Being a measure to counteract an increasing water scarcity in multiple regions of the world, water reuse is the subject of numerous investigations. The pan-European project DEMOWARE aims at tackling barriers related to water reuse to support further applications. At the project site of Braunschweig in Germany wastewater is reused historically to irrigate agricultural fields. Against the background of an ongoing debate in Germany to establish a legal basis for water reuse, options for a disinfection of secondary treated wastewater were tested at the wastewater treatment plant Steinhof. This thesis investigates the disinfection performance of two pilot scale plants (performic acid (PFA) dosage and UV irradiation) against the background of the compliance with wastewater-related standards, especially DIN 19650 and a WHO guideline regarding wastewater reuse. In order to meet recommendations of the latter, a noro- and rotavirus removal of 1.5 log was recommended by (1) for the site of Braunschweig. E. coli, intestinal enterococci (IE) and Clostridium perfringens were analyzed regarding their abundance and log removal concerning physicochemical properties. Serving as indicator organisms, they were related to the log removal of noro- and rotavirus. Differing doses were tested. The impact of the contact time was investigated for PFA by the presence or absence of sodium thiosulfate (STS) in the sampling bottles whereat the presence of STS terminates the disinfection process. The application of STS in the PFA sampling bottles caused a performance difference of 1.32 log for E. coli, 0.78 log for IE and 0.28 log for C. perfringens. Hence, the PFA reaction was not completed at the effluent sampling spot of the reactor (stirrer tank) and the determined minimum contact time of 3.5 min is not sufficient for PFA to develop its complete disinfection performance. The disinfection reactor did not provide the minimum recommended RT (10 min). Possibly, short circuits and zones with limited substance exchange occur. For full scale implementations, the PFA contact basins need to be designed carefully. A flow channel as used at full scale reference applications is preferable here. The PFA plant showed break-ins of the disinfection performance (to values < 0.5 log) for definable and indefinable reasons. Hence, its disinfection performance is not constant. Further investigations are necessary. Of the 3 doses per method deployed, a UV dose of 44 Wh/m³ and a PFA dose of 2 ppm (= 10 min, without STS) is proper to achieve quality class 3 of the DIN 19650 which is required for the present conditions and applications in Braunschweig. The requirements for a noro- and rotavirus removal of 1.5 log units according to the WHO guideline can be satisfied by a dose of 2 ppm of PFA and 35 Wh/m³, respectively, using an evaluation based on the mean value of the disinfection performance (both PFA and UV). By the application of a threshold-based evaluation the requirements are not satisfied for UV irradiation. Regarding PFA dosing, a dose of 2 ppm is sufficient as long as a sufficient contact time (= 10 min) is provided. The order of sensitivity against the disinfection methods was found for both UV irradiation and PFA dosage the same: E. coli > E. cocci > C. perfringens. Clostridium being used as an indicator for endospore-formers showed a remarkably lower sensitivity against both methods. A doseperformance-linearity can be suggested for the present range of dosage for E. coli and IE. C. perfringens does not show a correlation between the PFA/UV dose and the disinfection performance.