Use of MS2 Coliphage as a Surrogate for Enteric Viruses in Surface Waters Disinfected with Ozone

The purpose of this study was to determine the relative inactivation of MS2 coliphage (American Type Culture Collection strain 15597-B1) and heterotrophic plate count bacteria using raw surface water under a variety of naturally occurring conditions. It was found that the applied ozone dose and dissolved organic carbon had the most impact on ozone disinfection of MS2 coliphage and HPC bacteria. The dissolved organic carbon was found to compete for the ozone and significantly reduce the inactivation of both the coliphage and the bacteria. Furthermore, it was observed that the presence of any ozone residual inactivated greater than 4 logs MS2 coliphage and 2 logs heterotrophic plate count bacteria within a 30 second contact time. Ozone residuals greater than 0.20 mg/L inactivated greater than 5 logs MS2 coliphage and 3 logs heterotrophic plate count bacteria also within 30 second contact time. Comparison of inactivation studies indicate that MS2 coliphage is probably more sensitive to ozone than enteric viruses. It was concluded that the regulatory agencies should reevaluate their recommendations for using MS2 coliphage as an ozone disinfection indicator of enteric viruses.