Open bottom multiple channel gas delivery device for immersed membranes

Abstract

A method of air scouring an immersed membrane is described in this specification. The method comprises a step of adjusting one or more aeration parameters during a permeation cycle, or between a permeation cycle and a back pulse or relaxation cycle, or between successive cycles. The method may be used with a gas delivery device described in this specification in which a supply of gas is provided to a manifold with multiple ports connected to multiple conduits. The method may further comprise bringing a flow of pressurized gas into a tank to near or below the bottom of a membrane module. At about this elevation, the flow of pressurized gas is split into multiple flows of pressurized gas. Each of the multiple flows of pressurized gas is directed to a different lateral position and then released as bubbles.

We claim: 
     
         1 . A method of air scouring an immersed membrane comprising a step of adjusting one or more aeration parameters between successive permeation, back pulse or relaxation cycles; during a permeation cycle; or, between a permeation cycle and a backpulse or relaxation cycle. 
     
     
         2 . The method of  claim 1  wherein aeration is provided by a gas delivery device comprising,
 a) a manifold adapted to be connected to a source of a pressurized gas; and, 
 b) a plurality of channels, each of the plurality of channels being in fluid communication with the manifold through a distinct associated port, each of the plurality of channels having a generally open bottom. 
 
     
     
         3 . The method of  claim 1  wherein aeration is provided by a gas delivery device comprising,
 a) a distribution plenum adapted to be connected to a source of a pressurized gas; and, 
 b) 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 adapted to discharge gas, 
 wherein the ports have a smaller area than the channels and the ports are located close together relative to a spacing between the openings. 
 
     
     
         4 . The method of  claim 1  further comprising steps of,
 a) bringing a flow of pressurized gas into a tank to near or below the bottom of a membrane module; 
 b) splitting the flow of pressurized gas into multiple flows of pressurized gas; 
 c) directing each of the multiple flows of pressurized to a different lateral position; 
 d) releasing bubbles from the different lateral positions. 
 
     
     
         5 . The method of  claim 1  wherein an aeration flow rate is varied between successive permeation cycles. 
     
     
         6 . The method of  claim 1  wherein an aeration flow rate is increased during a backpulse or relaxation cycle relative to the aeration flow rate during a preceding permeation cycle. 
     
     
         7 . The method of  claim 1  wherein an aeration flow rate is increased within a permeation cycle. 
     
     
         8 . The method of  claim 1  wherein aeration is provided intermittently during a permeation cycle. 
     
     
         9 . The method of  claim 1  wherein aeration is provided only during a backpulse or a relaxation cycle. 
     
     
         10 . The method of  claim 1  wherein a continuous or instantaneous aeration flow rate increases generally linearly over time during a permeation cycle. 
     
     
         11 . The method of  claim 10  wherein the aeration flow rate increases further during a backpulse or relaxation cycle. 
     
     
         12 . A method of air scouring an immersed membrane comprising adjusting one or more aeration parameters: between successive permeation, back pulse 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. 
     
     
         13 . The method of  claim 12 , 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.   
     
     
         14 . The method of  claim 12 , 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.   
     
     
         15 . The method of  claim 12 , 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 gas travel a different distance from the manifold; and   releasing bubbles from the different lateral positions.   
     
     
         16 . The method of  claim 12 , wherein an aeration flow rate is varied between successive permeation cycles. 
     
     
         17 . The method of  claim 12 , 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. 
     
     
         18 . The method of  claim 12 , wherein aeration is provided only during a backpulse or a relaxation cycle. 
     
     
         19 . The method of  claim 13 , wherein an aeration flow rate is varied between successive permeation cycles. 
     
     
         20 . The method of  claim 13 , 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. 
     
     
         21 . The method of  claim 13 , wherein aeration is provided only during a backpulse or a relaxation cycle. 
     
     
         22 . The method of  claim 14 , wherein an aeration flow rate is varied between successive permeation cycles. 
     
     
         23 . The method of  claim 14 , 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.