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

Abstract

The influence of temperature, pH, alkalinity, and type and concentration of the dissolved organic matter (DOM) on the rate of ozone (O<sub>3</sub>) decomposition, O<sub>3</sub>-exposure, <b>·</b>OH-exposure and the ratio <i>R<sub>ct</sub> </i> of the concentrations of <b>·</b>OH and O<sub>3</sub> has been studied. For a standardized single ozone dose of 1 mg/L in all experiments, considerable variations in O<sub>3</sub>-exposure and <b>·</b>OH-exposure were found. This has important implications for water treatment plants regarding the efficiency of oxidation and disinfection by O<sub>3</sub>. 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 O<sub>3</sub> kinetics and <i>R<sub>ct</sub> </i> values are required to evaluate seasonal variations.