VADO_OSCURO Wastewater Treatment Plant, Piglio, Lazio, Italy

VADO_OSCURO is a wastewater treatment plant located in Piglio, a town in the province of Frosinone, Lazio, Italy. The facility serves a population of approximately 1,700 people, placing it in the small agglomeration category under Italian and EU regulations. Its designed capacity of 3,000 m³/day indicates it is sized to accommodate local domestic flows. The plant employs advanced treatment processes, which go beyond the secondary treatment standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for sensitive areas. This level of treatment typically includes nutrient removal (nitrogen and phosphorus) to protect receiving water bodies from eutrophication. As an Italian facility, it operates under the national implementation of the directive, overseen by regional environmental agencies. The treated effluent is discharged into local watercourses that eventually drain into the Tyrrhenian Sea via the Sacco River and the Liri-Garigliano basin. The advanced treatment helps safeguard downstream aquatic ecosystems, including the coastal marine environment of the Tyrrhenian Sea, which supports diverse marine life and is an important ecological and economic resource for the region.

The plant's discharge enters the Sacco River watershed, which flows into the Liri River and then the Garigliano River before reaching the Tyrrhenian Sea. This coastal sea is a semi-enclosed basin with limited water exchange, making it sensitive to nutrient inputs. Advanced treatment at VADO_OSCURO reduces the risk of eutrophication in the river system and the coastal zone, protecting habitats for fish, mollusks, and migratory birds that depend on these waters.