AWWA JAW11140

N-chloroorganic compounds, formed when N-organic precursors are chlorinated, react similarly with analytical reagents used to determine free available chlorine (FAC), and may lead to falsely positive tests for FAC and an overestimation of the presumed level of disinfection. Bacterial kill measurements were carried out using apparent FAC residuals of 0.2 (plus or minus 0.01) mg/L or 0.05 (plus or minus 0.01) mg/L free chlorine as Cl2. Disinfection periods of 15 and 5 minutes were used, respectively, at pH 7 and 25 degrees C. The results indicated no decrease in the disinfection levels of Escherichia coli in solutions that contained N-organic compounds compared with control solutions that did not contain such compounds. This lends support to the use of monitoring of 0.02 mg free chlorine residual as chlorine dioxide/L instead of actual bacteriological enumeration, as described in USEPA primary drinking water regulations for neutral waters containing these levels of measured FAC and nitrogenous materials. Includes 27 references, tables, figures.