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 (±0.01) mg/L or 0.05 (±0.01) mg/L free chlorine as Cl2. Disinfection periods of 15 and 5 min were used, respectively, at pH 7 and 25°C. The results indicated no decrease in the disinfection levels of E. coli in solutions that contained N‐organic compounds compared with control solutions that did not contain such compounds.
