GRESSONEY_TRINO Wastewater Treatment Plant, Gressoney-Saint-Jean, Italy

GRESSONEY_TRINO is a municipal wastewater treatment plant located in the hamlet of Trinò, within the municipality of Gressoney-Saint-Jean in the Valle d'Aosta region of northwestern Italy. The plant serves a population of 3,200 and is situated in the Lys Valley, a mountainous area in the Italian Alps near the border with Switzerland. The plant provides secondary treatment, which is the standard biological treatment required under the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. With a designed capacity of 20,000 m³/day, the facility has significant reserve capacity for future growth or seasonal tourism peaks. The current discharge volume is 633.49 m³/day, indicating low utilization relative to design. The treated effluent is discharged into the Lys River (Torrente Lys), a tributary of the Dora Baltea, which flows through the Aosta Valley and eventually joins the Po River near Turin. The Po River then drains into the Adriatic Sea. The plant plays a key role in protecting the local alpine water quality and the downstream ecosystems of the Po basin.

The plant discharges into the Lys River, a mountain stream that flows through the Lys Valley and joins the Dora Baltea near Pont-Saint-Martin. The Dora Baltea is a major tributary of the Po River, which drains into the Adriatic Sea. The alpine watershed supports sensitive aquatic habitats, including cold-water fish species such as brown trout. Secondary treatment ensures that organic pollutants and suspended solids are reduced before discharge, protecting the ecological integrity of the river and downstream water bodies.