Vilarandelo Wastewater Treatment Plant, Valpaços, Portugal

Vilarandelo is a wastewater treatment plant located in the parish of Vilarandelo, within the municipality of Valpaços, in the Vila Real district of northern Portugal. The plant serves a population of approximately 2,800 people, reflecting its role as a small-scale municipal facility in a rural inland region. The plant operates at secondary treatment level, which is the standard required under the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations with a population equivalent between 2,000 and 10,000. The designed capacity of 2,894 cubic meters per day indicates the plant is sized to accommodate future growth, while the current discharge volume of 466.85 cubic meters per day suggests ample reserve capacity. The treated effluent is discharged into the local river system, which ultimately drains into the Douro River basin. The Douro River flows westward through Portugal and empties into the Atlantic Ocean near Porto. The plant's operation helps protect downstream water quality in this ecologically important basin, which supports diverse aquatic life and is used for agriculture and recreation.

The plant discharges into a tributary of the Douro River, one of the Iberian Peninsula's major rivers. The Douro basin supports a variety of fish species, including migratory trout and eels, and its waters are used for irrigation and hydroelectric power. The secondary treatment provided by Vilarandelo reduces organic pollutants and suspended solids, helping to maintain the ecological health of the downstream river system.