Removal and transformation of pharmaceutical compounds in constructed wetlands: A comparative full-scale study

Abstract

Pharmaceutically active compounds (PhACs) need to be removed from wastewater, given the risks they may pose to biota and human health. Constructed wetlands (CW) offer a cost-efficient and eco-friendly solution. However, research is needed at full-scale level to understand the transformation processes of PhACs inside CW. This study aimed to evaluate and compare the removal and transformation of PhACs in 2 full-scale CW with different configurations and a passive treatment system at pilot scale (PP) as control wastewater system. The PP treated urban wastewater in a combination of horizontal and vertical filtering. The full-scale CW were: 1) a vertical flow CW (Orhei-OCW), treating urban wastewater, and 2) a free-water surface CW (Empuriabrava-ECW) treating the effluent of a secondary wastewater treatment plant, both planted with Phragmites australis. A set of 60 PhACs, including 10 metabolites, were analysed by UPLC-MS/MS and transformation products (TPs) by UPLC-HRMS through the treatment chain of the 3 systems. Antibiotics and beta-blockers were more efficiently removed in vertical flow CW (92 and 83% removal, respectively) compared to other configurations, while psychiatrics were the more persistent PhACs in the 3 configurations (Fig.1). Full-scale CW planted with Phragmites worked better compared to the plant-free PP, highlighting the role of macrophytes in the removal processes. Metabolites, however, were formed along the treatment, increasing their concentrations and possible risk to aquatic biota. Considering both parent and TPs, the risk of detected PhACs in fullscale CW decreased after treatment.