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1.
J Environ Sci (China) ; 104: 233-241, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33985726

RESUMO

Algal organic matter (AOM), including extracellular organic matter (EOM) and intracellular organic matter (IOM) from algal blooms, is widely accepted as essential precursors of disinfection byproducts (DBPs). This study evaluated the effect of ozonation or ozone combined with activated carbon (O3-AC) treatment on characteristic alternation and DBP formation with subsequent chlorination of Chlorella sp.. The effects of pH and bromide concentration on DBP formation by ozonation or O3-AC treatment were also investigated. Results showed that the potential formation of DBPs might be attributed to ozonation, but these DBP precursors could be further removed by activated carbon (AC) treatment. Moreover, the formation of target DBPs was controlled at acidic pH by alleviating the reactions between chlorine and AOM. Besides, the bromide substitution factor (BSF) value of trihalomethanes (THMs) from EOM and IOM remained constant after AC treatment. However, THM precursors could be significantly decreased by AC treatment. The above results indicated that O3-AC was a feasible treatment method for algal-impacted water.


Assuntos
Chlorella , Desinfetantes , Ozônio , Poluentes Químicos da Água , Purificação da Água , Carvão Vegetal , Desinfecção , Halogenação , Trialometanos/análise , Poluentes Químicos da Água/análise
2.
Water Res ; 198: 117138, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-33895589

RESUMO

Intensified sanitization practices during the recent coronavirus disease-2019 (COVID-19) led to the release of chlorine-based disinfectants in surface water, potentially triggering the formation of disinfection byproducts (DBPs) in the presence of dissolved organic nitrogen (DON). Thus, a comprehensive investigation of DON's spatial distribution and its association with DBP occurrence in the surface water is urgently needed. In this study, a total of 51 water samples were collected from two rivers and four lakes in May 2020 in Wuhan to explore the regional variation of nitrogen (N) species, DON's compositional characteristics, and the three classes of DBP occurrence. In lakes, 53.0% to 86.3% of N existed as DON, with its concentration varying between 0.3-4.0 mg N/L. In contrast, NO3--N was the dominant N species in rivers. Spectral analysis revealed that DON in the lakes contained higher humic and fulvic materials with higher A254, A253/A203, SUVA254, and PIII+IV/PI+II+V ratios, while rivers had higher levels of hydrophilic compounds. Trihalomethanes (THMs) were the most prevalent DBPs in the surface waters, followed by N-nitrosamines and haloacetonitriles (HANs). The levels of N-nitrosamines (23.1-97.4 ng/L) increased significantly after the outbreak of the COVID-19 pandemic. Excessive DON in the surface waters was responsible for the formation of N-nitrosamines. This study confirmed that the presence of DON in surface water could result in DBP formation, especially N-nitrosamines, when disinfectants were discharged into surface water during the COVID-19 pandemic.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Desinfecção , Halogenação , Humanos , Nitrogênio/análise , Pandemias , Trialometanos/análise , Poluentes Químicos da Água/análise
3.
Environ Pollut ; 281: 116950, 2021 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-33819670

RESUMO

Disinfection is considered as a vital step to ensure the supply of clean and safe drinking water. Various approaches are adopted for this purpose; however, chlorination is highly preferred all over the world. This method is opted owing to its several advantages. However, it leads to the formation of certain by-products. These chlorination disinfection by-products (DBPs) are genotoxic, carcinogenic and mutagenic. Still chlorination is being practiced worldwide. Present review gives insights into the occurrence, toxicity and factors affecting the formation of regulated (THMs, HAAs) and emerging DBPs (N-DBPs, HKs, HAs and aromatic DBPs) found in drinking water. Furthermore, remediation techniques used to control DBPs have also been summarized here. Key findings are: (i) concentration of regulated DBPs surpassed the permissible limit in most of the regions, (ii) high chlorine dose, high NOM, more reaction time (up to 3 h) and high temperature (up to 30 °C) enhance the formation of THMs and HAAs, (iii) high pH favors the formation of THMs while low pH is suitable of the formation of HAAs, (iv) high NOM, low temperature, low chlorine dose and moderate pH favors the formation of unstable DBPs (N-DBPs, HKs and HAs), (v) DBPs are toxic not only for humans but for aquatic fauna as well, (vi) membrane technologies, enhanced coagulation and AOPs remove NOM, (vii) adsorption, air stripping and other physical and chemical methods are post-formation approaches (viii) step-wise chlorination is assumed to be an efficient method to reduce DBPs formation without any treatment. Toxicity data revealed that N-DBPs are found to be more toxic than C-DBPs and aromatic DBPs than aliphatic DBPs. In majority of the studies, merely THMs and HAAs have been studied and USEPA has regulated just these two groups. Future studies should focus on emerging DBPs and provide information regarding their regulation.


