Robot vacuum will remove phosphorus-rich sludge from Danish lake

A giant robot vacuum will remove the top 20 centimetres of the lakebed at Snesere Sø near Tappernøje in November, DR reports.

The machine, named Søbotten, will target the part of the lakebed containing most of the lake’s phosphorus. The nutrient contributes to algae growth and has disrupted the lake’s ecological balance.

Søbotten is part of a research project led by Aarhus University. The robot is controlled using equipment positioned on the lake’s surface.

Næstved Municipality welcomed the inclusion of Snesere Sø in the project. Biologist Palle Mysen said the lake was chosen because it has almost no inflow or outflow, meaning that little from outside can alter its natural balance.

That will allow researchers to monitor whether the lake remains clean after the sludge has been removed, Mysen said.

The project aims to test new environmental technology and is funded by the Danish Agency for Green Land Transformation and Water Environment.

A prototype of Søbotten was tested in Ormstrup Sø near Bjerringbro in 2024. The robot will now undergo full-scale trials in three lakes, including Snesere Sø in southern Zealand.

The technology could have wider applications. According to the University of Southern Denmark, Denmark has more than 100,000 lakes and ponds, while similar problems affect millions of lakes across Europe.