San Leonardo 1 Wastewater Treatment Plant, Guardiagrele, Italy

San Leonardo 1 is a wastewater treatment plant located in the San Leonardo area of Guardiagrele, in the province of Chieti, Abruzzo, Italy. The plant serves a population of approximately 3,550 people and has a designed capacity of 5,000 cubic meters per day, with a reported discharge volume of 702.77 cubic meters per day. The plant provides secondary treatment, which is the standard level required under the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. Secondary treatment typically involves biological processes to reduce organic matter and suspended solids, ensuring compliance with EU effluent standards before discharge. The treated effluent is discharged into local watercourses that drain into the Adriatic Sea. The plant plays a key role in protecting the region's water quality, supporting aquatic ecosystems, and safeguarding downstream coastal environments. Its operation is part of Italy's commitment to EU water quality regulations.

The plant discharges into the local drainage network that flows toward the Adriatic Sea, a semi-enclosed sea with limited water exchange. The watershed supports diverse aquatic life and is important for regional biodiversity. The treatment plant helps reduce nutrient and pollutant loads, mitigating eutrophication risks in coastal areas.