The Experts below are selected from a list of 3480 Experts worldwide ranked by ideXlab platform
Florence Dossier-berne - One of the best experts on this subject based on the ideXlab platform.
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Concentration levels of urea in swimming pool water and reactivity of Chlorine with urea.
Water Research, 2010Co-Authors: Joseph De Laat, Wentao Feng, Diab Adams Freyfer, Florence Dossier-berneAbstract:Abstract This study investigated the reactivity of Chlorine with urea which is the main nitrogen contaminant introduced into swimming pool water by bathers. In the first part of this study, analyses showed that the mean concentrations of urea and TOC determined from 50 samples of municipal swimming pool were equal to 18.0 μM (s.d. 11.7) and 3.5 mg C L −1 (s.d. 1.6), respectively. The mean value for the urea contribution to the TOC content was 6.3% (s.d. 3.3). The rate of decomposition of urea in swimming pool water measured during the closure time of the facility was very slow (decay at the rate of ≈1% per hour in the presence of 1.6–1.8 mg L −1 of free Chlorine). In the second part of this work, experiments carried out with phosphate buffered solutions of urea ([Urea] 0 = 1 mM; [Cl 2 ] 0 /[Urea] 0 : 0.5–15 mol/mol; pH 7.4 ± 0.2; reaction time: 0–200 h) showed that long term Chlorine demand of urea was about 5 mol Cl 2 /mol of urea. Chlorination led to a complete mineralization of organic carbon into CO 2 for a Chlorine Dose of 3.5 mol/mol and to the formation of 0.7–0.8 mol NO 3 − /mol of urea for Chlorine Dose of 8–10 mol/mol. Experiments conducted with dilute solutions of urea ([Urea] 0 = 50 μM; pH ≈ 7.3) confirmed that the degradation rate of urea by Chlorine is very slow under conditions simulating real swimming pool water.
Naiyun Gao - One of the best experts on this subject based on the ideXlab platform.
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degradation of carbamazepine by uv Chlorine advanced oxidation process and formation of disinfection by products
Environmental Science and Pollution Research, 2016Co-Authors: Shiqing Zhou, Ying Xia, Tian Yao, Zhou Shi, Shumin Zhu, Naiyun GaoAbstract:Pharmaceuticals in water are commonly found and are not efficiently removed by current treatment processes. Degradation of antiepileptic drug carbamazepine (CBZ) by UV/Chlorine advanced oxidation process was systematically investigated in this study. The results showed that the UV/Chlorine process was more effective at degrading CBZ than either UV or chlorination alone. The CBZ degradation followed pseudo-first order reaction kinetics, and the degradation rate constants (kobs) were affected by the Chlorine Dose, solution pH, and natural organic matter concentration to different degrees. Degradation of CBZ greatly increased with increasing Chlorine Dose and decreasing solution pH during the UV/Chlorine process. Additionally, the presence of natural organic matter in the solution inhibited the degradation of CBZ. UV photolysis, chlorination, and reactive species (hydroxyl radical •OH and Chlorine atoms •Cl) were identified as responsible for CBZ degradation in the UV/Chlorine process. Finally, a degradation pathway for CBZ in the UV/Chlorine process was proposed and the formation potentials of carbonaceous and nitrogenous disinfection by-products were evaluated. Enhanced formation of trichloroacetic acid, dichloroacetonitrile, and trichloronitromethane precursors should be considered when applying UV/Chlorine advanced oxidation process to drinking water.
Zhang Jinqi - One of the best experts on this subject based on the ideXlab platform.
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Factors on the formation of disinfection by-products MX, DCA and TCA by chlorination of fulvic acid from lake sediments
Chemosphere, 2001Co-Authors: Chen Zhuo, Yang Chengyong, Zou Huixian, Lu Junhe, Zhang JinqiAbstract:[3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] (MX) and chlorinated acetic acids such as dichlorinated acetic acid (DCA) and trichlorinated acetic acid (TCA) have always been the focus of disinfection by-products (DBPs) studies. In order to find out the influences of reaction time, TOC, Chlorine Dose, pH and temperature on the formation of MX, DCA and TCA, we extracted fulvic acid (FA) from the sediment of Tai Lake, and conducted simulated chlorination of samples rich in FA. Results showed positive relationship between TOC and the yields of MX, DCA and TCA. But the influences of pH, Chlorine Dose, reaction time, and temperature are quite complex. The optimal chlorination condition for the formation of MX is pH = 2, T = 45 degrees C, C/Cl2 = 1/4, t = 12 h. Lower pH, longer time, greater Chlorine Dose can result in greater yield of both DCA and TCA, and there is a strong linear relationship between the formation of DCA and TCA.
