Performance evaluation of the UV activated chlorite process on trimethoprim: Degradation efficiency, energy consumption and disinfection by-products formation.

As the primary inorganic by-product species of ClO2, chlorite is believed to have negative toxicological effects on human health and therefrom greatly limits the wide application of ClO2 in water treatment. The synergistic trimethoprim (TMP) removal concerning degradation efficiency, energy consumption and disinfection by-products (DBPs) formation in the UV activated chlorite process accompanied by the simultaneously elimination of chlorite was comprehensively evaluated. UV/chlorite integrated process removed TMP far more rapidly than UV (1.52%) or chlorite (3.20%) alone due to the endogenous radicals (Cl•, ClO• and •OH), the contributing proportions of which were 31.96%, 19.20% and 44.12%. The second-order rate constants of TMP reaction with Cl•, ClO• and •OH were determined to be 1.75 × 1010, 1.30 × 109 and 8.66 × 109 M-1 s-1. The effects of main water parameters including chlorite dosage, UV intensity, pH as well as water matrixes (nature organic matter, Cl- and HCO3-) were examined. kobs obeyed the order as UV/Cl2>UV/H2O2≈UV/chlorite>UV, and the cost ranking via electrical energy per order (EE/O, kWh m-3 order-1) parameter was UV/chlorite (3.7034) > UV/H2O2 (1.1625) >UV/Cl2 (0.1631). The operational scenarios can be optimized to achieve the maximum removal efficiencies and the minimum energy costs. The destruction mechanisms of TMP were proposed by LC-ESI-MS analysis. The overall weighted toxicity in subsequent disinfection was assessed as UV/Cl2>UV/chlorite > UV, the values of which in post-chlorination were 6.2947, 2.5806 and 1.6267, respectively. Owing to the vital roles of reactive chlorine species (RCS), UV/chlorite displayed far higher TMP degradation efficiency than UV, and concurrently presented much less toxicity than UV/Cl2. In an effort to determine the viability of the promising combination technology, this study was devoted to reduce and reuse chlorite and synchronously realize the contaminants degradation efficiently.

The fate and transformation of iodine species in UV irradiation and UV-based advanced oxidation processes.

Iodinated disinfection byproducts (I-DBPs) formed in water treatment are of emerging concern due to their high toxicity and the tase-and-odor problems associated with iodinated trihalomethanes (I-THMs). Iodoacetic acid and dichloroiodomethane are currently regulated in Shenzhen, China and the Ministry of Health of the People's Republic of China has also been considering regulating I-DBPs. Iodide (I-), organoiodine compounds (e.g., iodinated X-ray contrast media [ICM]), and iodate (IO3-) are the three common iodine sources in aquatic environment that lead to I-DBP formation. While UV irradiation effectively inactivate a wide range of microorganisms in water, it induces the transformation of these iodine sources, enabling the formation of I-DBPs. This review focuses on the fate and transformation of these iodine sources in UV-based water treatment (i.e., UV irradiation and UV-based advanced oxidation processes [UV-AOPs]) and the formation of I-DBPs in post-disinfection. I- released in UV-based treatments of ICM and can be oxidized in subsequent disinfection to hypoiodous acid (HOI), which reacts with natural organic matter (NOM) to produce I-DBPs. Both UV and UV-AOPs are not able to fully mineralize ICM and completely oxidize the released I- to (except UV/O3). Results reveal that UV and UV-AOPs are adequate for I-DBP degradation but require high UV doses. While the ideal I-DBP mitigation strategy awaits to be developed, understanding their sources and formation pathways aids in informed selections of water treatment processes, empowers water suppliers to meet drinking water standards, and minimizes consumers' exposure to I-DBPs.

Comparison of UV-induced AOPs (UV/Cl2, UV/NH2Cl, UV/ClO2 and UV/H2O2 ) in the degradation of iopamidol: Kinetics, energy requirements and DBPs-related toxicity in sequential disinfection processes.

