CASTEJON Wastewater Treatment Plant, Valtierra, Navarra, Spain

The CASTEJON wastewater treatment plant is located in Valtierra, Navarra, Spain, serving a population of approximately 6,500. The plant is situated near the Autopista de Navarra and operates as part of the region's municipal wastewater infrastructure. As a secondary treatment facility, it provides biological treatment to reduce organic pollutants and suspended solids before discharge. Under the EU Urban Waste Water Treatment Directive (91/271/EEC), agglomerations with a population equivalent (PE) between 2,000 and 10,000 are required to have secondary treatment. With a population served of 6,500, CASTEJON meets this requirement. The plant's designed capacity of 6,533 m³/day indicates it is sized appropriately for its service area, and the current discharge volume of 900 m³/day suggests operational capacity is well within design limits. The treated effluent is discharged into the local water environment, likely contributing to the Ebro River basin, which drains into the Mediterranean Sea. The Ebro River is one of Spain's major rivers, supporting diverse aquatic ecosystems and agricultural activities. The plant's secondary treatment helps protect downstream water quality and ecological health.

The CASTEJON plant discharges into the Ebro River basin, which flows through northeastern Spain and empties into the Mediterranean Sea via the Ebro Delta. The delta is an ecologically sensitive area supporting diverse bird species and aquatic life. Secondary treatment reduces organic load and suspended solids, helping to maintain water quality in the river and downstream ecosystems.