Nusse Ritzerau Wastewater Treatment Plant, Nusse, Schleswig-Holstein

Nusse Ritzerau is a former wastewater treatment plant located in the municipality of Nusse, within the district of Herzogtum Lauenburg in Schleswig-Holstein, Germany. It served a small population of approximately 1,428 people, reflecting the rural character of the area. The plant is now closed, and its operational history is part of the regional wastewater infrastructure. During its operation, the plant provided secondary treatment, which is the standard biological treatment stage required under the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. The directive mandates secondary treatment for discharges into freshwater and estuaries from populations between 2,000 and 10,000, and for larger agglomerations. Although the plant served fewer than 2,000 people, it still met the secondary treatment standard. The designed capacity was 2,200 cubic meters per day, with an average discharge volume of 361.39 cubic meters per day. The plant's treated effluent was discharged into local watercourses that eventually drain into the Baltic Sea via the Trave River system. The region's watershed supports diverse aquatic life and is part of the larger Baltic Sea catchment, which is ecologically sensitive due to nutrient enrichment concerns.

The plant discharged into small streams that flow into the Trave River, which ultimately reaches the Baltic Sea near Lübeck. The Baltic Sea is a semi-enclosed brackish sea with limited water exchange, making it vulnerable to eutrophication from nutrient inputs. The local watershed in Schleswig-Holstein is characterized by agricultural land use, which can contribute to nutrient runoff. The plant's secondary treatment helped reduce organic pollutants and nutrients, protecting downstream aquatic ecosystems.