Arbra ARV Wastewater Treatment Plant, Koldemo, Sweden

Arbra ARV is a wastewater treatment plant located in Koldemo, Bollnäs kommun, Gävleborgs län, Sweden. The facility serves a population of around 2,356 people, classifying it as a small agglomeration under Swedish and EU regulations. The plant is situated inland, away from coastal areas, and treats wastewater from the local community. 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 small agglomerations like this, advanced treatment is often implemented to protect sensitive receiving waters. The designed capacity of 3,250 m³/day indicates the plant can handle peak flows, with a current discharge volume of 369.85 m³/day, suggesting ample capacity. The treated effluent is discharged into local watercourses that eventually drain into the Baltic Sea via the Ljusnan River system. The plant plays a key role in maintaining water quality in the region, supporting aquatic life and downstream ecosystems. Its advanced treatment helps reduce nutrient loads, which is critical for preventing eutrophication in the Baltic Sea.

The plant discharges into local streams that feed into the Ljusnan River, which flows eastward into the Gulf of Bothnia, part of the Baltic Sea. The Baltic Sea is a brackish water body sensitive to nutrient pollution, making advanced treatment important for controlling nitrogen and phosphorus loads. The surrounding watershed supports diverse aquatic habitats and is used for recreation and fishing.