Arronches Wastewater Treatment Plant | Secondary Treatment in Portalegre, Portugal

The Arronches wastewater treatment plant is located in the parish of Assunção, in the town of Arronches, within the Portalegre district of Portugal. This facility serves a population of approximately 2,100 residents, making it a small-scale municipal treatment plant. Its location in the inland Alentejo region places it away from coastal influences, with the treated effluent ultimately flowing into the local watershed. The plant operates with secondary treatment, which is the standard biological treatment required under the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations with a population equivalent between 2,000 and 10,000. The designed capacity of 2,733 cubic meters per day indicates that the plant has room for future growth, as the current discharge volume of 350.13 cubic meters per day represents only about 13% of its capacity. This suggests the plant is well-sized for the community it serves. The treated wastewater from Arronches is discharged into the local environment, eventually reaching the Tagus River basin via smaller tributaries. The Tagus River is one of the longest rivers in the Iberian Peninsula, flowing westward into the Atlantic Ocean near Lisbon. The plant's secondary treatment helps protect the ecological health of these downstream waters by reducing organic pollutants and suspended solids before discharge.

The Arronches plant discharges into the local watershed, which is part of the Tagus River basin. The Tagus River flows through central Portugal and Spain, supporting diverse aquatic life and providing water for agriculture and human consumption. The river ultimately reaches the Tagus Estuary near Lisbon, a vital ecosystem for migratory birds and marine species. Secondary treatment at this plant helps maintain water quality in this important river system.