The UV-induced advanced oxidation processes (AOPs, including UV/Cl2, UV/NH2Cl, UV/ClO2 and UV/H2O2 ) degradation kinetics and energy requirements of iopamidol as well as DBPs-related toxicity in sequential disinfection were compared in this study. The photodegradation of iopamidol in these processes can be well described by pseudo-first-order model and the removal efficiency ranked in descending order of UV/Cl2  > UV/H2O2  > UV/NH2Cl > UV/ClO2  > UV. The synergistic effects could be attributed to diverse radical species generated in each system. Influencing factors of oxidant dosage, UV intensity, solution pH and water matrixes (Cl- , NH4 + and nature organic matter) were evaluated in detail. Higher oxidant dosages and greater UV intensities led to bigger pseudo-first-order rate constants (Kobs) in these processes, but the pH behaviors exhibited quite differently. The presence of Cl- , NH4 + and nature organic matter posed different effects on the degradation rate. The parameter of electrical energy per order (EE/O) was adopted to evaluate the energy requirements of the tested systems and it followed the trend of UV/ClO2  > UV > UV/NH2Cl > UV/H2O2  > UV/Cl2 . Pretreatment of iopamidol by UV/Cl2 and UV/NH2Cl clearly enhanced the production of classical disinfection by-products (DBPs) and iodo-trihalomethanes (I-THMs) during subsequent oxidation while UV/ClO2 and UV/H2O2 exhibited almost elimination effect. From the perspective of weighted water toxicity, the risk ranking was UV/NH2Cl > UV/Cl2 > UV > UV/H2O2 > UV/ClO2 . Among the discussed UV-driven AOPs, UV/Cl2 was proved to be the most cost-effective one for iopamidol removal while UV/ClO2 displayed overwhelming advantages in regulating the water toxicity associated with DBPs, especially I-THMs. The present results could provide some insights into the application of UV-activated AOPs technologies in tradeoffs between cost-effectiveness assessment and DBPs-related toxicity control of the disinfected waters containing iopamidol.

Comparative evaluation of metoprolol degradation by UV/chlorine and UV/H2O2 processes.

The degradation of metoprolol (MTP), a ß-blocker commonly used for cardiovascular diseases, by UV/chlorine and UV/H2O2 processes was comparatively evaluated. MTP direct photolysis at 254 nm could be neglected, but remarkable MTP degradation was observed in both the UV/chlorine and UV/H2O2 systems. Compared with UV/H2O2, UV/chlorine has a more pronounced MTP degradation efficiency. In addition to primary radicals (OH and Cl), secondary radicals (ClO and Cl2-) played a pivotal role in degrading MTP by UV/chlorine process. The relative contributions of hydroxyl radicals (OH) and reactive chlorine species (RCS) in the UV/chlorine system varied at different solution pH values (i.e., the contribution of RCS increased from 57.7% to 75.1% as the pH increased from 6 to 8). The degradation rate rose as the oxidant dosage increased in the UV/chlorine and UV/H2O2 processes. The presence of Cl- slightly affected MTP degradation in both processes, while the existence of HCO3- and HA inhibited MTP degradation to different extents in both processes. In terms of the overall cost of electrical energy, UV/chlorine is more cost efficient than UV/H2O2. The degradation products during the two processes were identified and compared, and the degradation pathways were proposed accordingly. Compared with the direct chlorination of MTP, pre-oxidation with UV/chlorine and UV/H2O2 significantly enhanced the formation of commonly known DBPs. Therefore, when using UV/chlorine and UV/H2O2 in real waters to remove organic pollutants, the possible risk of enhanced DBP formation resulting from the degradation of certain pollutants during post-chlorination should be carefully considered.

Photochemical degradation of iodate by UV/H2O2 process: Kinetics, parameters and enhanced formation of iodo-trihalomethanes during chloramination.

In this paper, it was demonstrated that UV/H2O2 process can not only obviously promote the degradation rate of IO3-, but also greatly enhance iodo-trihalomethanes (I-THMs) formation in sequential chloramination. UV/H2O2 exhibited much faster IO3- decomposition than either UV or H2O2 treatment alone due to the contribution of highly reactive species including O-, OH and eaq-. The degradation rate of IO3- was affected by H2O2 dosages, pH, UV intensity as well as the presence of natural organic matter (NOM). The calculated pseudo-first order rate constant gradually increased with H2O2 dosages and solution pH, but behaved directly proportional to the UV intensity. Although NOM remarkably reduced the degradation rate of IO3- in UV/H2O2 process, their presence greatly enhanced the formation of I-THMs during subsequent chloramination. The overwhelming majority of iodoform at high UV fluences was also observed, which indicated improved iodination degrees of the detected I-THMs. UV/H2O2 was proved to be more capable on the evolution of IO3- to I- as well as I-THMs than UV and thereby enhanced the toxicity of disinfected waters in the following chloramination process. This study was among the first to provide a comprehensive understanding on the transformation of IO3- as the emerging iodine precursor to form I-THMs via diverse advanced oxidation process technologies like UV/H2O2.

