Column Experiments on Sorption Coefficients and Biodegradation Rates of Selected Pharmaceuticals in Three Aquifer Sediments

Aleksandra Kiecak,Friederike Breuer,Christine Stumpp

doi:10.3390/w12010014

Abstract

The presence of pharmaceuticals in the environment, and in groundwater, has been recognized as a great environmental concern. Biodegradation and sorption are the main processes leading to the removal of contamination from the water phase. The aim of this study was to determine the transport processes of selected pharmaceuticals (antipyrine, atenolol, carbamazepine, caffeine, diclofenac, ketoprofen, sulfamethoxazole) in selected sediments (coarse sand, medium sand, sandy loam) in laboratory experiments. Moreover, the impact of flow velocities on the sorption and degradation rates of the selected compounds was studied. Column experiments were performed at three flow velocities, under abiotic and biotic conditions, applying conservative (bromide) and reactive tracers (pharmaceuticals). From the breakthrough curves, retardation factors and degradation rates were determined and the influence of variable flow conditions on transport parameters was evaluated. Low observed concentrations and recoveries of atenolol indicated a strong influence of sorption on its transport. Diclofenac, caffeine, and carbamazepine were also affected by sorption but to a lesser extent. Sulfamethoxazole, ketoprofen, and antipyrine were recovered nearly completely, indicating an almost conservative transport behavior. Biodegradation was small for all the compounds, as the results from biotic and abiotic column experiments were similar. Transport of the tested pharmaceuticals was not influenced by different flow velocities, as similar modelled degradation rates and retardation factors were found for all tested flow velocities.

Highlights

Pharmaceuticals belong to emerging organic contaminants and have recently been the focus of research due to their high frequency of detection in the environment [1]
The sediment and groundwater, as well as the chemicals used in the experiment, were analogous to those described in Kiecak et al (2019) [31]
Modelling of the breakthrough curves with a conventional deterministic equilibrium convection dispersion equation resulted in a good fit of the calculated curves when compared to the observations

Summary

Introduction

Pharmaceuticals belong to emerging organic contaminants and have recently been the focus of research due to their high frequency of detection in the environment [1]. The behavior of pharmaceuticals in water systems is ruled by complex processes, which remain poorly understood, in groundwater [2,3,4,5]. The fate and transport of pharmaceuticals in groundwater as well as risks of possible groundwater contamination are difficult to predict. Improving the understanding of pharmaceuticals’ transport in heterogeneous and dynamic hydrogeological settings requires the knowledge of crucial processes and transport parameters, which are, difficult to determine at complex field sites. As noticed by Meckenstock et al (2015) [6], the true drivers controlling the degradation of low level contaminants are not yet understood well. Concerning mass transfer processes, the heterogeneity of the sediment is

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