Aigen im Ennstal Wastewater Treatment Plant, Ketten, Steiermark

The Aigen im Ennstal wastewater treatment plant is located in Ketten, a locality within the municipality of Aigen im Ennstal in the Bezirk Liezen district of Steiermark, Austria. It serves a population of approximately 4,621 residents, reflecting a medium-sized agglomeration in the Alpine region. 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 6,000 m³/day and an average discharge volume of 892.26 m³/day, the facility operates well within its capacity, ensuring effective treatment of municipal wastewater. The treated effluent is discharged into local watercourses that ultimately drain into the Enns River, a major tributary of the Danube. The Danube basin supports diverse aquatic ecosystems and is a critical water resource for Central Europe. The plant's advanced treatment helps protect downstream water quality in this sensitive Alpine watershed.

The plant discharges into the Enns River catchment, which flows into the Danube River and eventually reaches the Black Sea. The Enns River supports a variety of fish species, including brown trout and grayling, and its water quality is important for both ecological health and recreational use. The advanced treatment at Aigen im Ennstal reduces nutrient loads, helping to prevent eutrophication in downstream waters.