Oxidation of the ß-blocker propranolol by UV/persulfate: Effect, mechanism and toxicity investigation.

In this study, the degradation of propranolol (PRO) by UV/persulfate process was systematically investigated. Direct photolysis of PRO was limited due to its low quantum yield, while the PRO degradation efficiency can be greatly promoted by the combination of persulfate and UV irradiation. Radical scavenging tests showed that both SO4- and OH contributed to the removal of PRO, with SO4- playing a more important role. The degradation rate of PRO was improved by increasing the persulfate dose and initial solution pH consistent with pseudo-first-order reaction kinetics. The effects of common water constituents were species dependent. HCO3- and Cl- promoted PRO degradation. By contrast, NO3- and HA were found to inhibit PRO degradation. A total of nine degradation products were identified by LC/MS/MS, which mainly derived from the ring-opening attack on the naphthalene group or oxidation of the amino moiety by SO4- and OH. Finally, the toxicity of the reaction mixtures was also assessed using luminescent bacteria Vibrio fischeri, and the results indicated that UV/persulfate is capable of controlling the toxicity of PRO degradation.

Chlor(am)ination of iopamidol: Kinetics, pathways and disinfection by-products formation.

The degradation kinetics, pathways and disinfection by-products (DBPs) formation of iopamidol by chlorine and chloramines were investigated in this paper. The chlorination kinetics can be well described by a second-order model. The apparent second-order rate constants of iopamidol chlorination significantly increased with solution pH. The rate constants of iopamidol with HOCl and OCl- were calculated as (1.66 ± 0.09) × 10-3 M-1 s-1 and (0.45± 0.02) M-1 s-1, respectively. However, the chloramination of iopamidol fitted well with third-order kinetics and the maximum of the apparent rate constant occurred at pH 7. It was inferred that the free chlorine (i.e., HOCl and OCl-) can react with iopamidol while the combined chlorine species (i.e., NH2Cl and NHCl2) were not reactive with iopamidol. The main intermediates during chlorination or chloramination of iopamidol were identified using ultra performance liquid chromatography - electrospray ionization-mass spectrometry (UPLC-ESI-MS), and the destruction pathways including stepwise deiodination, hydroxylation as well as chlorination were then proposed. The regular and iodinated DBPs formed during chlorination and chloramination of iopamidol were measured. It was found that iodine conversion from iopamidol to toxic iodinated DBPs distinctly increased during chloramination. The results also indicated that although chloramines were much less reactive than chlorine toward iopamidol, they led to the formation of much more toxic iodinated DBPs, especially CHI3.

Phototransformation of iodate by UV irradiation: Kinetics and iodinated trihalomethane formation during subsequent chlor(am)ination.

The photodegradation of IO3- at 254nm and the formation of iodinated trihalomethanes (I-THMs) during subsequent chlorination or chloramination in the presence of natural organic matter (NOM) were investigated in this study. The thermodynamically stable IO3- can be degraded by UV irradiation with pseudo-first order kinetics and the quantum yield was calculated as 0.0591moleinstein-1. Solution pH posed no remarkable influence on the photolysis rate of IO3-. The UV phototransformation of IO3- was evidenced by the determination of iodide (I-) and hypoiodous acid (HOI) in solution. NOM sources not only enhanced the photodegradation rate of IO3- by photoejecting solvated electrons, but also greatly influenced the production I-THMs in subsequent chlor(am)ination processes. In UV irradiation and sequential oxidation processes by chlorine or chloramine, the I-THMs formation was susceptible to NOM sources, especially the two major fractions of aqueous humic substances (humic acid and fulvic acid). The toxicity of disinfected waters greatly increased in chloramination over chlorination of the UV photodecomposed IO3-, as far more I-THMs especially CHI3, were formed. As "the fourth iodine source" of iodinated disinfection by-products, the occurrence, transportation and fate of IO3- in aquatic environment should be of concern instead of being considered a desired iodine sink.

Formation of iodinated trihalomethanes during UV/chloramination with iodate as the iodine source.

