Membrane bioreactor, process and aerator

Abstract

A reactor has an aerobic tank, an anoxic tank and a sealed membrane tank with conduits for circulating mixed liquor between them. Permeation starts when the mixed liquor reaches a high level and stops when the mixed liquor reaches a low level. A sensor, for detecting the mixed liquor level, may stop and start permeation. Pressure builds in the membrane tank when membrane air is on. Transmembrane pressure is also provided by gravity flow or siphon. Membrane air generates an air lift which drives the mixed liquor circulation. The total amount of air provided by an air source is divided and varied in time between the membrane aerator and the process aerator. The process aerator acts as a screening inlet to the conduit to the membrane tank. Chemical maintenance cleaning is provided by gravity flow.

1 . An apparatus comprising, 
 a) one or more process tanks or zones for one or more of aerobic digestion, nitrification or denitrification;    b) an immersed membrane tank or zone;    c) a conduit or passage for mixed liquor to flow from the membrane tank or zone to the one or more process tanks or zones;    d) a conduit or passage for mixed liquor to flow from the one or more process tanks or zones to the membrane tank or zone;    e) an inlet for feed to enter into one or more of the tanks or zones;    f) an outlet for permeate to exit the membrane tank or zone; and,    g) a level sensor for detecting a selected maximum mixed liquor level and a selected minimum mixed liquor level in one of the one or more process tanks or zones.    
   
   
       2 . The apparatus of  claim 1  wherein the level sensor is operatively connected to devices for one or more of (a) stopping and starting permeation, (b) increasing and decreasing the total air supply provided by an air supply or (c) altering a regime of cyclic aeration.  
   
   
       3 . An aeration system comprising, 
 a) one or more process aerators;    b) one or more membrane aerators;    c) an air supply;    d) a process air line which provides a path for air from the air supply to the one or more process aerators;    e) a membrane air line which provides a path for air from the air supply to the one or more membrane aerators;    wherein the air supply is adapted to provide at least a higher flow rate of air and a lower flow rate of air.    
   
   
       4 . The aeration system of  claim 3  combined with the apparatus of  claim 1  wherein the level sensor is operatively connected to the air supply to control when air is provided at the higher rate of flow and the lower rate of flow.  
   
   
       5 . An apparatus comprising, 
 a) one or more process tanks or zones for one or more of aerobic digestion, nitrification or denitrification;    b) an immersed membrane tank or zone;    c) a conduit or passage for mixed liquor to flow from the membrane tank or zone to the one or more process tanks or zones;    d) a conduit or passage for mixed liquor to flow from the one or more process tanks or zones to the membrane tank or zone;    e) an inlet for feed to enter into one or more of the tanks or zones;    f) an outlet for permeate to exit the membrane tank or zone;    g) a level sensor for detecting a selected maximum mixed liquor level and a selected minimum mixed liquor level in one of the one or more process tanks or zones; and,    h) an aeration system, wherein the aeration system comprises,    i) one or more aerators in the process tanks or zones and one or more aerators in the membrane tank or zone; ii) an air supply, wherein the air supply is adapted to provide at least a higher flow rate of air and a lower flow rate of air; and, iii) air lines which provide a path for air from the air supply to the one or more aerators in both the process tanks or zones and the membrane tank or zone;    wherein the level sensor is operatively connected to the air supply to control when air is provided at the higher rate of flow and the lower rate of flow.    
   
   
       6 . The aeration system of  claim 5  wherein air is provided at the higher rate of flow whenever the level of mixed liquor is above a high level, the high level related to the need for the higher rate of flow to meet process requirements.  
   
   
       7 . The aeration system of  claim 5  wherein air is provided at the higher rate of flow from the time that the mixed liquor reaches the maximum mixed liquor level to the time when the mixed liquor reaches the minimum mixed liquor level.  
   
   
       8 . The aeration system of  claim 5  wherein the aerator is a fine bubble aerator.