Open bottom multiple channel gas delivery device for immersed membranes

1. A method of air scouring an immersed membrane comprising adjusting one or more aeration parameters: between successive permeation, backpulse or relaxation cycles; during a permeation cycle; or between a permeation cycle and a backpulse or relaxation cycle wherein air scouring during the backpulse or relaxation cycle comprises releasing a series of bursts of bubbles;

wherein aeration is provided by a gas delivery device comprising:

a manifold adapted to be connected to a source of a pressurized gas; and

a plurality of open-bottomed channels, each of the plurality of channels having a single outlet and being in fluid communication with the manifold through a distinct associated port.

2. A method of air scouring an immersed membrane comprising adjusting one or more aeration parameters: between successive permeation, backpulse or relaxation cycles; during a permeation cycle; or between a permeation cycle and a backpulse or relaxation cycle wherein air scouring during the backpulse or relaxation cycle comprises releasing a series of bursts of bubbles;

wherein aeration is provided by a gas delivery device comprising:

a distribution plenum adapted to be connected to a source of a pressurized gas; and,

a plurality of channels, each of the plurality of channels being in fluid communication with the distribution plenum through a distinct associated port, each of the plurality of channels having an outlet at the end of the channel adapted to discharge gas,

wherein the ports have a smaller area than the channels and the ports are located close together relative to a variation in the lengths of the channels.

3. A method of air scouring an immersed membrane comprising adjusting one or more aeration parameters: between successive permeation, backpulse or relaxation cycles; during a permeation cycle; or between a permeation cycle and a backpulse or relaxation cycle wherein air scouring during the backpulse or relaxation cycle comprises releasing a series of bursts of bubbles;

and further comprising:

bringing a flow of pressurized gas into a tank to a manifold near or below the bottom of a membrane module;

splitting the flow of pressurized gas into multiple flows of pressurized gas extending from the manifold;

directing each of the multiple flows of pressurized gas to a different lateral position, such that each of the multiple flows of pressurized travel a different distance from the manifold; and

releasing bubbles from the different lateral positions.

4. The method of claim 1 , wherein an aeration flow rate is varied between successive permeation cycles.

5. The method of claim 1 , wherein air scouring during the permeation cycle comprises releasing a series of bursts of bubbles and an aeration flow rate is increased during a backpulse or relaxation cycle relative to the aeration flow rate during a preceding permeation cycle.

6. The method of claim 1 , wherein an aeration flow rate is increased within a permeation cycle.

7. The method of claim 1 , wherein aeration is provided intermittently during a permeation cycle.

8. The method of claim 1 , wherein aeration is provided only during a backpulse or a relaxation cycle.

9. The method of claim 1 , wherein a continuous or instantaneous aeration flow rate increases generally linearly over time during a permeation cycle.

10. The method of claim 2 , wherein an aeration flow rate is varied between successive permeation cycles.

11. The method of claim 2 , wherein air scouring during the permeation cycle comprises releasing a series of bursts of bubbles and an aeration flow rate is increased during a backpulse or relaxation cycle relative to the aeration flow rate during a preceding permeation cycle.

12. The method of claim 2 , wherein an aeration flow rate is increased within a permeation cycle.