A robotic underwater vacuum called “Søbotten” will remove the top 20 centimeters of sediment from Snesere Sø near Tappernøje to strip out phosphorus.
The machine is part of a research project led by Aarhus University, DR reports. It will vacuum away the uppermost layer of the lakebed, where most of the lake’s phosphorus is stored.
According to DR, the phosphorus drives algal growth and has pushed the lake out of ecological balance. The robot is steered by equipment placed on the lake surface, and the work is scheduled for November.
The project is financed by the Styrelsen for Grøn Arealomlægning og Vandmiljø, known as SGAV. Its stated purpose is to test entirely new environmental technology under real conditions.
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Næstved Kommune describes the same operation as a restoration of Snesere Sø, and states on September 3, 2026 that it will take place in October. The municipality says roughly 20 centimeters of sediment will be taken out.
Nutrients have built up in that layer over about 50 years, per the municipality. Phosphorus is singled out as the main problem substance in the accumulated material.
How the sediment is handled
The removed material will be pumped to biotubes and settling tanks on land, according to Næstved Kommune. Water is cleaned there and returned to the lake, while the nutrient-rich sludge is held back.
The retained sludge is then removed from the site at a later stage, the municipality states. The stated aim is to improve the lake’s ecological condition and reduce algal blooms.
Næstved Kommune also expects better conditions for plants, animals and fish in the lake. Similar restoration methods have been used elsewhere in Danish freshwater management, including at monitored sites where authorities explore nature in Denmark for long-term data.
Why this lake was chosen
Palle Mysen, a biologist at Næstved Kommune, tells DR that the choice of Snesere Sø was not random. He points to the lake having almost no inflow and no outflow.
Because of that, nothing from outside can change the natural balance, according to Mysen. He says this makes it possible to follow the lake and see whether it stays clean once the vacuuming is finished.
The municipality says it is pleased that Snesere Sø was taken in under the research project. The lake lies on Sjælland, where other monitoring work has fed into EU conservation law.
DR issued a correction to its own report, noting that its headline first referred to nitrogen. The correct substance is phosphorus, the outlet states.
