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Stengaarden – Denmark

Case study 1

The aquifer underneath the Stengaarden dumpsite in Denmark faces significant environmental challenges, being heavily polluted with pesticides since the 1970s. To safeguard the water supply at this site, remediation efforts are crucial. In the UPWATER project, Aarhus University, together with the other project partners, aims to remove these pesticide residues by exploring innovative bio-based solutions.


The Stengaarden dumpsite, once an old gravel pit, is located in the Region of Zealand (native name Sjælland). This part of Denmark has a Nordic, maritime climate, with an average temperature of nine degrees. The landscape on Zealand is dominated by shallow hills, agriculture, fjords and lakes. The area is predominantly rural, with 80 percent agriculture and 20 percent rural habitation. The water sources in the Stengaarden region provide, amongst other places, the drinking water for Copenhagen, the Danish capital with 1.5 million inhabitants.

Water on top of the dumpsite, Stengaarden

Main challenges

The Stengaarden dumpsite has been filled up since the 1970s, primarily with municipal waste, but also with production residues from local pesticide production. Especially the leaching pesticide residues deteriorate groundwater quality and challenge its use for drinking water production, which is relevant as there is a drinking water production side for the city of Copenhagen in the vicinity. The groundwater at the site also has considerable amounts of iron. This iron usually produces sludges, causing clogging problems in various processes.

To protect the drinking water resources of 1.5 million people, the authorities have started to use a pump and treat facility using activated carbon, which improved the groundwater quality considerably. It is expected that the spreading of the pollution is stopped and the pesticide concentrations will slowly decrease. However, this approach is expensive as well as energy intensive (production of the activated carbon).

Nationwide recognition

Stengaarden is one of a few groundwater remediation showcases in the National Soil and Groundwater protection network and the Danish Soil Partnership network. These networks are established to encourage and facilitate development, demonstration and maturation of new techniques and products for site investigations and remediation.

Innovative methods in this case study

MBBR set-up in container

In this UPWATER case study pilot, a combination of two biofilm approaches is used: Moving Bed Biofilm Reactors (MBBR) and Biofiltration. The Region Zealand, authority of the ground since 2013, has kindly made a container and two biofilter reactors available at the site. The two biofilters have been installed outside of the container. In the container, AU has put two MBBR reactors for pesticide pre-removal and iron management.  AU is on the forefront of developing MBBRs for micropollutant removal as an effective, energy efficient and environmentally friendly technology. Additionally, AU is working on the deployment of CPS and DGT at this case study site. Validation of these passive samplers in the three case studies is a big part of UPWATER.

  • Moving Bed Biofilm Reactors (MBBR)
  • Biofiltration
  • CPS
  • DGT

Are you interested in delving deeper into the methodologies employed in the Stengaarden case study, or the methodologies employed in the other UPWATER case studies? For more detailed information, please continue reading on the dedicated methods page.

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