Removal of natural organic matter and emerging contaminants from groundwater using ozonation and GAC filtration

Abstract

This work presents results from a pilot-scale drinking water treatment plant used to investigate the performance of ozone oxidation and granulated activated carbon (GAC) adsorption in removing natural organic matter (NOM) and specific organic micropollutants from groundwater. The investigated groundwater has a relatively low NOM content (1.83?1.01 mg C/L total organic carbon, TOC). Using gas chromatography/mass spectrometry (GC/MS) screening analysis, a variety of different organic compounds were identified, including benzophenone, 2-phenoxyethanol, butylated hydroxytoluene and benzoic acid, all contaminants of emerging concern (CEC) identified by NORMAN. The application of the ozonation process resulted in a 4-20% NOM reduction, based on the TOC values. Estimated removal of CECs by ozone increased with increasing ozone dose (up to 1.0 g O3/m3) and was in the range 24-70%. Adsorption on GAC further improves total NOM and CECs removal compared to the ozonation alone. Combined use of ozone and GAC provides up to 16-33% TOC reduction as well as 70-82% CECs removal. UV absorbance values at 254 nm can serve as an indicator of aromatic carbon content in water, and were significantly reduced after ozonation and GAC filtration (by up to 50%). Among the CECs investigated, benzophenone was the most prone to oxidation/adsorption treatment. In addition to the naturally present organic matter, CECs detected can serve as indicators of anthropogenic pollution which may alter drinking water quality. Tracking their behaviour during treatment allows assessment of the efficiency of the technological line and optimization of the oxidation process in the case of groundwater pollution by infiltration.