After 40 years of operation, the old circular grit chamber with circular scrapers at Düsseldorf-Süd Wastewater Treatment Plant was replaced by a new grit chamber with two stainless steel longitudinal scrapers. The new scrapers, each weighing 4,5 tons, with a span of 13 meters, run over two parallel sand-trap basins. In January 2017, the demolition works of the old plant began, as the previous plant components were no longer economically feasible to overhaul. The renovation and renewal of the mechanical treatment stage is carried out while maintaining the treatment plant in operation. DAHLEM provides the project and technical design planning (construction technology, structural design, technical equipment) through to the construction supervision.