Inverted cavity aerator for membrane module

• US 20050006308A1
• Filed: 05/10/2004
• Published: 01/13/2005
• Est. Priority Date: 08/11/1995
• Status: Active Grant

• Current Assignee: Zenon Technology Partnership
• Original Assignee: Zenon Technology Partnership
• Inventors: Cote, Pierre Lucien, Behmann, Henry, Pedersen, Steven Kristian
• Granted Patent: US 7,087,173 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 2321/185 Aeration
• CPC Class Codes: B01D 61/18 Apparatus therefor
• CPC Class Codes: B01D 61/20 Accessories; Auxiliary operations
• CPC Class Codes: B01D 63/021 Manufacturing thereof
• CPC Class Codes: B01D 63/022 Encapsulating hollow fibres
• CPC Class Codes: B01D 63/023 Encapsulating materials
• 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: C02F 1/444 by ultrafiltration or microfiltration
• CPC Class Codes: C02F 2303/16 Regeneration of sorbents, filters
• CPC Class Codes: C02F 3/20 using diffusers
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage

Abstract

An aerator for immersed filtering membranes has an aerator shell with openings for discharging bubbles from its upper surface and a shape capable of temporarily containing a volume of air in fluid communication with the openings. The shell is open to tank water below it and located so that discharged bubbles will rise through an assembly of the filtering membranes. The shell may be wholly or partially made of parts of the assemblies of filtering membranes. A supply of air is provided to the air space in the aerators alternating between a high flow rate and a low flow rate in short cycles of between about 10 seconds and 100 seconds. A filtration system has an inlet for adding substrate and an outlet for retentate are located so as to create a horizontal flow of substrate through the tank. Membrane assemblies are located within the horizontal flow of substrate. Aerators as described above are provided and operated as described above.

Claims

1. An aerator for filtering membranes immersed in a tank of liquid, comprising:

an upper surface having holes for discharging bubbles below the membranes;

sides extending downwardly from the upper surface which surround a space for trapping a variable volume of air in communication with the holes; and

an opening to the liquid in the tank below the volume of trapped air so that liquid can be displaced from or enter into the aerator as the column of trapped air changes.

2. A method of aerating immersed filtering membranes comprising the steps of:

providing an aerator as described in claim 1;

and

providing a supply of air to the space in the aerator wherein air may be trapped alternating between a high flow rate and a low flow rate in short cycles of between about 10 seconds and 100 seconds in duration.

3. The method of claim 2 wherein the rate of air flow during the period of low flow is 10% or less than the rate of air flow during the period of high flow.

4. The method of the claim 3 wherein there is substantially no air flow during the period of low air flow.

5. The method of claim 2 wherein the period of high flow is between about ⅛

and ½

of the total cycle duration.

6. The method of claim 2 wherein the change between the high flow rate and low flow rate is performed in less than about 6 seconds.

7. The method of claim 6 wherein the change between the high flow rate and low flow rate is performed in less than about 3 seconds.

8. The method of claim 2 wherein the aerator is sized in relation to the duration and rate of air flow provided during a cycle such that air flows through the holes throughout each cycle.

9. The method of claim 2 wherein the aerator is sized in relation to the duration and rate of air flow provided during a cycle such that no air flows through the holes during at least part of the cycle such that liquid in the tank may flow into the holes.

10. The method of claim 9 wherein air flows through the holes of the aerator for between about ⅓

and ¾

of the cycle duration.

11. The method of claim 10 wherein air flows through the holes for about ½

of the cycle duration.

12. An aerator for filtering membranes immersed in a tank of liquid comprising:

a plenum below the membranes, the plenum defined by an upper surface and sides extending downwards from the upper surface, the plenum adapted to contain a volume of air;

a plurality of air tubes each having one end with an opening extending downwardly from the upper surface into the plenum and another end with an opening extending upwardly from the upper surface such that air in the plenum may flow through the air tubes and be discharged between the membranes.