Oxidative abatement of saccharin by ozone and its influence on DBPs formation during postchlorination

Abstract

As one of artificial sweeteners, saccharin (SAC) is widely used in food, personal care products and animal feed industry. SAC cannot be effectively metabolized by organisms and most of them are discharged into the water environment through multiple channels, leading to general detection in water source. In this study, the fate of SAC in the advanced ozone treatment of drinking water and subsequent chlorination disinfection was investigated. The results showed ozone could effectively degrade SAC and >99 % of 20 mg/L SAC could be removed under 7.10 mg/min ozone flow within 60 min. While, the mineralization was comparably low by 80 %, which indicated that ozone converted SAC into organic intermediate products. Therefore, SAC characterized with anti-chlorination property was changed to disinfection by-product precursor. Disinfection by-products including trichloromethane (TCM), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA) and dichloroacetonitrile (DCAN) were found during subsequent chlorination. The yields of TCM, DCAA, TCAA and DCAN were found to be 8.1, 0.4, 1.2 and 0.1 μg/mg SAC, respectively, 3, 39, 41 and 178 times of those produced by direct chlorination. In addition, the increase of ozone flux promoted the formation of disinfection by-products. Meta-alkalescence was conducive to the formation of DCAA, TCAA and DCAN in pH range of 6 to 8. The presence of anions including Cl−, NO3− and CO32− reduced the formation of TCM, DCAA and DCAN.