ARZAL Keroux Wastewater Treatment Plant, Arzal, Bretagne, France

ARZAL Keroux is a municipal wastewater treatment facility located in Arzal, in the Bretagne region of northwestern France. The plant serves a population of approximately 2,516 people, classifying it as a small agglomeration under French and EU regulations. Its location near the Vilaine estuary places it in a sensitive coastal environment. The plant provides secondary treatment, which is the standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for discharges into coastal waters. With a designed capacity of 5,500 m³/day, the current discharge volume of 448.85 m³/day indicates a utilization rate well below capacity. The facility operates under the French regulatory framework, which implements the EU directive through national legislation. The treated effluent from ARZAL Keroux is discharged into the Vilaine River estuary, which flows into the Bay of Biscay (Atlantic Ocean). This coastal area supports diverse marine life and is an important ecological zone. The plant's proximity to the coast necessitates careful management to protect water quality in the estuary and adjacent marine environment.

The plant discharges into the Vilaine River estuary, which flows into the Bay of Biscay, part of the Atlantic Ocean. This coastal region supports diverse aquatic ecosystems, including fish nurseries and migratory bird habitats. The estuary is ecologically sensitive due to its role in nutrient cycling and as a spawning ground for marine species. Proper wastewater treatment is essential to prevent eutrophication and maintain water quality in this dynamic coastal environment.