Vinhais Wastewater Treatment Plant, Bragança, Portugal

The Vinhais wastewater treatment plant is located in Eiró, near the town of Vinhais in the Bragança district of northern Portugal. It serves a population of approximately 3,700 people, classifying it as a small agglomeration under Portuguese and EU regulations. The plant provides secondary treatment, which is the minimum standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for freshwater discharges from agglomerations of this size. The designed capacity is 3,793 m³/day, with an average daily discharge volume of 616.9 m³/day, indicating ample reserve capacity. The treated effluent is discharged into a local watercourse that ultimately drains into the Tua River, a tributary of the Douro River, which flows into the Atlantic Ocean near Porto. The plant plays a key role in protecting the water quality of the Tua River basin, which supports diverse aquatic life and is used for agriculture and recreation.

The Vinhais plant discharges into a small stream that flows into the Tua River, a major tributary of the Douro River. The Douro River basin is one of the largest in the Iberian Peninsula, supporting diverse ecosystems and providing water for irrigation and drinking. The Tua River is ecologically sensitive, hosting species such as the Iberian barbel and the Douro nase. The plant's secondary treatment helps reduce organic pollution and nutrient loads, protecting downstream water quality in the Douro and the Atlantic coastal zone.