Laboratory and pilot-scale UV, UV/H2O2, and granular activated carbon (GAC) treatments for simultaneous removal of five chemicals of emerging concerns (CECs) in water

Abstract

This study assessed the efficacy of laboratory and pilot-scale (1) UV photolysis, (2) combined UV and hydrogen peroxide oxidation (UV/H2O2), (3) granular activated carbon (GAC) adsorption, and (4) UV/H2O2 followed by GAC, for simultaneous removal of contaminants of emerging concerns (CECs) in water. Five globally relevant CECs from five different contaminant classes were selected as target CECs to represent the wide range, i.e., N-nitrosodimethylamine (NDMA) as a disinfection by-product, trimethoprim (TMP) as a pharmaceutical, triclosan (TCS) as a personal care product, atrazine (ATZ) as a herbicide, and estrone (E1) as a steroid hormone. Highly photosensitive compounds like NDMA and TCS were easily degraded by UV (>75%) and UV/H2O2 (>80%) with direct photolysis as the main removal mechanism. Their removal efficiencies were less affected by the presence of other CECs and the water matrix than the other CECs. The effects of competitive adsorption among CECs and the water matrix was more profound for moderately hydrophobic or less hydrophilic compounds, e.g., TMP, ATZ, and E1. The laboratory-scale results showed the application of a single treatment could not efficiently remove the target CECs. Hence the combination of treatments was employed in the pilot-scale experiments, which assessed the effectiveness of UV/H2O2 (1000 mJ/cm2 and 4 mg/L H2O2) followed by GAC (empty bed contact time 3.5–28 min) in removing target CECs at their environmentally relevant concentrations. Our findings suggest that UV/H2O2 followed by GAC would serve as an excellent multi-barrier for efficiently removing a wide range of CECs in water.