Montigny-sur-Loing Wastewater Treatment Plant, Moret-Loing-et-Orvanne, France

The Montigny-sur-Loing wastewater treatment plant is located in the commune of Moret-Loing-et-Orvanne, in the Seine-et-Marne department of the Île-de-France region. It serves a population of 1,470 people, classifying it as a small agglomeration under French and EU regulations. The plant is situated near the Loing River, a tributary of the Seine. The facility provides secondary treatment, which is the minimum standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for freshwater discharges from agglomerations of this size. The plant has a designed capacity of 2,500 m³/day and currently discharges an average of 262.25 m³/day, indicating ample reserve capacity. As a French municipal plant, it operates under national water law (Code de l'environnement) and is subject to permits issued by the local water agency (Agence de l'Eau Seine-Normandie). The treated effluent is discharged into the Loing River, which flows into the Seine River and eventually reaches the English Channel. The plant plays a key role in protecting the Loing's water quality, which supports diverse aquatic life and is used for recreation and drinking water downstream. Its secondary treatment ensures compliance with EU standards for biochemical oxygen demand and suspended solids.

The plant discharges into the Loing River, a tributary of the Seine, which flows through the Paris Basin before reaching the English Channel. The Loing supports a variety of fish species and is part of a regional ecological network. The Seine estuary is a critical habitat for migratory birds and fish, making upstream treatment essential for maintaining downstream water quality and biodiversity.