Saint-Arnoult-en-Yvelines Wastewater Treatment Plant, Île-de-France, France

The Saint-Arnoult-en-Yvelines wastewater treatment plant is located in the commune of Saint-Arnoult-en-Yvelines, within the Rambouillet arrondissement of Yvelines, Île-de-France, France. This facility serves a population of about 5,645 residents, making it a small agglomeration under the EU Urban Waste Water Treatment Directive (UWWTD). As a French plant serving fewer than 10,000 people, it falls under the category of small agglomerations. Under the EU UWWTD, such plants are generally required to provide appropriate treatment, which may include secondary treatment or equivalent, depending on the sensitivity of the receiving environment. The plant operates within the national regulatory framework of France, which implements the EU directive through the French Code de l'Environnement. The treated effluent from the plant is discharged into the local watershed, which ultimately drains into the Seine River basin. The Seine flows through Paris and into the English Channel, supporting diverse aquatic life and providing water for agriculture and industry. The plant plays a role in protecting the water quality of this important river system.

The plant discharges into the Seine River basin, which flows through Île-de-France and eventually reaches the English Channel. The Seine supports a variety of fish species and is an important ecological corridor. Downstream, the estuary and bay provide habitat for migratory birds and marine life. The plant's treatment helps reduce nutrient and pollutant loads, contributing to the health of this watershed.