ALCAZAREN Wastewater Treatment Plant, Hornillos de Eresma, Castilla y León

ALCAZAREN is a wastewater treatment plant located in Hornillos de Eresma, within the province of Valladolid in the autonomous community of Castilla y León, Spain. The facility serves a population of approximately 2,200 residents and is situated in an inland rural area. The plant provides secondary treatment, which is the standard level required under the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size, ensuring effective removal of organic matter and suspended solids. As a secondary treatment plant, ALCAZAREN processes wastewater through biological treatment stages to reduce biochemical oxygen demand and suspended solids before discharge. The plant's designed capacity of 2,200 m³/day matches the population served, indicating adequate infrastructure for the local community. The facility operates under Spain's national water regulations, which transpose EU directives and are enforced by regional authorities in Castilla y León. The treated effluent from ALCAZAREN is discharged into the local hydrological network, which ultimately drains into the Duero River basin. The Duero River flows westward through Spain and into Portugal, reaching the Atlantic Ocean near Porto. The plant's operations contribute to protecting the water quality of the Eresma River and downstream ecosystems, supporting aquatic life and agricultural water use in the region.

ALCAZAREN discharges treated wastewater into the Eresma River, a tributary of the Duero River. The Duero basin is one of the largest in the Iberian Peninsula, supporting diverse aquatic habitats and irrigated agriculture. The plant's secondary treatment helps reduce nutrient loads that could otherwise contribute to eutrophication in downstream reservoirs and the Atlantic coastal zone.