The disinfection efficacy of chlorine and chlorine dioxide as disinfectants of Bacillus globigii, a surrogate for Bacillus anthracis, in water networks: A comparative study

Intentional contamination of drinking water with anthrax spores is a concern to water utilities. The spores may become embedded in the distribution pipe corrosion and biofilm, where they will be protected from residual disinfectants. This paper compares the disinfection effectiveness of chlorine and chlorine dioxide on Bacillus globigii, a surrogate for B. anthracis. Batch experiments were performed using both disinfectants. Data was analyzed using the delayed Chick-Watson model to determine the corresponding CT_lag (CT = concentration  ×  time) values and Watson plots, which indicate the dominant factors affecting disinfection kinetics. Chlorine dioxide had CT_lag values almost one tenth of those observed for chlorine. However, Watson plots showed that exposure time and disinfectant concentrations have equal weights on the inactivation rate of both disinfectants.