Stein a d Enns Wastewater Treatment Plant, Mitterberg-Sankt Martin, Styria

The Stein a d Enns wastewater treatment plant is located in Mitterberg-Sankt Martin, a municipality in the Styria region of Austria. The plant serves a population of approximately 2,013 people, reflecting a small to medium-sized agglomeration typical of rural Alpine communities. 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. Advanced treatment includes nutrient removal (nitrogen and phosphorus) to protect sensitive receiving waters. The plant has a design capacity of 3,070 m³/day and currently treats 333 m³/day, indicating ample capacity for future growth. The treated effluent is discharged into local waterways that ultimately drain into the Enns River, a tributary of the Danube. The Danube flows into the Black Sea, making this plant part of a large international river basin. The advanced treatment helps protect downstream aquatic ecosystems and supports water quality in the Danube River Basin.

The plant discharges into the Enns River watershed, which flows into the Danube River and eventually reaches the Black Sea. The Enns River supports diverse aquatic life, including fish species such as grayling and brown trout. The advanced treatment at this plant helps reduce nutrient loads, preventing eutrophication in downstream water bodies and maintaining ecological balance in the sensitive Alpine river environment.