Hollenegg Wastewater Treatment Plant, Trag, Steiermark, Austria

The Hollenegg wastewater treatment plant is located in Trag, a locality in the municipality of Bad Schwanberg, within the Bezirk Deutschlandsberg district of Steiermark, Austria. The plant serves a population of approximately 1,990 people and operates with advanced treatment technology, ensuring high-quality effluent. Austrian wastewater treatment plants are regulated under the EU Urban Waste Water Treatment Directive (91/271/EEC), which mandates advanced treatment for sensitive areas. For a plant of this scale, secondary treatment is standard, but the advanced level here indicates additional nutrient removal or polishing steps. The plant's designed capacity is 2,500 m³/day, with a current discharge volume of 301.56 m³/day, suggesting ample reserve capacity. The treated effluent is discharged into local watercourses that ultimately drain into the Mur River, a major tributary of the Drava, which flows into the Danube and then the Black Sea. The plant plays a key role in protecting the local aquatic ecosystem and downstream water quality in the Mur-Drava-Danube basin.

The plant discharges into small streams that feed the Mur River, part of the Danube basin. The Mur supports diverse aquatic life and is an important migratory corridor for fish species. Downstream, the Drava and Danube rivers host ecologically sensitive habitats, making advanced treatment crucial for nutrient and pollutant control.