The lack of detailed knowledge about the interaction of the velocity field and suspended sludge poses an obstacle in designing more effective sedimentation tanks. This study investigates the use of CFD analysis of hydraulic processes and the influence of seasonal temperature change on a waste water treatment sedimentation tank. The object analysed in this pilot research is a part of the WWTP in Nitra-Dolné Krškany, SK. The analysis was conducted using the CFD model ANSYS Fluent ® , supported by field measurement data, which was gathered on two separate occasions in July 2015 and February 2016 at the sedimentation tank during operation. Three parameters were collected in 400 measurement points throughout the tank. During the research we analysed the data, looking for correlation with the CFD simulation to verify the results and correlations between the winter and summer period to determine the influence of varying temperatures. Graphical abstract