Lumbier Wastewater Treatment Plant, Navarra, Spain

The Lumbier wastewater treatment plant is located in the town of Lumbier, within the province of Navarra in northern Spain. This facility serves a population of 1,346, classifying it as a small agglomeration under EU regulations. The plant is situated along the Carretera de la Foz, near the scenic Foz de Lumbier canyon. The plant provides secondary treatment, which is the minimum standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for freshwater discharges from agglomerations of this size. It treats an average daily flow of 916 m³ against a designed capacity of 4,167 m³, indicating ample reserve capacity. As a small inland facility, it does not require advanced nutrient removal unless the receiving water is designated as sensitive. The treated effluent is discharged into a local watercourse that ultimately drains into the Irati River, a tributary of the Aragón River, which flows into the Ebro River and then to the Mediterranean Sea. The plant plays a key role in protecting the water quality of the Ebro basin, supporting aquatic life and downstream uses such as irrigation and recreation.

The plant discharges into a tributary of the Irati River, part of the Ebro River basin that drains into the Mediterranean Sea. The Ebro basin supports diverse aquatic ecosystems, including fish species such as the Ebro barbel and European eel. The surrounding area includes the Foz de Lumbier, a limestone canyon with riparian habitats that rely on clean water. The plant's secondary treatment helps prevent organic pollution and eutrophication in this ecologically sensitive region.