Variations Of Biotoxicity Of Drinking Water Containing Estradiol During Chlorine Disinfection Process

In recent years,envrionmental hormone in drinking water has been constantly detected.These pollutants will produce various disinfection by-products during chlorine disinfection process in drinking water,which are likely to have greater biological toxicity than the precursors and impose a threat to human health.Therefore,it warrants detailed studies on the biological toxicity of such pollutants in water before and after chlorination.17β-estradiol(E2)as frequently exposed to drinking water,was selected as the research object,and variations of acute toxicity and the genotoxicity of drinking water containing E2 before and after chlorination were investigated.The acute toxicity was studied by the algae toxicity test,which was shown as the growth inhibition and the changes of enzyme activity of Chlorella vulgaris.Vicia faba root tip micronucleus test was used for analyzing the genotoxicity.The genotoxicity of E2 and the chlorinated products was evaluated by the average micronucleus rate and the micronucleus index of Vicia faba root tip cells.The results of acute toxicity test showed that under the single exposure condition of different concentrations of E2(0,2,4,8,16 mg/L),the growth inhibition rate of Chlorella vulgaris showed obvious dosage effect.with an increase in the exposure concentration of E2,Chlorella vulgaris growth inhibition rate increased correspondingly.With a high chlorine dosage(E2 and chlorine molar ratio of 1:2 and 1:5),the growth inhibition rate of water samples to Chlorella vulgaris was higher than that before chlorination,but under the condition of low chlorine dosage(E2 and chlorine molar ratio of 4:1 and 1:1),the growth inhibition rate of water samples to Chlorella vulgaris was lower than that before chlorination.These results indicated that a low chlorine dosage could reduce the acute toxicity of water quality.The enzyme activity tests showed that none of the Superoxide Dismutase activity,Catalase activity and Malondialdehyde content had a noticeable correlation effect with the exposure of E2 or the chlorination,indicating that E2 did not have a significant impact on the enzyme activity of Chlorella vulgaris before and after chlorination.The results of Vicia faba root tip micronucleus tests showed that chlorination was able to effectively reduce the genotoxicity of E2 system,and the higher amount of chlorine dosed,the greater the effect was.