Many stormwater retention basins currently in operation still have shortcomings in terms of particulate retention through sedimentation. At the Aschbach stormwater overflow basin in Saarland, CFD methods are being used to investigate, as an example, the extent to which retrofitting with inclined clarifier elements can improve particle retention and contribute to more effective protection of surface waters.

Specifically, the retention capacity of particles with diameters ranging from 5 to 200 µm through sedimentation and storage in the water body was determined for three variants. In two variants, counter-current lamellas were integrated and compared to a control variant without retrofitting. The lamellae in the sedimentation chamber demonstrate a significant increase in particle retention. At the lowest hydraulic load, the retention efficiency increases by up to 32.7%, and at the highest hydraulic load, by up to 27.3%.