Evaluation of Process Control Alternatives for the Inactivation of Escherichia coli, MS2 Bacteriophage, and Bacillus subtilis Spores during Wastewater Ozonation

Dissolved ozone concentration integrated over time (CT) is a reliable indicator of disinfection efficacy in drinking water treatment. However, ozone CT may not be measurable in some wastewater ozone applications. In this study, alternative process control parameters, specifically ozone to total organic carbon (O-3:TOC) ratio, differential UV254 absorbance (UV254), and differential total fluorescence (TF), were correlated with the inactivation of Escherichia coli, the bacteriophage MS2, and Bacillus subtilis spores in five secondary wastewater effluents. CT values greater than 9 mg-min/L were generally required for measurable inactivation of B. subtilis spores, and CT values of 1 and 2 mg-min/L consistently achieved greater than 6- and 5-log inactivation of MS2 and E. coli, respectively. The O-3:TOC, UV254, and TF correlations for MS2 and B. subtilis were useful for predicting inactivation, while those of E. coli were characterized by greater variability.