LA ARBOLEDA Wastewater Treatment Plant, Valle de Trápaga-Trapagaran, Euskadi, Spain

LA ARBOLEDA is a wastewater treatment facility located in the Barrio Larreineta area of Valle de Trápaga-Trapagaran, in the province of Bizkaia, Euskadi, Spain. The plant serves a population of approximately 2,000 residents and is situated in a hilly, industrial region near the Nervión River basin. As a small-scale municipal plant, it plays a key role in local sanitation and environmental protection. The plant employs advanced treatment processes, which go beyond the secondary treatment standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. Advanced treatment typically includes nutrient removal (nitrogen and phosphorus) and disinfection, ensuring high-quality effluent. The plant's designed capacity is 2,000 m³/day, and it currently discharges 362.49 m³/day, indicating significant spare capacity. The treated effluent is discharged into a local watercourse that ultimately flows into the Nervión River, which drains into the Bay of Biscay (Atlantic Ocean). The plant's proximity to the coast (within 10 km) means that its discharge can affect coastal water quality. By providing advanced treatment, LA ARBOLEDA helps protect the sensitive marine environment of the Bay of Biscay, which supports diverse aquatic life and is important for fisheries and tourism.

The plant discharges into the Nervión River basin, which flows through the Bilbao metropolitan area and empties into the Bay of Biscay. This coastal region is ecologically sensitive, supporting diverse marine habitats and serving as a migratory corridor for fish species. Advanced treatment at LA ARBOLEDA reduces nutrient loading, helping to prevent eutrophication in the coastal waters and protecting the ecological balance of the estuary and adjacent marine areas.