ARENAS DE SAN JUAN Wastewater Treatment Plant, Arenas de San Juan, Castilla-La Mancha, Spain

ARENAS DE SAN JUAN is a wastewater treatment plant located in Arenas de San Juan, a municipality in the province of Ciudad Real, within the autonomous community of Castilla-La Mancha, Spain. The plant serves a population of approximately 1,876 residents, reflecting its role in managing domestic wastewater for this small inland community. The plant employs advanced treatment processes, which go beyond the secondary treatment standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. Advanced treatment typically includes nutrient removal (nitrogen and phosphorus) or additional polishing steps, ensuring high-quality effluent suitable for discharge into sensitive environments. The treated effluent is discharged into local watercourses that ultimately drain into the Guadiana River basin, one of Spain's major river systems. The Guadiana flows westward through Castilla-La Mancha and Extremadura before reaching the Gulf of Cádiz (Atlantic Ocean). The advanced treatment helps protect the ecological health of the Guadiana basin, which supports diverse aquatic life and agricultural activities.

The plant discharges into the Guadiana River basin, a vital waterway in central Spain that flows through the La Mancha region and eventually reaches the Atlantic Ocean via the Gulf of Cádiz. The Guadiana supports important wetland ecosystems, including the Tablas de Daimiel National Park, a floodplain wetland that is ecologically sensitive and dependent on groundwater and surface water inflows. Advanced treatment at this plant helps reduce nutrient loading, protecting downstream water quality and biodiversity.