The settling velocity describes the speed at which particles in a liquid sink by gravity. It is a decisive parameter in sedimentation tanks and clarification processes, where solids are separated from the water by sedimentation. The settling velocity varies depending on the density and size of the particles. In practice, the settling velocity is used to determine the size and dimensioning of sedimentation tanks. For example, larger particles such as sand settle faster than fine sludge, which is why the process in water treatment is supported by the addition of flocculants to accelerate sedimentation.