CAULNES PRES LOT DES MOTTES Wastewater Treatment Plant, Caulnes, Brittany

CAULNES PRES LOT DES MOTTES is an advanced wastewater treatment facility located in Caulnes, a commune in the Côtes-d'Armor department of Brittany, France. The plant serves a population of around 4,037 and is designed to handle a capacity of 6,583 cubic meters per day, with a current discharge volume of 720.19 cubic meters per day. As an advanced treatment plant, it goes beyond secondary treatment to remove nutrients and other pollutants, aligning with France's implementation of the EU Urban Waste Water Treatment Directive (91/271/EEC). For agglomerations of this size (under 10,000 population equivalent), the directive requires appropriate treatment, and France often mandates advanced treatment in sensitive areas to protect water quality. The plant's treated effluent is discharged into the local watershed, which ultimately drains into the English Channel via the Rance River basin. This coastal region supports diverse aquatic life and is important for migratory fish species. The plant's inland location (more than 10 km from the coast) reduces direct marine impact, but its proximity within 50 km means careful nutrient management is essential to prevent eutrophication in downstream coastal waters.

The plant discharges into the Rance River basin, which flows into the English Channel near Saint-Malo. This coastal zone is ecologically sensitive, supporting diverse marine life and important bird populations. The advanced treatment helps reduce nutrient loading, protecting the downstream estuary and coastal waters from eutrophication and algal blooms.