Nature-based solutions under climate change: An overview of key findings from the UNSFA pilot site within the DALIA and SWIM projects

Constructed wetlands (CWs) are nature-based solutions increasingly applied for domestic wastewater treatment, yet their performance is sensitive to climatic conditions. This study presents an overview of key findings from the Gložan CW pilot site in Vojvodina, Serbia, assessed within the framework of the DALIA and SWIM Horizon Europe projects. Long-term treatment performance analysis demonstrated high and stable removal efficiency for organic matter, with average BOD₅ removal exceeding 90%, while phosphorus and suspended solids exhibited greater variability. Seasonal analysis indicated significantly lower BOD₅ removal during summer. Future climate projections were analysed using an ensemble of eight bias-corrected Euro-CORDEX regional climate models under the RCP8.5 scenario. Results indicate a progressive increase in thermal stress, with tropical days nearly doubling by 2071-2100, alongside a 49% reduction in frost days, a 21% increase in maximum one-day precipitation, and a modest decline in the Seljaninov Hydrothermal Coefficient. These changes present both opportunities - through extended frost-free operational seasons - and challenges, including increased hydraulic loading from extreme rainfall and moisture deficits during the growing season. Integrating climate adaptation into the long-term management of nature-based wastewater treatment systems is strongly recommended.