S Joao de Lobrigos Wastewater Treatment Plant, Santa Marta de Penaguião, Portugal

S Joao de Lobrigos is a municipal wastewater treatment plant located in the parish of Alvações do Corgo, within the municipality of Santa Marta de Penaguião, in the Vila Real district of northern Portugal. The plant serves a population of approximately 3,000 residents and has a designed capacity of 3,283.00 m³/day, with an average daily discharge volume of 500.19 m³/day. 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. Secondary treatment typically involves biological oxidation and sedimentation to remove organic matter and suspended solids, ensuring compliance with EU effluent quality standards. The treated effluent is discharged into the local watercourse, which ultimately drains into the Corgo River, a tributary of the Douro River. The Douro River flows through the Douro Valley wine region and empties into the Atlantic Ocean at Porto. The plant plays a key role in protecting the water quality of the Corgo and Douro rivers, supporting aquatic life and downstream ecosystems.

The plant discharges into a small watercourse that flows into the Corgo River, a tributary of the Douro River. The Douro River basin is ecologically significant, supporting diverse aquatic species and providing water for agriculture and tourism in the Douro Valley. The downstream environment includes the Douro Estuary, a productive coastal ecosystem. Secondary treatment helps reduce organic pollution and nutrient loads, protecting these water bodies from eutrophication and maintaining ecological balance.