Coverage and treatment practices in nordic wastewater treatment plants under the recast EU urban wastewater treatment directive

Abstract Understanding the coverage and treatment processes of wastewater treatment plants (WWTPs) is essential not only for assessing system readiness for wastewater surveillance (WWS) and nutrient recovery but also supporting both regulatory compliance and sustainable sanitation goals. The recast Urban Wastewater Treatment Directive (UWWTD), effective in early 2025, mandates enhanced urban wastewater management across the European Union (EU) and European Economic Area (EEA), including routine antimicrobial resistance (AMR) surveillance of both influent and effluent. Beyond regulatory compliance, these measures enhance environmental health, public health monitoring and resource recovery. This study examined the coverage, treatment processes and operational challenges of WWTPs in the Nordic countries (Finland, Sweden, Norway, Denmark, Iceland and their autonomous regions). A Webropol survey targeting environmental authorities, wastewater experts and policymakers was conducted and complemented by a systematic review of peer-reviewed literature and grey literature, primarily government documents. According to the findings, ~ 85–90% of the Nordic population is connected to centralized WWTPs, highlighting the feasibility of WWS for public health monitoring. Treatment processes vary depending on the population density, coastal or inland location and sensitivity of the recipient waters body. Secondary treatment is nearly universal in Sweden and Finland but occurs in only about 4% of WWTPs in Iceland. Finland, Sweden and Denmark enforce strict effluent standards, while Norway and Iceland face challenges due to the harsh terrain, cold climates and the option to discharge into the turbulent, oligotrophic Atlantic Ocean, in which limited effluents volumes are considered rapidly diluted with minimal aesthetic impact. Overall, the Nordic region is generally well positioned for WWS under the new UWWTD, but diverse conditions, such as cold climates, challenging terrain and legacy discharge practices, require flexible, locally adapted strategies. This study highlighted both regional strengths and implementation gaps, emphasizing the need for resilient infrastructure, advanced treatment technologies and integrated policies to achieve sustainable sanitation and protect public health. Graphical abstract