SLAGELSE Wastewater Treatment Plant, Slagelse, Denmark

SLAGELSE wastewater treatment plant is located at Elmedalsvej 7 in Slagelse, Denmark, serving a population of approximately 57,905 in the Region Sjælland. The plant is situated within 50 km of the coast, indicating its discharge may influence coastal waters. As a medium-sized agglomeration, it falls under the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment for populations between 10,000 and 150,000, with potential tertiary treatment if discharging to sensitive areas. Under Danish implementation of the EU directive, plants serving over 15,000 people typically employ biological treatment with nutrient removal to protect the Baltic Sea catchment. The plant is likely operated by the municipality of Slagelse as part of its public wastewater infrastructure. The treated effluent from SLAGELSE ultimately drains to the Great Belt (Storebælt), a strait connecting the Baltic Sea to the Kattegat and North Sea. This water body is ecologically sensitive, supporting diverse marine life including fish, seabirds, and benthic communities. Nutrient discharges from wastewater plants in this region can contribute to eutrophication in the Baltic Sea, a semi-enclosed sea with limited water exchange.

The plant's discharge enters the Great Belt (Storebælt), a major waterway connecting the Baltic Sea to the Kattegat. This area supports important fisheries and migratory bird populations. The Baltic Sea is particularly sensitive to nutrient pollution due to its brackish water and restricted circulation, making effective nutrient removal at treatment plants critical for preventing algal blooms and oxygen depletion.