StJohann id Haide Wastewater Treatment Plant - Sankt Johann in der Haide, Styria, Austria

StJohann id Haide is an advanced wastewater treatment plant located in Sankt Johann in der Haide, a municipality in the Bezirk Hartberg-Fürstenfeld district of Styria, Austria. The plant serves a population of 1,854 and has a designed capacity of 3,000 m³/day, with a current discharge volume of 239 m³/day. The plant employs advanced treatment processes, which go beyond secondary treatment to remove nutrients and other pollutants. As an Austrian facility, it operates under the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires advanced treatment for sensitive areas and agglomerations of this scale. The treated effluent is discharged into local watercourses that eventually drain into the Danube River basin, contributing to the protection of the Black Sea ecosystem. The plant plays a key role in maintaining water quality in the region's streams and rivers.

The plant discharges into local streams that flow into the Raab River, a tributary of the Danube. The Danube ultimately drains into the Black Sea, making the plant part of a large international watershed. The region's aquatic ecosystems support diverse species, and the plant's advanced treatment helps reduce nutrient loading that could cause eutrophication downstream.