Oliveira de Frades Wastewater Treatment Plant, Viseu, Portugal

The Oliveira de Frades wastewater treatment plant is located in the town of Oliveira de Frades, in the Viseu district of central Portugal. It serves a population of approximately 2,000 residents, making it a small-scale municipal facility. The plant is situated inland, away from coastal areas, and treats wastewater from the local community. 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. With a designed capacity of 2,000 m³/day and a current discharge volume of 333.46 m³/day, the facility operates well below its capacity. The treatment process ensures that effluent meets regulatory standards before discharge. The treated effluent is discharged into a local watercourse, which eventually drains into the Vouga River basin and flows into the Atlantic Ocean near Aveiro. The plant plays a key role in protecting the local watershed from pollution, supporting aquatic life and downstream water quality in the Vouga River and its estuary.

The plant discharges into a small watercourse that is part of the Vouga River basin. The Vouga River flows westward through the Aveiro region and empties into the Atlantic Ocean via the Ria de Aveiro, a coastal lagoon system. This lagoon is ecologically sensitive, supporting diverse aquatic life and serving as an important habitat for migratory birds. The plant's secondary treatment helps reduce organic pollution and nutrient loads, protecting the downstream environment.