Mels Weisstannen Wastewater Treatment Plant, St. Gallen, Switzerland

Mels Weisstannen is a wastewater treatment plant located in the Weisstannen valley near Mels, in the canton of St. Gallen, Switzerland. The plant serves a small population of 377 residents, reflecting its role in a rural alpine community. The plant provides secondary treatment, which is appropriate for its scale. Under Swiss regulations, small agglomerations like this are required to meet national water protection standards, ensuring adequate treatment before discharge. The plant has a designed capacity of 883 m³/day, with current discharge volumes at 171.13 m³/day, indicating spare capacity. The treated effluent is discharged into the local stream system, which flows into the Seez River and eventually into Lake Walen (Walensee). This water body supports diverse aquatic life and is part of the Rhine basin, ultimately draining into the North Sea. The plant's operation helps protect the sensitive alpine watershed from nutrient pollution.

The plant discharges into the Weisstannen stream, a tributary of the Seez River, which flows into Lake Walen (Walensee). Lake Walen is a deep, oligotrophic lake that supports a variety of fish species and is used for recreation. The downstream waters are part of the Rhine basin, eventually reaching the North Sea. Protecting this alpine watershed is important for maintaining water quality in the lake and downstream ecosystems.