This project, which is a collaboration with the group of Prof. von Gunten, is situated in an active research area of environmental engineering, namely the use of advanced oxidation technologies in (waste)water treatment. Ozonation is an increasingly popular component of (waste)water treatment. In Switzerland recent legislation mandates that the 100 largest wastewater treatment plants upgrade to include advanced treatment, such as ozonation. While the main purpose of this upgrade is the removal of micropollutants, the use of ozone will also significantly improve the microbial quality of the wastewater effluent. This aspect, however, is yet understudied. Specifically for this project, we have developed an experimental approach with which we can quantify the efficacy of ozone toward waterborne viruses, and unravel the associated mechanisms. The data will be validated in environmental matrices, and in a pilot-scale treatment plant. Ultimately, this project will provide unique information regarding the efficacy of ozone toward viruses, and it will provide practical tools for treatment engineers and regulators to estimate virus inactivation in treatment plants.