The Model Establishment For THMs And THMs Disinfection By-Products Formation And Distribution In Different Water Treatment Processes And Finished Water Of Water Plant With The Huangpu River As Water Source

Disinfection by-products (DBPs) are a series of harmful substances which were formed by chloric disinfectant reacting with natural organic matters, pollutants, chloride, bromide and iodide. It was inevitably pollutants after chlorination disinfection. Epidemiological studies and toxicological studies demonstrated that disinfection by-products could lead to colon cancer, bladder cancer and rectal cancer, and adverse reproductive outcomes. It therefore was concerned. In view of the possible health hazards by disinfection by-products (DBPs), every country in accordance with his own situations set up corresponding standards to control the concentration of DBPs in drinking water.Chlorination disinfection by-products generated depends on multiple factors including the concentration of organic precursors, the type of disinfectant and dosage, reaction time, halogen ion concentration, pH, temperature of water. When the raw water quality is constant, the formation of trihalomethanes and haloacetic acids is related with the choice of disinfectant and the water processing technology. At present about 600-700 species have been found in drinking water, trihalomethanes (THMs) and haloacetic acids (HAAs) are the highest concentration. Four THMs (Chloroform, dichlorobromomethane, dibromochloromethane and bromoform) and five HAAs (monobromoacetic acid, dibromoacetic acid, monochloroacetic acid, dichloroacetic acid and trichloroacetic acid) were regulated disinfection by-products (DBPs) by US.EPA. In addition, the scale of water supply over 100 000 people need to monitor bromomonochloroacetic acid level. In China, The standards for drinking water quality is not list mobromoacetic acid, dibromoacetic acid, mochloroacetic acid and chlorobromoacetic acid.The formation of disinfection by-products related to many factors in the treatment technology and disinfection process. Therefore, the formation and tendency of THMs and HAAs in different processes, and the establishment of DBPs formation forecast models to understand the level of DBPs will provide a scientific basis for control DBPs formation in the processess and improvement of technology. On the other hand, during the process of transmission and distribution, irremovable organic matters in water will react with the residual chlorine to form of DBPs continuously. Investigation of THMs and HAAs with the variation of distance and time, and set up of DBPs distribution models will predict the concentration of THMs and HAAs in different distances that could accurately determine THMs and HAAs exposure of the population.Up to now, there are multiple methods to determine the THMs and HAAs levels in water. The Standards for drinking water quality of China (GB/T 5705.1～5705.12-2006) recommended head-space gas-chromatography and liquid-liquid-extraction gas-chromatography as methods to determine THMs and HAAs, respectively. However, the detection limits of these two methods are higher and the target analytes within an injection are fewer. The EPA 502.2 and 551.1 recommended purger-trap gas-chromatography (GC) and liquid-liquid-extraction (LLE) gas-chromatography method to determine the THMs and HAAs, respectively. Comparison of national standard methods recommended by China, U.S.EPA methods for THMs and HAAs have much advantageous basing on their higher sensitive, more effective, lower detection limits and multiple target analytes within an injection. Detection limit is lower than our current methods one or two orders of magnitude. U.S.EPA methods for THMs and HAAs have been widely referred by many countries. Since the limitation of the technical conditions, our country is not widely used.In view of above analysis, base on the method EPA recommend, in this study the pretreatment and detection conditions were improved and optimized to establish a high efficient and sensitive method for determining trihalomethanes and haloacetic acid and then to explore the formation and distribution rules of DBPs. It will lay a foundation for the accurately pollution exposure estimation in the study of DBPs on health effects.Part One The Establishment of Method for Determining Disinfection By-Products in Drinking WaterBase on the EPA 551.1 and 552.3 methods, the pretreatment and detection conditions had been improved and optimized in this study, and the methods for determining trihalomethanes (THMs) and haloacetic acid (HAAs) in drinking water had been established respectively; The THMs (THM4: chloroform, dichlolobromomethane, dibromochloromethane and bromoform) and HAAs (HAA6: mobromoacetic acid, dibromoacetic acid, mochloroacetic acid, dichloroacetic acid and trichloroacetic acid and chlorobromoacetic acid) were detected in different treatment processes samples and finished water of water plant with the Huangpu River as the water source to validate the reliability and applicability of these methods; And the sample holding time and stability in extract were also researched to lay a foundation for sample accurate analysis.The THMs and HAAs levels in water were detected using LLE-GC method and LLE-derivation-GC method, respectively. The results of this study showed that: the separation effects of these methods were good; the linear range of target chemicals were 1～100μg/L, the R2 were all higher than 0.9990 except mochloroacetic acid; the recoveries were 88.59%～97.04% in laboratory fortified blank solutions and were 73.68%～124.3% in sample fortified solutions; relative standard deviations(RSD) for all target chemicals were 2.339%～6.369%; the limits detection were 8.608ng/L～236.7ng/L; so the methods are stable, reliable, high accuracy, high sensitivity, and good repeatability. Different water treatment processes, finish water and tap water were detected using the proposed method, the chromatograms suggested that the pollutions which exist in the samples didn't influent the determination of THMs and HAAs, so the methods could be successfully used in different water samples. This study also investigated the changes of THMs and HAAs levels in water samples with holding time and their stability in extract: Two water samples from pipeline network were collected and added 10μg/Lof THMs mixed standards and 10μg/L of HAAs mixed standards respectively. The concentration of