Alcoentre Wastewater Treatment Plant, Azambuja, Portugal

Alcoentre is a wastewater treatment plant located in the parish of Alcoentre, within the municipality of Azambuja, in the Lisbon district of Portugal. The plant serves a population of approximately 4,200 people, placing it in the small agglomeration category under Portuguese and EU regulations. The facility provides secondary treatment, which is the standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size discharging into freshwater or estuaries. The plant has a designed capacity of 4,715 m³/day and currently discharges an average of 700.27 m³/day, indicating significant spare capacity. The treated effluent is discharged into a local watercourse that ultimately drains into the Tagus River basin, one of the major river systems in the Iberian Peninsula. The Tagus River flows westward through Portugal and into the Atlantic Ocean near Lisbon. The plant's operation helps protect the ecological health of the Tagus watershed, which supports diverse aquatic life and provides water for agriculture and urban use downstream.

Alcoentre's treated wastewater discharges into a tributary of the Tagus River, which flows through central Portugal and empties into the Atlantic Ocean at the Tagus Estuary near Lisbon. The Tagus basin is ecologically significant, supporting diverse fish populations and migratory bird species. The estuary is a productive ecosystem that relies on good water quality from upstream treatment plants like Alcoentre to maintain its ecological balance.