Overview
Frossos wastewater treatment plant serves the city of Braga, Portugal, with a population equivalent of 158,500. The facility is located near the Cávado River and operates under EU Urban Waste Water Treatment Directive standards.
Frossos is a wastewater treatment plant located in the parish of Merelim (São Pedro) e Frossos, serving the city of Braga in northern Portugal. The plant is situated along the Cávado River, a major watercourse in the region, and handles wastewater from a population equivalent of 158,500, classifying it as a large agglomeration under EU regulations. As a plant serving over 150,000 people, Frossos is subject to the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment as a minimum and tertiary treatment in sensitive areas. The plant's designed capacity is 1. Portuguese wastewater infrastructure is regulated by the national water authority, with permits issued under EU directives. The treated effluent from Frossos is discharged into the Cávado River, which flows westward through the Minho region and eventually reaches the Atlantic Ocean near the city of Esposende. The Cávado basin supports diverse aquatic life and is an important ecological corridor in northern Portugal. The plant's operation helps protect downstream water quality and the coastal environment.
Environmental context
The Frossos plant discharges treated wastewater into the Cávado River, which flows approximately 135 km from its source in the Serra do Larouco to the Atlantic Ocean at Esposende. The Cávado basin is a key water resource for the region, supporting agriculture, industry, and biodiversity. Downstream, the river estuary provides habitat for migratory fish species and waterfowl, making effective treatment essential for maintaining ecological health.
Frequently asked questions
The Frossos plant is located in the parish of Merelim (São Pedro) e Frossos, near the Cávado River, in the city of Braga, northern Portugal.
The plant serves a population equivalent of 158,500, classifying it as a large agglomeration under EU regulations.
Treated effluent from Frossos is discharged into the Cávado River, which flows westward to the Atlantic Ocean.
As a plant serving over 150,000 people, Frossos is required to meet secondary treatment standards under the EU UWWTD, with potential for tertiary treatment if the receiving waters are designated as sensitive areas.
In Portugal, large agglomerations like Frossos typically employ secondary biological treatment, often with nutrient removal, to comply with EU standards and protect the Cávado River and Atlantic coastal waters.
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