Method and apparatus for maximizing nitrogen removal from wastewater

Abstract

A reactor and control method for maximizing nitrogen removal and minimizing aeration requirements through control of transient anoxia and aerobic SRT, repression of NOB, and control of dynamic DO concentrations or aeration interval by keeping the reactor NH 4 and NO x concentrations approximately equal. Controls are provided for maximizing the potential for TIN removal through nitrification, limited nitritation, nitritation, denitrification, limited denitritation, denitritation making use of 1) real time measurement of ammonia, nitrite, nitrate, 2) operational DO and the proper use of DO setpoints, and 3) proper implementation of transient anoxia within a wide range of reactor configurations and operating conditions.

1 - 10 . (canceled) 
     
     
         11 . A method of removing nitrogen from wastewaters in a reactor comprising:
 a. oxidizing a fraction of an influent ammonia load to produce nitrite and nitrate, wherein the oxidation is conducted by providing an amount of aeration that is sufficient to oxidize only a fraction of the influent ammonia for which there is a sufficient amount of chemical oxygen demand (COD) in a reactor that will subsequently reduce the oxidized nitrogen species;   b. measuring a concentration of ammonia and a concentration of oxidized nitrogen in the reactor, wherein the concentration of oxidized nitrogen corresponds to a sum of a concentration of nitrite and a concentration of nitrate; and   c. controlling a concentration of dissolved oxygen (DO) supplied to the reactor, and/or a frequency at which aeration occurs in the reactor, based on a ratio of the [concentration of ammonia] to the [sum of the concentrations of nitrite and nitrate].   
     
     
         12 . The method of  claim 11 , wherein the concentration of dissolved oxygen supplied to the reactor and/or the frequency at which aeration occurs in the reactor is increased if the ratio of the [concentration of ammonia] to the [sum of the concentrations of nitrite and nitrate] is greater than 1. 
     
     
         13 . The method of  claim 11 , wherein the concentration of dissolved oxygen supplied to the reactor and/or the frequency at which aeration occurs in the reactor is decreased if the ratio of the [concentration of ammonia] to the [sum of the concentrations of nitrite and nitrate] is less than 1. 
     
     
         14 . The method of  claim 11 , wherein the concentration of dissolved oxygen supplied to the reactor and/or the frequency at which aeration occurs in the reactor is maintained if the ratio of the [concentration of ammonia] to the [sum of the concentrations of nitrite and nitrate] is 1. 
     
     
         15 . The method of  claim 11 , further comprising controlling a limited aerobic sludge retention time in the reactor, based on the ratio of the [concentration of ammonia] to the [sum of the concentrations of nitrite and nitrate]. 
     
     
         16 . The method of  claim 11 , further comprising controlling an extension and/or volume of anoxic periods based on the ratio of the [concentration of ammonia] to the [sum of the concentrations of nitrite and nitrate]. 
     
     
         17 . The method of  claim 11 , further comprising enhancing an oxygen uptake rate (OUR) to facilitate a plurality of rapid transitions from an aerobic condition to an anoxic condition by maintaining a concentration of a mixed liquor solid (MLSS) that is higher than 2 g/L or by maintaining equivalent biomass quantities in a biofilm system. 
     
     
         18 . The method of  claim 17 , wherein an aeration control system is used to control a frequency of the transitions between the aerobic and anoxic conditions. 
     
     
         19 . The method of  claim 11 , wherein the reactor is a sequencing batch reactor or a completely mixed reactor. 
     
     
         20 . The method of  claim 11 , wherein the method is an oxidation ditch process or a plug flow process. 
     
     
         21 . The method of  claim 11 , further comprising at least one of a suspended growth process, a granular process, a biofilm process or a combination thereof. 
     
     
         22 . The method of  claim 11 , further comprising a separation process using a settler, a dissolved air flotation device, a filter or a membrane. 
     
     
         23 . The method of  claim 11 , further comprising feeding a minimum mass-flow of organic carbon to the reactor to facilitate a rapid transition to an anoxic state from an aerated state and to provide additional competition for nitrite to improve repression of NOB. 
     
     
         24 . The method of  claim 11 , further comprising supplying the reactor with an anammox organism to provide competition for nitrite to improve repression of NOB. 
     
     
         25 . (canceled) 
     
     
         26 . (canceled) 
     
     
         27 . A method of removing nitrogen from wastewaters comprising:
 a. oxidizing a fraction of an influent ammonia load to produce nitrite and nitrate, wherein the oxidation is conducted by providing an amount of aeration that is sufficient to oxidize only a fraction of the influent ammonia for which there is a sufficient amount of chemical oxygen demand (COD) in at least one reactor that will subsequently reduce the oxidized nitrogen species;   b. measuring a concentration of ammonia and a concentration of oxidized nitrogen in the at least one reactor, wherein the concentration of oxidized nitrogen corresponds to a sum of a concentration of nitrite and a concentration of nitrate;   c. controlling a concentration of dissolved oxygen (DO) supplied to the at least one reactor, and/or a frequency at which aeration occurs in the at least one reactor, based on a ratio of the [concentration of ammonia] to the [sum of the concentrations of nitrite and nitrate], wherein such conditions repress nitrite oxidizing bacteria;   d. producing an effluent stream from the at least one reactor containing approximately equal proportions of ammonia and nitrite or oxidized nitrogen on an as nitrogen basis, such that further nitrogen removal can be accomplished using anammox in a fully anoxic suspended or biofilm process.   
     
     
         28 . The method of  claim 27 , further comprising adding acetate or acetic acid or other organic substrate to the effluent stream to accomplish denitratation (nitrate reduction to nitrite) and subsequent anammox growth on the provided ammonia and denitratation-produced nitrite. 
     
     
         29 . The method of  claim 27 , further comprising feeding the effluent stream into a downstream reactor for post-anammox polishing. 
     
     
         30 . The method of  claim 27 , wherein the at least one reactor comprises multiple reactors in series.