Figueras Ria del EO Wastewater Treatment Plant, Castropol, Asturias

Figueras Ria del EO is a secondary wastewater treatment plant located in the parish of Granda, San Juan, within the municipality of Castropol, Asturias, Spain. The plant serves a population of approximately 6,000 people and is situated in a coastal area near the Ria del EO estuary, which forms the border between Asturias and Galicia. As a secondary treatment facility, it provides biological treatment to remove organic matter and suspended solids, meeting the standards required under Spanish and European regulations. The plant has a designed capacity of 11,600 cubic meters per day, with a reported discharge volume of 962.67 m³/day, indicating it operates well below its maximum capacity. Under the EU Urban Waste Water Treatment Directive (91/271/EEC), agglomerations of this size (6,000 population equivalent) are required to provide secondary treatment, which Figueras Ria del EO fulfills. The directive also mandates appropriate treatment for discharges into coastal waters and estuaries, which applies here given the plant's proximity to the coast. The treated effluent is discharged into the Ria del EO, a tidal estuary that flows into the Cantabrian Sea (Atlantic Ocean). The estuary supports diverse aquatic life, including fish and bird species, and is an important ecological area. The plant's operation helps protect the water quality of the estuary and the downstream marine environment from nutrient pollution and pathogens.

Figueras Ria del EO discharges into the Ria del EO estuary, which flows into the Cantabrian Sea, part of the Atlantic Ocean. The estuary is a dynamic coastal ecosystem that supports migratory birds, fish nurseries, and shellfish populations. The plant's secondary treatment reduces organic load and suspended solids, helping to maintain the ecological balance of the estuary and prevent eutrophication in the coastal zone.