Pharmaceutical compounds were investigated in river and riverbank filtration (RBF) water at the Mosina-Krajkowo site (Poland), in 6 sampling campaigns between November 2019 and June 2020. All of the ten phar maceutical compounds tested for were detected in the water. Carbamazepine, fluconazole, tramadol, sulphamethoxazole and sulphapyridine were the most frequently found, the highest concen trations being observed in surface water. There was a reduction in their levels in the horizontal well (HW) with drains located below the river bottom, averaging 17%. Significantly higher reductions ( 53-71%) were observed in vertical wells (VWs). Mix ing, sorption and biodegradation were distinguished as processes conditioning the reduction of pharmaceutical compounds along flow paths from the river to the wells. Their reduc tion in the HW occurs due to sorption onto fine sediments with high or ganic mat ter content and aerobic biodegradation, while in the VWs it is the effect of aerobic biodegradation and water mixing with unpolluted groundwater. Sorption on riverbed fine sediments can also occur, especially during low water levels in the river. Biodegradation develops in oxic conditions with aerobic bacteria. VWs lo cated at similar distances from the river yielded different concentrations of pharmaceutical compounds, because of differences in geological structure, hydrogeological conditions and well opera tion parameters.