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Factors on the formation of strong mutagen [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] MX by chlorination of syringaldehyde
Water Research, 2000Co-Authors: Yang Chengyong, Chen Zhuo, Zou Huixian, Lu Junhe, Zhang JinqiAbstract:Abstract Syringaldehyde (4-hydroxy-3,5-dimethoxybenzaldehyde) was chlorinated in the laboratory at different reaction time, temperature, pH and Chlorine Dose, and MX was determined and quantified by GC/MS. The finding suggests that the optimal chlorination conditions are as follows: temperature=298 K, pH=5, Cl:syrin. (mol:mol)=9:1. We also found that the formation of MX increased with the syringaldehyde concentration in a linear relationship. In addition, when syringaldehyde was chlorinated with a different Chlorine Dose in an alkaline condition, no MX was detected. This study will conduce to elucidating the kinetic process for the formation of MX from syringaldehyde and will be of great help for better control of MX in drinking water.
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Screening the precursors of strong mutagen [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] MX from chlorinated water
Water Research, 2000Co-Authors: Zou Huixian, Yang Chengyong, Chen Zhuo, Lu Junhe, Zhang Jinqi, Zhou WenAbstract:Abstract In this study, 21 suspected precursors of MX were chlorinated in laboratory condition. Only 8 of selected compounds syringaldehyde, acetosyringone, ferulic acid, 3-ethoxy-4-hydroxy-benzaldehyde, 3,4,5-trimethoxy-benzaldehyde, vanillin, tryptophan, and tyrosine were screened as precursors of MX. The yields of MX by chlorination of syringaldehyde are the highest and decreased with Chlorine Dose, but the yields of MX by the other 7 compounds increased with Chlorine Dose. It may be possible to elucidate the reaction mechanism for the formation of MX in light of the reaction of these screened precursors with Chlorine.
Qinyan Yue - One of the best experts on this subject based on the ideXlab platform.
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Effect of powdered activated carbon (PAC) on MBR performance and effluent trihalomethane formation: At the initial stage of PAC addition.
Bioresource technology, 2016Co-Authors: Yue Gao, Baoyu Gao, Qinyan Yue, Xia HuangAbstract:In this study, the MBR was used to treat municipal wastewater for reuse. Effects of powdered activated carbon (PAC) addition on MBR system in terms of effluent water quality, trihalomethane (THM) formation and membrane organic fouling tendency of MBR sludge supernatant at the initial stage of PAC addition were investigated. Effects of Chlorine Dose and contact time on THM formation and speciation were also studied. PAC addition enhanced the removal of organic matters, especially aromatic components, which improved the UV254 removal rate from 34% to 83%. PAC addition greatly reduced the membrane organic fouling tendency of MBR sludge supernatant. PAC addition reduced the MBR effluent trihalomethane formation potential (THMFP) from 351.29 to 241.95μg/L, while increased THM formation reactivity by 42%. PAC addition enhanced the formation of higher toxic bromine-containing THMs. High Chlorine Dose and contact time resulted in higher THM formation but lower proportion of bromine-containing THMs.
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Factors affecting trihalomethane formation and speciation during chlorination of reclaimed water.
Water science and technology : a journal of the International Association on Water Pollution Research, 2015Co-Authors: Baoyu Gao, Yan Wang, Qinyan YueAbstract:A hybrid process with membrane bioreactor (MBR) and powdered activated carbon (PAC), PAC/MBR, was used for real municipal wastewater treatment and reuse. The roles of Chlorine Dose, contact time, pH and bromide in trihalomethane (THM) formation and speciation during chlorination of the reclaimed water were investigated. Total trihalomethane (TTHM) yield exponentially increased to maximum with increasing Chlorine Dose (correlation coefficient R2 = 0.98). Prolonging substrate Chlorine contact time significantly promoted TTHM formation. Less than 40% of THMs formed in the first 24 h, indicating that the PAC/MBR effluent organic matters were mostly composed of slow-reacting precursors. Increasing pH and bromide concentration facilitated THM formation. Higher Chlorine Dose and contact time enhanced chloro-THM formation. The bromo-THM formation was favored at near neutral condition. Despite the variation of Chlorine Dose, contact time and pH, the yield of THM species in order was usually CHCl3 > CHBrCl2 > CHBr2Cl > CHBr3. However, THM speciation shifted from chlorinated species to brominated species with increasing bromide concentration.
