Membrane filter for water treatment

Abstract

The invention relates to a membrane filter for water treatment, comprising a head piece including a permeate collecting chamber with a permeate outlet, and at least one fiber bundle made from capillary membranes, which are secured into the head piece with an end that is open towards the permeate collecting chamber and sealed on the opposite end thereof. The head piece contains an air duct to which the mouth piece that protrudes into the fiber bundle is connected with at least one air outlet. At its other end, the fiber bundle terminates in freely movable manner in the untreated water.

1 . A method to dislodge fouling materials from external surfaces of hollow fiber membranes immersed vertically in a tank containing a slow moving or captive feed liquid under ambient pressure comprising the steps of:
 a) vertically mounting a plurality of porous hollow fiber membranes having fixed lower ends fixed in a head piece and freely moveable sealed upper ends adapted to prevent accumulation of deposits along the external surfaces and upper regions of the of the membranes, wherein the head piece comprises:
 i) a permeate collecting chamber sealed from the feed liquid and in fluid communication with the lower open ends of each of the hollow fiber membranes and opposite the sealed, freely movable upper ends; and 
 ii) a gas duct contained in the head piece and connected to a mouth piece positioned within and surrounded by the hollow fiber membranes, the mouth piece having at least one outlet for a gas; 
   b) immersing the porous hollow fiber membranes in the head piece into the feed liquid;   c) applying a pressure less than the feed liquid pressure to the permeate collecting chamber to cause permeate to pass through the pores of the hollow fiber membranes in to the permeate collecting chamber; and   d) providing pressurized gas to the gas duct to form bubbles that flow through a bundle of hollow fiber membranes from the inside to the outside of the bundle of membranes and partially flow away in the lengthwise direction, contact external surfaces of the hollow fiber membranes over the entire length of the membranes to remove fouling materials from the hollow fiber membranes independent of the flow velocity of the feed liquid and cause the hollow fiber membranes to sway.   
   
   
       2 . The method of  claim 1  wherein the pressurized gas is provided constantly. 
   
   
       3 . The method of  claim 1  wherein the pressurized gas is provided intermittently. 
   
   
       4 . The method of  claim 1  further comprising the step of providing a liquid to internal surfaces of the hollow fiber membranes to backwash the hollow fiber membranes. 
   
   
       5 . The method of  claim 4  wherein the liquid is permeate. 
   
   
       6 . A module for a membrane filter to treat untreated water contained in a tank or basin at an ambient pressure comprising:
 a) a plurality of head pieces arranged parallel to one another, wherein the headpieces are block-shaped elements having a plurality of vertical fiber bundles that are a dense packing of capillary membranes having fixed lower ends and sealed, freely movable upper ends adapted to prevent accumulation of deposits along external surfaces and upper regions of the of the membranes;   b) a plurality of gasification devices arranged to introduce air into the fiber bundles to provide bubbles that flow through the bundle of capillary membranes from the inside to the outside of the bundle of membranes and partially flow away in the lengthwise direction, move upwardly, and contact the capillary membranes over the external surfaces and upper regions of the membranes to remove fouling materials from the capillary membranes independent of the flow velocity of the untreated water;   c) a basket connected to the head pieces to limit lateral sway of the capillary membranes; and   d) connecting devices for attachment to a frame which can be lowered into a tank or basin containing untreated water.   
   
   
       7 . The module of  claim 6  further comprising a frame for immersing the plurality of head pieces into the tank or basin. 
   
   
       8 . The module of  claim 6  wherein the capillary membranes are packed relative to one another so as to produce a rubbing effect between the membranes when moved. 
   
   
       9 . The module of  claim 6  wherein the bubbles are provided constantly. 
   
   
       10 . The module of  claim 6  wherein the bubbles are provided intermittently.