Wattwil Wastewater Treatment Plant, Bunt, St. Gallen, Switzerland

The Wattwil wastewater treatment plant is located in Bunt, within the St. Gallen canton of Switzerland. It serves a population of around 13,467 people, placing it in the medium agglomeration category under Swiss water protection legislation. The plant is situated in the Toggenburg region, a rural area characterized by rolling hills and proximity to the Thur River basin. Switzerland enforces stringent wastewater treatment standards under the Federal Water Protection Act (Gewässerschutzgesetz). For agglomerations of this size, secondary treatment with nutrient removal is typically required to protect sensitive water bodies. The plant's designed capacity is 1.00 (units unspecified), which aligns with the population served. Swiss plants commonly employ activated sludge systems with biological phosphorus and nitrogen removal to meet strict effluent limits. The treated effluent from Wattwil likely discharges into a local stream that feeds into the Thur River, a major tributary of the Rhine. The Rhine ultimately flows into the North Sea, making this plant part of a transboundary watershed. The region supports diverse aquatic life, including fish species such as brown trout and grayling, and the plant's performance is critical to maintaining water quality in this ecologically sensitive area.

The Wattwil plant discharges into the local drainage network that flows into the Thur River, a key tributary of the Rhine. The Rhine basin is one of Europe's most important waterways, supporting diverse ecosystems and providing drinking water for millions. The Toggenburg region's aquatic habitats are sensitive to nutrient pollution, and the plant's treatment standards help protect downstream biodiversity, including fish spawning grounds and macroinvertebrate communities.