WIZERNES SE Wastewater Treatment Plant, Wizernes, Hauts-de-France

WIZERNES SE is an advanced wastewater treatment plant located in Wizernes, a commune in the Pas-de-Calais department of Hauts-de-France, northern France. The plant serves a population of 3,757 and is designed to handle up to 7,000 m³ of wastewater per day, with an average daily discharge of 670.24 m³. It operates under the French regulatory framework, which implements the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. The plant provides advanced treatment, which includes tertiary processes beyond secondary biological treatment, ensuring high-quality effluent. For a small agglomeration like Wizernes (under 10,000 population equivalent), the EU directive requires appropriate collection and treatment systems, and the advanced level here exceeds the minimum secondary treatment standard. The treated effluent is discharged into the local water system, which ultimately drains into the Aa River and then the North Sea. The plant plays a key role in protecting the Aa River basin and the coastal environment of the English Channel, supporting aquatic life and recreational uses downstream.

The plant discharges into the Aa River basin, which flows through the Pas-de-Calais region before reaching the North Sea near Gravelines. This coastal area supports diverse aquatic ecosystems, including fish spawning grounds and migratory bird habitats. The advanced treatment helps reduce nutrient loads and pollutants, protecting the sensitive estuarine and marine environment from eutrophication and contamination.