Investigation And Study Of Removal Efficiency And Health Security Of Drinking Water Treatment Devices In Schools Of Hai Kou City

Background:Water is the indispensable material to support life and human health. But with the development of industrialization and urbanization, source water has been polluted in different degrees. A large number of water treatment plants through the coagulation - sedimentation-filter-chlorination to purify source water, but this method has limited removal efficiency for pollutants in degree and scope. Urban Water Supply Network is very complicated, and because of the poor pipe material, pipe aging, poor management, or affected by the ground complex environment such as construction, etc, Water pollution is often happen, in big cities, with the increasing of high buildings, a lot of secondary compression systems had been set up, and these secondary compression systems also can cause secondary pollution. Because of the contradiction between people’s growing health demands and reality, the advanced treatment technologies of drinking water get more and more concerns. Water treatment device is consisted of different advanced drinking water treatment technologies, it takes the municipal water or other Centralized water supply as source water, removes the harmful substances from the source water during the purification process to improve the water quality. Water treatment device is originate from the United States in the early 1980s, and modern advanced water purification technologies are originate from the United States also.75% of households have water treatment devices in developed countries, and the growth rate is between 10% to 15% a year. In our country, because the different habit of drinking water, backward production technology, poor product quality, the penetration rate is only 1% or so, but the growth rate is as high as 30% to 50%, particularly in big cities such as Beijing and Shanghai, the growth rate is up to 100%. With the improvement of living standard and the development of health consciousness, water treatment device is forming a new consumption hotspot. The health security of water-related products is related to public health, water treatment device, as an important part of water-related products, establish the health standard is becoming more and more important. The NSF standard of water treatment device is widely used in Europe and America. The related department of National Health and Family Planning Commission of People’s Republic of China takes NSF Standard and other standards as reference standards, makes the detailed instructions and regulations for Health security and Function evaluation of water treatment devices, which are parts of Appendixes in 《sanitary standards for drinking water》 [2001] 161. The amount of test Parameters for health security evaluation is less than NSF Standard. In recent years, water treatment devices are widely used in such places as enterprises, schools which have a big need of pure water and rural areas which have poor water quality. At the same time. the investigations and studies about health security.removal efficiency of water pollutants and secondary pollution of water treatment devices are increasing quickly. How to choose a safe, reliable and efficient water treatment device according to the water quality and water purification process gets more and more concerns.Objective:Paired samples from 57 water treatment devices before and after purification in 39 schools of Haikou city were determined by appropriate methods after optimized experimental conditions. The drinking water quality will be evaluated of Haikou city. The information about removal efficiency and secondary pollution will be found by comparing the water quality indexes change. And also this study will be helpful to improve 《health security and function evaluation standards of water treatment device》in a certain degree. And also it will be useful for the further popularization of water treatment device.Method:The Paired samples from 57 water treatment devices before and after purification in 39 schools of four administrative regions in HaiKou city, the contents of the water quality indexes will be acquired by determining the paired samples through the appropriate test methods. Source water will be divided into municipal water and well water, water treatment devices will be divided to ultra filtration membrane water treatment device and reverse osimosis(RO) membrane water treatment device. The water quality indexes will be described and inferenced through appropriate statistical methods by SAS9.2. If the contents of water quality indexes is normal distribution, the distribution characteristic is shown as x±s, if not, shown as quartile(P25%,P50%, P75%, P100%).Through the statistical analysis of the water quality indexes contents according to their distribution characteristic, it will be proved that if there is a significant difference between the compared sample, comparative t-test for normal distribution, Wilcoxon’s signed rank test for abnormal distribution. If P<0.05,there will be a significant difference between the compared sample.Results:The correlation coefficients(r) of standard curves about 17 elements were more than 0.999, the range of detection limit of the elements by direct Analysis was 0.01 ug/L to 0.48μg/L. within-day precision was between 0.5% to 3.0%, day to day precision was between 0.9% to 7.9%.The recovery rates of actual samples Were between 80% tol 12%.The range of correlation coefficients (r) of standard curves about 54 VOCs was 0.991 to 0.999, and the range of detection limit was 0.02μg/L-0.68μg/L. Within-day precision was 2.8% to 10.9%, and day to day precision was 1.9% to 14.4%. The recovery rates of actual samples was from 80.4% to 113.1%.The determined water quality indexes of 14 municipal water samples Comply with the requirements of 《standards for drinking water quality》 GB5749-2006.14 well water samples do not comply with the requirements of 《standards for drinking water quality》 GB5749-2006, nonconforming water quality indexes are shown as Total plate count and Total coliform group indicator.one direct-drinking water sample which use municipal water as source water do not comply with the requirements of《standard for purified drinking water》 CJ94-2005.the nonconforming water quality index are shown as pH.11 direct-drinking water samples which use well water as source water do not comply with the requirements of 《standard for purified drinking water》 CJ94-2005. the nonconforming water quality indexes are shown as Total plate count、 Total coliform group indicator、manganese.Reverse Osimosis(RO) membrane water treatment devices whichare used in urban schools, statistical results show that there are significant differences of the Chemical oxygen demand (COD). Total Hardness. Total dissolved solids(TDS). Chloride. Fluoride. Sulphate. Nitrate. As、A1、Sb、Ba、Mo、U. Mn、Trichloromethane Dibromochloromethane. Bromodichloromethane. Tribromethane between water samples before and after purification. According to the changes of the contents, this kind of water treatment device has removal efficiency for these water quality indexes except Mn.Ultrafiltration membrane water treatment devices whichare used in rural schools statistical results show that there are significant differences of Total plate count. Total coliform group indicator. Turbidity. pH. Chemical oxygen demand (COD). Chloride. Sulphate. Sb、Ba、Cu、Pb、Mn、Ni、Zn between water samples before and after purification. According to the changes of the contents, this kind of water treatment device has removal efficiency for Total plate count、 Total coliform group indicator. Turbidity. Chemical oxygen demand (COD). Chloride. Sulphate. And the contents of Sb、Ba、Cu、Pb、Mn 、Ni、Zn. Chloride. Sulphate rosein using process.Conclusion These two methods, which have good precision and accuracy, are applicable to determinate 17 elements and 54 VOCs in different kinds of drinking water.According to the results of the survey, the municipal water is in good condition in Haikou, but the well water in rural areas is polluted by microorganism, so the water quality is poor.Reverse osimosis(RO) membrane water treatment devices have removal efficiency for most of water quality indexes. The percent of pass for water samples purified by reverse osimosis(RO) membrane water treatment devices is up to 93%.Ultra filtration membrane water treatment devices have removal efficiency for just parts of water quality indexes. The percent of pass for water samples purified by ultra filtration membrane water treatment devices is 74%.According to the study, in urban schools, after purification by reverse osimosis(RO) membrane water treatment devices, the content of Mn in drinking water were rising.In rural schools, after purification by ultrafiltration membrane water treatment devices, the contents of Sb、Ba、Cu、Pb、Mn、Ni、Zn in drinking water were rising. These elements contents in drinking water comply with the requirement of《standards for drinking water quality》 GB5749-2006 and 《standard for purified drinking water》 CJ94-2005.but this result show that these elements will remove to drinking water from water treatment devices during purification, and it is worth to get more concerns.