ARA Karlstein 1475 WT - Advanced Wastewater Treatment in Obergrünbach, Niederösterreich

ARA Karlstein 1475 WT is an advanced wastewater treatment plant located in Obergrünbach, a village in the municipality of Karlstein an der Thaya, in the Niederösterreich region of Austria. The plant serves a population of 1,291 and is part of the local municipal wastewater infrastructure. The plant provides advanced treatment, which goes beyond secondary treatment to remove nutrients such as nitrogen and phosphorus. With a designed capacity of 2,700 m³/day and an actual discharge volume of 327.47 m³/day, the plant operates well below its capacity. Under the EU Urban Waste Water Treatment Directive (91/271/EEC), agglomerations of this size (under 2,000 population equivalent) are typically required to provide appropriate treatment, and Austria's national regulations mandate advanced treatment for sensitive areas. The treated effluent is discharged into the local water system, which ultimately drains into the Thaya River, a tributary of the Morava River, which flows into the Danube. The Danube then carries the water to the Black Sea. The plant plays a key role in protecting the Thaya River and downstream ecosystems from nutrient pollution.

The plant discharges into the Thaya River basin, which flows into the Morava River and then the Danube, ultimately reaching the Black Sea. The region is part of the Danube River Basin, a transboundary watershed supporting diverse aquatic life and important for migratory fish. Advanced treatment helps reduce nutrient loads, protecting downstream water quality and preventing eutrophication in sensitive areas.