A full-scale ozonation reactor was characterised with respect to the overall oxidation budget by coupling laboratory kinetics with reactor hydraulics. The ozone decomposition kinetics and the ratio of the OK radical to the ozone concentration were determined in laboratory batch experiments. With the computer model AQUASIM these parameters could be coupled with the hydraulics of the ozonation reactor which allowed the prediction of the behaviour of ozone, chlorine, and micropollutants (e.g. atrazine) in the reactor. The comparison of measured and modelled concentration showed an excellent agreement. The present study summarises a general approach of how full scale ozonation reactors can be calibrated to assess disinfection, oxidation and minimise disinfection by-products, such as bromate.