Couco Wastewater Treatment Plant, Couço, Santarém, Portugal

Couco wastewater treatment plant is located in Couço, a town in the Santarém district of central Portugal. The facility serves a population of around 3,000 and operates under Portugal's implementation of the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment for agglomerations of this size. The plant provides secondary treatment, which is the standard biological treatment stage that removes organic matter and suspended solids. Its designed capacity is 3,350 m³/day, with a reported discharge volume of 500.19 m³/day, indicating it operates well below capacity. As a small agglomeration, it meets the EU directive's requirements for secondary treatment in freshwater areas. The treated effluent is discharged into the local watershed, which ultimately drains into the Tagus River basin. The Tagus River flows westward through Portugal to the Atlantic Ocean near Lisbon. The plant's operations help protect the Tagus estuary and coastal waters from nutrient pollution, supporting aquatic life and water quality downstream.

The plant discharges into the Tagus River basin, one of the Iberian Peninsula's major river systems. The Tagus flows through central Portugal and empties into the Atlantic Ocean at the Tagus Estuary, a vital habitat for migratory birds and diverse aquatic species. The estuary supports important fisheries and is an ecologically sensitive area that benefits from controlled nutrient inputs from upstream treatment plants.