SAINT ETIENNE DE MONTLUC Saint Thomas Wastewater Treatment Plant, Pays de la Loire

The SAINT ETIENNE DE MONTLUC Saint Thomas wastewater treatment plant is located in the commune of Saint-Étienne-de-Montluc, within the Loire-Atlantique department of the Pays de la Loire region in western France. The facility serves a population equivalent of 4,480 and has a designed capacity of 6,000 cubic meters per day, with an average discharge volume of 799.22 m³/day. The plant employs advanced treatment processes, which go beyond the secondary treatment requirements of the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. Advanced treatment typically includes nutrient removal (nitrogen and phosphorus) to protect sensitive receiving waters. The plant operates under French regulations that transpose the EU directive, with permits issued by the local water agency (Agence de l'Eau Loire-Bretagne). The treated effluent is discharged into the local watershed, which ultimately drains into the Loire River estuary and the Bay of Biscay (Atlantic Ocean). The plant plays a key role in protecting the Loire estuary ecosystem, which supports diverse aquatic life and is an important migratory corridor for fish species such as Atlantic salmon and European eel.

The plant discharges into the Loire River basin, which flows into the Loire estuary and then the Bay of Biscay in the Atlantic Ocean. The Loire estuary is a dynamic environment supporting rich biodiversity, including migratory fish and bird populations. The advanced treatment helps reduce nutrient loads that could contribute to eutrophication in the estuary and coastal waters.