Circular lake restoration

RePair will directly address seven of the 17 UN SDGs, by promoting sustainable management of resources, protecting the environment, using applied research to assist good education, and mitigating GHG emissions.
Our goal is to promote a paradigm shift in lake management by restoring freshwater bodies by transforming lake sediment and P polluted lake water into a valuable resource without any harmful effects on the environment. Our vision will be achieved through a unique and well-aligned constellation of interdisciplinary research between four Danish universities and relevant stakeholders from industry, agriculture, and lake managers. An integral part of the RePair project will be the interdisciplinary training of students by teams of academic supervisors providing cross-sectoral research collaborations among the students.

The major initiatives taken to ensure a successful outcome of the project are:
1: Develop a dredging technique, which results in only minimal disturbances of the lake ecosystem.
2: Reduce sludge handling volumes by mechanical dewatering, thus reducing sediment water content.
3: Remove dissolved P and nitrogen from the reject water so that it can be immediately returned to the lake without the need for further treatment while recovering nutrients for reuse.

These initiatives will be conducted in Lake Ormstrup (12 ha), which will serve as our demonstration lake during the project period. The project will be a showcase for how lake restorations of the future should be undertaken, develop the new future technologies required and successfully develop a “tool box” of technologies, which can be combined based on lake specific requirements, while demonstrating how P in lake sediment and lake water can be recovered and used as a fertilizer product. Furthermore, unwanted compounds in the sediment such as heavy metals and problematic organic compounds can be selectively
removed from the sediment. The project will demonstrate dewatering and handling of the sediment in ways, which require no harmful chemicals or synthetic polymers. It is expected that the technologies developed
will increase sediment dry matter to over 60 % and in a handling time of less than 24 hours. The technologies will ensure that even P and nitrogen in low concentrations can be removed from lake water and recovered in a manner that enables their reuse as a fertilizer. It is expected that this highly interdisciplinary project will not only impact future best practices in lake restoration but will also be applied to manure management and sludge treatment in wastewater treatment plants (WWTPs), where ever-increasing volumes of sludge and
manure are proving an insurmountable global issue.