Alter do Chao Wastewater Treatment Plant, Alter do Chão, Portugal

The Alter do Chao wastewater treatment plant is located in Alter do Chão, Portalegre District, Portugal. It serves a population of approximately 2,600 residents, placing it in the small agglomeration category under Portuguese and EU regulations. The plant employs advanced treatment processes, exceeding the EU Urban Waste Water Treatment Directive's minimum requirement of secondary treatment for agglomerations of this size. Its designed capacity matches the population served at 2,600, with a reported discharge volume of 433.50 units. The treated effluent is discharged into the local watershed, which ultimately drains into the Tagus River basin and then to the Atlantic Ocean. The plant plays a key role in protecting local water quality and downstream ecosystems in the Alentejo region.

The plant discharges into a tributary of the Tagus River basin, which flows westward through Portugal to the Atlantic Ocean near Lisbon. The Alentejo region is characterized by a Mediterranean climate with seasonal rainfall, making consistent wastewater treatment important for maintaining stream flows and water quality. The downstream environment supports diverse aquatic life and agricultural water use.