Fate of antifungal drugs climbazole and fluconazole in constructed wetlands-Diastereoselective transformation indicates process conditions

Sochacki A., Maršík P., Chen ZB., Šíša M.,Vymazal J.

Keywords: Antifungal drugs, Constructed wetlands, Plant uptake, Stereoselective transformation, Transformation products
Abstract: Climbazole (CBZ) and fluconazole (FCZ) belong to the class of azole antifungal drugs that are widely used in medicine and as ingredients of cosmetics, and in result have been frequently detected in municipal and domestic wastewater and in natural watercourses. So far, the behaviour of azole antifungal drugs in constructed wetlands has been scarcely reported. In this study the fate of CBZ and FCZ was investigated in constructed wetlands with various water saturation levels and with or without the vegetation. The experimental column system was operated in outdoor conditions for 122 days and was fed with artificial wastewater containing CBZ or FCZ at 10 μg/L, each. The removal of FCZ was negligible and the removal of CBZ was ≥90% in unsaturated and partially saturated conditions and in saturated columns with plants. Unvegetated saturated columns provided only moderate removal of CBZ (56%). Plants took up only small portion of FCZ or CBZ (1–2%) as referred to the influent load. Contrasting translocation factor (roots-leaves) was observed for CBZ (TF = 0.1) and FCZ (TF = 4.6). The transformation products of CBZ in the effluents were: reduced CBZ (CBZ-alcohol) and hydroxylated (oxidized) CBZ. CBZ-alcohol was detected in two diasteromers that were quantified throughout the experiment. The ratio of the diastereomers depended on the water saturation level and to a lesser extent on the presence of plants and was in the range from 0.10 for saturated columns to 2.02 in unsaturated columns, which suggested stereoselective formation/degradation reactions. CBZ-alcohol was probably further degraded and its degradation efficiency corresponded to CBZ removal. In contrast to CBZ, CBZ-alcohol was translocated to the above-ground tissues of the plants. The translocation of CBZ-alcohol was deemed a stereoselective process.
DOI: 10.1016/j.cej.2020.127783
IEB authors: Miroslav Šíša