Arosa Luen Wastewater Treatment Plant, Lüen, Graubünden

Arosa Luen is a municipal wastewater treatment plant located in the village of Lüen, within the Arosa region of Graubünden, Switzerland. The plant serves a small population of 187 residents, reflecting the rural and alpine character of the area. It operates as a secondary treatment facility, which is the standard for small agglomerations under Swiss water protection regulations. As a Swiss plant, Arosa Luen is subject to the Federal Water Protection Act (Gewässerschutzgesetz), which mandates secondary treatment for all discharges into surface waters. The plant's designed capacity of 438 m³/day and actual discharge of 84.88 m³/day indicate it operates well below capacity, typical for seasonal tourist areas. The treatment process ensures compliance with national effluent standards for organic matter and suspended solids. The treated effluent is discharged into a local stream that flows into the Plessur River, a tributary of the Rhine. The Rhine ultimately drains into the North Sea. The plant plays a key role in protecting the sensitive alpine watershed, which supports diverse aquatic life and is important for downstream water quality in the Rhine basin.

The plant discharges into a small stream that feeds the Plessur River, part of the Rhine basin. The Rhine flows through Switzerland, Germany, and the Netherlands before reaching the North Sea. The alpine watershed is ecologically sensitive, supporting cold-water fish species and serving as a critical water source for downstream communities. The plant's secondary treatment helps maintain water quality in this high-altitude environment.