AWWA ACE68640

This powerpoint presentation begins by providing a brief overview of pathogen disinfection research in water network biofilms, along with pathogen surrogates, unique research aspects of pathogen adhesion to biofilm, and chlorine dioxide as an alternative disinfectant. The objectives of this research were to: develop a correlation between chlorine and chlorine dioxide during disinfection of B. globigii; determine the CT values at different concentrations needed to reach 1, 2 and 3 log reductions; identify the CT_lag value that each disinfectant requires to overcome mass transfer limitations due to its properties at the specified disinfection pH and spore surface charge by using the delayed Chick-Watson model; and, determine the effect of exposure time and concentration on the inactivation rate. Initial experiments consisted of the following: model distribution system was a Biofilm Annular Reactor (BAR) with iron coupons; surrogates were pulse injected (lebsiella pneumoniae (Burkholderia mallei) and Bacillus globigii (Bacillus anthracis)); and, the objective was to determine the disinfection of these organisms in biofilms growing on rusted iron using chlorine. Topics presented include: preliminary B. globigii disinfection research with chlorine; bulk disinfection experiment results; delayed Chick Watson Model; Watson Plot Analysis; Watson Plots for bulk experiments; biofilm development; biofilm disinfection Watson Plots; chlorine dioxide results; cement and cement-lined pipe; results relative to cast iron pipe; and, concrete pipe conclusions. Includes figures.