Effects of Combined Chlorine Dioxide and Chlorine Disinfection on the Formation of Disinfection Byproducts

Abstract

To investigate the effects of combined chlorine dioxide (ClO₂) and chlorine disinfection on disinfection byproduct formation, this study controlled disinfection conditions (temperature, pH, dosing sequence) and organic matter types to analyze their influences on byproduct generation, and explored the practical application characteristics based on disinfection experiments of natural water samples. The results showed that combined disinfection could effectively reduce the formation of disinfection byproducts.The reaction rate of ClO₂ in the combined disinfectant was less affected by temperature than chlorine. The formation ratio of CHCl₃ increased with rising temperature, while that of ClO₂⁻ decreased. With increasing solution pH, the formation of ClO₂⁻ increased gradually, ClO₃⁻ first decreased and then increased, and CHCl₃ formation reached the maximum under neutral conditions and the minimum under acidic and alkaline conditions. Dosing ClO₂ first could effectively reduce the formation of the organic byproduct CHCl₃ and lower the compliance rate of generated byproducts. The reactivity order of combined disinfectants with organic matters was: TA > HA > BSA > SA. Fluorescence spectroscopy analysis before and after disinfection of natural water showed that the main precursors of combined disinfection were humic acid and fulvic acid-like substances.