Marcillac Vallon Wastewater Treatment Plant | Marcillac-Vallon, Occitanie, France

The Marcillac Vallon wastewater treatment plant is located in the commune of Marcillac-Vallon, within the Aveyron department of the Occitanie region in southern France. The facility serves a population of approximately 3,010 residents, placing it in the small agglomeration category under French and European regulations. The plant 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. Its designed capacity is 6,500 m³/day, with an average daily discharge volume of about 537 m³/day, indicating ample reserve capacity for future growth or seasonal variations. The treated effluent is discharged into the local watershed, which ultimately drains into the Lot River and then the Garonne River, contributing to the Gironde estuary and the Atlantic Ocean. The plant plays a key role in protecting the water quality of these downstream water bodies, supporting aquatic life and recreational uses.

The plant discharges into a tributary of the Lot River, which flows into the Garonne River and eventually reaches the Gironde estuary on the Atlantic coast. The watershed supports diverse aquatic ecosystems, including fish species such as Atlantic salmon and European eel. The advanced treatment helps reduce nutrient loading, protecting downstream water quality and preventing eutrophication in sensitive areas.