Cumieira Wastewater Treatment Plant, Santa Marta de Penaguião, Portugal

Cumieira wastewater treatment plant is located in the parish of Cumieira, within the municipality of Santa Marta de Penaguião in the Vila Real district of northern Portugal. The plant serves a population of approximately 3,600 residents, making it a small to medium-sized facility in the region. 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. It has a designed capacity of 3,800 m³/day and currently treats an average daily flow of 600.23 m³/day, indicating significant spare capacity for future growth or seasonal variations. The treated effluent is discharged into the local watershed, which ultimately drains into the Douro River basin. The Douro River flows westward through the Douro Valley, a region known for its vineyards and biodiversity, before reaching the Atlantic Ocean near Porto. The plant's operation helps protect the water quality of the Douro River and its downstream ecosystems.

The plant discharges into the Douro River basin, which flows through the UNESCO-recognized Douro Valley wine region and empties into the Atlantic Ocean at Porto. The Douro River supports diverse aquatic life, including migratory fish species such as lamprey and shad. The plant's secondary treatment reduces organic pollutants and nutrients, helping to maintain the ecological health of the river and its estuary.