Solmax GeotubeSustainability

Recycling sediment and sludge from Ishøj Lake with Solmax Geotube®

Over the years, the artificially created Ishøj Lake has filled up considerably with sediment and silt. During the summer months, this accumulation has contributed to the occurrence of oxygen depletion in the lake with consequences for fish and birds living in and around the lake.


Ishøj Forsyning A/S


Recycling/reclamation of sediment from lake dewatered on Geotubes


Ishøj Lake, Denmark



For Ishøj Utility, the solution to the problem has been to use the revolutionary and simple dewatering technology called Solmax Geotube®. Here, sludge or sediment with an appropriate amount of polymer added is pumped into a bag. The polymer ensures good floc formation and thus optimal separation of sludge and reject water, so that the sediment can be reused for recreational purposes such as landscaping.

As a result of road water flowing in from Baldersbækken and Lille Vejle Å, Lake Ishøj has over the years been filled with clay, sand and organic particles including nutrients.

By using Solmax Geotube® bags, Ishøj Lake has been cleaned of bottom sediment and accumulated nutrients have been removed. Thus, improved water quality and water clarity have been achieved.

Ishøj Lake has its sources in respectively Høje-Taastrup, Greve and Ishøj Municipalities.

An efficient work process with minimum environmental impact

The solution chosen by the three municipalities in close collaboration with Ishøj Forsyning is Solmax Geotube®, which is distributed by Envidan in Denmark. It’s a revolutionary yet extremely simple dewatering technology for all types of sludge and sediment.

Solmax Geotube® consists of large bags of a synthetic canvas that retains solid material but allows excess water to drain off. This has provided the three municipalities with an environmentally clean method of clean-up with minimal impact on the local environment.

The beauty of the technology is also that it does not require permanent facilities or fixed installations.

Minimal energy consumption and less landfill

It is a sustainable method chosen by the municipalities to clean up the lake, as the technology requires minimal energy consumption. The dried sediment takes up much less space after treatment, so landfill costs are significantly reduced and the dewatered sludge is easier and cheaper for municipalities to dispose of.

In this case, the sediment has been reused to shape a popular recreational leisure area.

Envidan has provided technical advice, assistance and coordination as well as consultancy for the implementation of the project.

Advantages of Solmax GeoTube®


  • Pumping and dewatering the sludge in bags ensures a clean working process and the least possible environmental impact on the local environment.
  • Efficient dry matter retention (>99 %) ensures good drainage water quality and hence minimal environmental impact.
  • No odor nuisance during the dewatering procedure and storage.
  • Significant energy and CO2 savings in the handling of the sediment.


  • Significant reduction in the number of truck trips for sediment disposal.
  • Can be built locally directly into the dewatering bags, minimizing the cost of technical aids and machinery, etc.
  • Can be incorporated and used for harbor piers, coastal protection works, etc. involving high costs for stone, gravel and earth materials for incorporation into piers, embankments, etc.


  • Solmax Geotube® bags are easy to use, effective and highly flexible.
  • High hydraulic and processing capacity.
  • Available in virtually any size to suit the customer’s needs.
  • Can be used on all types of sludge.
  • Dewatering and sludge storage are done in one process.
  • High dry matter content, depending on the type of sludge, a dry matter content of 15-50 % can be expected.
  • The drainage bags can be delivered at short notice.

Want to know more about Solmax Geotube®?

You are always welcome to contact us for more information.

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