Grossklein Wastewater Treatment Plant, Großklein, Steiermark, Austria

The Grossklein wastewater treatment plant is located in the municipality of Großklein, in the Steiermark region of Austria. It serves a population of 1,659 people, placing it in the small agglomeration category under Austrian and EU regulations. The plant is situated in a rural area near the Sulm river basin, which ultimately drains into the Mur River and then the Drava and Danube rivers. The plant employs advanced treatment processes, which go beyond the secondary treatment required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. Advanced treatment typically includes nutrient removal (nitrogen and phosphorus) to protect sensitive receiving waters. The plant's designed capacity is 2,400 cubic meters per day, and it currently discharges 393 cubic meters daily, indicating ample reserve capacity. The treated effluent is discharged into local watercourses that feed into the Sulm river system. This area is part of the Danube basin, one of Europe's most significant river systems. The advanced treatment helps protect downstream aquatic ecosystems, including the Mur River and the Danube Delta, which support diverse fish populations and migratory bird species.

The plant discharges into the Sulm river catchment, a tributary of the Mur River, which flows into the Drava and then the Danube. The Danube basin is a major European watershed supporting diverse aquatic life, including sturgeon and other migratory fish. The advanced treatment at Grossklein helps reduce nutrient loading, protecting downstream ecosystems from eutrophication.