Inactivation kinetics of Enterococcus faecium, a pathogen surrogate, by aqueous ozone in purified water at different salt contents, pH, and treatment temperatures.

In recent years, the demand for purified bottled water modified with dissolved solids, with or without elevated pH, has increased. Verifying the efficacy of decontamination technologies on these alternative types of bottled water is important for ensuring consumer's safety. Hence, this study was initiated to determine if waters having different chemical compositions need to be ozone-treated differently than purified bottled water without modifications. To meet this goal, (a) the relationship between ozone dose (Ct, min.mg/L) applied to these nonconventional waters and the associated reduction in the population (Δ log10 (CFU/mL)) of Enterococcus faecium, a pathogen surrogate, was modeled, and (b) the lower bounds of the 95% confidence for these dose-response plots were calculated to determine the minimum ozone treatment required to process these waters. When the dose-response relationship for different treated waters was modeled, an exponential model optimally described this relationship. Based on the ozone dose-response function representing the lower bounds of the 95%-confidence, 0.318-0.467 min.mg/L were the least ozone Ct values sufficient to exert 5-log reduction in E. faecium populations in neutral water at 4 °C, with or without added salt. These cardinal Ct values were much smaller than the value observed in a previous study (0.786 min.mg/L) when neutral purified water was treated at 21 °C. On the contrary, purified alkaline water required 0.884 min.mg/L when treated at 4 °C and 3.346 min.mg/L when treated at 21 °C. These data emphasize the importance of revising the ozone-based water decontamination technology when the composition of purified water is modified.