Innovation Measures: Lake Ormstrup, Denmark
Lake Ormstrup has been the focus of research projects since 2020. Being strongly affected by nutrients, two research projects seek to clean the lake by regulating fish populations and removing phosphorus-laden sediment.
Most of the phosphorus in Ormstrup Lake is concentrated in the top 20 cm of the lakebed (sediment), from where it is released into the water column.
The accumulation of phosphorus in Ormstrup Lake is largely due to the release and feeding of up to 3,000 ducks per year in the lake, which took place 30-40 years ago.
The projects rePair and Sustainable Lake Stewardship are funded by the Grundfos Foundation, majority owner of Grundfos, a global leading company in water solutions. Data and innovations from both projects will be included in the FutureLakes’ European Lakes Digital Innovation Hub.
Digital twinning of Lake Ormstrup
Sustainable Lake Stewardship is focusing on creating a better understanding of the mechanisms involved in lake restoration.
The aim is to enable lake managers and stakeholders to select and optimize the most effective lake restoration measures, resulting in a clear-water lake with high biodiversity, where the clear-water state is maintained for as long as possible.
The lake has been partly restored through several rounds of biomanipulation, where non-predatory fish are removed from the lake. Subsequently, computer models are used to investigate the effects of climate change on lakes.
In the project, a measurement buoy has been placed at the deepest point of the lake, measuring temperature profiles every 15 minutes and oxygen concentration at the top and bottom (4 meters depth). Additionally, water samples are collected and analyzed weekly for chemical and biological water quality elements, including nutrient and chlorophyll concentrations.
“The projects will lead to new open-source model and decision support tools that can be used for other lakes nationally and internationally. They will, among other things, be included in the authorities' continued work with the Danish water plans and constitute the decision-making knowledge base in a more active management strategy for the restoration of lakes,” says prof. Martin Søndergaard from Aarhus University, WP lead in Futurelakes.
Examples of other methods include "space-for-time" studies, where lakes across a climate gradient are compared; mesocosm experiments, where smaller test tanks attempt to replicate lake conditions; paleolimnology, where the composition of bottom sediment is examined and dated; and long time series of observational data.
The rePair technology
In close collaboration with the rePair project, the engineering consultancy DIS/CREADIS has developed a new method to remove sediment from lakes and shallow waters with minimal negative impact on the environment.
It is a self-governing system that does not require permanent staffing. The goal is to create a cost-effective process that contributes to the sediment and its nutrient-rich content being reused as a resource in a circular economy. This project will be integrated in FutureLakes’ sister project FERRO
Like a robotic vacuum cleaner, the system steers itself around the water and locates the nutrient-rich sediment layers. The robot is quiet for the sake of wildlife and works gently and with high precision. The specially designed suction head gently sucks up the nutrient-rich sediment layers.
To create improvements with a long-term effect, it is crucial to remove the top nutrient-rich sediment layers gently and without releasing the nutrients.
In addition to gentle sediment removal, the rePair project also works with technologies for effective reduction of water content in sludge – HTC (hydrothermal carbonization technology), electro-osmotic dewatering, and removal of heavy metals and recovery of phosphorus using electrodialysis.