Study On Safety Of Drinking Water Disinfection By Chlorine Dioxide Technology

As a highly effective disinfectant,Chlorine dioxide has been widely used in the field of drinking water disinfection.However,there are few systematic researches on disinfection exposure time or disinfection by-products generation and their impact factors on the application of chlorine dioxide.In addition,many countries and regions have chlorine dioxide and its by-products included in the drinking water quality standards,but vary in the choice of indicators and limits.Therefore,it is necessary to do basic research on chlorine dioxide disinfection technology.Based on researches on the effect of E.coli disinfection,the rules and impact factors of the production of chlorine dioxide disinfection by-products,the effect of drinking water pipes made to chlorine dioxide disinfection to study the safety of chlorine dioxide drinking water disinfection.1.Most of China's water bodies are subject to different levels of organic pollution,in order to better simulate natural water bodies,the secondary sewage treatment plant effluents from the sedimentation tank was chosen in this research,and prepared water samples after the UF.2.E.coli was the indicating bacteria,and the adding number was 500-2000cfu /100ml based on "Norms of hygiene and safety evaluation on drinking water disinfectants and disinfection equipment"(Trial).Exposure time,water temperature, and chlorine dioxide dosage were chosen to do experiment,by comparing survival colonies under different conditions.The results showed that Chlorine dioxide dosage, water temperature,and exposure time all affected the effect of chlorine dioxide disinfection.When the water temperature fixed,chlorine dioxide had a better disinfection effect with the increased dosage of chlorine dioxide.When the dosage fixed,chlorine dioxide had a better disinfection effect with the increased water temperature.When the dosage and water temperature both fixed,chlorine dioxide had a better disinfection effect with the increased exposure time.3.Study the formation of chlorite and chlorate under different conditions of exposure time,chlorine dioxide dosage,and organic compounds concentration in water(COD).Water samples with COD 1,3,5,8 mg / L were got by gradually dilution. Certain amount of chlorine dioxide solution was added to make the water samples with chlorine dioxide concentration of 1,2,3,5 and 8 mg/ L.Sealed in dark place and sampled after 1,3,5,10,20,30,45,60 min.HACH DR/2400 portable spectrophotometer fast testing was used to test the concentration of chlorine dioxide in water samples, and ion chromatogram to test the concentrations of chlorite and chlorate.The formation of chlorite was related to the dosage of Chlorine dioxide, exposure time,and organic compounds concentration.The experiment found that chlorite was produced right after chlorine dioxide added into the water.Its 5min production was more than 60%of the 60min's,and with chlorine dioxide dosage increased,the proportion is also increased.5min after the reaction,produce much less chlorite.The effect of organic compounds concentration on chlorite was related to the concentration of chlorine dioxide.When chlorine dioxide was sufficient,the more organic compounds,the more chlorite formed.When chlorine dioxide was not sufficient,the production of chlorite increased following the increase of organic compounds concentration in the early stage.When chlorine dioxide was reduced completely,a further increase in organic compounds concentration,the formation of chlorite would not change significantly.The effect of the concentration of chlorine dioxide on chlorite was related to organic compounds concentration.When organic compounds concentration was sufficient,the more chlorine dioxide,the more chlorite formed.When organic compounds concentration was not sufficient,the production of chlorite increased following the increase of chlorine dioxide concentration in the early stage.When organic compounds concentration was reduced completely,a further increase in chlorine dioxide concentration,the formation of chlorite would not change significantly.Exposure time and organic compounds concentration have no significant effect on the formation of chlorate.The increasing chlorate formation followed an increasing chlorine dioxide dosage was mainly due to the impurity of the chlorine dioxide solution,and the actual formation of chlorate was much less,and with no big change.4.7 common used drinking water pipes were selected for dunking test.After the pre-treatment,0.8 mg / L of chlorine dioxide solution was filled into the pipe and sealed at the normal temperature and pressure.Sampled after 12,24,48h respectively, and tested the chlorine dioxide and chlorite concentrations.Brown glass tube was used as controll.The results showed that water pipe material have an impact on the consumption of chlorine dioxide.The longer the dunking time,the more chlorine dioxide reduced. Most chlorine dioxide reduced after 12h,and was about 74-100%of the initial concentration.The residual chlorine dioxide was 0-0.11 mg/L after 48h.The metal pipe had a relatively larger impact than plastic pipe.All dunking water tested chlorite except the copper pipe's,and the generated amount reduced followed by the sequence of PVC-U,galvanized steel pipe,PE, aluminum-plastic,PB,PPR.The concentration of chlorite generated in water dunked in PVC-U and galvanized steel pipe was 0.57-0.64 mg /L,PE and the aluminum-plastic was 0.11-0.23 mg / L,PB and PPR was 0.10-0.14 mg / L.PVC-U, galvanized steel pipe,PB,and PPR appeared the maximum amount after 12h,and PE, aluminum-plastic needed 24h to form the maximum chlorite.