Method and apparatus for treating wastewater

Abstract

The invention is directed to a method an apparatus for treating wastewater. The wastewater treatment system includes an aeration system that cycles between biological multiple biological basins. The system also includes one or more membrane basins. A method of the invention includes controlling the introduction of air into each biological basin in response to one or more operating conditions.

1 - 21 . (canceled)  
     
     
         22 . A process of nitrifying and denitrifying wastewater and reducing or minimizing the DO concentration in a denitrification zone of a nitrification/denitrification system that includes an aerobic reactor having one or more immersed membranes contained therein comprising: 
 alternatively directing a wastewater influent into first and second zones;    at various times during the process maintaining the first zone as a nitrification zone and maintaining the second zone as a denitrification zone, and at various other times, maintaining the first zone at a denitrification zone and the second zone as a nitrification zone;    directing wastewater from either of the first or second zones to the downstream aerobic reactor having the one or more immersed membranes therein;    aerating the aerobic reactor;    directing wastewater in the aerobic reactor into the one or more immersed membranes and separating the wastewater into a permeate and return activated sludge;    pumping the permeate from the one or more immersed membranes in the aerobic reactor;    returning activated sludge from the aerobic reactor to either of the first or second zones; and    during the process reducing or minimizing the DO concentration in the denitrification zones by selectively directing the return activated sludge to one of the first or second zones being maintained as a nitrification zone and switching the flow of the return activated sludge during the process between the first and second zones so as to direct the return activated sludge to the first or second zone being maintained as the nitrification zone.    
     
     
         23 . The process of  claim 22 , wherein the wastewater flow from the first and second zones to the downstream aerobic reactor is switched such that the flow of wastewater to the downstream aerobic reactor is from the zone being maintained as a nitrification zone.  
     
     
         24 . The process of  claim 23 , wherein at various times both the first and second zones are maintained as nitrification zones.  
     
     
         25 . The process of  claim 22 , wherein at various times one of the first or second zones is maintained as a denitrification zone and the other zone is maintained as a nitrification zone.  
     
     
         26 . A process of nitrifying and denitrifying wastewater utilizing first and second reactors and a downstream third aerobic reactor having one or more immersed membrane filters contained therein, the process comprising: 
 alternatively directing influent wastewater into the first and second reactors;    alternatively nitrifying and denitrifying the wastewater in the first and second reactors such that at one time the first reactor performs a nitrification function while the second reactor performs a denitrification function, and at another time the first reactor performs a denitrifying function while the second reactor performs a nitrifying function;    alternatively directing influent from the first and second reactors to the downstream third aerobic reactor having the one or more immersed membrane filters contained therein;    filtering the wastewater in the downstream third aerobic reactor by directing the wastewater into the immersed membrane filter and separating the wastewater into filtered effluent and activated sludge;    pumping the filtered effluent from the immersed membrane filter; and    returning activated sludge from the downstream third aerobic reactor having the immersed membrane filtered therein to one of the first or second reactors functioning to nitrify the wastewater.    
     
     
         27 . The process of  claim 26 , wherein during the process of treating the wastewater each of the first and second reactors switch between nitrifying and denitrifying the wastewater; and wherein there is provided a return activated sludge line between the downstream third aerobic reactor and each of the first and second reactors, and wherein the flow of return activated sludge is switched between the two return activated sludge lines such that return activated sludge is recycled to the first or second reactor nitrifying the wastewater.