HVALSO Wastewater Treatment Plant, Lejre, Denmark

HVALSO is a wastewater treatment plant located in Lejre, Region Sjælland, Denmark. It serves a population of approximately 4,980 people, classifying it as a small to medium agglomeration under EU classification. The plant is situated near Tadre Møllevej in the Lejre Kommune. As a Danish facility, HVALSO operates under the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment for agglomerations of this size. Denmark has fully transposed the directive into national law, and plants serving over 2,000 population equivalents must meet secondary treatment standards. The plant's designed capacity is 1.00 (likely in thousand cubic meters per day or similar unit), indicating it is sized appropriately for its service population. The plant discharges treated wastewater into the local watershed, which ultimately drains into the Isefjord or Roskilde Fjord, both part of the Kattegat sea area. This coastal region supports diverse marine life and is important for local fisheries and recreation. The plant's location within 50 km of the coast means its effluent can influence coastal water quality, making treatment standards critical for protecting the marine environment.

The plant's treated effluent enters local watercourses that flow into the Isefjord or Roskilde Fjord, both of which are part of the Kattegat marine ecosystem. This area supports diverse aquatic life, including fish, shellfish, and migratory birds. The fjords are ecologically sensitive due to nutrient loading risks, and the plant's treatment level helps protect downstream habitats from eutrophication.