Membrane module system with bundle enclosures and pulsed aeration and method of operation

A method of scouring external surfaces of hollow fiber membranes arranged in a substantially vertical orientation that are immersed in a liquid in a tank, the method comprising:

• operating the module submerged in the liquid wherein the module includes:
• a header;
• a bundle containing a plurality of hollow fiber membranes, wherein a lower end of each hollow fiber membrane is fixed in the header;
• a gasification device adapted to periodically generate a gaseous bubble and configured to release the gaseous bubble within the bundle, wherein the gaseous bubble travels through an air tube that starts from the gasification device and goes into the header;
• and
• an enclosure that substantially surrounds the bundle that extends from a lower region to an upper region of the membrane bundle, wherein the enclosure is configured to retain the liquid introduced into the enclosure such that the liquid surrounds the membrane bundle;
• applying a pressure that is less than an ambient pressure of the tank to a permeate collection chamber, that is in fluid communication with the hollow fiber membranes, wherein applying the pressure is configured to cause a portion of the liquid to pass through the hollow fiber membranes as permeate into the permeate collection chamber;
• supplying a gas stream to the gasification device to produce the gaseous bubble;
• wherein the enclosure causes the gaseous bubble to substantially fill the cross-sectional area of the enclosure and to maintain contact with the bundle along the entire length of the bundle, thereby the gaseous bubble scours the surface of the hollow fiber membranes and removes and lifts debris from the bundle.

A method of desludging a hollow fiber membrane module, comprising:

• temporarily ending a vacuum pressure applied to the module, wherein the membrane module includes:
• a header;
• a bundle containing a plurality of hollow-fiber membranes,
• wherein a lower end of each hollow membrane is fixed in the header;
• a gasification device adapted to periodically generate a gaseous bubble and configured to release the gaseous bubble within the bundle, wherein the gaseous bubble travels through an air tube that starts from the gasification device and goes into the header;
• and
• an enclosure that substantially surrounds the bundle that extends from a lower region to an upper region of the membrane bundle, wherein the enclosure is configured to retain the liquid introduced into the enclosure such that the liquid surrounds the membrane bundle;
• supplying a gas stream to the gasification device to generate a plurality of gaseous bubbles, wherein the gaseous bubbles each substantially fill the cross-sectional area of the enclosure and maintain contact with the bundle along the entire length of the bundle;
• and
• wherein the gaseous bubbles desludge the hollow-fiber membranes by breaking apart and lifting the sludge up and out the top of the enclosure.