APRIORA: Turning Pharmaceutical Pollution Data into Risk-Based Decisions

Led by the University of Rostock, APRIORA is an Interreg Baltic Sea Region project that ran from November 2023 to October 2026. It addressed a practical question facing water authorities and utilities: where should investment in advanced wastewater treatment go first? The revised Urban Wastewater Treatment Directive calls for micropollutant removal through advanced treatment, which will require substantial investment. Because not every plant can be upgraded at once, APRIORA looked beyond individual treatment plants and assessed pharmaceutical risks across entire river basins.

A risk framework in three modules

APRIORA’s first main result is a streamlined framework, documented in a background document and flowcharts for authorities, plant operators and other stakeholders. Module A guides monitoring, from selecting target compounds and sampling sites to setting sampling frequency and establishing laboratory procedures and data management. The project identified 72 pharmaceuticals in regulatory and other relevant documents, narrowed the list to 30, and selected 10 for its pilots. Module B estimates pharmaceutical loads discharged from treatment plants using sales statistics in a mass-balance model. These load estimates are then combined with hydrological modelling to calculate concentrations at different points in the river network. Module C assesses environmental risks, the potential to promote antimicrobial resistance, and risks to human health through drinking water and fish consumption. These three dimensions are brought together in a cumulative index to help rank sites for action.

A decision-support tool anyone can use

The second result is the APRIORA QGIS plugin, an open-source decision-support tool that puts the framework into practice. It enables users to model and map risks at catchment scale and assess how upgrading a particular treatment plant could affect those risks before investment decisions are made. The plugin is available in the official QGIS repository, and a step-by-step manual is available online. During a hands-on workshop at the APRIORA Final Conference in Helsinki, participants tried the tool and shared feedback on its practical use. National training workshops have also been provided to regional stakeholders, particularly the EPAs responsible in the partner countries

Tested in five river catchments

The third result is evidence from the pilots. The approach was applied in five river catchments across Finland, Germany, Latvia, Poland and Sweden. The pilots showed that priorities differ by region, while also generating lessons that can be adapted elsewhere.

Challenges along the way and what we learned

Data availability was the most persistent challenge. Nearly 500 pharmaceuticals have been analysed at least once in the Baltic Sea Region, but most results come from project-based screening campaigns, and long-term time series remain rare. Analytical work is also demanding: laboratories typically report measurement uncertainties of around 40%; suitable analytical methods were not commercially available for every compound on the project list; and a single sample can cost thousands of euros. This made it especially important to select a small, meaningful set of target compounds. Practices also differ between countries, and river flow is not always measured alongside concentration data, limiting mass-balance calculations. APRIORA responded by harmonising its approach through flowcharts and being transparent about uncertainty in the input data.

Five lessons from APRIORA

• River-basin scale matters: Water-quality and mass-flow modelling can help identify where measures are most needed and guide more targeted investment in advanced wastewater treatment.
• Risk-based approaches are essential: Pharmaceutical residues and antimicrobial resistance call for an integrated understanding of sources, pathways, risks and potential mitigation measures.
• Solutions need to be context-specific: Pilots in five river catchments showed that priorities differ by region, while offering transferable lessons for the wider Baltic Sea Region.
• Treatment is only part of the solution: Advanced end-of-pipe treatment should be embedded in a broader strategy that also tackles hazardous substances upstream through targeted source-control measures.
• Digital tools can support implementation: The APRIORA QGIS plugin demonstrates how data and modelling can inform practical water-management decisions.

Taken together, these lessons point to APRIORA’s central message: advanced end-of-pipe treatment is important, but it is only part of a broader strategy that also tackles hazardous substances at source. We hope the framework, plugin and pilot experience will support authorities and utilities in the Baltic Sea Region and beyond as they implement the revised directive. We are pleased to share these outputs with the HAZGONE community.

• APRIORA project page and pilot results: https://interreg-baltic.eu/project/apriora/
• Final Conference report: https://interreg-baltic.eu/project-posts/apriora/apriora-final-conference-in-helsinki-from-pilot-results-to-practical-tools-for-cleaner-waters/
• QGIS plugin: https://plugins.qgis.org/plugins/apriora/ and QGIS manual: https://hosting-apriora-manual.readthedocs.io/en/latest/index.html

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