Caldas de Aregos Wastewater Treatment Plant, Freigil e Miomães, Resende, Portugal

Caldas de Aregos is a wastewater treatment plant located in the parish of Freigil e Miomães, within the municipality of Resende, Viseu District, Portugal. The plant serves a population of approximately 2,600 people and is part of the municipal wastewater infrastructure for the region. The plant operates with secondary treatment, which is the standard level 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 is 2,645 m³/day, and the current discharge volume is 433.50 m³/day, indicating operational headroom. The treated effluent is discharged into the local watershed, which ultimately drains into the Douro River basin. The Douro River flows westward through northern Portugal and into the Atlantic Ocean at Porto. The plant's operations help protect the water quality of the Douro River and its tributaries, supporting aquatic life and downstream uses.

The plant discharges into the Douro River basin, one of the major river systems in the Iberian Peninsula. The Douro River flows through Portugal and Spain, supporting diverse aquatic ecosystems and providing water for agriculture and human consumption. The downstream environment includes the Douro International Natural Park, a transboundary protected area, and the river's estuary near Porto, which is an important habitat for migratory fish and bird species. Proper wastewater treatment is essential to prevent nutrient enrichment and maintain ecological balance in this sensitive watershed.