OUE Wastewater Treatment Plant, Hadsund, Denmark - Closed Advanced Treatment Facility

OUE is a former wastewater treatment plant located in Hadsund, within the Mariagerfjord Municipality of Region Nordjylland, Denmark. The facility was designed with a capacity of 7,372 cubic meters per day and provided advanced treatment, indicating a high level of nutrient removal and effluent quality. As a closed plant, it no longer operates, but its infrastructure reflects the standards applied in Danish wastewater management. Denmark implements the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires advanced treatment for discharges into sensitive areas. Plants of this scale typically serve agglomerations of several thousand people, with tertiary treatment to protect receiving waters. The plant's advanced treatment level aligns with Danish environmental policies aimed at reducing nitrogen and phosphorus loads to coastal waters. The plant is located inland, more than 10 km from the coast, but within 50 km of the Kattegat sea. Its treated effluent would have discharged into local streams or rivers that drain into the Mariager Fjord, a significant coastal inlet. The fjord supports diverse marine life and is an important area for bird migration and fish spawning. The advanced treatment helped minimize nutrient pollution, safeguarding the ecological health of the fjord and the broader Kattegat ecosystem.

The plant is situated inland in the Mariagerfjord catchment, with its treated effluent likely flowing into local watercourses that drain into Mariager Fjord, a 35-km-long fjord connected to the Kattegat Sea. The fjord is a nutrient-sensitive environment, supporting eelgrass beds, fish nurseries, and migratory birds. Advanced treatment at OUE would have reduced nitrogen and phosphorus loads, helping to prevent eutrophication in the fjord and downstream coastal waters.