Recycling various wastes as substrates in constructed wetlands: A review on enhancing contaminants removal and potential risks

Under the perspectives of circular economy, coupling waste management and environmental engineering to foster sustainable pollution control solutions has gained particular attention. Particularly in constructed wetlands (CWs) as a nature-based solution, recycling various wastes as substrates for enhancing the removal of various pollutants have become a recent hotspot in recent years. In this review, physicochemical properties, enhanced removal performance and mechanism of various pollutants, and potential risks of waste-derived substrates including industrial and municipal wastes, agricultural by-products, and waste synthetic substrates were summarized comprehensively. It is indicated that agricultural by-products have the best chemical oxygen demand (COD) and total nitrogen (TN) removal with the average removal efficiency of 91.23 % and 83.68 %, while industrial and municipal wastes have the best total phosphorus (TP) removal efficiency (86.70 %). The main impacts and risks of waste-derived substrates included: the secondary pollution, toxic to plants and microorganisms, and potential clogging. This review could provide theoretical basis for the future exploration and application of recycling waste as substrates in CWs.