Hydroxyl radical ozone ratios during ozonation processes. I-The R-ct concept

The ozonation of model systems and several natural waters was examined in b ench-scale batch experiments. In addition to measuring the concentration of ozone (O-3), the rate of depletion of an in situ hydroxyl radical probe co mpound was monitored, thus providing information on the transient steady-st ate concentration of hydroxyl radicals (. OH). A new parameter, R-ct, repre senting the ratio of the . OH-exposure to the O-3-exposure was calculated a s a function of reaction time. For most waters tested, including pH-buffere d model systems and natural waters, R-ct was a constant value for the major ity of the reaction. Therefore, R-ct corresponds to the ratio of the . OH c oncentration to the O-3 concentration in a given water (i.e. R-ct = [. OH]/ [O-3]). For a given water source, the degradation of a micropollutant (e.g. atrazine) via O-3 and . OH reaction pathways can be predicted by the O-3 r eaction kinetics and R-ct.