Changing climate conditions will imply heavier rainfall in Denmark putting a growing pressure on wastewater treatment and sewer systems. Paved surfaces in urban areas prevent infiltration and instead the rainwater is led to the sewers, which have limited capacity resulting in overflow and outlet to lakes and harbours with the risk of potential water contamination of vital natural habitats. Rainwater from urban areas is not clean and must not be discharged directly into our lakes, streams and the sea. The rainwater contains large amounts of sand and nutrients, which bind to particles in the rainwater.


The Municipality of Viborg

Energi Viborg

Møller & Grønborg


Svend E. Madsen

The Danish Foundation for Cultureand Sports Facilities



The Danish Nature Agency


Carsten Ingemann


The Municipality and Utility of Viborg, Denmark, created the recreationalarea sØnæs to expand the treatment facilities of the urban area with amultifunctional wastewater treatment park. The cleaning pond is cleaning rainwater from rooftops and roads from separate sewer systems inViborg, before the rainwater is discharged to Sønder Lake. The dischargedrainwater derives from an area of 50 ha. corresponding to 100 footballfields. The water surface in the cleaning pond is approximately 2.6 ha. Theteam combined the need for climate adaptation, wastewater treatment,recreational facilities, climate-change education and improvement ofnature and environment in one. The area facilitates water related sportsand playgrounds, and puts the treatment techniques, water circulationand natural resources on display. Parts of the park have a permanentwater surface, while other parts are designed to be resistant to flooding.The cleaning process in the cleaning pond is carried out by sedimentation. The water in the large cleaning pond is almost stagnant, which willcause sand, particles and impurities to seek to the bottom. In this way thewater is purified and can be discharged to the lake. In case of an extremerain event, the water will flow from the treatment basin to several overflowbasins ensuring that the water is always clean before reaching the lake.

Location of sØnæs
Location of sØnæs

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