Immersed membrane filtration system and overflow process

Abstract

Modules of ultrafiltration or microfiltration membranes are arranged in a tank open to the atmosphere to substantially cover the cross sectional area of the tank. A filtration cycle has permeation steps and deconcentration steps. During permeation, supply of feed substantially equals feed removed and little if any aeration is used. During deconcentration, aeration with scouring bubbles is provided with one or both of backwashing and feed flushing. In feed flushing, feed water is supplied to the tank from below the modules. Excess tank water created during deconcentration flows generally upwards through the modules and out through a retentate outlet or overflow at the top of the tank.

1 . A filtering reactor comprising, 
 a) a tank open to the atmosphere;    b) one or more modules of suction driven filtering membranes in the tank for withdrawing a filtered permeate;    c) an inlet to add feed water to the tank from below the one or more modules;    d) one or more open channels spanning a portion of the tank above the one or more modules; and,    e) a retentate outlet connected to the one or more open channels to discharge water containing retained solids from the tank from above the one or more modules.    
   
   
       2 . The reactor of  claim 1  wherein the modules cover most of the horizontal cross sectional area of the tank.  
   
   
       3 . The reactor of  claim 1  wherein the filtering membranes are hollow fibres oriented horizontally.