Suben StMarienkirchen Wastewater Treatment Plant, Schnelldorf, Austria

Suben StMarienkirchen is an advanced wastewater treatment plant located in Schnelldorf, within the municipality of Suben in Oberösterreich, Austria. The plant serves a population of approximately 4,181 people and has a designed capacity of 5,500 cubic meters per day, with a current discharge volume of 940.70 cubic meters per day. As an advanced treatment facility, the plant goes beyond secondary treatment to remove nutrients such as nitrogen and phosphorus, which is typical for plants discharging into sensitive water bodies under the EU Urban Waste Water Treatment Directive (91/271/EEC). Austria implements this directive strictly, requiring advanced treatment for agglomerations above 10,000 population equivalent in sensitive areas, though smaller plants like this one may also adopt advanced processes to protect local water quality. The plant's treated effluent is discharged into the local watershed, which ultimately drains into the Inn River and then the Danube River, flowing into the Black Sea. The region is characterized by agricultural land use and the Inn River supports diverse aquatic life, making advanced treatment important for maintaining ecological balance.

The plant discharges into the Inn River basin, a tributary of the Danube, which flows into the Black Sea. The Inn River in this region supports fish species such as grayling and brown trout, and the advanced treatment helps protect downstream water quality and aquatic habitats from nutrient enrichment.