VARENNES SUR ALLIER Wastewater Treatment Plant, Paray-sous-Briailles, France

VARENNES SUR ALLIER is an advanced wastewater treatment plant located in Paray-sous-Briailles, within the Allier department of Auvergne-Rhône-Alpes, France. The facility serves a population of approximately 5,300 and has a designed capacity of 5,800 m³ per day, with an average discharge volume of 945.51 m³ per day. As an advanced treatment plant, it goes beyond secondary treatment to remove nutrients such as nitrogen and phosphorus, meeting stringent standards under the EU Urban Waste Water Treatment Directive (91/271/EEC). For agglomerations of this scale (5,300 PE), the directive requires secondary treatment, but the plant's advanced level indicates it operates in a sensitive area or under additional local requirements. The plant discharges treated effluent into the local watershed, which ultimately drains into the Allier River, a major tributary of the Loire. The Loire basin is ecologically significant, supporting diverse aquatic life and migratory fish species. The plant's advanced treatment helps protect downstream water quality in this important river system.

The treated effluent from VARENNES SUR ALLIER flows into the Allier River, a major tributary of the Loire River, which empties into the Atlantic Ocean. The Allier is known for its dynamic riverine ecosystems and supports a variety of fish species, including salmonids. The plant's advanced treatment reduces nutrient loading, helping to prevent eutrophication in the Loire estuary and coastal waters.