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Effects of chlorination operating conditions on trihalomethane formation potential in polyaluminum chloride-polymer coagulated effluent.
Journal of hazardous materials, 2014Co-Authors: Baoyu Gao, Qinyan Yue, Hongyan Rong, Shenglei Sun, Fang Wang, Yan WangAbstract:Abstract In this study, coagulation performance of polyaluminum chloride (PAC) and PAC-lignin acrylamide (PAC + LAM) in reservoir water treatment was contrastively analyzed. Effects of operating conditions including Chlorine Dose, contact time and pH on the formation potential of trihalomethanes (THMs) during chlorination in coagulated effluent were also investigated. Comparing with PAC, PAC + LAM achieved higher efficiency in the removal of THMs precursors. TTHM yield in unfiltered water samples (UW) was greater than that of filtered water (FW) due to the residual dissolved organic matter (DOM) in the suspended particles or micro flocs. Meanwhile, operating conditions during chlorination had a significant influence on THMs formation potential. With Chlorine Dose rising, mass ratio of CHCl3 to TTHM increased, whereas that of CHBr2Cl decreased due to higher Cl2/Br− molar ratio. TTHM and CHCl3 levels rose with the increase of pH. Under a given chlorination condition, there was a minor effect of contact time on THM speciation.
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Evaluation of a submerged membrane bioreactor (SMBR) coupled with Chlorine disinfection for municipal wastewater treatment and reuse
Desalination, 2013Co-Authors: Baoyu Gao, Yan Wang, Dianxun Hou, Qinyan YueAbstract:Abstract In this study, municipal wastewater was treated by a SMBR system and further disinfected with Chlorine to produce reclaimed water. The primary objective was to examine the water quality with a focus on trihalomethanes (THMs). As disinfection conditions are important aspects in controlling the formation of THMs, influences of Chlorine Dose and contact time on THM formation and speciation were also investigated. High quality reclaimed water was generated though the SMBR system with regard to five-day biological oxygen demand (BOD5), suspend solid (SS) and turbidity. However the concentration of total trihalomethanes (TTHM) in the chlorinated SMBR effluent was up to 160 μg/L, demonstrating that the SMBR was insufficient in the removal of THM precursors. TTHM levels increased with Chlorine Dose and contact time. As Chlorine Dose increased, the yields of trichloromethane (CHCl3) and bromodichloromethane (CHBrCl2) increased, whereas both tribromomethane (CHBr3) and dibromochloromethane (CHBr2Cl) decreased due to the rise of Cl2/Br− ratio. In order to reduce health risks of reclaimed water, efficient removal of disinfection by-product precursor and opportune Chlorine disinfection conditions are recommended.
Xiang Liu - One of the best experts on this subject based on the ideXlab platform.
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Mechanism insight of acetaminophen degradation by the UV/Chlorine process: kinetics, intermediates, and toxicity assessment
Environmental Science and Pollution Research, 2019Co-Authors: Jiaqi Li, Siqi Zhou, Erdeng Du, Miao Li, Xiang LiuAbstract:The removal of acetaminophen (AAP) in aqueous solution by the UV/Chlorine process was evaluated. The effect of Chlorine Dose, the initial AAP concentration, pH value, and UV intensity on the reaction were also investigated. The degradation mechanism and the ecological risk were further discussed. The results indicated that AAP degradation fitted pseudo-first-order kinetics. Compared with UV alone or dark chlorination, the combination of UV and Chlorine significantly accelerated the degradation process. The AAP degradation was positively affected by Chlorine Dose and UV intensity, while negatively affected by the initial AAP concentration and ammonia nitrogen concentration during the UV/Chlorine process. The frontier orbital theory analysis shows that the C5 position in the benzene ring of AAP is likely to be the first site attacked by HO• and Cl• radical to form the products. Twelve intermediates were identified by Q-TOF and GC-MS. The possible degradation pathways were also proposed. Luminescent bacteria experiment and ECOSAR prediction both revealed that acute toxicity of AAP degradation could only be partially reduced. Ecological risks during the UV/Chlorine process need to be further evaluated.