As far as flocculation is concerned, the agglomeration of suspended particles into flocs is highly linked to the hydraulic behaviour of the agitation. The Turbomix® is a special design of mixing tank; its design was developed to better control the flow during the flocculation stage. It enables a significant decrease in footprint of the process. The combination of the Turbomix® and ballasted flocculation has been studied during pilot trials in terms of treatment efficiency. Its controlled hydraulic behaviour explains the efficiency of the process as proved by CFD investigation.