CUADROS Wastewater Treatment Plant, Carbajal de la Legua, Castilla y León

CUADROS is a wastewater treatment plant located in Carbajal de la Legua, within the province of León in the Castilla y León region of Spain. The facility serves a population of approximately 2,500 people and is designed with a capacity of 2,500 cubic meters per day. It operates under Spain's implementation of the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment for agglomerations of this size. The plant employs secondary treatment processes, meeting the standard required for inland freshwater discharges under EU regulations. With a discharge volume of 490.60 m³/day, the facility operates well within its design capacity. The plant's location in the interior of Spain, far from coastal areas, means its treated effluent is discharged into local rivers that ultimately flow into the Atlantic Ocean via the Duero River basin. The receiving water body is part of the Duero River watershed, which supports diverse aquatic ecosystems and provides water for agricultural and urban uses downstream. The plant's secondary treatment helps protect water quality in this important basin, reducing organic load and suspended solids before discharge.

The plant discharges into the Duero River basin, which flows westward through Castilla y León into Portugal and eventually reaches the Atlantic Ocean near Porto. This watershed supports a variety of fish species, including barbel and nase, and is an important corridor for migratory birds. The secondary treatment provided by CUADROS helps maintain the ecological health of the river system by reducing nutrient loads and organic pollution.