SLU carries out lake restoration in Latvia

News published:  21/08/2025

Researchers from SLU have recently taken part in lake restoration in Latvia. Sweden is at the forefront of lake restoration using aluminium treatment in eutrophic lakes.

Aluminium treatment of lakes is used to reduce nutrient loads. 

When carried out correctly, aluminium treatment has proven to be highly effective in preventing phosphorus leakage from lake sediments. “It is effective both in practice and economically, says researcher Oskar Agstam-Norlin.

The treatment involves binding phosphorus with aluminium, which is added to the bottom of lakes. For two years, researchers at the Department of Aquatic Sciences and Assessment have participated in a project transferring knowledge across the Baltic Sea and testing how aluminium treatment works in Latvia. A small urban lake in Riga was treated with promising results.

 

After the treatment, nutrient loading from the sediments decreased drastically, water transparency improved, and chlorophyll levels are expected to decline over time. This sets the lake into a new state, making it a better environment for biodiversity and a source of cleaner, usable water. “Suddenly it is possible to swim in the lake, and in the long term even the fish community may recover and become more balanced, Oskar explains.

The project is part of the Baltic Sea Interreg EU project, TRUST ALUM, where researchers have gained several valuable insights.

It is possible to apply the restoration methods we use in Sweden in other countries—and they work. The process of carrying out aluminium treatment looks different from country to country. Permit processes, infrastructure, laws and regulations vary, but with a little patience it is entirely feasible, says Oskar.

Within the project, the participants developed tools showing how to correctly carry out aluminium treatment—a kind of instruction manual.

The project and the developed tools

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