Membrane cleaning with pulsed airlift pump

Abstract

A method of cleaning a membrane surface immersed in a liquid medium with a fluid flow, including the steps of providing a randomly generated intermittent or pulsed fluid flow along the membrane surface to dislodge fouling materials therefrom. A membrane module is also disclosed comprising a plurality of porous membranes ( 6 ) or a set of membrane modules ( 5 ) and a device ( 11 ) for providing a generally randomly generated, pulsed fluid flow such that, in use, said fluid flow moves past the surfaces of said membranes ( 6 ) to dislodge fouling materials therefrom.

What is claimed is: 
     
         1 . A method of cleaning a membrane surface immersed in a liquid medium and disposed within a membrane module of an array of membrane modules comprising:
 introducing a gas to a chamber of a device positioned below the membrane surface, a single device positioned below each single module in the array of membrane modules and each single module in the array of membrane modules associated with a single device, such that the liquid medium in the chamber is displaced downward by the gas until a hydraulic seal is broken, whereupon a substantial portion of the gas introduced into the chamber is released to the membrane surface as a bubble slug.   
     
     
         2 . The method of  claim 1 , wherein the bubble slug is drawn rapidly up through a tube positioned within the device and having a first end in fluid communication with the membrane surface. 
     
     
         3 . The method of  claim 2 , wherein the tube has a second end in fluid communication with the liquid medium such that the liquid medium enters the second end following the release of the bubble slug. 
     
     
         4 . The method of  claim 2 , wherein a volume of the gas introduced to the chamber displaces a sufficient volume of the liquid medium such that a level of the liquid medium reaches an opening in the tube. 
     
     
         5 . The method of  claim 1 , wherein the gas is introduced to an upper portion of the chamber. 
     
     
         6 . The method of  claim 1 , wherein introducing the gas includes introducing the gas continuously. 
     
     
         7 . The method of  claim 1 , wherein the chamber has an open lower end. 
     
     
         8 . The method of  claim 1 , further comprising flooding the device with the liquid medium prior to introducing the gas. 
     
     
         9 . The method of  claim 1 , further comprising removing fouling materials from the membrane surface using the bubble slug. 
     
     
         10 . A water treatment system comprising:
 a tank comprising a water to be treated;   a liquid chamber fluidly connected to the tank;   a gas chamber fluidly connected to the liquid chamber;   a gas transfer system comprising a suction side connected to the liquid chamber and a discharge side connected to the gas chamber; and   a membrane module vessel containing a membrane module, the membrane module vessel hydraulically connected to the tank.   
     
     
         11 . The water treatment system of  claim 10 , further comprising a source of gas fluidly connected to the liquid chamber. 
     
     
         12 . A method of operating a membrane bioreactor, the membrane bioreactor including a bioreactor tank and a membrane module positioned in a membrane tank, the membrane module including a plurality of porous hollow fiber membranes, the bioreactor tank and the membrane tank coupled by an inverted gas collection chamber, the method comprising:
 introducing feed to the membrane tank and the bioreactor tank;   applying a vacuum to the plurality of porous hollow fiber membranes to withdraw filtrate therefrom;   introducing a pressurized gas to a first chamber of the inverted gas collection chamber;   producing a surge of gas using the pressurized gas, the first chamber, and a second chamber of the inverted gas collection chamber; and   flowing the gas from the second chamber of the inverted gas collection chamber past surfaces of the plurality of porous hollow fiber membranes.   
     
     
         13 . The method of  claim 12 , wherein producing the surge of gas also produces a rapid reduction of gas within the first chamber that causes feed to be siphoned from the bioreactor tank into the membrane tank. 
     
     
         14 . The method of  claim 12 , wherein the pressurized gas is introduced to the first chamber through a port controlled by a valve.