Abstract

Combined sewer overflow (CSO) discharges pose a significant challenge to urban water management. Constructed wetlands (CWs) are a promising blue-green infrastructure solution for CSO management and water quality improvement, with recognized economic, social, and environmental benefits. This review synthesizes the state-of-the-art in CSO treatment using CWs over the past 30 years and explores current trends and future projections. A bibliometric analysis of 68 papers from the Web of Science Core Collection revealed that although CWs have been applied at a full scale for CSO treatment since the 1990s, they remain an emerging research topic. Germany, France, Italy, the United Kingdom and the United States of America lead in literature production and application. However, there is a significant lack of information from the Global South (developing countries) and tropical/subtropical regions. Reports from temperate developed countries indicate good performance, with removal efficiencies above 70 % for conventional pollutants such as solids, organic matter, and nutrients (nitrogen and phosphorus). However, pathogen removal was limited. Contaminants of emerging concern such as pharmaceuticals, polycyclic aromatic hydrocarbons (PAHs), and microplastics, have also been investigated in CW-treated CSOs with divergent results. This review also discusses various aspects, including regulations, design, environmental performance, and trade-offs. While CWs demonstrate substantial potential for preventing surface water pollution, their application and associated knowledge must expand beyond developed temperate regions, mirroring the global adoption of CWs for domestic wastewater and stormwater treatment. This expansion is crucial for CWs to be considered a truly global solution for CSO treatment. © 2025 Elsevier B.V.