Paris Seine Aval Wastewater Treatment Plant - Versailles, Île-de-France, France

Paris Seine Aval is a large-scale wastewater treatment plant located in Versailles, Île-de-France, France. It serves a population of approximately 4.3 million, making it one of the largest agglomerations in the European Union. The plant is a critical component of the Paris metropolitan area's sanitation infrastructure, treating wastewater from a densely populated urban region. As a facility serving over 150,000 population equivalent, Paris Seine Aval is classified as a 'large agglomeration' under the EU Urban Waste Water Treatment Directive (91/271/EEC). This directive mandates advanced treatment (tertiary) for such agglomerations discharging into sensitive areas, which includes the Seine River basin. The plant's treatment processes are designed to meet stringent nutrient removal standards to protect water quality. The treated effluent from Paris Seine Aval is discharged into the Seine River, which flows through Paris and eventually into the English Channel via the Seine estuary. The Seine River supports diverse aquatic life and is an important ecological corridor. The plant's operations help reduce nutrient pollution and safeguard downstream ecosystems, including the estuary and coastal waters.

Paris Seine Aval discharges treated wastewater into the Seine River, which flows through the Paris basin and into the English Channel. The Seine estuary is an ecologically sensitive area that supports migratory fish species and diverse bird populations. The plant's advanced treatment helps mitigate eutrophication risks in the river and coastal zone, protecting water quality for both human use and aquatic habitats.