Unravelling the role of vegetation in the attenuation of contaminants of emerging concern from wetland systems: Preliminary results from column studies.

Water pollution with contaminants of emerging concern (CECs) is widespread in water bodies due to the low effectiveness of industrial and urban wastewater treatment systems. In recent decades, the implementation of vegetation-based wastewater treatment systems such as wetlands has been observed to help solve this issue. However, there is a lack of knowledge regarding the removal percentage attributable to plants and how plants affect this removal improvement. In this study, we monitored planted (Phragmites australis) and unplanted sand columns to assess the effect of vegetation on the attenuation of 5 well-known CECs (benzotriazole, sulfamethoxazole, carbamazepine, bisphenol A, and diclofenac) and link it to the presence of different root exudates. The columns were operated in a continuous feeding mode for more than 6 months at 3 hydraulic loading rates (HLRs) (70, 140, and 280 mm d-1). We found that the presence of vegetation increased CEC attenuation from no effect to more than 200% compared to the unplanted columns. The highest effect was observed for carbamazepine (94-200%), followed by diclofenac (22-171%), benzotriazole (48-127%), and sulfamethoxazole (no effect to 43%), depending on the tested HLR. Furthermore, the greater CEC attenuation in planted columns was linked to the release of certain root exudates that may shape the root microbiome. We expect our assay to be a starting point for exploring the role of root exudates in enhancing CEC removal efficiency in wastewater.