| Objective:In order to learn the pollution situation and the seasonal distribution of the chlorinated disinfection by-products (CDBPs) in Qingdao municipal water, so as to master the regularity of organics secondary pollution in domestic water, the resulting safety hazards and the potential harm to the health of consumers. The CDBPs in Qingdao municipal water were sampled and analyzed in this study. In addition, the processing mode of water to control the generation of CDBPs effectively was studied, not only to ensure the safety and controllability of microbiological indicators, but also to keep the amount of the CDBPs at a low level, so as to provide scientific data for regulatory authorities to take effective measures and theoretical basis for the safety of drinking water of the public.Method:The source water and the municipal water were sampled to be detected. Under the premise of the pH, the concentration of free residual chlorine and the water temperature were changed, the main CDBPs, including four kinds of Trihalomethane (THMs)and three kinds of haloacetic acid (HAAs) were sampled. By controlling the amount of chlorine, the changes of CDBPs in different chlorine residue concentration were known, and the water disinfection treatment which can effectively kill the pathogenic microorganisms in the case of the amount of liquid chlorine as small as possible was gained. The HAAs was detected by ion chromatography and the others was detected according to’standard test method of drinking water’(GB/T 5750-2006).The results were analyzed and evaluated based on the standards of drinking water (GB 5749-2006)Results:The detection of HAAs by ion chromatography with conductivity test reached to the requirement with the results of RSD<4.56%, the recovery range of 85.0%～104.0% and no significant difference compared with the method of national standard.The data of 283 water samples and 2425 indicators detected in laboratory were analyzed. The range of the pH of the chlorinated water and the tap water was 7.32～ 8.21, which in summer was slightly higher than the other seasons. The CDBPs were not detected both in source water and control water, but detected in chlorinated water and tap water which the concentration range was 16.7μg/L～49.7μg/L and 17.7 μg/L～55.3μg/L, the total average concentration was 38.7 μg/L and 40.5μg/L respectively. The content of CDBPs in tap water was higher than chlorinated water. The content of CDBPs was changed with the seasons, the total average concentration of which were respectively:40.0μg/L in Spring,52.3μg/L in summer,40.5μg/L in autumn and 30.2μg/L in winter. The average concentration of THMs in summer was 2 times of winter, but the change of HAAs was relatively small. The indicators of CDBPs in municipal water of Qingdao did not exceed the requirements of’health standard of drinking water’(GB 5749-2006), but the average concentration of Chlorodibromomethane 1 g was 10.2μg/L, which was higher. There were no significant differences with the level of CDBPs in tap water from school, hospital and community, the same as the water from secondary water and atmospheric water. The content of HAAs was not changed with the reasons in municipal water, but THMs increased significantly with temperature. The results showed that the amount of disinfectant was reduced to decrease CDBPs and the pathogenic microorganisms were effectively eliminated when the content of chlorine residual in chlorine water was 0.6 mg/L-0.7mg/L in summer and 0.4 mg/L-0.5mg/L in winter.Conclusion:1.By ion chromatography to detect HAAs, the problem that the detection result of the traditional liquid-liquid extraction gas chromatography did not reach the requirements could be resolved, and the poison to personnel and the pollution to environment from toxic derivative reagent were avoided, which saved time and effort, reached the requirements.2. The CDBPs were produced from chemical reaction between the disinfector and the organic precursor in the process of drinking water chlorination, but were not produced in unsterilized control water.3. CDBPs in municipal water of Qingdao did not exceed the requirements of ’health standard of drinking water’, but the content of Chlorodibromomethane 1 g was higher after the water in water plants was chlorine disinfected under the current situation of water quality and water production process. This should be paid attention.4. Prechlorination should be reduced or avoided. By putting appropriate amount of chlorine in domestic water at different temperature, the amount of CDBPs could be effectively reduced to control the organic matter secondary pollution at a low level in domestic water.5.In order to avoid incidents related to drinking water, protect the safety and the health of public, ensure the sustainable development of economic construction in Qingdao, we suggested that the environment of municipal water sources should be paid high attention by relevant authorities, and the water quality should also be monitored routinely. |
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