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The results in Table 3 show that using the most conservative chloramine decay reaction, the nitrite -N MCL of 1 mg/L could theoretically be exceeded if the chloramine dose is at 3 or 4 mg/L (as total chlorine), and the C12:NH3-N ratio is less than 5:1. As the chlorine to ammonia -N ratio decreases, more ammonia becomes available for the nitrification process. This calculation is quite conservative as it is unlikely that 100% of chloramine decay will occur according to one single pathway. Valentine et al (1998) conducted a series of mass and redox balances on solutions of varying pH, NOM concentration, and initial chloramine concentration. For all conditions that were studied, the amount of nitrate formed as a percentage of monochloramine decay was less than 15 percent, and for all but three cases the amount was less than 10 percent. The authors concluded that although nitrate is an important decomposition product of monochloramine decay, it is not the major nitrogen -containing decay species. Using data from a survey of 40 utilities that use chloramine as a disinfectant and an earlier survey by Hack (1984), Wilczak et al. (1996) indicate that nitrite and nitrate levels may increase on the order of 0.005 to 0.5 mg/L, although increases of greater than 1 mg/L are possible. The authors concluded that changes in nitrite and nitrate levels in drinking water usually caused by nitrification are not substantial enough to exceed regulatory requirements as long as source related levels are not near the regulatory MCLs. Nitrite levels during nitrification episodes have been reported ranging from 0.005 to 0.5 mg/L as NOz - N, with levels more frequently ranging from 0.015 to 0.1 mg/L (Wolfe et al. 2001). Figure 1 compares treatment plant effluent and distribution system nitrite concentrations in nine chloraminating utilities (Kirmeyer et al. 1995). This figure demonstrates that nitrite levels during nitrification events can vary from as little as 0.05 mg/L to as much as 1 mg/L. 01 001 Nitrite -nitrogen 8 0 130 O O 8 - Q B O O O 001 .01 .1 Concentration in plant effluent (mg/L) Figure 1 Comparison Between Plant Effluent and Distribution System Concentrations of Nitrite Source: Kirmeyer et al. 1995 Prepared by AWWA with assistance from Economic and Engineering Services, Inc. E N T O Winter Sampling N C O a O Summer Sampling m Observations located above diagonal �o rn c E indicate greater concentration in the 0 distribution system than in treatment plant effluent. C U U C O U 01 001 Nitrite -nitrogen 8 0 130 O O 8 - Q B O O O 001 .01 .1 Concentration in plant effluent (mg/L) Figure 1 Comparison Between Plant Effluent and Distribution System Concentrations of Nitrite Source: Kirmeyer et al. 1995 Prepared by AWWA with assistance from Economic and Engineering Services, Inc.