Calanca Arvigo Wastewater Treatment Plant, Arvigo, Graubünden

Calanca Arvigo is a wastewater treatment plant located in the village of Arvigo, in the Moësa valley of the Graubünden canton, Switzerland. The plant serves a small population of 171 residents, reflecting the rural and alpine character of the region. The facility provides secondary treatment, which is the standard biological treatment stage required under Swiss water protection legislation. With a designed capacity of 400 m³/day and an actual discharge volume of 77.62 m³/day, the plant operates well below its capacity, indicating adequate headroom for current demand. The treated effluent from Calanca Arvigo flows into the Calanca stream, a tributary of the Moësa River, which eventually joins the Ticino River and drains into Lake Maggiore. This water body supports diverse aquatic life and is part of the larger Po River basin, which ultimately reaches the Adriatic Sea.

The plant discharges into the Calanca stream, which flows into the Moësa River, a tributary of the Ticino River. The Ticino River feeds Lake Maggiore, a large subalpine lake shared by Switzerland and Italy. The downstream environment includes sensitive aquatic habitats that support fish species such as brown trout and grayling, as well as migratory birds. The region's alpine hydrology means stream flows vary seasonally, with snowmelt-driven peaks in spring and lower flows in winter.