Castilblanco de los Arroyos Wastewater Treatment Plant, Andalucía, Spain

The Castilblanco de los Arroyos wastewater treatment plant is located in the municipality of Castilblanco de los Arroyos, in the province of Seville, Andalucía, Spain. The plant serves a population of approximately 4,532 people, classifying it as a small agglomeration under the EU Urban Waste Water Treatment Directive (UWWTD). The plant provides secondary treatment, which is the minimum required by the EU UWWTD for freshwater discharges from agglomerations of this size. With a designed capacity of 8,125 m³/day and an average discharge volume of 821.41 m³/day, the plant operates well below its capacity, indicating potential for future growth or seasonal variability. The treated effluent is discharged into a local watercourse that ultimately drains into the Guadalquivir River basin, which flows into the Atlantic Ocean at the Gulf of Cádiz. The plant plays a key role in protecting the local aquatic environment and downstream ecosystems from untreated wastewater pollution.

The plant discharges into a tributary of the Guadalquivir River, which flows through Andalucía and into the Atlantic Ocean at the Gulf of Cádiz. The Guadalquivir basin supports diverse aquatic life, including migratory fish species, and its estuary is ecologically sensitive. The plant's secondary treatment helps reduce organic load and nutrient pollution, safeguarding water quality in the river and downstream coastal areas.