| Chlorination is still the most commonly used and most effective disinfection method in China.However,in the disinfection process,disinfectants react with natural organic matter?NOM?and dissolved organic matter?DOM?in the water to form disinfectant by-products?DBPs?.Haloacetic acids?HAAs?and trihalomethanes?THMs?are the two most important.Studies have shown that HAAs are teratogenic,mutagenic and carcinogenic,and HAAs account for 91.9%of the total carcinogenic risk of disinfection by-products.THMs are carcinogenic and mutagenic.The International Agency for Research on Cancer?IARC?has listed CHCl3,CHBr3,CHBr2Cl and CHBrCl2 as possible or suspected carcinogens in humans.DBPs in drinking water can be ingested or contacted by the human body through drinking,bathing and swimming,thereby endangering human health.This study developed a method for the detection and analysis of HAAs and THMs in drinking water samples.This method was used to study different sampling sites?raw water,finish water,pipe network water and different process water?in A water plant and B water plant in Shihezi City,Xinjiang.The pollution levels and distribution characteristics of HAAs and THMs in different sampling sites,and preliminary assessment of the health risks of local residents through drinking water intake of THMs and dichloroacetic acid?DCAA?.The main findings are as follows:The analytical method of HAAs and THMs in tap water samples was established by liquid-liquid extraction combined with GC-?ECD.The pretreatment methods were optimized.Compared with the addition of different amounts of MTBE and 10%Acidification of HAAs with methanol,sodium sulfate and saturated sodium bicarbonate.The results showed that the most suitable amount of MTBE added was 4.0 mL,the best 10%acidified methanol added 4.5mL,7 mL sodium sulfate solution is the best choice,the optimal sodium bicarbonate added1mL,the target can be better recovery.The contamination status of HAAs and THMs in A water plant?raw water,finish water and pipe network water?of Shihezi City was studied.Some HAAs were also detected in the raw water,HAAs were also detected in the finish water and pipe network water,and the content level is similar to the previous research results,THMs were not detected in the raw water and were detected in both the finish water and the pipe network water,indicating that the THMs were generated in the water treatment process.In the seasonal changes,the concentrations of HAAs were higher in summer and lower in winter,and the concentrations changed to summer>autumn>spring>winter.The concentration of total HAAs in the water of the finish water exceeded 80?g·L-1 in summer and the concentration of HAAs in the finish water was 31?g·L-1 in summer.This may be related to the temperature.In summer,the temperature increases and the activity of organic substances increases,the formation of HAAs reduces the winter temperature,inhibits the activity of organic compounds,and reduces the concentration of HAAs.HAAs are positively correlated with temperature,negatively correlated with pH,and positively correlated with UV254.A survey of organic contamination of effluents from different processes at B watertreatments in Shihezi City found that the total removal rate of UV254 in conventional water treatment processes was 75%.The filtration had little effect on the removal of organic matter,and the concentration remained almost unchanged.The concentration of HAAs reached 13.3?g·L-1 in the precipitation process,the filtration process did not reduce the concentration of HAAs,39.7%more than the precipitation process,and then increased to nearly 40?g·L-1 in clean-water reservoir.In the precipitation process,the THMs precursor concentration continued to decrease,which was a decrease of 37.6%relative to the raw water.The concentration of THMs in the effluent from the filtration process increased significantly by 59.4%,reaching 21.16?g·L-1,and the finish water concentration was 10.07?g·L-1.The process comparison between B water treatment in Shihezi and St.Cloud water treatment plant in the United States was compared.During the removal of THMs,the removal rate of THMs by anthracite and sand filtration was found when hydrogen peroxide and ozone were disinfected.During ozone disinfection,the removal rate of THMs by activated carbon adsorption filtration is higher than that of THMs by anthracite and sand filtration.HAAs removal process found that,whether hydrogen peroxide mixed with ozone disinfection,or only ozone disinfection,are activated carbon adsorption filtration is better than anthracite and sand filtration.It is suggested that Shihezi city water treatment plant can increase the ozone disinfection process,and the activated carbon adsorption filtration process,so that disinfection by-products and the removal rate of organic matter are also increased,water quality and safety are more secure.By calculating the human health risk assessment of THMs and HAAs in Shihezi water treatment plant and establishing the risk model to evaluate the health risk of THMs,the results showed that the total amount of THMs in Shihezi drinking water did not exceed the standard limit of Chinese drinking water,the potential carcinogenic risk of THMs to human health is within the acceptable limits of the US Environmental Protection Agency?USEPA?(1.0×10-6-1.0×10-4/a)and the health hazards generated by the drinking water route.Index below 1,will not cause health damage,in line with safety requirements.Exposure to skin through exposure to TCM has a carcinogenic risk of<1.0×10-6/a and does not pose a potential carcinogenic risk.DBCM and BDCM are between 1.0×10-6 and 1.0×10-4/a.Risk can be accepted.There is no potential cancer risk.The carcinogenic risk of the three compounds ingested by the breath was<1.0×10-6/a,and there was no potential carcinogenic risk.Through the contribution of human exposure to DCAA,the average daily intake of DCAA in people of different age groups was calculated.It was found that the HQ values in the four groups?children,students,middle-aged and elderly?were all below 1,and they did not generate health damage to the human body.And carcinogenic risk were<1.0×10-6/a,no potential carcinogenic risk,in line with safety requirements. |
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