Alto Nabao Wastewater Treatment Plant, Ourém, Portugal

Alto Nabao is a wastewater treatment plant located in Ourém, in the Santarém district of central Portugal. It serves a population of approximately 17,300 people, classifying it as a medium-sized agglomeration under EU standards. The plant is situated inland, away from coastal areas, and its operations are part of the municipal wastewater infrastructure for the region. As a Portuguese facility, Alto Nabao operates under the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment for agglomerations of this size. The directive also mandates more advanced treatment if the receiving waters are sensitive. The regulatory framework ensures that the plant meets European standards for effluent quality. The treated wastewater from Alto Nabao is discharged into local watercourses that ultimately drain into the Tagus River basin, one of the major river systems in the Iberian Peninsula. The Tagus River flows westward to the Atlantic Ocean near Lisbon, supporting diverse aquatic ecosystems and providing water for agriculture and urban use. The plant's operations contribute to protecting the water quality of these downstream environments.

Alto Nabao discharges into local streams that are part of the Tagus River basin. The Tagus River is the longest river in the Iberian Peninsula, flowing through Spain and Portugal before reaching the Atlantic Ocean at Lisbon. The river supports a variety of fish species and provides critical habitat for migratory birds. The watershed is ecologically sensitive, with areas of riparian woodland and wetlands that rely on good water quality. The plant's treatment helps maintain the ecological health of this important river system.