Iodinated trihalomethanes (I-THMs) are a group of emerging disinfection by-products with high toxicity, and iodide (I(-)) as well as iodinated organic compounds are expected to be their iodine sources. Nevertheless, in this study, iodate (IO3(-)) was proven to be a new iodine source of I-THM formation during UV/chloramination. In the iodate-containing waters (without any other iodine sources), I-THM formation increased with the increase of UV dose, IO3(-) and NH2Cl concentrations. With the increase of Br(-)/IO3(-) molar ratio, I-THM formation (especially for the brominated species) increased. Besides, NOM species could affect I-THM formation from IO3(-) during UV/chloramination. Fulvic acid could promote IO3(-) phototransformation to I(-) but humic acid impeded the production of I(-) during UV irradiation. Under realistic drinking water treatment conditions (DOC = 5.0 mg-C/L, IO3(-) = 12.7 µg-I/L, UV dose = 50 mJ/cm(2), NH2Cl = 5 mg-Cl2/L), CHCl2I was detected as 0.17 µg/L using solid-phase microextraction method, and the production rate of I-THMs from IO3(-) was about 7% of that from I(-).

Effect of UV irradiation on the proportion of organic chloramines in total chlorine in subsequent chlorination.

This study investigated the changes of chlorine species and proportion of organic chloramines during the chlorination process after UV irradiation pretreatment in drinking water. It was found that the UV pretreatment could enhance the percentage of organic chloramines by increasing free chlorine consumption in the chlorination of raw waters. The percentage of organic chloramines in total chlorine increased with UV intensity and irradiation time in raw waters. However, for the humic acid synthesized water, the percentage of organic chloramines increased first and then decreased with the increase of UV irradiation time. The value of SUVA declined in both raw and humic acid synthesized waters over the UV irradiation time, which indicated that the decomposition of aromatic organic matter by UV could be a contributor to the increase of free chlorine consumption and organic chloramine proportion. The percentage of organic chloramines during chlorination of raw waters after 30-min UV irradiation pretreatment varied from 20.2% to 41.8%. Total chlorine decreased obviously with the increase of nitrate concentration, but the percentage of organic chloramines increased and was linearly correlated to nitrate concentration.

A comparison of iodinated trihalomethane formation from chlorine, chlorine dioxide and potassium permanganate oxidation processes.

This study compared the formation of iodinated trihalomethanes (I-THMs) from iodide-containing raw waters oxidized by chlorine, chlorine dioxide (ClO2) and potassium permanganate (KMnO4) at different oxidant concentrations, reaction times, pHs, initial iodide concentrations and bromide to iodide mass ratios. Among the six investigated I-THMs, iodoform was the major species formed during the oxidation using chlorine, ClO2 and KMnO4. When oxidant concentration increased from 0.1 to 3.0 mg/L, the formation of I-THMs increased and then decreased for chlorine and ClO2, but kept increasing for KMnO4. As the reaction time went by, I-THM concentration increased to a plateau within 10 h (ClO2 within only 1 h, especially) for all the three oxidants. I-THM formation gradually increased from pH 3.0 to 9.0 and remained stable at pH values higher than 7.5 for chlorine; however, for ClO2 and KMnO4 the highest I-THM formation showed at pH 7.0 and 7.5, respectively. As initial iodide concentration increased from 20 to 800 µg/L, the total amount and species of I-THMs increased for the three oxidants. Iodide contributed to I-THM formation much more significantly than bromide.

Kinetic models and pathways of ronidazole degradation by chlorination, UV irradiation and UV/chlorine processes.

Degradation kinetics and pathways of ronidazole (RNZ) by chlorination (Cl2), UV irradiation and combined UV/chlorine processes were investigated in this paper. The degradation kinetics of RNZ chlorination followed a second-order behavior with the rate constants calculated as (2.13 ± 0.15) × 10(2) M(-2) s(-1), (0.82 ± 0.52) × 10(-2) M(-1) s(-1) and (2.06 ± 0.09) × 10(-1) M(-1) s(-1) for the acid-catalyzed reaction, as well as the reactions of RNZ with HOCl and OCl(-), respectively. Although UV irradiation degraded RNZ more effectively than chlorination did, very low quantum yield of RNZ at 254 nm was obtained as 1.02 × 10(-3) mol E(-1). RNZ could be efficiently degraded and mineralized in the UV/chlorine process due to the generation of hydroxyl radicals. The second-order rate constant between RNZ and hydroxyl radical was determined as (2.92 ± 0.05) × 10(9) M(-1) s(-1). The degradation intermediates of RNZ during the three processes were identified with Ultra Performance Liquid Chromatography - Electrospray Ionization - mass spectrometry and the degradation pathways were then proposed. Moreover, the variation of chloropicrin (TCNM) and chloroform (CF) formation after the three processes were further evaluated. Enhanced formation of CF and TCNM precursors during UV/chlorine process deserves extensive attention in drinking water treatment.

