ARNEDILLO Wastewater Treatment Plant, Arnedillo, La Rioja, Spain

ARNEDILLO is a municipal wastewater treatment plant located in Arnedillo, a small town in the La Rioja region of northern Spain. The plant serves a population of approximately 2,183 residents, reflecting its role in managing domestic wastewater for this rural community. Its location along the Via Verde Cidacos places it within the scenic Cidacos River valley. The plant provides secondary treatment, which is the standard biological treatment required under the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. Secondary treatment typically involves biological oxidation and sedimentation to reduce organic matter and suspended solids. The plant has a designed capacity of 5,500 m³/day, indicating it can handle peak flows beyond current discharge volumes. Treated effluent from the plant is discharged into the Cidacos River, a tributary of the Ebro River, which ultimately flows into the Mediterranean Sea. The Cidacos River supports local aquatic life and is part of the Ebro basin, a major ecological and agricultural region. The plant's operation helps protect water quality in this sensitive river system.

The plant discharges into the Cidacos River, a tributary of the Ebro River, which flows into the Mediterranean Sea. The Cidacos River valley is an ecologically sensitive area supporting diverse aquatic habitats and migratory bird species. The Ebro basin is one of Spain's most important agricultural regions, making nutrient control from wastewater critical to prevent eutrophication downstream.