PARIS Seine Gresillons Wastewater Treatment Plant, Villennes-sur-Seine, France

PARIS Seine Gresillons is a large wastewater treatment plant located in Villennes-sur-Seine, in the Île-de-France region of France. It serves a population of approximately 893,683, making it a significant facility in the Paris metropolitan area. The plant is situated along the Seine River, which flows through the heart of the region. As a large agglomeration under the EU Urban Waste Water Treatment Directive (91/271/EEC), the plant is required to provide secondary treatment at a minimum, with tertiary treatment expected for sensitive areas. The Seine River basin is designated as a sensitive area due to eutrophication risks, so advanced treatment is likely implemented to reduce nitrogen and phosphorus loads. The plant's capacity and treatment processes are designed to meet these stringent standards. The treated effluent is discharged into the Seine River, which flows northwest through Paris and eventually into the English Channel via the Seine estuary. The Seine supports diverse aquatic life and is an important ecological corridor. The plant's operations are critical for protecting water quality in the river and downstream environments, including the estuary and coastal waters.

The plant discharges into the Seine River, which flows through Paris and into the Seine estuary before reaching the English Channel. The Seine basin is a sensitive area under the EU Urban Waste Water Treatment Directive, requiring advanced treatment to prevent eutrophication. The river supports diverse fish species and migratory birds, and its estuary is an ecologically important zone for marine life. Protecting water quality here is vital for both local ecosystems and downstream coastal environments.