Aeration device for filtration system

1. An aeration device configured to be fitted to a membrane filtration module having membranes mounted therein, the aeration device comprises:

a sleeve configured to at least partially surround the membrane filtration module, the sleeve having one end adapted to engage with the membrane filtration module and another end adapted to engage with a filtrate collection conduit or manifold, the sleeve comprising:

an outer wall and an inner wall spaced therefrom, the inner wall and the outer wall downwardly extending co-axially from a joining portion, the outer wall and the inner wall defining a chamber therebetween having an open lower end at a distal end of the inner wall and a closed upper end at the joining portion where the inner wall and the outer wall of the sleeve are joined, a gap being defined between the distal end of the inner wall and the outer wall about an entire periphery of the inner wall;

a gas inlet distinct from the open lower end of the chamber and disposed at an upper end of the chamber between the outer and inner wall, the gas inlet configured to communicate gas from a source of gas to the chamber;

one or more aeration openings defined in the inner wall of the sleeve and configured to provide fluid communication between the chamber and the membranes of the membrane filtration module; and

one or more drain openings defined in the outer wall of the sleeve and configured to provide fluid communication between the membranes of the membrane filtration module and an outside of the sleeve.

2. The aeration device of claim 1 , wherein the aeration device is engaged to the filtrate collection conduit or manifold by a threading engagement between complimentary screw threads provided on the respective filtrate collection conduit or manifold and the one end of the outer wall of the sleeve.

3. The aeration device of claim 1 , wherein the inner wall extends downwardly part way along a length of the outer wall of the sleeve.

4. The aeration device of claim 3 , wherein a first set of portions of the inner wall extend downwardly along the length of the outer wall of the sleeve to a greater extent than a second set of portions of the inner wall extend downwardly along the length of the outer wall of the sleeve.

5. The aeration device of claim 4 , wherein the first set of portions of the inner wall extend downwardly along the length of the outer wall and terminate below an upper extent of the one or more drain openings.

6. The aeration device of claim 5 , wherein the second set of portions of the inner wall extend downwardly along the length of the outer wall and terminate above the upper extent of the one or more drain openings.

7. The aeration device of claim 1 , wherein a plurality of aeration openings are provided in the inner wall of the sleeve, the aeration openings being circumferentially spaced from one another around the periphery of the inner wall of the sleeve.

8. The aeration device of claim 7 , wherein a first set of the plurality of aeration openings have lower ends disposed below an upper extent of the one or more drain openings.

9. The aeration device of claim 8 , wherein a second set of the plurality of aeration openings have lower ends disposed above an upper extent of the one or more drain openings.

10. The aeration device of claim 7 , wherein the plurality of aeration openings are formed as vertically extending slots.

11. The aeration device of claim 10 , wherein the slots are open at their lower ends and taper inwardly towards upper closed ends of the slots.

12. The aeration device of claim 11 , wherein the taper is stepped with an initial taper along part of a lower portion of the slot then an inward step of reduced width and a further taper from the step to the upper end of the slot.

13. The aeration device of claim 1 , wherein the gas inlet is provided at the joining portion of the sleeve.

14. The aeration device of claim 1 , wherein the one or more drain openings include a plurality of circumferentially spaced drain openings defined in the outer wall of the sleeve.

15. A membrane filtration system comprising a plurality of vertically extending membrane filtration modules mounted in a rack, each membrane filtration module including membranes in fluid communication with upper and lower filtrate collection manifolds, wherein each membrane module is provided with an aeration device according to claim 1 and wherein the aeration device is engaged with the lower filtration collection manifold.

16. The aeration device of claim 1 , wherein the one or more drain openings are configured to provide fluid communication between the membranes of the membrane filtration module and an internal volume of a vessel in which the membrane filtration module is configured to be mounted.