Wolf, Camillevon Gunten, UrsKohn, Tamar2018-03-012018-03-012018-03-012017-05-15https://infoscience.epfl.ch/handle/20.500.14299/145116Disinfection is an important step in (waste)water treatment to prevent the transmission of waterborne diseases. Ozone is an effective disinfectants against all types of waterborne pathogens, including viruses. While ozone has typically been used to treat drinking water, its application to wastewater (WW) has also been tested. However, in particular for virus inactivation, data regarding its efficacy remain scarce. In Switzerland, a new regulation mandates the upgrade of major WW treatment plants with an advanced treatment step such as ozonation, for the abatement of micropollutants. This measure could also result in the inactivation of enteric viruses, though to an unknown extent. There are many practical limitations to directly monitoring concentration and infectivity of enteric viruses during WW ozonation. However, inactivation may be estimated if the ozone exposure, the virus inactivation rate constants and their susceptibility to environmental parameters (pH, temperature, dissolved organic matter (measured as DOC)) are known. Alternatively inactivation may be monitored based on an “easy-to-measure” proxy. For example, the decrease in UV254 absorbance (ΔUV254) is indicative of the extent of micropollutant removal during ozonation of WW. ΔUV254 is an indirect measure of the ozone exposure, which in turn, depends on the specific ozone dose (mg O3/mg DOC). Similar proxies may exist for viruses. The objectives of this study were (1) to quantify the second order ozone inactivation rate constants (kO3-Virus) for several enteric viruses and bacteriophages in buffered solutions and assess their dependence on temperature and pH; (2) to assess the influence of DOC on inactivation in differing water matrices; and (3) to test the utility of ΔUV254 as a proxy for inactivation. To determine kO3-Virus in buffered solutions, an experimental system was developed that allows to track ozone exposure and virus inactivation accurately and simultaneously. Experiments were conducted over a temperature range of 2-22° C and a pH range of 6.5-8.5. Due to the relatively fast decay kinetics, ozone exposure in environmental water matrices were determined by a quenched-flow method. The kO3-Virus of all viruses tested spanned a narrow range of 105 to 106 M-1s-1. Q was the most susceptible, and T4 and an environmental isolate of CoxB5 were the most resistant. Interestingly, significant differences in the rate constants of differing CoxB5 isolates and its lab strain were observed. Both pH and temperature increases resulted in higher kO3-Virus values, though the effect of temperature was more pronounced. In buffered solutions, the ozone exposures to inactivate 99% of viruses were about 100x lower than those reported for ClO2 and free chlorine. Effects of DOC on kO3-Virus and correlations between ΔUV254 and virus inactivation in WW are currently under investigation. Overall, our findings demonstrate that ozone is an effective disinfectant for viruses in WW effluent.text::conference output::conference poster not in proceedings