Messy Gressy Wastewater Treatment Plant, Messy, Île-de-France

The Messy Gressy wastewater treatment plant is located in the commune of Messy, within the Seine-et-Marne department of Île-de-France, France. It serves a population of approximately 2,091 people, classifying it as a small agglomeration under French and EU regulations. The plant is situated in a rural-urban fringe area near the D 139 road in Moulignon. The facility employs advanced treatment processes, which go beyond the secondary treatment standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. With a designed capacity of 2,800 m³/day and an average daily discharge of 373.03 m³/day, the plant operates well within its capacity, indicating efficient management. Advanced treatment typically includes nutrient removal to protect sensitive receiving waters. The treated effluent is discharged into local watercourses that ultimately drain into the Seine River basin, which flows through Paris and into the English Channel. The Seine basin supports diverse aquatic life and is a critical water resource for the region. The plant's advanced treatment helps reduce nutrient loads and protect downstream ecosystems, including the Seine estuary and marine environment.

The plant discharges into local streams that are part of the Seine River basin. The Seine flows northwest through Paris and eventually reaches the English Channel via the Seine estuary. This watershed supports a variety of fish species and is an important ecological corridor. Advanced treatment at the plant helps minimize nutrient pollution, which is crucial for preventing eutrophication in the downstream river and coastal waters.