Formation,Quantification,and Identification Of Bromine/Iodine Containing Disinfection By-Products In Drinking Water

Drinking water disinfection is one of the most significant public measures in the 20th century,avoiding epidemics caused by drinking water pollution.However,in the disinfection process,the applied disinfectants can react with natural organic matter and environmental pollutants in the source water.A variety of disinfection by-products（DBPs）would occur,causing potential threat to human health.Their carcinogenecity,genotoxicity,or reproductive toxicity have been demonstrated by toxicological and epidemiological studies.At present,most identified DBPs are halogen-containing DBPs,among which DBPs containing bromine（Br）or iodine（I）with higher toxicity over chlorinated DBPs have attracted extensive attention.With the rapid development of morden industry and agriculture,more and more environmental pollutants containing Br/I enter the source water,which makes the components of Br/I DBPs more complex.However,the occurrence and transformation of Br/I species in drinking water system（e.g.,the drinking water system along the Changjiang River which provides drinking water for 400 million people）are not clear;part of the DBPs with low concentratiosn in drinking water have not been identified.Therefore,it is significant to develop new analytical methods to quantify and identify Br/I DBPs,and to comprehensively understand the occurrence and formation of Br/I DBPs.The aim of dissertation is to use mulitiple analytical techniques to determine the species of Br/I in drinking water supply system and to explore the formation of Br/I DBPs in drinking water supply system;to analyze volatile and polar Br/I DBPs in tap water and simulated disinfection water samples with the common target Br/I DBPs quantitafied and the unknown Br/I DBPs screened and identified;and to explore the formation of Br/I DBPs in two source waters（the Changjian River and the Han River）with different disinfectants.The major contents of this dissertation are described as follows:（1）The occurrence of Br/I species and their proportion and transformation in the drinking water supply system along the Changjiang River were investigated.96 water samples were collected from eight drinking water treatment plants under conditions of low,normal,and flood water regimes.Total Br/I concentrations were quantified by inductively coupled plasma mass spectrometry（ICPMS）and inorganic Br/I species（bromide,bromate,iodide,and iodate）were determined by high performance liquid chromatography（HPLC）-ICPMS.Concentrations of organic Br/I were calculated as the difference between total Br/I and inorganic Br/I.The results demonstrated that Br/I species existed extensively in the drinking water supply system along Changjiang River,and their concentrations showed an increase tendency with the direction of flow.Apparent increase of total Br and total I concentrations after water treatment were observed,which indicated the possibility of Br/I introduction by chlorine-containing disinfectant.In addition,total Br and I concentrations correlated with the concentrations of artificial sweeteners（acesulfame and sucralose as a kind of wastewater indicator）,suggesting the influence of domestic sewage on Br and I in the river.In untreated water,bromide was the main Br species,and after treatment more than 50%was transformed into organic Br.Organic I were the majority of I species in raw water and were partly transformed into iodate after treatment.Overall,the Br/I species have accumulation potential in the Changjiang River and organic forms occupy high proportion in treated water samples,which should be paid more attention.（2）A method based on gas chromatography（GC-MS）was established for quantitative analysis and non-target screening of volatile Br/I DBPs.Under the optimized conditions,the analytical performance of the method for the quantification of 17 common volatile DBPs was evaluated.The limit of detection（LOD）of 17 DBPs was 0.01-0.54μg/L,the relative standard deviation（RSD）was 1.61%-15.4%（C=5μg/L,n=7）.The analytical method was applied to quantitafy 17 DBPs in 8 tap water samples,and the frequency of detection was discussed.In addition,with the aid of SIM mode(scanned ions are ³⁵Cl,³⁷Cl,⁷⁹Br,⁸¹Br,¹²⁷I),the sample results acquired by full scan mode were analyzed,and 12 DBPs containing Br/I were tentatively screened and identified,including 9 new DBPs（2-propanol,1-iodo-2-methyl,2-methyl-3-bromo—2-pentanol,propyl bromoacetate,1-bromo-2,2-dimetyoxypropane,5-Bromopentan-1-ide,m-Xylyl bromide,2-bromooctane,Ethro-2-methyl-3-bromo-4-chloro-2-butaol,1-bromononadecane）.（3）A method based on microfluidic liquid chromatography electrospray ionization quadrupole time of flight mass spectrometry（micro LC-ESI-QTOF MS）was established for taget quantification and non-target screening of polar Br/I DBPs.Using the SWATH-MS variable window mode of QTOF MS,the data for the quantification of 13 target haloacetic acid DBPs and the non-target screening of unknown DBPs could be achieved at the same time.Under the optimized conditions,the analytical performance for quantification of 13 target haloacetic acids was investigated.The LOD（S/N=3）for the 13 haloacetic acids was 0.03-1.6μg/L,the RSD was 4.6-15.9%（c=5μg/L,n=7）.Compared with the reported method,the sensitivity of this method was equivalent to that of GC-MS or LC-MS with multi reaction monitoring（MRM）mode.This method was applied to the quantification of 13 target haloacetic acids and the screen of unkonown DBPs in 8 tap water samples.The results showed that haloacetic acids containing chlorine and bromine were ubiquitous,while most of iodoacetic acid were not detected except for monoiodoacetic acid with the detection frequency of 62.5%.Moreover,a total of 15 DBPs containing halogen were tentatively screened,including 6 new DBPs containing bromine and iodine.（4）Three disinfectants（sodium hypochlorite,chlorine dioxide and ozone）were used to simulate the disinfection of the Changjiang River and the Han River,and the transformation of Br/I species after disinfection were investigated.The concentraion of 30 target Br/I DBPs were determined,and the unknown DBPs were analyzed.According to the concentrations of total Br/I before and after disinfection,it was found that a certain amount of Br/I was introduced into treated water after the disinfection of sodium hypochlorite or chlorine dioxide.After sodium hypochlorite disinfection,the production of organic Br was higher than that occurred after ozone or chlorine dioxide disinfection.After disinfection with ozone or sodium hypochlorite,almost all bromide in raw water transformed into bromine containing DBPs（bromate and brominated DBPs）.After chlorine dioxide disinfection,most of the bromide in the source water are transformed into brominated DBPs.The quantitative results of target 30DBPs showed that there was no significant difference in the frequency of detection and the concentratios in the simulated water samples from the Hanjiang River and the Changjiang River.Similarly,there was no significant difference in the compounds formed by sodium hypochlorite or chlorine dioxide,while the DBPs produced by ozonation were significantly less than that produced by the other two disinfectants.The screening results of unknown Br/I DBPs showed that the number of Br/I DBPs screened was the most in the water after sodium hypochlorite disinfection,followed by chlorine dioxide and ozone disinfection.Most of the Br/I DBPs screened in the simulated disinfected water samples were also detected in the tap water samples,and mostly are haloalcohols.Among the screened Br/I DBPs,1-bromo-2-methyl-2-propanol,a known DBP formed by ozonation disinfection,has the detection frequence of 100%in tap water and was also identified as a DBPformed by sodium hypochlorite and chlorine dioxide disinfection.A total of 16 new DBPs including 11 volatile DBPs and 5 polar DBPs were screened in the simulated water samples after disinfection,of which 10 were also detected in tap water samples.