Pharmaceutically active compounds in streams and rivers of urbanised areas: adsorption in sediments and efficiency of the riverbank filtration

A significant part of the world's population lives around rivers. The riparian zone is not only a source of drinking water for urbanised areas; streams and rivers are also sinks for wastewater. As a result of the increased consumption of pharmaceutically active compounds (PhACs) in past decades, wastewater untreated and treated is a continuous load of these compounds (and their metabolites) to fluvial systems. The water supply for these kinds of urbanised areas is partly provided by riverbank filtration plants which can be significantly affected by PhACs loading. Riverbank filtration is effective for most pollutants. However, the filtering efficiency for these molecules is poorly known. This presentation focuses on the spatial and temporal distribution of more than a hundred PhACs in the streams and rivers of the Budapest Metropolitan Area. Our presentation demonstrates that bank filtration can also be effective for the filtration of organic micro-pollutants in highly urbanised areas.

Samples were collected during five sampling campaigns. The streams, rivers, and drinking water wells were sampled. The stream sediments were also sampled. Altogether 111 PhACs were measured. In small streams and rivers, eighty-one PhACs were systematically detected, while fifty-three PhACs were detected in the Danube. The quantification of 19 PhACs in the Budapest section of the river was without any precedent, and 10 PhACs were present in >80% of the samples. More PhACswere detectable in the small watercourses, and the concentrations were significantly higher than in the Danube. Sediments always contain fewer PhACs than water. This is mainly due to the high sorption capacity of sediments.

The most frequent PhACs showed higher concentrations in winter than in summer. In the drinking water wells 32 PhACs were quantified. For the majority of PhACs, the bank filtration efficiency was higher than 95%. Concentrations of the compounds did not influence the efficiency of filtering. For some PhACs (e.g. carbamazepine lidocaine, tramadol, and lamotrigine), low filtration efficiency was observed. These frequently occurring PhACs in surface waters have a relatively even distribution, and their sporadic appearance in wells is a function of both space and time, which may be caused by the constantly changing environment and micro-biological parameters, the dynamic operating schedule of abstraction wells, and the resulting sudden changes in flow rates.

This research was funded by the National Research, Development, and Innovation Office (NKFIH), grant numbers: K-142865 and 2020-1.1.2-PIACI-KFI-2021-00309.