Efficacy of Chlorine Dioxide as a Disinfectant for Bacillus Spores in Drinking-Water Biofilms

Abstract

This paper presents results describing the effectiveness of chlorine dioxide penetration into a drinking-water distribution system biofilm/corrosion matrix and decontamination of adhered Bacillus globigii spores, a surrogate for Bacillus anthracis. Biofilm and corrosion products were developed using biofilm annular reactors containing oxidized scaled, iron coupons. Reactors were inoculated with B. globigii spores after biofilm development, and decontamination was undertaken with bulk-phase chlorine dioxide concentrations of 5, 10, 15, and 25 mg/L. Initial biofilm viable B. globigii spore densities of 106 CFU/cm2 were reduced to 50 to 300 CFU/cm2 at chlorine dioxide concentrations of 25 and 15 mg/L, respectively, within 6 days. B. globigii spore distribution throughout the biofilm/corrosion matrix depth and the change in viable spore count during chlorine dioxide disinfection were examined using a microslicing technique. Four layers of 360 μm thickness were sliced, and these showed that B. globigii spo...