Objective To explore the effect of water disinfection and disinfection by-products after exchanging of disinfection reagents from liquid chlorine to sodium hypochlorite.

Methods A total of 22 water samples were collected from 6 water plants before and after exchanging disinfection reagents; the disinfection effect and the concentrations of 13 disinfection by-products were detected.

Results The disinfection effect of the two disinfection reagents and that of 13 disinfection by-products were all qualified; the concentrations of free residual chlorine, dichlorodibromomethane, dichloro-1-bromomethane, tribromomethane, trihalomethane and trichloroacetaldehyde in the factory water disinfected by sodium hypochlorite were higher than those by liquid chlorine disinfection, for which the differences were statistically significant (P < 0.05); when the concentration of free residual chlorine in the factory water was more than or equal to 1 mg/L, the concentrations of dichlorodibromomethane, dichloro bromomethane, tribromomethane, trihalomethane and trichloroacetaldehyde in the water were higher than those in factory water, in which the concentration of free residual chlorine was < 1 mg/L, and the differences were statistically significant (P < 0.05). The 10% available chlorine content for sodium hypochlorite decreased to 67.40% of the original content at 32 ℃ and 89.51% of the original content at 4 ℃ disinfectant when the 10% available chlorine content in sodium hypochlorite stored for one month.

Conclusions Though sodium hypochlorite and liquid chlorine have good disinfection effect, the contents of some disinfection by-products is effected by the types of disinfectant and the content of available chlorine in disinfactants.