Modeling the Transformation of Chromophoric Natural Organic Matter during UV/H2O2 Advanced Oxidation

This research developed a differential kinetic model to predict the partial degradation of natural organic matter (NOM) during ultraviolet plus hydrogen peroxide (UV/H2O2) advanced oxidation treatment. The absorbance of 254 nm UV, representing chromophoric NOM (CNOM) was used as a surrogate to track the degradation of NOM. To obtain reaction rate constants not available in the literature, i.e., reactions between the hydroxyl radical ((OH)-O-center dot) and NOM, experiments were conducted with synthetic water, using isolated Suwannee River NOM, and parameter estimation was applied to obtain the unknown model parameters. The reaction rate constant for the reaction between (OH)-O-center dot and total organic carbon (TOC), k(center dot OH,TOC), was estimated at 1.14(+/- 0.10) x 10(4) Lmg(-1) s(-1), and the reaction rate constant between (OH)-O-center dot and CNOM, k(center dot OH,CNOM), was estimated at 3.04(+/- 0.33) x 10(4) Lmol(-1) s(-1). The model was evaluated on two natural waters to predict the degradation of CNOM and H2O2 during UV/H2O2 treatment. Model predictions of CNOM degradation agreed well with the experimental results for UV/H2O2 treatment of the natural waters, with errors up to 6%. For the natural water with additional alkalinity, the model also predicted well the slower degradation of CNOM during UV/H2O2 treatment, owing to scavenging of (OH)-O-center dot by carbonate species. The model, however, underpredicted the degradation of H2O2, suggesting that, when NOM is present, mechanisms besides the photolysis of H2O2 contribute appreciably to H2O2 degradation. DOI: 10.1061/(ASCE)EE.1943-7870.0000390. (C) 2011 American Society of Civil Engineers.