HOUDAN Wastewater Treatment Plant, Houdan, Île-de-France, France

The HOUDAN wastewater treatment plant is located in Houdan, a commune in the Yvelines department of Île-de-France, France. It serves a population of approximately 5,698 residents, classifying it as a small agglomeration under the EU Urban Waste Water Treatment Directive (91/271/EEC). The plant is situated inland, more than 50 km from the coast, and its operations are part of the regional wastewater infrastructure managed by local authorities. As a small agglomeration in France, the plant is required to provide secondary treatment or equivalent under the EU UWWTD. The directive mandates that all agglomerations with a population equivalent (PE) above 2,000 must have collecting systems and treatment, with secondary treatment being the standard for discharges into freshwater. It operates within the regulatory framework of the French water law and the EU directive, ensuring compliance with discharge standards. The treated effluent from the HOUDAN plant is discharged into local watercourses that eventually drain into the Seine River basin. The Seine flows through Paris and into the English Channel, supporting diverse aquatic ecosystems and providing water for agriculture, industry, and recreation. The plant plays a key role in protecting the water quality of the Seine basin by reducing organic pollutants and nutrients before discharge.

The HOUDAN plant discharges into the local hydrological network that feeds the Seine River basin. The Seine River flows northwest through the Paris region and into the English Channel, supporting a variety of aquatic life and serving as a critical water resource. The downstream environment includes sensitive ecosystems such as the Seine estuary, which is an important migratory corridor for fish and birds. The plant's treatment helps mitigate nutrient loading and organic pollution, contributing to the ecological health of the Seine basin.