AWWA JAW49888

This research investigated the use of fluorescent-dyed polystyrene microspheres to assess drinking water disinfection efficiency in full-scale ozone contactors. A demonstration was conducted with one of two parallel full-scale ozone bubble-diffuser contactors at the Alameda County Water District Water Treatment Plant in Fremont, California. Microsphere suspensions were anlyzed by flow cytometry to determine changes in fluorescence distribution. Selection of threshold fluorescence intensities allowed the determination of microsphere "survival" ratios that were correlated with Cryptosporidium parvum inactivation curves. Compared with the concentration times contact time (CxT) concept, use of the surrogate indicators offered a potentially simpler and more accurate approach for assessing and optmizing ozone disinfection efficiency achieved in full-scale contactors and for demonstrating compliance with disinfection requirements. Includes 9 references, tables, figures.