ROA Wastewater Treatment Plant, Roa, Castilla y León, Spain

ROA is a wastewater treatment plant located in Roa, a municipality in the province of Burgos, Castilla y León, Spain. The plant serves a population of approximately 6,500 people, making it a small-to-medium agglomeration under Spanish and EU classification. It is situated near the Duero River basin, which is the primary drainage system for this region. The plant operates with secondary treatment, which is the standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size in non-sensitive areas. The designed capacity is 6,500 cubic meters per day, matching the population served, and the reported discharge volume is 625.88 cubic meters per day. Secondary treatment typically involves biological processes to reduce organic matter and suspended solids. The treated effluent is discharged into the local water environment, ultimately contributing to the Duero River basin. This river flows westward through Spain and into Portugal, where it empties into the Atlantic Ocean near Porto. The plant plays a key role in protecting the water quality of the Duero basin, which supports agricultural irrigation, aquatic life, and downstream ecosystems.

The plant discharges into the Duero River basin, which drains a large area of northern Spain and flows into the Atlantic Ocean. The Duero is a major river supporting diverse aquatic habitats and is used for irrigation and drinking water supply. The region's semi-arid climate makes water quality management critical for maintaining ecological balance and supporting local agriculture.