Sermaize Ville Wastewater Treatment Plant, Sermaize-les-Bains, Grand Est

Sermaize Ville is an advanced wastewater treatment plant located in Sermaize-les-Bains, a commune in the Marne department of the Grand Est region, France. The plant serves a population of approximately 2,469 residents, classifying it as a small agglomeration under French and EU regulations. It is situated along Route d'Alliancelles, near the Ornain river valley. The plant provides advanced treatment, which goes beyond the secondary treatment required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. Advanced treatment typically includes nutrient removal (nitrogen and phosphorus) to protect sensitive water bodies. The designed capacity is 2,500 m³/day, with a reported discharge volume of 440.47 m³/day, indicating operational headroom. The treated effluent is discharged into the local watershed, which drains into the Ornain River, a tributary of the Saulx, then the Marne, and ultimately the Seine River. This river system flows through the Paris Basin and into the English Channel. The plant's advanced treatment helps protect downstream aquatic ecosystems and supports water quality in the Seine-Normandy basin.

The plant discharges into the Ornain River, which flows into the Saulx, then the Marne, and finally the Seine River before reaching the English Channel. The Seine basin supports diverse aquatic life and is an important ecological corridor. Advanced treatment at this plant reduces nutrient loading, helping to prevent eutrophication in downstream waters, including the Seine estuary.