Almeirim_Alpiarca Wastewater Treatment Plant, Alpiarça, Santarém, Portugal

The Almeirim_Alpiarca wastewater treatment plant is located in Alpiarça, Santarém District, Portugal, serving a population of 27,800. The plant is situated near the Tagus River basin, a major watercourse in the Iberian Peninsula. As a medium-sized agglomeration, the plant is subject to the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment for discharges into freshwater and estuaries. The directive also mandates more advanced treatment if the receiving waters are designated as sensitive areas, such as those prone to eutrophication. The treated effluent from the plant ultimately drains into the Tagus River, which flows westward to the Atlantic Ocean near Lisbon. The Tagus estuary is an ecologically significant area that supports diverse aquatic life, including migratory fish species and waterbirds. Proper treatment at this plant helps protect water quality in the river and downstream coastal environment.

The plant discharges into the Tagus River basin, which flows through central Portugal and empties into the Atlantic Ocean via the Tagus estuary. The estuary is a critical habitat for migratory birds and fish, including species such as the European eel and lamprey. The plant's treatment performance directly influences water quality in this ecologically sensitive transition zone between freshwater and marine environments.