AOIZ Wastewater Treatment Plant, Aoiz/Agoitz, Navarra, Spain

The AOIZ wastewater treatment plant is located in Aoiz/Agoitz, a town in the Pirinioaurrea region of Navarra, Spain. It serves a population of approximately 5,417 people, classifying it as a small agglomeration under Spanish and EU regulations. The plant is currently closed, with its operational status listed as closed. As a secondary treatment facility, AOIZ would have provided biological treatment to remove organic matter and suspended solids, meeting the standards required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. The designed capacity of 7,083 m³/day suggests the plant was built to handle peak flows, though current discharge volume is 981.82 m³/day. The plant's treated effluent would have been discharged into a local watercourse, likely a tributary of the Irati River, which flows into the Aragón River and eventually the Ebro River, draining into the Mediterranean Sea. The surrounding area is characterized by agricultural and rural landscapes, and the plant's operation would have been important for protecting local water quality and downstream ecosystems.

The AOIZ plant is situated inland in the Pyrenean foothills, within the Ebro River basin. Treated effluent would have entered a local stream, flowing into the Irati River, then the Aragón River, and finally the Ebro River, which discharges into the Mediterranean Sea. The Ebro Delta is an ecologically sensitive area supporting diverse aquatic life and migratory birds, making nutrient and pollutant control upstream critical for downstream ecosystem health.