Kalwang Wastewater Treatment Plant, Schattenberg, Steiermark, Austria

The Kalwang wastewater treatment plant is located in Schattenberg, a locality in the municipality of Kalwang, Bezirk Leoben, Steiermark, Austria. It serves a population of approximately 1,945 people, placing it in the small agglomeration category under Austrian and EU regulations. 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. With a designed capacity of 5,000 m³/day and an average discharge volume of 326.48 m³/day, the plant operates well below its capacity, indicating room for future growth or seasonal variations. The treated effluent is discharged into local watercourses that ultimately drain into the Danube River basin, contributing to the Black Sea watershed. The advanced treatment level ensures high-quality effluent, protecting downstream aquatic ecosystems and supporting the ecological health of the region's rivers and streams.

The plant discharges into small streams in the Mur River catchment, part of the Danube basin. The Mur River flows through Steiermark and into Slovenia, Croatia, and Hungary before joining the Drava and eventually the Danube. The region supports diverse aquatic life, including fish species such as brown trout and grayling. Advanced treatment helps minimize nutrient loading and protects downstream water quality in this sensitive alpine-to-lowland transition zone.