Sonnino Scalo Wastewater Treatment Plant, Sonnino, Lazio, Italy

Sonnino Scalo is an advanced wastewater treatment plant located in Sonnino, a municipality in the Lazio region of central Italy. The facility serves a population of approximately 1,000 residents and has a designed capacity of 2,000 m³/day, with an average discharge volume of 197.96 m³/day. Its location near the Tyrrhenian Sea places it in a coastal environment where treatment standards are critical for marine protection. The plant employs advanced treatment processes, which go beyond secondary treatment to remove nutrients and other pollutants. Under the EU Urban Waste Water Treatment Directive (91/271/EEC), Italy classifies sensitive areas where advanced (tertiary) treatment is required. Although the plant serves a small agglomeration, its advanced treatment level aligns with coastal discharge requirements to protect bathing waters and marine ecosystems. The treated effluent is discharged into local watercourses that eventually reach the Tyrrhenian Sea. This coastal region supports diverse marine life and is important for tourism and fisheries. The advanced treatment helps minimize nutrient loading and pathogen release, safeguarding water quality in the Gulf of Gaeta and adjacent coastal zones.

The plant discharges into small streams that flow toward the Tyrrhenian Sea, a semi-enclosed basin of the Mediterranean. The coastal waters near Sonnino support seagrass meadows and fish nurseries, making nutrient and pathogen control essential. Advanced treatment reduces the risk of eutrophication and protects recreational beaches in the area.