SILLEDA Wastewater Treatment Plant, Silleda, Galicia, Spain

SILLEDA is a wastewater treatment plant located in Silleda, a municipality in the province of Pontevedra, Galicia, Spain. The plant serves a population of approximately 6,400 people, classifying it as a small to medium agglomeration under Spanish and EU regulations. It operates within the Deza region, an inland area known for its agricultural landscape and river systems. As a plant serving fewer than 10,000 population equivalent, SILLEDA falls under the EU Urban Waste Water Treatment Directive (91/271/EEC) requirements for secondary treatment. The plant is expected to meet the directive's standards for biological treatment and nutrient removal where necessary. The facility is part of Spain's national wastewater infrastructure, regulated by the regional water authority in Galicia. The treated effluent from SILLEDA is discharged into local watercourses that drain into the Deza River, a tributary of the Ulla River. The Ulla River flows into the Ria de Arousa, an estuary on the Atlantic coast of Galicia. This estuary supports diverse aquatic life, including shellfish beds and migratory fish species, making proper wastewater treatment essential for protecting downstream ecosystems and coastal water quality.

The SILLEDA plant discharges into the Deza River basin, which flows into the Ulla River and ultimately reaches the Ria de Arousa estuary on the Atlantic coast. This estuary is ecologically important, supporting shellfish aquaculture and serving as a habitat for migratory birds and fish. The plant's location inland, about 50 km from the coast, means its effluent travels through freshwater systems before reaching the marine environment, where nutrient loading could impact estuarine productivity.