Altenmarkt bei St Gallen Wastewater Treatment Plant, Weißenbach an der Enns, Steiermark

The Altenmarkt bei St Gallen wastewater treatment plant is located in Weißenbach an der Enns, a small settlement in the municipality of Sankt Gallen, Bezirk Liezen, in the state of Steiermark, Austria. The plant serves a population of 5,678 people, placing it in the small-to-medium agglomeration category under Austrian and EU regulations. The plant employs advanced treatment processes, which go beyond the secondary treatment standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. With a designed capacity of 7,500 m³/day and an actual discharge volume of 575.28 m³/day, the plant operates well below its capacity, indicating robust infrastructure for current loads. As an Austrian facility, it operates under the national Water Act (Wasserrechtsgesetz) and is subject to strict discharge limits. The treated effluent is discharged into the local water system, which ultimately drains into the Enns River, a major tributary of the Danube. The Enns River flows through the mountainous region of Steiermark and supports diverse aquatic life. The advanced treatment helps protect the downstream water quality in the Danube basin, which is ecologically sensitive and supports numerous species.

The plant discharges into the Enns River catchment, which flows northward to join the Danube near Enns. The Enns River is a significant alpine river supporting fish species such as brown trout and grayling. The advanced treatment ensures minimal nutrient and pollutant loading, protecting the downstream aquatic ecosystem in the Danube basin, which is a vital European waterway.