Lyon Saint Fons Wastewater Treatment Plant: Serving the Lyon Metropolitan Area

Lyon Saint Fons is a major wastewater treatment plant located in Saint-Fons, part of the Lyon metropolitan area in the Auvergne-Rhône-Alpes region of France. Serving a population of over 720,000, it is one of the largest treatment facilities in the region, playing a critical role in managing the wastewater of the Lyon urban agglomeration. As a large agglomeration (>150,000 population equivalent), the plant is subject to the EU Urban Waste Water Treatment Directive 91/271/EEC, which requires advanced treatment (tertiary) for discharges into sensitive areas. The Rhône River basin, where the plant is located, is designated as a sensitive area due to eutrophication risks, necessitating nutrient removal. The plant's treatment process likely includes biological treatment with nitrogen and phosphorus removal to meet stringent effluent standards. The treated effluent is discharged into the Rhône River, which flows south to the Mediterranean Sea. The Rhône is a major European river supporting diverse aquatic ecosystems and providing water for agriculture, industry, and drinking water. The plant's operations are essential for protecting water quality in the Rhône and the Gulf of Lion, a marine area of ecological significance.

The plant discharges into the Rhône River, which flows through southeastern France into the Mediterranean Sea via the Camargue delta. The Rhône basin supports diverse aquatic life, including migratory fish species such as European eel and Atlantic salmon. Downstream, the Gulf of Lion is a productive marine area with seagrass meadows and important fisheries. Nutrient loading from wastewater can contribute to eutrophication, so the plant's nutrient removal is critical for maintaining ecological balance.