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Materials in constructed wetlands for wastewater remediation: A review

The wastewater treatment industry is constantly evolving to abate emerging contaminants and to meet stringent legislative requirements. The existing technologies need to be modified, or new innovative treatment techniques need to be developed to ensure environmental protection and secure sustainability in the future. Emphasis is mainly on nutrient recovery, energy‐efficient systems, zero waste generation, and environmentally friendly techniques. Constructed wetlands (CWs) have evolved as natural, eco‐friendly, economical, and low‐maintenance alternatives for wastewater remediation. These wetlands employ several materials as adsorbents for the treatment, commonly known as media/substrate. This review paper presents an assessment of various materials that can be used as substrates in CWs for the efficient removal of organic and non‐biodegradable pollutants in different types of wastewaters. The effect of pH, mineral composition, specific surface area, and porosity of various natural materials and agricultural and industrial wastes used as media in CWs for wastewater remediation was discussed. The study showed that different substrates like alum sludge, limestone, coal slags, rice husk, and sand had removal efficiency for chemical oxygen demand (COD): 71.8%–82%, total phosphorous (TP): 77%–80%, and total nitrogen (TN): 52%–82% for different types of wastewaters. It also highlights the challenges related to the long‐term sustainability of these materials.