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Reaction Description <br />Overall Reaction <br />1. Ammonium and nitrite utilization <br />NH3 + OZ -> NOZ + 3H++ 2e- <br />eNO2 <br />5:1 <br />4 <br />NO2-+ H2O -> NO3 + 2H+ +2e- <br />2e2. <br />2. <br />Release of ammonia through chloramine decay <br />3NH2C1 N2 + NH3 + 3C1 + 3H+ <br />1.0 <br />autodecom osition <br />3:1 <br />3. <br />Release of ammonium through oxidation of organic <br />1/10 C5H702N +NH2C1 + 9/1OH20 -+ 4/100O2 + 1/IOHCO3 <br />5:1 <br />matter by chloramine <br />+ 11/lONH4++Cl" <br />4. <br />Release of ammonium through reaction of chloramine <br />1/2NH2C1 + W+ Fe 2+ --> Fe3++ 1/2NH ++ 1/2C1- <br />4 <br />0.8 <br />with corrosion products at pipe surfaces* <br />3:1 <br />5. <br />Release of ammonia through catalysis reactions of <br />3NH2C1 N2 + NH3 + 3C1" + 3H+ <br />5:1 <br />chloramine atpipe surfaces <br />0.4 <br />6. <br />Release of ammonia through oxidation of nitrite byNH <br />Cl + NO " + H O CNH + NO3'+ HCl <br />2 2 2 3 <br />0.5 <br />chloramine* <br />3:1 <br />Source: Adapted from Woolschlager et al. 2001 <br />* These equations may not be significant in distribution systems, especially in situations of biologically -accelerated <br />chloramine decay. <br />In this case, ammonium is released through oxidation of organic matter by chloramine. Greater <br />than one mole of ammonium is produced (11/10 mole), all of which can be converted to nitrate, <br />based on the molar ratios presented in Reaction 1. Many of these reactions can occur <br />simultaneously; however, a conservative approach for predicting maximum nitrite/nitrate <br />formation would be to use Reaction 3 in Table 2. Based on this approach, Table 3 was <br />developed to assess the impact of C12:NH3-N ratio, total chloramine dose, and chloramine decay <br />on theoretical nitrite/nitrate-N formation through nitrification. <br />Chlorine to Ammonia -N <br />Ratio <br />'Cotal Chlorine Dose <br />(mg/L) <br />Ammonia -N Dose <br />(mg/L) <br />Nitrite/Nitrate-N Produced* <br />(mg/L) <br />5:1 <br />4 <br />0.8 <br />0.9 <br />4:1 <br />4 <br />1.0 <br />1.1 <br />3:1 <br />4 <br />1.3 <br />1.5 <br />5:1 <br />3 <br />0.6 <br />0.7 <br />4:1 <br />3 <br />0.8 <br />0.8 <br />3:1 <br />3 <br />1.0 <br />1.1 <br />5:1 <br />2 <br />0.4 <br />0.4 <br />4:1 <br />2 <br />0.5 <br />0.6 <br />3:1 <br />2 <br />0.7 <br />0.7 <br />5:1 <br />1 <br />0.2 <br />0.2 <br />4:1 <br />1 <br />0.3 <br />0.3 <br />3:1 <br />1 <br />0.3 <br />0.4 <br />* Assumes: (1) 100% of chloramine <br />decav according to reaction: ,,,A C�H2O,N + NH,C1 + a„nH2O -> d,,,,CO, + <br />iiioHCO3 + 1 i/1oNH4+ + Cl-, (2) 100% conversion of ammonia to nitrite/nitrate. <br />Prepared by AWWA with assistance from Economic and Engineering Services, Inc. 6 <br />