Objective   To study the decrease of disinfection by-products in water samples disinfected by combination of chlorine dioxide and chlorine.

  Methods   The raw water samples collected from the Wuhan Hanjiang were treated by the different doses combination of chlorine dioxide and chlorine.The amounts of disinfection by-products(DBPs)in water samples were detected and compared by using chenical analysis and biological tests.

  Results   The amounts of chlorite were influenced by levels of pH in water samples disinfected by the different combined doses of chlorine dioxide and chlorine.Decrease in amounts of chlorite showesd a consistent patterns in different pH water samples, with decrease in order pH6 > pH7 > ph8.By statistical analysis, the amounts of chlorite had an obvious difference in the water between pH6 and pH7, pH8.Compared with the water samples disinfected by chlorine alone, the amounts of trichloromethane, dichloroaceic acid and trichoroacetic acid were respectively decreased 50%~86%, 20%~63% and 35%~85% in water samples disinfected by combination with chlorine dioxide and chlorine.The mutagenic activities of non-volatile organic compounds(NVOCs)in water samples disinfected by the different combined doses of chlorine diox ide and chlorine were lower than those of the water samples disinfected by chlor ine alone.

  Conclusion   While the combined doses of chlorine dioxide and chlorine were 0.5+4, 1.0+2, 1.0+4, 1.5+2, 1.5+4mg/L, the amounts of DBPs and mutagenic activities of NVOCs were lower than those of the water samples disinfected by chlorine.