Oleiros Wastewater Treatment Plant | Oleiros, Castelo Branco, Portugal

The Oleiros wastewater treatment plant is located in the municipality of Oleiros, in the Castelo Branco district of central Portugal. It serves a population of approximately 3,000 residents, making it a small agglomeration under Portuguese and EU classifications. The plant is situated inland, away from coastal areas, and operates as part of the region's municipal wastewater infrastructure. The plant provides secondary treatment, which is the standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for freshwater discharges from agglomerations of this size. It has a designed capacity of 3,600 m³/day and currently treats an average daily flow of 500.19 m³/day, indicating ample reserve capacity. The treated effluent is discharged into a local watercourse within the Tagus River basin, which ultimately flows into the Atlantic Ocean near Lisbon. The plant plays a key role in protecting the region's water quality, supporting aquatic life in the local streams and contributing to the ecological health of the Tagus estuary downstream.

The plant discharges into a tributary of the Tagus River, one of the Iberian Peninsula's major rivers, which flows west to the Atlantic Ocean near Lisbon. The Tagus basin supports diverse aquatic ecosystems, including migratory fish species such as the European eel and lamprey. The plant's secondary treatment helps reduce organic pollution and nutrient loads, protecting downstream water quality in this ecologically sensitive river system.