Constructed Wetlands as a Nature-Based Solution for Sustainable Heavy Metal Remediation

Heavy metal contamination presents significant challenges to the environment, human health, and socio-economic development, necessitating effective and sustainable treatment strategies. Constructed wetlands (CWs) have emerged as a promising nature-based solution for treating metal-contaminated wastewater due to their low cost, minimal energy requirements, and ecological co-benefits. This chapter synthesizes current knowledge on the mechanisms governing heavy metal removal in CWs, highlighting the integrated roles of physical, chemical, and biological processes. In particular, it emphasizes the importance of redox-driven transformations, substrate reactivity, and plant–microbe interactions in controlling metal speciation, immobilization, and long-term stability. Key system components – including substrates, aquatic plants, and microbial communities – are critically evaluated, together with design and operational factors such as hydraulic conditions and system configuration. Recent advances in functional substrate development, plant and microbial management, and hybrid CW systems are discussed as effective strategies to enhance treatment performance. Practical applications demonstrate that CWs can successfully treat diverse wastewater, including mine, industrial, and agricultural effluents, while providing additional ecological and socio-economic benefits. Despite these advantages, challenges such as land requirements, variable loading conditions, and long-term stability remain. Future research should focus on smart CW systems, life cycle assessment, and circular economy approaches to further improve efficiency and sustainability. Overall, CWs represent a flexible and integrated platform for sustainable heavy metal management.