Hydroxyl Radical/Ozone Ratios During Ozonation Processes. II. The Effect of Temperature, pH, Alkalinity, and DOM Properties

The influence of temperature, pH, alkalinity, and type and concentration of the dissolved organic matter (DOM) on the rate of ozone (O₃) decomposition, O₃-exposure, ·OH-exposure and the ratio Rct of the concentrations of ·OH and O₃ has been studied. For a standardized single ozone dose of 1 mg/L in all experiments, considerable variations in O₃-exposure and ·OH-exposure were found. This has important implications for water treatment plants regarding the efficiency of oxidation and disinfection by O₃. In oligotrophic surface waters and groundwaters, minimal calibration experiments are needed to model and control the ozonation process, whereas in eutrophic surface waters more frequent measurements of O₃ kinetics and Rct values are required to evaluate seasonal variations.