Dissolved Air Flotation (DAF) has received more attention recently as separation technique in both drinking water production as well as wastewater treatment. However, the process as well as the preceding flocculation step is complex and not completely understood. Therefore, given, the multiphase nature of the process (liquid, solids and gas) research in the field of DAF requires fluid dynamics studies in order to understand and optimize the system in terms of operation and design. The present study simulates the flow patterns inside a large DAF tank (WPC Kluizen, Belgium), employing computational fluid dynamics (CFD). An Euler-Langrangian approach is used for the multiphase flow in 2D. The flow patterns are found to be strongly dependent on the flow conditions at the inlet and the injectors.