[Effects of different pre-oxidants on DBPs formation potential by chlorination and chloramination of Yangtze River raw water].

Yangtze River raw water from Yangshupu Water Plant, Shanghai was studied in this paper for reduced formation potential of chlorination and chloramination disinfection by-products (DBPs) after pre-oxidation by three kinds of common pre-oxidants, whiich were potassium permanganate, chlorine and chlorine dioxide. Results of chlorination showed that removal effectiveness of all the selected oxidants on total chlorination DBPs was not significant, and the reduction percentages by ClO2, Cl2 and KMnO4 were 8.4%, 5.7% and 3.9%, respectively. The order of DBPs control effect was ClO2, > Cl2 > KMnO4. As to Yangtze River raw water in case of chlorine disinfection, using ClO2 as pre-oxidation agent showed relatively better effect on removal of DBPs. However, chloramination results demonstrated that impacts of the three preoxidants on DBPs formation potential were quite different, and the reduction percentages by ClO2 and KMnO4 were 18.1% and 4.1%, respectively, while pre-chlorination increased the potential by 12.3%. These results revealed that ClO2 had the highest removal effectiveness, meanwhile pre-chlorination should be avoided due to its notable increase in DBPs formation.

Photodegradation kinetics of iopamidol by UV irradiation and enhanced formation of iodinated disinfection by-products in sequential oxidation processes.

The photochemical degradation of iopamidol with low-pressure UV lamps and the formation of iodinated disinfection by-products (I-DBPs) during sequential oxidation processes including chlorine, monochloramine and chlorine dioxide were investigated in this study. Iopamidol can be effectively decomposed by UV irradiation with pseudo-first order reaction kinetics. The evaluated quantum yield was found to be 0.03318 mol einstein(-1). Results showed that iopamidol degradation rate was significantly increased by higher UV intensity and lower initial iopamidol concentration. However, the effect of solution pH was negligible. Degradation of iopamidol by UV photolysis was subjected to deiodination and hydroxylation mechanisms. The main degradation products including -OH substitutes and iodide were identified by UPLC-ESI-MS and UPLC-UV, respectively. Increasing the intensity of UV irradiation promoted the release of iodide. Destruction pathways of iopamidol photolysis were proposed. Enhanced formation of I-DBPs were observed after iopamidol photolysis followed by disinfection processes including chlorine, monochloramine and chlorine dioxide. With the increase of UV fluence, I-DBPs formation were significantly promoted.

Degradation kinetics and chloropicrin formation during aqueous chlorination of dinoseb.

The kinetics of chlorination of dinoseb and the corresponding formation of disinfection by-products (DBPs) were studied between pH 4 and 9 at room temperature (25±1°C). The reactivity shows a minimum at pH 9, a maximum at pH 4 and a medium at neutral conditions. pH profile of the apparent second-order rate constant of the reaction of dinoseb with chlorine was modeled considering the elementary reactions of HOCl with dinoseb species and an acid-catalyzed reaction. The predominant reactions at near neutral pH were the reactions of HOCl with the two species of dinoseb. The rate constants of 2.0 (±0.8)×10(4)M(-2)s(-1), 3.3 (±0.6) and 0.5 (±0.1)M(-1)s(-1) were determined for the acid-catalyzed reaction, HOCl reacted with dinoseb and dinoseb(-), respectively. The main degradation by-products of the dinoseb formed during chlorination have been separated and identified by GC-MS with liquid-liquid extraction sample pretreatment. Six volatile and semi-volatile DBPs were identified in the chlorination products, including chloroform (CF), monochloroacetone, chloropicrin (TCNM), 1,1-dichloro-2-methy-butane, 1,2-dichloro-2-methy-butane, 1-chloro-3-methy-pentanone. A proposed degradation pathway of dinoseb during chlorination was then given. TCNM and CF formation potential during chlorination of dinoseb reached as high as 0.077 and 0.097µMµM(-1) dinoseb under the traditional condition (pH=7 and Cl2/C=2). Their yields varied with Cl2/C, pH and time. The maximum yields of TCNM appeared at molar ratio as Cl2/C=1 and pH 3, while the maximum of CF appeared at molar ratio as Cl2/C=4 and pH 7. [TCNM]/[CF] decreased with reaction time and increased solution pH.

