Removal of Chlorinated Organic Pollutants from Groundwater Using a Vacuum-UV-Based Advanced Oxidation Process

Abstract

The presence of chlorinated organic compounds, such as trichlorethylene (TCE) and tetrachlorethylene (PCE), in water sources requires particular attention due to their slow rate of decomposition, carcinogenicity, and toxicity. Advanced oxidation processes (AOPs) have been addressed for treating such organic pollutants, most commonly using UV-C radiation (254 nm) with the addition of different chemicals (e.g., TiO2 and H2O2). Although these previous AOP studies were proven to be effective, chemical dosing often complicates the treatment process and increases its costs. The current study examines the removal kinetics of TCE and PCE under combined UV-C/vacuum-UV radiation in different water matrixes (distilled water, synthetic solutions, and real groundwater). Faster degradation of both pollutants and their transformation products were observed in the presence of vacuum-UV radiation (using Hg lamps emitting at 185 and 254 nm), with the most significant effect in distilled-water solutions. In more realistic water matrixes (groundwater), pollutants removal still occurred but at lower efficiency due to the presence of interfering compounds that react with the photogenerated hydroxyl radicals and/or absorb UV/vacuum-UV radiation. An investigation of the effect of such substances enabled to identify the main interfering compounds (e.g., carbonate system ions and chloride) and to develop an appropriate pretreatment for their removal, improving the treatment effectiveness.