Abstract:Saccharin (SAC) is the earliest artificial sweetener applied as additive in food, beverage, medicine and forage. SAC is hardly digested by human body and other organisms, and discharged into the water environment mostly. Characterized with high detection frequency and concentration, outstanding persistence and toxicity risk, SAC has been recognized as an emerging organic contaminant. Focused on UV/H₂O₂ process, the degradation of SAC by pre-chlorine, ozonation and UV/H₂O₂ was compared from the aspect of degradation efficiency and kinetics. The influencing factors including oxidant dosage, UV radiation intensity, initial SAC concentration, the pH value of solution, water temperature, and common anions ($\mathrm{Cl}^{-}, \mathrm{CO}_3^{2-}, \mathrm{NO}_3^{-}, \mathrm{SO}_4^{2-} $) on the degradation of SAC in oxidation system were explored. The results were listed as follows: 1) The removal of SAC by chlorination, UV and H₂O₂ alone is 21.17%, 9.74% and 7.69%, respectively., while ozonation and UV/H₂O₂ exhibit significant degradation of SAC (as the degradation efficiency more than 85% after 30 minutes of oxidation), and faster reaction and mineralization rate in UV/H₂O₂ system. By ozonation with continuous flux 7.10 mg/min for 60 min, the degradation of SAC reaches the similar level as that under oxidation condition of H₂O₂ (20.4 mg/L) irradiated by UV intensity of 1.46 mW/cm² for 60 min. 2) In the investigation of the influencing factors of UV/H₂O₂ combined process, the increase of H₂O₂ dosage accelerates the degradation rate of SAC, however, the over dosage of H₂O₂ inhibates the degradation. The increase of UV light intensity promotes the degradation, while the increase of the initial concentration of SAC decreases the degradation rate. Acidity and higher temperature promotes the reaction. The optimum oxidation conditions of UV/H₂O₂ system is 20.4 mg/L H₂O₂, 1.46 mW/cm² UV intensity, pH 3, and the reaction water temperatureof 30 ℃. The degradation of SAC by UV/H₂O₂ is inhibited by common ions in water, following the sequence of $\mathrm{NO}_3^{-}>\mathrm{SO}_4^{2-}>\mathrm{CO}_3^{2-}>\mathrm{Cl}^{-} $. 3) The degradation of SAC by UV/H₂O₂ mainly by the hydroxyl radical, and the main pathway may be that the benzene ring is hydroxylated by the free radical and the C—N bond is broken. Although ozonation has a high degradation efficiency of SAC, the oxidant consumption is much. While UV/H₂O₂ treats SAC more efficiently, however, the energy consumption is higher. Therefore, it is still necessary to explore the low-carbon demand and high efficient process to remove trace organic pollutants like SAC in source water.