The EMPEREST project represents a major step forward for the protection of the Baltic Sea and its catchment area – by combining science, technology, and capacity building across borders, it established a comprehensive and ready framework to address the problem of hazardous substances in the water cycle. This problem is one of the most pressing environmental challenges in the Baltic Sea Region as identified in the latest holistic assessment of the Baltic Sea (HOLAS 3). 

Launched in January 2023 under the Interreg Baltic Sea Region Programme, EMPEREST brought together 14 partner organisations and a broad network of stakeholders, including water utilities and local authorities. To achieve its ambitious goals, the project cooperated broadly with over 15 international projects and initiatives in the BSR and Europe-wide. 

Supporting stakeholders in implementing new European requirements

The main driver behind the EMPEREST project was EU legislation change, namely the revision of the directive regulating urban wastewater treatment. This Directive, finalized during the EMPEREST years, sets many new requirements, including a new treatment step for the removal of organic micropollutants from wastewater. 

To support the implementation of the Directive in the Baltic Sea Region, EMPEREST tested advanced wastewater treatment technologies via mobile pilot-scale plants in seven different cities: from Tartu, Tallinn, and Turku to Gdańsk, Szczecin, Kaunas, and Riga. These mobile plants tested a variety of treatment methods (e.g. ozonation, granular activated carbon, ion exchange, nanofiltration) and combinations thereof to evaluate their effectiveness and viability for full-scale application under varying operational conditions. This practical, comparative piloting enabled water utilities to make informed decisions about future investments needed to implement the upcoming regulatory requirements. EMPEREST thereby lowered barriers for utilities to adopt advanced treatment needed for effective micropollutant removal.

Advancing cross-border cooperation in PFAS assessment

On the regional level, EMPEREST – holistically approaching the elimination of organic micropollutants and especially PFAS (per- and polyfluoroalkyl substances) – made a significant input into the harmonization of PFAS monitoring and assessment. Coordinated by the HELCOM Secretariat, the project developed comprehensive methodological recommendations for PFAS in the aquatic environment. These guidelines, published in early 2025, drew upon PFAS monitoring data from 2000–2022 across water, sediment, and biota in the Baltic Sea Region, collected through a large regional data call. This harmonised approach enabled consistent and comparable assessment of PFAS pollution across countries – moving beyond narrow legacy-substance metrics to capture the true scale and complexity of contamination. The preliminary assessment based on the recommended parameters and collected data revealed PFAS contamination in biota at levels many times higher than the prospective thresholds, underscoring the urgency of coordinated action.  

Strengthening the capacities to act locally

Recognising that long-term environmental protection depends on local action, the EMPEREST partner City of Riga developed a PFAS risk-assessment framework and a user-friendly, Excel-based tool aimed at cities and municipalities. This enabled local authorities and water utilities to map potential PFAS sources along the municipal water cycle (from water abstraction and supply to sewage collection and discharge), identify hotspots, and plan targeted mitigation. The risk-assessment tool was tested in over 20 BSR municipalities, offering a practical first step for local governments to engage with PFAS challenges and prepare for effective action. 

EMPEREST complemented these technical and regulatory-oriented outputs with capacity building and awareness-raising. Despite the increasing media coverage and general interest on PFAS and hazardous substances overall, there are still considerable knowledge gaps on the topic. A comprehensive training programme, developed by Berlin University of Technology, took place during the project implementation years. This programme, consisting of a series of workshops, webinars, study visits, tutorials, with a pinnacle at the final conference in Berlin, brought together stakeholders from across the region, fostering knowledge exchange and aligning practices. All these events and related work resulted in a training materials package offering structured learning materials, short videos, and resources on PFAS, organic micropollutants, monitoring, removal technologies, and risk assessment. These materials, tailored for water and wastewater operators, local authorities, and environmental professionals, are available in the Baltic Smart Water Hub. 

Scalable solutions – solid foundation for wider replication

Thanks to this integrated, four-strand approach, EMPEREST significantly contributed to a cleaner state of the Baltic Sea and laid a solid foundation for other cities and water utilities to follow with the implementation of new stringent European regulations.

Even before the project had ended, the transfer effects were already evident: EMPEREST results have reached the intended stakeholders. The monitoring guidelines and gathered data are used to support the implementation of actions under the Baltic Sea Action Plan and have attracted interest from actors in the North Sea region for partial uptake. Promotional campaigns based on the training materials have engaged a broad range of professionals, and the constructed mobile pilots are actively used for further testing. The municipal risk-assessment tool attracted a lot of interest and has been further localised to encompass even a wider scope by several organisations and initiatives. 

As regulatory frameworks evolve and demands on water quality intensify, EMPEREST delivered both the knowledge and the practical means for the Baltic Sea Region to move decisively toward a PFAS-aware, resilient, and pollution-free water future.