Caffeine vs. carbamazepine as indicators of wastewater pollution in a karst aquifer

Noam Zach Dvory,Yakov Livshitz,Ovadia Lev,Michael Kuznetsov,Irena Pankratov,Guy Gasser,Alexander Yakirevich,Eilon Adar

doi:10.5194/hess-22-6371-2018

Abstract

Abstract. This paper presents the analysis of caffeine and carbamazepine transport in the subsurface as a result of wastewater release in the Sorek creek over the outcrops of the carbonate, Yarkon-Taninim, aquifer in Israel. Both caffeine and carbamazepine were used as indicators of sewage contamination in the subsurface. While carbamazepine is considered conservative, caffeine is subject to sorption and degradation. The objective of the study was to quantify differences in their transport under similar conditions in the karst aquifer. Water flow and pollutant transport in a “vadose zone–aquifer” system were simulated by a quasi-3-D dual permeability numerical model. The results of this study show that each of these two pollutants can be considered effective tracers for characterization and assessment of aquifer contamination. Carbamazepine was found to be more suitable for assessing the contamination boundaries, while caffeine can be used as a contaminant tracer only briefly after contamination occurs. In instances where there are low concentrations of carbamazepine which appear as background contamination in an aquifer, caffeine might serve as a better marker for detecting new contamination events, given its temporal nature. The estimated caffeine degradation rate and the distribution coefficient of a linear sorption isotherm were 0.091 d−1 and 0.1 L kg−1, respectively, which imply a high attenuation capacity. The results of the simulation indicate that by the end of the year most of the carbamazepine mass (approximately 95 %) remained in the matrix of the vadose zone, while all of the caffeine was completely degraded a few months after the sewage was discharged.

Highlights

Sewage infiltration into the subsurface can cause groundwater pollution
In this paper we provide a short description of those processes, for the convenience of readers, and include only details which are essential for understanding of the presented material
Observations revealed that the wastewater and surface water infiltration had an immediate impact on the water level in the aquifer and on contaminant concentrations (Fig. 3)

Summary

Introduction

Sewage infiltration into the subsurface can cause groundwater pollution. Carbonate aquifers present a higher risk for groundwater quality contamination due to the presence of preferential flow paths. Predicting and quantifying sewage infiltration and transport in carbonate aquifers is complicated due to exchanges between slow flow in the matrix and fast flow in conduits (Geyer et al, 2007). The micropollutants carbamazepine (CBZ) and caffeine (CAF) are both widely used as indicators of anthropogenic contamination in groundwater (Seiler et al, 1999). Several studies have detected higher concentrations of CAF, as opposed to CBZ, in the groundwater as well

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Conclusion