Assuntos
Desinfetantes , Água Potável , Poluentes Químicos da Água , Purificação da Água , Cloro , Desinfetantes/análise , Desinfecção , Água Potável/análise , Halogenação , Humanos , Trialometanos/análise , Poluentes Químicos da Água/análise
4.
Molecules ; 26(5)2021 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-33800798

RESUMO

The adsorptive removal of trihalomethanes (THMs) from spiked water samples was evaluated with a series of modified polysaccharide adsorbents that contain ß-cylodextrin or chitosan. The uptake properties of these biodegradable polymer adsorbents were evaluated with a mixture of THMs in aqueous solution. Gas chromatography employing a direct aqueous injection (DAI) method with electrolytic conductivity detection enabled quantification of THMs in water at 295 K and at pH 6.5. The adsorption isotherms for the polymer-THMs was evaluated using the Sips model, where the monolayer adsorption capacities ranged between 0.04 and 1.07 mmol THMs/g for respective component THMs. Unique adsorption characteristics were observed that vary according to the polymer structure, composition, and surface chemical properties. The modified polysaccharide adsorbents display variable molecular recognition and selectivity toward component THMs in the mixed systems according to the molecular size and polarizability of the adsorbates.


Assuntos
Polímeros/química , Trialometanos/análise , Trialometanos/isolamento & purificação , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Quitosana/química , Propriedades de Superfície , beta-Ciclodextrinas/química
5.
Environ Sci Technol ; 55(8): 5547-5558, 2021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33788559

RESUMO

Recently, we suggested that hypobromous acid (HOBr) is a sink for the marine volatile organic sulfur compound dimethyl sulfide (DMS). However, HOBr is also known to react with reactive moieties of dissolved organic matter (DOM) such as phenolic compounds to form bromoform (CHBr3) and other brominated compounds. The reaction between HOBr and DMS may thus compete with the reaction between HOBr and DOM. To study this potential competition, kinetic batch and diffusion-reactor experiments with DMS, HOBr, and DOM were performed. Based on the reaction kinetics, we modeled concentrations of DMS, HOBr, and CHBr3 during typical algal bloom fluxes of DMS and HOBr (10-13 to 10-9 M s-1). For an intermediate to high HOBr flux (≥10-11 M s-1) and a DMS flux ≤10-11 M s-1, the model shows that the DMS degradation by HOBr was higher than for photochemical oxidation, biological consumption, and sea-air gas exchange combined. For HOBr fluxes ≤10-11 M s-1 and a DMS flux of 10-11 M s-1, our model shows that CHBr3 decreases by 86% compared to a lower DMS flux of 10-12 M s-1. Therefore, the reaction between HOBr and DMS likely not only presents a sink for DMS but also may lead to suppressed CHBr3 formation.


Assuntos
Bromatos , Trialometanos , Sulfetos
6.
Sci Total Environ ; 771: 144885, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33736131

RESUMO

Dissolved nitrogenous organic matter in water can contain precursors of disinfection by-products (DBPs), especially nitrogenous DBPs (N-DBPs). Amino acids are ubiquitous as dissolved nitrogenous organic matter in source water and can pass through drinking water treatment processes to react with disinfectants in finished water and in the distribution system. Phenylalanine (Phe) was selected as a model amino acid precursor to investigate its derived DBPs and their variations during a chlorination regime that simulated water distribution with residue chlorine. The 7-day DBPs formation potential (DBPsFP) test with chlorine revealed chlorination by-products of phenylalanine including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and halonitromethanes (HNMs), but not trichloronitromethane (TCNM) which was a significant N-DBP detected during the first 48 h of chlorine contact. The formation of most carbonaceous DBPs (C-DBPs) increased with chlorination time; however N-DBPs and non-chlorinated byproducts of phenylacetonitrile and phenylacetaldehyde reached their highest concentration after 2 h of reaction, and then gradually decreased until below detection after 7 days. The chlorination influencing factors indicated that light enhanced the peak yield of DBPs; the pH value showed different influences associated with corresponding DBPs; and the presence of bromide ions (Br-) generated a variety of bromine-containing DBPs. The DBPsFP test with chloramine reduced C-DBPs generation to about 1/3 of the level observed for chlorine disinfection and caused an increase in dichloroacetonitrile. Surveillance of DBPs during drinking water distribution to consumers should consider the varying contact times with disinfectants to accurately profile the types and concentrations of C-DBPs and N-DBPs present in drinking water.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Cloro , Desinfecção , Halogenação , Fenilalanina , Trialometanos , Poluentes Químicos da Água/análise
7.
Sci Total Environ ; 770: 144767, 2021 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-33736400

