| Objective:Two kinds of drinking water quality evaluation methods were applied to analyze the monitoring data of drinking water quality in a city from 2017 to 2019,and the drinking water quality of urban and rural residents in the city was analyzed,so as to understand the changes of water quality indexes and the main existing problems in the city,and to provide a scientific basis for taking effective intervention measures and protecting public health.Methods:Using conventional methods and comprehensive water quality index evaluation method,this research evaluated the monitoring data of drinking water quality in a city from 2017 to 2019,and analyzed the drinking water quality of the city’s residents.According to GB 5749-2006 "Sanitary Standards for Drinking Water",the city has monitored 102 water quality indicators,mainly focusing on 41 conventional indicators and ammonia nitrogen in unconventional indicators.The conventional method refers to the calculation of the qualified rate of each monitoring index,in which if any index is not qualified,then the monitoring water sample is determined as not qualified.The comprehensive water quality index refers to the dimensionless relative number generated by the statistical treatment of the water quality monitoring index,and the GB5749-2006 "Sanitary Standard for Drinking Water" was used as the evaluation standard to objectively and quantitatively evaluate the water quality of drinking water.Results:1.Monitoring results of drinking water quality in a city in 2017(1)In 2017,the sources of urban drinking water in a city were shallow wells,deep wells and reservoirs.The water samples from shallow wells were few and not included.The comprehensive water quality index from excellent to inferior was 0.48±0.15 for reservoir and 0.75±0.04 for deep well,and the qualified rate of water quality was 97.77%and 71.60%,respectively.The source of rural drinking water was only deep well,and water quality index was 5.12±0.83 and the qualified rate of water quality was 71.17%.(2)In 2017,the different types of urban drinking water samples a city were finished water,secondary water and tap water.The comprehensive water quality index from excellent to inferior was 0.07±0.01 for the secondary water,0.39±0.07 for the tap water and 0.59±0.15 for the finished water.The qualified rates of water quality were89.66%,90.65% and 86.84%,respectively.While,the different types of rural drinking water samples included finished water and tap water.The comprehensive water quality index was 2.10±0.29 and 3.72±0.48,and qualified rates of water quality was 69.92%and 72.28%.(3)In 2017,the water treatment methods of urban drinking water in a city included conventional treatment,disinfection only and untreatment.The untreated water samples were few and not calculated.The comprehensive water quality index from excellent to inferior was 0.07±0.01 for disinfection only and 0.69±0.15 for conventional treatment,and the qualified rate of water quality was 100.00% and 90.04%,respectively.The water treatment methods of rural drinking water included conventional treatment,sedimentation and filtration,disinfection only and untreatment.The order of comprehensive water quality index from best to second was as follows: 1.53±0.25 for conventional treatment,1.75±0.46 for disinfection only,2.17±0.14 for sedimentation and filtration and 2.39±0.73 for untreatment.The qualified rates of water quality were83.45%,75.54%,36.36% and 69.30%,respectively.(4)In 2017,the different disinfection methods of urban drinking water in a city included non-disinfection,chlorine dioxide and liquid chlorine.The non-disinfected water samples were few and not calculated.The comprehensive index of water quality from excellent to inferior was: liquid chlorine 0.07±0.01 and chlorine dioxide0.69±0.15,and the qualified rate of water quality was 99.24% and 82.26%,respectively.The different disinfection methods of rural drinking water were non-disinfection,ozone and ultraviolet.The comprehensive water quality index from excellent to inferior was:ozone 1.98±0.14,UV 2.95±0.46 and non-disinfection 3.49±0.79.The qualified rates of water quality were 36.11%,84.32% and 57.22%,respectively.2.Monitoring results of drinking water quality in a city in 2018(1)In 2018,the sources of urban drinking water in a city were reservoirs and deep wells.The comprehensive water quality index was 0.52±0.15 for reservoirs and0.93±0.15 for deep wells,and the qualified rate of water quality was 98.89% and85.71%,respectively.The source of rural drinking water was only deep wells,and the comprehensive water quality index was 5.54±0.69 and the qualified rate of water quality was 63.53%.(2)In 2018,the water sample types of urban drinking water in a city included finished water,secondary water and tap water.The comprehensive water quality index from excellent to inferior was 0.07±0.01 for secondary water,0.39±0.07 for tap water and 0.59±0.15 for finished water.The qualified rates of water quality were 95.35%,94.93% and 82.50%,respectively.The water sample types of rural drinking water were finished water and tap water,the comprehensive water quality index was 4.06±0.17 and5.98±0.51,respectively,and the qualified rate of water quality was 67.50% and 59.26%,respectively.(3)In 2018,the water treatment methods of urban drinking water in a city included conventional treatment,disinfection only and untreatment.Due to the few untreated water samples,they were not included in comparison.The comprehensive water quality index from excellent to inferior was 0.54±0.17 for conventional treatment and0.89±0.15 for disinfection only,and the qualified rate of water quality was 96.55% and75.00%,respectively.The water treatmne methods of rural drinking water included conventional treatment,sediment and filtration,disinfection only and untreatment.The order of comprehensive water quality index from best to second was as follows:0.96±0.17 for conventional treatment,1.88±0.35 for disinfection only,2.95±0.30 for sedimentation and filtration and 5.44±0.66 for untreatment.The qualified rates of water quality were 74.42%,69.54%,33.33% and 44.53%,respectively.