Colmenar de Oreja Wastewater Treatment Plant - Comunidad de Madrid, Spain

The Colmenar de Oreja wastewater treatment plant is located in the Comunidad de Madrid, Spain, serving a population of 5,323. The facility operates with secondary treatment, meeting the standard requirements for inland communities under Spanish and EU regulations. As a secondary treatment plant, it provides biological treatment to reduce organic matter and suspended solids. The plant has a designed capacity of 5,550 m³/day and currently processes 758.88 m³/day of wastewater, indicating ample reserve capacity. This scale of plant is typical for small agglomerations under the EU Urban Waste Water Treatment Directive (91/271/EEC), which mandates secondary treatment for inland freshwater discharges. The plant discharges treated effluent into the local watershed, which ultimately drains into the Tagus River basin. The Tagus River flows westward through Spain and Portugal, reaching the Atlantic Ocean near Lisbon. The plant's operations help protect downstream water quality and aquatic ecosystems in the Tagus basin.

The plant discharges into the Tagus River basin, one of the Iberian Peninsula's major river systems. The Tagus flows through central Spain and Portugal, supporting diverse aquatic life and providing water for agriculture and urban use. Downstream, the river forms the Tagus Estuary near Lisbon, a vital wetland habitat for migratory birds and fish species. The plant's secondary treatment helps reduce nutrient and organic pollution, safeguarding the ecological health of this transboundary watershed.