In Switzerland, newly introduced regulation mandates the upgrade of major wastewater treatment plants (WWTP) with an advanced treatment step such as ozonation. This offers a unique opportunity to study the inactivation of enteric virus during ozonation of wastewater. In order to create generally applicable results, a better understanding of kinetics of inactivation by ozone is required. These kinetics are difficult to determine, because viruses become inactivated very rapidly and the ozone exposure is difficult to determine. The first challenge was thus to develop an experimental strategy to measure ozone exposure (concentration x time) as well as virus inactivation in clean water matrices, in order to derive inactivation rate constants. This poster will present the experimental strategy, and demonstrate the rate constants that have been measured for several bacteriophages and enteric viruses, along with their pH and T dependence.