Boulogne-sur-Mer Wastewater Treatment Plant, Outreau, Hauts-de-France

The Boulogne-sur-Mer wastewater treatment plant is a major municipal facility serving the urban agglomeration of Boulogne-sur-Mer and surrounding areas, located in the commune of Outreau in the Hauts-de-France region of northern France. With a population equivalent of 195,550, it is classified as a large agglomeration under European Union regulations. As a large agglomeration, the plant is subject to the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment as a minimum, and tertiary treatment if the receiving waters are designated as sensitive areas. The plant's designed capacity is 1.00 (likely in cubic meters per day or population equivalent units), indicating a substantial infrastructure to handle the region's wastewater. The plant discharges treated effluent into the English Channel via the Liane River estuary, which flows through Boulogne-sur-Mer. This coastal discharge is in a sensitive marine environment that supports diverse aquatic life and is important for local fisheries and tourism. The plant plays a critical role in protecting the water quality of the Channel and the surrounding coastal ecosystem.

The plant discharges into the Liane River, which flows into the English Channel near Boulogne-sur-Mer. The coastal waters are ecologically sensitive, supporting diverse marine life including fish, crustaceans, and migratory birds. The area is part of the wider Channel ecosystem, which is important for commercial fishing and marine biodiversity. Proper treatment is essential to prevent nutrient enrichment and protect the coastal environment.