Presles Wastewater Treatment Plant, Presles, Val-d'Oise, France

The Presles wastewater treatment plant is located in the commune of Presles, within the Val-d'Oise department of the Île-de-France region, France. It serves a population of approximately 4,491 residents, classifying it as a small agglomeration under French and EU regulations. The plant operates under the national regulatory framework implementing the EU Urban Waste Water Treatment Directive (91/271/EEC). The plant provides secondary treatment, which is the standard required by the EU directive for freshwater discharges from agglomerations of this size. Its designed capacity is 5,000 m³ per day, with an average daily discharge volume of 801.19 m³, indicating significant spare capacity. Secondary treatment typically involves biological processes to reduce organic matter and suspended solids. The treated effluent is discharged into the local watershed, which ultimately drains into the Oise River, a major tributary of the Seine River. The Seine flows through Paris and into the English Channel. The plant plays a key role in protecting the Oise and Seine river systems from untreated wastewater, supporting aquatic life and downstream water quality.

The Presles plant discharges into the Oise River basin, which flows into the Seine River and eventually reaches the English Channel. The Oise River supports diverse aquatic ecosystems and is an important water resource for the region. The plant's secondary treatment helps reduce nutrient and organic pollution, mitigating eutrophication risks in the downstream Seine estuary and coastal waters.