This wrap-up has been compiled by the Programme
Priority   2 Water-Smart societies
Objective  2.1 Sustainable waters
TRUST ALUM:
Wrap-up of project achievements
Eutrophication occurs when an excess of nutrients, including phosphorus stored in lake sediments, fuels algal blooms that degrade water quality in lakes and the Baltic Sea. Although the ALUM treatment method has been used successfully to reverse this process in lakes in Sweden for decades, it has remained largely unknown in Estonia, Latvia, and Lithuania. The Interreg project TRUST ALUM introduced this method to public authorities in these countries, building confidence in its use and equipping them with the knowledge and tools needed to apply it more widely. Â
Highlights
TRUST ALUM
Highlights
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The TRUST ALUM project helped public authorities in Estonia, Latvia, and Lithuania better understand and apply ALUM treatment – a proven method for permanently binding phosphorus in lake sediments to improve water quality and counteract eutrophication.
Through practical demonstration, knowledge transfer, and policy dialogue, the project delivered:
- ALUM Treatment ToolboxÂ
- Expertise linking hub for ALUM treatmentÂ
- Restoring lakes using the ALUM method in the Baltic statesÂ
Project
Details
Project type
Small project
Project duration
August 2023 – July 2025
Contribution to the EUSBSR
PA Nutri
Budget in million
EURO
Involved
Countries
Lead partner
Project partners
Project Details
Project type
Small project
Project duration
August 2023 – July 2025
Contribution to the EUSBSR
PA Nutri
Budget in million EURO
0.5 total // 0.4 ERDF // 0.0 Norway
Involved Countries
Lead Partner: Latvia
Project Partners: Estonia // Sweden // Latvia // Lithuania
ALUM Treatment Toolbox
Best practice guidance for advanced wastewater treatment
The project developed the ALUM Treatment Toolbox for national, regional and local public authorities as well as other organisations involved in water management. It consists of recommendations, technical documentation, monitoring requirements, and a step-by-step roadmap to support the preparation, implementation, and monitoring of ALUM treatment.
The project worked with organisations from Estonia, Latvia, and Lithuania to adapt decades of Swedish experience to the environmental, regulatory, and practical needs of these countries. The value of the transnational cooperation lies in transferring proven know-how from countries where the method is already established to countries where it was previously unknown. Thanks to this, public authorities now have a practical tool that reduces uncertainty and supports the wider use of effective lake restoration measures.
Pilot activity
The project tested and demonstrated the ALUM treatment in Lake Velnezers in Riga, Latvia. The pilot activity addressed one of the main barriers to wider use of the method in the Baltic countries: the lack of practical examples.
The pilot demonstrated that ALUM treatment can safely and effectively bind phosphorus in lake sediments, thereby reducing internal nutrient loading and improving water quality. Just as importantly, it gave public authorities, water management experts, and other organisations the opportunity to observe the treatment in practice, build confidence in the method, and gain first-hand experience for future applications.
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In numbers
15 organisations cooperating across borders
25 directly benefitting from project solutions
Interreg pays off
Solutions in use
Interreg pays off: Solutions in use
By demonstrating the effectiveness and safety of ALUM treatment, the project built trust among public authorities, experts, and other organisations, and launched a permanent expertise hub that connects practitioners and researchers across borders. The pilot generated valuable evidence and provided a practical example that can encourage the wider use of ALUM treatment across the Baltic Sea region. As a follow-up to the pilot activity, the project plans to monitor water quality parameters in Lake Velnezers in Latvia for at least the next five years.
By transferring proven solutions across borders, the project has created lasting capacity for more effective lake restoration and eutrophication management across the region.
One of the project’s greatest achievements was contributing to regulatory changes in Latvia. The project’s pilot activities, scientific evidence, and dialogue helped pave the way for amendments to existing regulations that recognise ALUM treatment as a valid measure to improve water quality. This removes a key barrier to future implementation and creates favourable conditions for wider uptake of the method.
Project Wrap-Up
Thanks to Interreg funding and transnational cooperation, TRUST ALUM helped overcome barriers to the use of ALUM treatment in Estonia, Latvia and Lithuania. The project demonstrated the method in practice, equipped public authorities with practical implementation tools, and contributed to regulatory improvements. Now, public authorities across the Baltic Sea region are better equipped to restore eutrophic lakes, improve water quality and reduce phosphorus pollution reaching the Baltic Sea.