(4)In 2018,the disinfection methods of urban drinking water in a city included bleaching powder,non-disinfection,chlorine dioxide and liquid chlorine.The water samples of non-disinfection and bleaching powder were few and not calculated.The comprehensive index of water quality from excellent to inferior was: liquid chlorine0.07±0.01 and chlorine dioxide 0.92±0.15,and the qualified rate of water quality was99.24% and 90.83%,respectively.The disinfection methods of rural drinking water were non-disinfection,ozone and ultraviolet.The comprehensive water quality index from excellent to inferior was as follows: ozone 1.96±0.17,UV 2.88±0.46 and nondisinfection 5.94±0.52.The qualified rates of water quality were40.00%,80.07% and42.07%,respectively.3.Monitoring results of drinking water quality in a city in 2019(1)In 2019,the sources of urban drinking water in a city were deep wells and reservoirs.The comprehensive water quality index from excellent to inferior was0.39±0.11 for reservoirs and 0.78±0.05 for deep wells,and the qualified rate of water quality was 98.88% and 88.24%,respectively.The sources of rural drinking water included shallow wells and deep wells.The water samples from shallow wells were less and not included in calculation.The comprehensive water quality index of deep wells was 3.76±0.45,and the qualified rate of water quality was 62.13%.(2)In 2019,the water sample types of urban drinking water in a city included finished water,secondary water and tap water.The comprehensive water quality index from excellent to inferior was 0.19±0.05 for secondary water,0.28±0.05 forfinished water and 0.52±0.07 for tap water.The qualified rates of water quality were 95.35%,97.50% and 94.93%,respectively.The water sample types of rural drinking water were finished water and tap water,and the comprehensive water quality index was 2.74±0.41 and 3.51±0.40,respectively,and the qualified rate of water quality was 60.63% and63.38%,respectively.(3)In 2019,the water treatment methods of urban drinking water in a city included conventional treatment,disinfection only and non-treatment.The untreated water samples were few and not calculated.The comprehensive water quality index from excellent to inferior was 0.07±0.01 for disinfection only and 0.39±0.11 for conventional treatment,and the qualified rate of water quality was 100.00% and 96.55%,respectively.The water treatment methods of rural drinking water included conventional treatment,sediment and filtration,disinfection only and non-treatment.The order of comprehensive water quality index from best to second was as follows: conventional treatment 0.86±0.22,disinfection only 1.25±0.24,sediment and filtration 2.07±0.19 and non-treatment 2.51±0.47.The qualified rates of water quality were 54.95%,68.69%,47.37%,and 66.67%,respectively.(4)In 2019,the disinfection methods of urban drinking water in a city included bleaching powder,unlabeled,chlorine dioxide and liquid chlorine.The water samples of non-disinfected and bleaching powder were few and not calculated.The comprehensive water quality index from excellent to inferior was chlorine dioxide0.39±0.11 and liquid chlorine 0.54±0.16,and the qualified rate of water quality was92.50% and 99.24%,respectively.The disinfection methods of rural drinking water included non-disinfected,ozone,sodium hypochlorite,ultraviolet light and unlabeled.The water samples of sodium hypochlorite and unlabeled were few and not calculated.The comprehensive water quality index from best to second was ozone 1.95±0.16,nondisinfected 2.06±0.41 and UV 2.60±0.30,the qualified rates of water quality were57.81%,64.06% and 66.00%,respectively.4.According to GB 5749-2006 "Sanitary Standards for Drinking Water",the main unqualified indicators of drinking water in a city from 2017 to 2019 included total coliforms,heat-resistant coliforms,total number of colonies,nitrate nitrogen,chloride,fluoride,chroma,manganese,iron,turbidity,total dissolved solids,total hardness,ammonia nitrogen,sulfate,oxygen consumption.Conclusion:1.The water quality of urban drinking water in a city from 2017 to 2019 was better than that of rural drinking water.2.The water quality of urban reservoir in a city from 2017 to 2019 was better than that of deep wells.The main source of rural drinking water was deep wells,and the comprehensive water quality index was high and the qualified rate of water quality was low.3.There was no statistical difference in the qualified rate of water quality between different types of water samples in a city from 2017 to 2019.By comparison of comprehensive index of water quality,the quality of secondary water was better than that of finished water and tap water.There was no statistical difference between the qualified rate of the finished water and tap water in rural areas,and the comprehensive water quality index showed that the finished water was better than that of tap water.4.The main water treatment method in a city from 2017 to 2019 was conventional treatment,with a low water quality index and a high qualified rate of water quality.The results of the water quality of different water treatment methods in rural areas showed that the water quality of conventional treatment and only disinfection were better than that of sedimentation and filtration and untreated water.5.The main disinfection methods of drinking water in a city from 2017 to 2019 were chlorine dioxide and liquid chlorine,and the water quality of liquid chlorine disinfection was better than that of chlorine dioxide disinfection.The comparison of different disinfection methods in rural areas with comprehensive water quality index showed that the ozone disinfection method was better than the ultraviolet disinfection method.The comparison of qualified rate of water quality showed that ultraviolet disinfection was superior to non-disinfection and ozone disinfection.6.In this study,two methods were used to evaluate the water quality of domestic drinking water in a city from 2017 to 2019,and the results of the two methods were basically consistent,but the comprehensive water quality index method was more suitable for the evaluation of urban drinking water quality. |
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