FATE AND TRANSPORT OF CARBAMAZEPINE IN PALYGORSKITE-MONTMORILLONITE MEDIUM FILTER

Carbamazepine (CMZ), an anticonvulsant and analgesic drug is an emerging contaminant with potentially harmful ecosystem and human health impacts. It is one of the few most frequently detected drugs in the environment as most sewage treatment plants (STPs) often fail to remove the compound. In a recently completed study by Water Research Foundation (2010), the Great Miami River (GMR) in southwest Ohio and the associated groundwater systems were found to have both the largest number and type of trace organic contaminants including CMZ. It is therefore very important to explore inexpensive technologies that might help prevent such river contamination in the first place thereby protecting ecosystem as well as human health.

In this study, palygorskite-montmorillonite medium (PMM) known for its high sorption capacity for a wide variety of compounds was investigated as a potential filter material that could be used in STPs. Scanning electron microscope (SEM) and x-ray diffractometer (XRD) were used to characterize the medium. Sorptive properties were explored using both batch sorption and column-transport experiments with pH, specific conductance and temperature conditions typical of STP effluent. Three different PMM granule sizes (less than 1 mm, 1.7-2.0 mm and 2-2.8 mm) were tested to explore optimization of both sorption and flow rate. Water samples were analyzed with high performance liquid chromatography-ultraviolet-visible (UV-Vis) spectrophotometer. Sorption batch experiments were used to develop sorption isotherms. PMM granules were incorporated into laboratory columns for pulse-source transport experiments. Hydraulic conductivity of all columns was determined and bromide was used as a conservative tracer to determine column dispersivities and effective porosities. CMZ was then injected and column effluent was collected over time. Observed breakthrough curves were simulated with a 1-D advection-dispersion-reaction model and, using the sorption results, appropriate transport parameter values were determined through calibration. Based on these results, PMM was evaluated as a potential sewage-treatment medium.