate side to at least partially fill the filtrate side with the chemical cleaning solution by applying a pressure differential across the membrane wall;

isolating the outer side of the membrane;

causing flow of the chemical cleaning solution back to the outer side through the membrane wall by applying a pressurized gas to the filtrate side;

accumulating the increased pressure developed on the outer side of the membrane as a result of the flow of the chemical cleaning solution; and

causing flow of the chemical cleaning solution though the membrane wall from the outer side to the filtrate side under the effect of the accumulated pressure on the outer side of the membrane wall by releasing the pressure applied by the pressurized gas to the filtrate side of the membrane wall.

3. The method according to claim 1, wherein applying the pressurized gas to the filtrate side comprises applying gas such that the filtrate side is substantially drained of the chemical cleaning solution.

4. The method of claim 1, wherein accumulating the increased pressure comprises accumulating the increased pressure in a gas space provided on the outer side of the membrane wall.

5. The method of claim 1, wherein accumulating the increased pressure comprises accumulating the increased pressure in a bladder arrangement.

6. The method of claim 1, wherein applying the pressure differential comprises applying gas pressure to the outer side of the membrane wall.

7. The method of claim 1, wherein applying the pressure differential comprises applying a vacuum to the filtrate side.

25. The method of claim 1, wherein the chemical cleaning solution comprises an oxidizing solution.

26. The method of claim 25, wherein the chemical cleaning solution comprises chlorine.

2. (canceled)

8. A method of cleaning a permeable, hollow membrane, the permeable, hollow membrane comprising a wall, a one side, and another side, the method comprising:

applying a chemical cleaning solution comprising at least one of an acid, a caustic solution, and an oxidizing solution to the one side of the membrane wall;

causing flow of the chemical cleaning solution though the wall from the one side of the membrane wall to the other side of the membrane wall by applying a pressure differential across the membrane wall; and

causing flow of the chemical cleaning solution through the wall from the other side of the membrane wall back to the one side of the membrane wall by applying a reverse pressure differential across the membrane wall.

9. The method of claim 8, wherein applying the pressure differential comprises applying gas pressure to the one side of the membrane wall.

10. The method of claim 8, wherein applying the pressure differential comprises applying a vacuum to the other side of the membrane wall.

11. The method of claim 8, wherein applying the reverse pressure differential comprises applying gas pressure to the other side of the membrane wall.

12. The method of claim 8, wherein applying the reverse pressure differential comprises applying a vacuum to the one side of the membrane wall.

27. The method of claim 8, wherein the chemical cleaning solution comprises citric acid.

28. The method of claim 8, wherein the chemical cleaning solution comprises chlorine.

13. (canceled)

14. A method of cleaning a permeable, hollow membrane, the permeable, hollow membrane comprising a wall, a filtrate side, and an outer side, the method comprising:

removing liquid from the filtrate side of the membrane;

removing liquid from the outer side of the membrane;

applying a chemical cleaning solution comprising at least one of an acid, a caustic solution, and an oxidizing solution to the outer side of the membrane;

causing flow of the chemical cleaning solution though the wall from the outer side of the membrane into the filtrate side of the membrane to at least partially fill the filtrate side with the chemical cleaning solution by applying a pressure differential across the membrane wall; and

causing flow of the chemical cleaning solution through the wall from the filtrate side of the membrane back to the outer side of the filtrate side by applying a reverse pressure differential across the membrane wall.

15. The method of claim 14, wherein applying the reverse pressure differential comprises applying a pressurized gas to the filtrate side of the membrane wall.

16. The method of claim 14, wherein the steps of the cleaning method are repeated in cycles such that the chemical cleaning solution is alternately moved from a first side of the membrane to a second side of the membrane through the membrane wall.

29. The method of claim 14, wherein the chemical cleaning solution comprises citric acid.

30. The method of claim 14, wherein the chemical cleaning solution comprises chlorine.

17-24. -24. (canceled)