VIHIERS Wastewater Treatment Plant, Lys-Haut-Layon, France

VIHIERS is a wastewater treatment plant located in Lys-Haut-Layon, within the Pays de la Loire region of France. The plant serves a population of approximately 3,195 residents and is part of the municipal infrastructure for the area. It operates under France's implementation of the EU Urban Waste Water Treatment Directive (91/271/EEC), which sets standards for treatment levels based on agglomeration size and receiving water sensitivity. The plant provides advanced treatment, which goes beyond the secondary treatment required by the EU directive for agglomerations under 10,000 population equivalent. Advanced treatment typically includes nutrient removal (nitrogen and phosphorus) to protect sensitive water bodies. The designed capacity of 4,100 m³/day indicates the plant can handle peak flows, with a current discharge volume of about 570 m³/day, suggesting ample reserve capacity. The treated effluent is discharged into local watercourses that eventually drain into the Loire River basin, a major French river system flowing into the Atlantic Ocean. The plant's advanced treatment helps protect downstream aquatic ecosystems, including the Loire estuary and its diverse fish and bird populations. The region's agricultural landscape also benefits from reduced nutrient loading in surface waters.

The plant discharges into local streams that are part of the Loire River basin, one of France's largest watersheds. The Loire River flows over 1,000 kilometers to the Atlantic Ocean, supporting diverse habitats including migratory fish species such as Atlantic salmon and European eel. Advanced treatment at VIHIERS reduces nutrient pollution, helping to prevent eutrophication in downstream waters and protecting the ecological health of the Loire estuary.