Transport of primidone, carbamazepine, and sulfamethoxazole in thermally treated sediments—laboratory column experiments

Zusammenfassung

Purpose: The transport behavior of human pharmaceuticals in groundwater depends on a multitude of factors such as the physico-chemical conditions in the aquifer and the organic carbon content of the sediment, and, in particular, on the redox conditions in the groundwater. This is of special interest at managed aquifer recharge sites where the occurrence of trace organics is important for drinking water production. The aim of this study was to evaluate the possibility of influencing the redox system of the aquifer in a way that optimizes the potential of managed aquifer recharge systems to reduce the amount of trace organics. Materials and methods: Column studies were performed using natural and thermally treated sediments from an infiltration basin of the Berlin area, Germany. Special emphasis was placed on thermal treatment of the sediments to influence the total organic carbon (TOC) content in the sediment. In one experiment, the sediment was thermally pretreated at 550 °C, in two experiments the sediment was pretreated at 200 °C, and in one the sediment was untreated. Furthermore, the influence of ozonation, a very common disinfectant used in drinking water production, was studied in the experiments. The retardation and degradation parameters for primidone (PMD), carbamazepine (CBZ), and sulfamethoxazole (SMX) under different redox conditions were evaluated. Results and discussion: Oxic conditions were obtained in the experiment with low TOC (0. 06 wt%) in the sediment pre-treated at 550 °C. Anoxic conditions were predominant in two column experiments with a TOC content of 0. 17 wt% in the sediment, irrespective of the mode of treatment (natural or 200 °C). All three pharmaceutical compounds show almost conservative transport behavior with retardation factors between 1. 02 and 1. 25 for PMD, between 1. 06 and 1. 37 for CBZ, and between 1. 00 and 1. 08 for SMX. Differences in the transport behavior were observed depending on the TOC content of the sediment. For CBZ, and to a minor extent for PMD, the higher retardation factors were observed in the sediment with a TOC content of 0. 17 wt% under anoxic conditions. The ozonation of the influent water affects the influent concentrations of PMD, CBZ and SMX. However, it has no influence on the oxygen concentration of the column outflow. Conclusions: CBZ and PMD are retarded in the presence of organic matter in the aquifer. Variations of the TOC content of the sediment have a direct influence on the retardation of CBZ and PMD. The three human pharmaceuticals may be ranked in order of decreasing retardation: CBZ & PMD & SMX. The microbial activity in the experiments was not studied, although it can be assumed that the thermal pretreatment influences the microbial activity in the sediments. In particular, the microbial activity was severely inhibited at 550 °C, resulting in a shift of the redox conditions.

Publikation
Journal of Soils and Sediments 13 (5): 953–965 10.1007/s11368-013-0671-9