US 7,147,778 B1 · Method and system for nitrifying and denitrifying wastewater

Abstract

A wastewater treatment system is provided that includes first and second reactors, each operative to nitrify or denitrify wastewater contained therein. Downstream from the first and second reactors is a membrane reactor that operates under aerobic conditions and includes one or more submersed membranes for separating solids. Extending between the membrane reactor and each of the first and second reactors is a return activated sludge line with appropriate controls for permitting return activated sludge to be directed to one of the reactors at a time. To nitrify and denitrify wastewater, a wastewater influent stream is alternatively directed to the anoxic reactors which are alternatively operated under aerobic and anoxic conditions so as to nitrify or denitrify the wastewater contained therein. To reduce or minimize the dissolved oxygen return from the membrane reactor to the first and second reactors, the flow of return activated sludge is controlled such that generally return activated sludge is returned to the reactor operating under aerobic conditions.

Claims17

Dependent claims

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:

a. alternatively directing a wastewater influent into first and second zones;
b. 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;
c. directing wastewater from either of the first or second zones to the downstream aerobic reactor having the one or more immersed membranes therein;
d. aerating the aerobic reactor;
e. directing wastewater in the aerobic reactor into the one or more immersed membranes and separating the wastewater into a permeate and return activated sludge;
f. pumping the permeate from the one or more immersed membranes in the aerobic reactor;
g. returning activated sludge from the aerobic reactor to either of the first or second zones;
and
h. 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.

6 more elements

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:

a. alternatively directing influent wastewater into the first and second reactors;
b. 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;
c. 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;
d. 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;
e. pumping the filtered effluent from the immersed membrane filter;
and
f. 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.

4 more elements

Dependencies are inferred from the claim text.

Method and system for nitrifying and denitrifying wastewater

Life of this patent

Method and system for nitrifying and denitrifying wastewater

Life of this patent

Abstract

Claims17