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

Abstract

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 (O₃:TOC) ratio, differential UV₂₅₄ absorbance (ΔUV₂₅₄), and differential total fluorescence (ΔTF), 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 O₃:TOC, ΔUV_254, and ΔTF correlations for MS2 and B. subtilis were useful for predicting inactivation, while those of E. coli were characterized by greater variability. [Supplementary materials are available for this article. Go to the publisher's online edition of Ozone: Science & Engineering for the following free supplemental resources: additional figures and data tables.]

Keywords:

• Ozone
• Advanced Oxidation
• Disinfection
• Wastewater Treatment
• Absorbance
• Fluorescence
• CT
• Bacteria
• Virus
• Spore

ACKNOWLEDGMENTS

This study was made possible through funding from the WateReuse Research Foundation (WRF-08-05, WRF-08-08, and WRF-09-10). The comments and views detailed herein may not necessarily reflect the views of WateReuse, its officers, directors, employees, affiliates or agents. The authors would like to thank members of the Applied Research and Development Center at the Southern Nevada Water Authority for all of their efforts during this study. The authors would also like to thank the technology partners, particularly APTwater, Hydranautics, and s::can Messtechnik for their generous contributions to the project. The personnel at the various study sites were also instrumental in the design, scheduling, and implementation of the sampling efforts.