DENEZY Wastewater Treatment Plant, Montanaire, Vaud, Switzerland

DENEZY is a wastewater treatment plant located in the locality of Denezy, part of the municipality of Montanaire in the canton of Vaud, Switzerland. The plant serves a small population of 107 people, reflecting its role in a rural or peri-urban setting within the Gros-de-Vaud district. Its location in the Swiss Plateau region places it within a landscape of rolling hills and agricultural land. The plant provides secondary treatment, which is the standard biological treatment stage required under Swiss wastewater regulations. Swiss law, aligned with the EU Urban Waste Water Treatment Directive, mandates secondary treatment for agglomerations of this size. The plant has a designed capacity of 250 m³/day and currently discharges 48.57 m³/day, indicating it operates well below its capacity. The treated effluent is discharged into local watercourses that ultimately drain into the Rhone River basin via the Broye or Mentue rivers, which flow into Lake Geneva (Lac Léman). Lake Geneva is a large, ecologically sensitive alpine lake that supports diverse aquatic life and provides drinking water for the region. The plant's secondary treatment helps protect downstream water quality in this important watershed.

The DENEZY plant discharges into local streams that are part of the Rhone River basin, flowing into Lake Geneva (Lac Léman). Lake Geneva is a deep, oligotrophic alpine lake with high ecological value, supporting fish species such as Arctic char and whitefish. The surrounding watershed includes agricultural areas and forests, making nutrient and pollutant control important for maintaining lake water quality. Secondary treatment reduces organic load and suspended solids, contributing to the protection of this sensitive aquatic ecosystem.