From road runoff to natural water


About Author

HOFOR  is the largest utility company in Denmark in our core business areas: water supply, wastewater management, district heating, district cooling and gas supply. We also build wind turbines. We focus on sustainable supply, renewable energy, adjustment to the climate changes and improved handling of extreme rain. The aim of our activities is to create sustainable cities - in cooperation with municipalities, other companies and our customers.

See partner

Featuring the latest water filtering technology developed by the University of Copenhagen, a new water treatment plant rinses road runoff and keeps the nature of Kalvebod Fælled nourished.

When you walk through any town, you cannot fail to see that roads are an indispensable feature of urban life. However, our roads are unfortunately also an invisible cesspit of microplastics, sediments, heavy metals and residual particles from tyres, the soil and airborne dust from construction sites. After a cloudburst, pollutants are suspended in water and are potential problems for our water table and natural environment – and pollutants bring pressure to bear on our sewerage systems.

In collaboration with CPH City & Port Development, Watercare (a supplier of water treatment systems) and Rambøll (consultant engineers), HOFOR has built Denmark’s largest road runoff treatment plant in Ørestad South. The plant uses an innovative water filtering technique. It is an efficient, cost-effective and green solution to road water runoff.

Away from the sewers and back to the natural environment

If channelled directly into the environment, road runoff effluent can contaminate the natural environment and water table. In Denmark, we often invest in pumping road runoff to a water treatment plant. The new technology processes road runoff water locally and the product is clean water that is beneficial to the local area and its environment. The process uses neither electricity nor chemicals. The new treatment method is so compact that it is suitable for integration in densely populated urban areas.

Developed by Professor Marina Bergen Jensen from the University of Copenhagen, the new technology mimics natural rainwater filtering processes: substances are filtered out of the water as it runs down through different soil layers. The new plant can clean 110 litres of contaminated water per second. The water is collected from a 30-hectare area of Ørestad.

Green tech and recycled road runoff

The contaminated water flows through a filter that filters out coarse particles, such as leaves, waste, etc. Powered only by gravity, the water then flows into double-porous sandwich filters. The filters capture very small particles and other pollutants in the water. Finally, the clean water is channelled out into Naturpark Amager, where it benefits flora and fauna, including large flocks of wading birds.

The water treatment method is so efficient that road runoff water is suitable for many purposes, including toilet flush, car washes and watering the city’s trees. As the plant is effective and compact, it is an efficient solution to the environmental issues urban developers face when engaged to channel water away from the road system.

A 3VAND partner

We are an active partner in 3VAND – a strategic collaborative partnership consisting of the leading water utilities in Denmark: HOFORBIOFOS, Aarhus Vand and VCS Denmark.

Did you like this solution?

  • 12 Solutions
  • 4 News
Primary contact
Astrid Skotte
+45 33953395


Looking for our logo?

Find it in the State of Green Toolbox together with loads of materials to help you promote Denmark’s green solutions abroad.
Visit toolbox