THMs and HAAs was measured on the day after sampling,3 days,7 days and 14 days, and compared the changes with holding time. The extract with THMs or HAAs mixed standards in the preserving of the day,7days,14days,21days and 30 days were measured by the concentration of THMs and HAAs, compared the changes of targets concentration with holding time. The results of this study showed that, the impact of sample holding time was an important factor in the concentration of the targets which significantly decreased with the extension of the time. The concentration of targets in extract except dicholoacetic acid, kept stable in the periods of measurement.Part Two The study of Regulated Trihalomethanes and Haloacetic Acids Level in Raw Water of Yangtze River and Huangpu River, Different Treatment Processes and Pipeline NetworkRegulated THMs and HAAs were detected using the method had been founded in raw water, different treatment processes and finished water of A water plant with the Huangpu River as the water source and B/C water plant with the Yangtze River as the water source, and the corresponding point of the main pipeline of transmission and distribution. The date in this research showed:the total trihalomethanes (THM4) concentration in different treatment processes of A water plant was ND～9.64μg/L, dichlorobromomethane was the highest (6.43μg/L). The THM4 concentration in B and C water plant was from ND to 38.06μg/L, dibromochloromethane (12.24μg/L) and bromoform (14.07μg/L) was the highest in the B and the C water plant, respectively. In addition to trichloroacetic acid in A water plant from the raw water, the other HAAs came from different treatment processes. The total haloacetic acids (HAA6) concentration of different treated processes in A water plant was 3.21～22.97μg/L, mobromoacetic acid (9.03μg/L) was the highest. Dibromoacetic acid was the highest both in B (8.25μg/L) and C (8.84μg/L) water plant, HAA6 concentration was between ND～27.18μg/L. The highest and the lowest concentration of THM4 were founded from the main water pipes network of C and A water plant, respectively, but the concentration of HAA6 in the main water pipes network of A water plant was the highest, and the lowest in C water plant. The concentration of THMs was between 21.11～31.18μg/L in C water plant and 6.72～8.51μg/L in A water plant. The concentration of HAA6 was 25.02～37.31μg/L in A water plant and 18.69～23.32μg/L in C water plant. Brominated disinfection by-products in B and C water plant were higher than A water plant, and higher than the chlorinated disinfection by-products. So, the THM4 concentrations of finished water treated from Huangpu River was lower than finished water from the Yangtze River, while the HAA6 concentrations in finish water from Huangpu River was higher than the two water plants of Yangtze River. The fluctuations of THMs and HAAs concentration in pipeline network were low during transmission and distribution process.Part Three Model Establishment for DBPs Formation and Distribution in different water treatment processes of Water Plant with the Huangpu River as Water Source and in corresponding Pipeline NetworkThe object of this study is to investigate the impact of factors in various water treatment processes on the THMs and HAAs formation in Y water plant with the Hangpu River as water source, and the relationship between relevant factors and the levels of THMs and HAAs at sites with different distance in the corresponding main pipeline network. Consequently, the model of DBPs formation and transformation is established. Based on the treatment process of Y plant, raw water, coagulation basin, sedimentation basin and finished water were selected as sampling sites to collect water samples for DBPs formation model. Finished water and 4 sites with different distance in the main pipeline were selected as sampling sites to collect water samples for DBPs distribution model. The results showed that with the extension of water treatment processes, the COD of water samples declined significantly. When the water entered the pipeline network, the COD increased obviously but showed no change with the extension of pipeline network. The maximum level of residual chlorine was in the coagulation basin and the level declined in the sedimentation basin. Because of the post chlorination, the residual chlorine increased again in the finished water. In the distribution of pipeline network, the residual chlorine declined with the increase of water transmission distance. THMs were not detected in almost all raw water samples. With the extension of treatment processes and the extending of contact time between disinfects and organic chemicals in raw water, the concentrations of THMs showed persistent elevation. In the distribution of pipeline network, the levels of THMs were low (<10μg/L) and stable. The HAAs levels varies in some raw water samples, there existed HAAs with various concentrations and the main of them was chlorobromoacetic acid. After chlorine disinfection, the levels of HAAs increased significantly at the end of coagulation basin, but didn't change with the extension of subsequent water treatment processes. When the finished water entered pipeline network, HAAs levels increased significantly and were stable with the extension of pipeline network.The formation and distribution of DBPs were predicted by principle component regression (PCR) and stepwise multivariate regression (SMR). The PCR model for DBPs formation was y=-0.0905z1+0.1611z2+0.0474z3+1.9103z4+0.2250z5+23.667, the R2 was 0.2331 and the adjusted R2 (adjR2) was 0.0588. The Pr>F was 0.2855, so the statistical significance of the model was poor. The PCR model for DBPs distribution was y=1.0512z1+1.585z2-0.4261z3+1.6488z4+23.2782, the R2 and the adjR2 were 0.3322 and 0.3174 respectively. The Pr>F is 0.0000, so the statistical significance of the model was ideal. The SMR model for DBPs formation was y= 17.07ln(COD)×10^(7-pH)-16.74×10^(7-pH)+23.21, the R2 and the adjR2 were 0.7317 and 0.7001 respectively. The Pr>F was 0.0000, so the statistical significance of the model was ideal. the SMR model for DBPs transformation was y= (8.54 ln(COD)-0.45O2-3.75Cl2+10.34)×T/T-4.86, the R2 and the adjR2 were 0.828 and 0.686 respectively. The Pr>F was 0.0000, so the statistical significance of the model was perfect. Compared to the PCR model, the SMR model showed higher statistical significance and better predication accuracy of prediction.