In the recent years, an increasing number of organic micropollutants (OMPs) such as pharmaceuticals, industrial chemicals etc. have been detected within the water cycle. Conventional municipal wastewater treatment plants (WWTPs) are an important entry path of OMPs into the surface waters, as they can only partly eliminate OMPs. Thus, advanced wastewater treatment options such as activated carbon and/or ozonation can be used to reduce the amount of OMPs entering the receiving waters. Especially for the operation of an ozonation plant, aspects such as monitoring of the OMP elimination as well as an adaption of the ozone dose to a varying water quality are of great importance. Practical experiences in the last years have shown that the reduction of UVA254 (delta UVA254) by the ozonation can be used for the regulation of the ozone dose [1] and to monitor the ozonation process as it is recommended by the Swiss Water Association (VSA) in addition to a periodic measurement of the OMP elimination [2]. As an alternative to UVA254, usage of fluorescence online sensors have been also in discussion as its decrease due to the ozonation process also shows a good correlation with the OMP elimination [3]. Currently, fluorescence online measurements are used for detecting algae blooms in lakes or oil in water. However, practical experiences of the operation of fluorescence online sensors at ozonation plants used for OMP elimination are limited. Within this presentation results of the operation of a fluorescence online measurement at an ozonation pilot plant will be shown and compared to the operation of a UVA254 online measurement regarding sensitivity, impact of the water matrix, fouling effects as well as maintenance efforts.