The ROH,UV concept to characterize and the model UV/H2O2 process in natural waters

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,R-UV concept is defined as the experimentally determined (OH)-O-center dot radical exposure per UV fluence. R-OH,R-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,R-UV was found to be affected greatly by water quality, specifically background (OH)-O-center dot radical scavenging, which competed for the formed (OH)-O-center dot radical with the probe compound, and background UV absorbance, which screened UV irradiation from the hydrogen peroxide. The R-OH,R-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,R-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)-O-center dot radical model to improve the prediction of the oxidation of endocrine-disrupting compounds 17-alpha-ethinyl estradiol and 17-beta-estradiol in the natural waters.