[Chlorination byproducts formation potentials of typical nitrogenous organic compounds in water].

Twelve typical nitrogenous organic compounds including herbicides, pesticides, amino acids, industrial products etc in polluted raw water were selected to investigate formation of typical carbonaceous and nitrogenous DBPs during chlorination and chloramination. To indentify the formation mechanism of carbonaceous and nitrogenous disinfection byproducts from nitrogenous chemicals, chlorination and chloroamination of urea herbicides, triazine herbicides, amino acid, and other compounds were investigated. As a result, the potential precursors for different DBPs were defined as well. It has been identified that widely used urea herbicides could produce as many as 9 specific DBPs. The chlorotoluron shows highest reactivity and yields chloroform (CF), monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), 1,1-dichloro-acetone (1,1-DCP), 1,1,1-trichloro-acetone (1,1,1-TCP), chloropicrin (NTCM), dichloro-acetonitrile (DCAN), dimethylnitrosamine (NDMA). The results indicated that aldicarb and dinoseb are important precursors of CF, DCAA, MCAA, NTCM as well. High concentrations of CF and DCAA were found during L-tryptophan chlorination. Furthermore, DBPs formation pathways and mechanisms were suggested during chlorination and chloramination of chlorotoluron, ametryn, dinoseb L-tryptophan.

Chlorination of chlortoluron: kinetics, pathways and chloroform formation.

Chlortoluron chlorination is studied in the pH range of 3-10 at 25 ± 1°C. The chlorination kinetics can be well described by a second-order kinetics model, first-order in chlorine and first-order in chlortoluron. The apparent rate constants were determined and found to be minimum at pH 6, maximum at pH 3 and medium at alkaline conditions. The rate constant of each predominant elementary reactions (i.e., the acid-catalyzed reaction of chlortoluron with HOCl, the reaction of chlortoluron with HOCl and the reaction of chlortoluron with OCl(-)) was calculated as 3.12 (± 0.10)×10(7)M(-2)h(-1), 3.11 (±0.39)×10(2)M(-1)h(-1) and 3.06 (±0.47)×10(3)M(-1)h(-1), respectively. The main chlortoluron chlorination by-products were identified by gas chromatography-mass spectrometry (GC-MS) with purge-and-trap pretreatment, ultra-performance liquid chromatography-electrospray ionization-MS and GC-electron capture detector. Six volatile disinfection by-products were identified including chloroform (CF), dichloroacetonitrile, 1,1-dichloropropanone, 1,1,1-trichloropropanone, dichloronitromethane and trichloronitromethane. Degradation pathways of chlortoluron chlorination were then proposed. High concentrations of CF were generated during chlortoluron chlorination, with maximum CF yield at circumneutral pH range in solution.

Measurement of dissolved organic nitrogen in a drinking water treatment plant: size fraction, fate, and relation to water quality parameters.

This paper investigates the characteristics of dissolved organic nitrogen (DON) in raw water from the Huangpu River and also in water undergoing treatment in the full-scale Yangshupu drinking water treatment plant (YDWTP) in Shanghai, China. The average DON concentration of the raw water was 0.34 mg/L, which comprised a relatively small portion (~5%) of the mass of total dissolved nitrogen (TDN). The molecular weight (MW) distribution of dissolved organic matter (DOM) was divided into five groups: >30, 10-30, 3-10, 1-3 and <1 kDa using a series of ultrafiltration membranes. Dissolved organic carbon (DOC), UV absorbance at wavelength of 254 nm (UV254) and DON of each MW fraction were analyzed. DON showed a similar fraction distribution as DOC and UV254. The <1 kDa fraction dominated the composition of DON, DOC and UV254 as well as the major N-nitrosodimethylamine formation potential (NDMAFP) in the raw water. However, this DON fraction cannot be effectively removed in the treatment line at the YDWTP including pre-ozonation, clarification and sand filtration processes. The results from linear regression analysis showed that DON is moderately correlated to DOC, UV254 and trihalomethane formation potential (FP), and strongly correlated to haloacetic acids FP and NDMAFP. Therefore, DON could serve as a surrogate parameter to evaluate the reactivity of DOM and disinfection by-products FP.