The ROH,UV Concept to Characterize and the Model UV/H2O2 Process in Natural Waters

Abstract

A new concept is introduced to characterize and model the UV/H₂O₂ advanced oxidation process (AOP) in water. Similar to the R_Ct concept used to describe OH radical exposure per ozone dose, the R_OH,UV concept is defined as the experimentally determined ^•OH radical exposure per UV fluence. R_OH,UV was determined by examining the destruction of a probe compound, para-chlorobenzoic acid in four different waters: DI water and three natural waters. R_OH,UV was found to be affected greatly by water quality, specifically background ^•OH radical scavenging, which competed for the formed ^•OH radical with the probe compound, and background UV absorbance, which screened UV irradiation from the hydrogen peroxide. The R_OH,UV values determined in the experiments using low-pressure Hg lamp were greater than those for the medium-pressure Hg lamp . Finally, the R_OH,UV concept was utilized to calculate an overall scavenging factor for each water matrix, and this was successfully utilized in conjunction with the steady-state ^•OH radical model to improve the prediction of the oxidation of endocrine-disrupting compounds 17-α-ethinyl estradiol and 17-β-estradiol in the natural waters.