ARNAD Wastewater Treatment Plant, Arnad, Valle d'Aosta, Italy

The ARNAD wastewater treatment plant is located in Arnad, a commune in the Valle d'Aosta region of northwestern Italy. This facility serves a population of approximately 1,700 residents, providing secondary treatment for municipal wastewater. The plant's designed capacity is 13,000 m³/day, indicating it is sized to accommodate future growth or seasonal variations in flow. As a secondary treatment plant, ARNAD employs biological processes to reduce organic matter and suspended solids, meeting the standards required under Italian and European regulations. The EU Urban Waste Water Treatment Directive (91/271/EEC) mandates secondary treatment for agglomerations of this size, ensuring that the effluent quality protects receiving waters. The plant operates within Italy's national framework, which implements the directive through regional authorities. The treated wastewater is discharged into the local hydrological network, which ultimately drains into the Dora Baltea River, a major tributary of the Po River. The Po River flows eastward across northern Italy into the Adriatic Sea. The plant's location in the Alpine valley means the receiving waters are sensitive to nutrient loading, and secondary treatment helps mitigate eutrophication risks in downstream ecosystems.

The ARNAD plant discharges into the Dora Baltea River, which flows through the Aosta Valley and joins the Po River near Turin. The Po River is Italy's longest river and drains into the Adriatic Sea, supporting diverse aquatic life and important agricultural regions. The Alpine watershed is ecologically sensitive, with cold-water fisheries and riparian habitats that benefit from the plant's secondary treatment reducing organic pollution.