RESUMO

Ozone is a strong oxidant commonly used in drinking water treatment, but its role in the transformation/formation of organic matters (OMs) and disinfection by-products (DBPs) in the drinking water treatment chain had not been systematically studied. In this work the occurrence and building up of OMs, DBPs of trihalomethanes (THMs) and nitrosamines (NAs) during water purification steps under different pre-ozonation dosages have been studied through lab-scale and pilot-scale studies. Results indicated that 0-0.4 mg/L of pre-ozonation dosage could reduce organic load of following-up process steps but insufficient to control DBPs. Seasonal performances of a pilot plant indicated that the accumulation of DBPs was much less in summer than in winter. Furthermore the formation potential of NAs was higher in winter than summer when 0.4 mg/L pre-ozonation was dosed while the maximum removal efficiency of organic matter was found at a pre-ozonation dosage of 0.8 mg/L in summer. Finally a seasonal trade-off control strategy for both OMs and DBPs was proposed with an elucidated role of pre-ozonation in the drinking water treatment chain. This study provided working principles on optimizing pre-ozonation dosage and a seasonal control strategy for trade-off control of both OMs and DBPs in drinking water treatment plants.


Assuntos
Desinfetantes , Água Potável , Ozônio , Poluentes Químicos da Água , Purificação da Água , Desinfetantes/análise , Desinfecção , Halogenação , Trialometanos/análise , Poluentes Químicos da Água/análise
8.
Water Res ; 194: 116964, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33652228

RESUMO

Drinking water treatment plants (DWTPs) produce filter backwash water (FBW) and sedimentation sludge water (SSW) that may be partially recycled to the head of DWTPs. The impacts of key disinfection conditions, water quality parameters (e.g., disinfection times, disinfectant types and doses, and pH values), and bromide concentration on controlling the formation of trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and haloacetamides (HAMs) during disinfection of FBW and SSW were investigated. Concentrations of most disinfection byproducts (DBPs) and associated calculated toxicity increased with extended chlorination for both FBW and SSW. During chlorination of both FBW and SSW, elevated chlorine doses significantly increased THM yields per unit dissolved organic carbon (DOC), but decreased HAN and HAM yields, with minimum effect on HAA yields. Chloramine disinfection effectively inhibited C-DBP formation but promoted N-DBPs yields, which increased with chloramine dose. Calculated toxicities after chloramination increased with chloramine dose, which was opposite to the trend found after free chlorine addition. An examination of pH effects demonstrated that C-DBPs were more readily generated at alkaline pH (pH=8), while acidic conditions (pH=6) favored N-DBP formation. Total DBP concentrations increased at higher pH levels, but calculated DBP toxicity deceased due to lower HAN and HAM concentrations. Addition of bromide markedly increased bromo-THM and bromo-HAN formation, which are more cytotoxic than chlorinated analogues, but had little impact on the formation of HAAs and HAMs. Bromide incorporation factors (BIFs) for THMs and HANs from both water samples all significantly increased as bromide concentrations increased. Overall, high bromide concentrations increased the calculated toxicity values in FBW and SSW after chlorination. Therefore, while currently challenging, technologies capable of removing bromide should be explored as part of a strategy towards controlling cumulative toxicity burden (i.e., hazard) while simultaneously lowering individual DBP concentrations (i.e., exposure) to manage DBP risks in drinking water.


Assuntos
Desinfetantes , Água Potável , Poluentes Químicos da Água , Purificação da Água , Cloro , Desinfetantes/análise , Desinfecção , Halogenação , Esgotos , Trialometanos , Poluentes Químicos da Água/análise
9.
Zhonghua Yu Fang Yi Xue Za Zhi ; 55(3): 418-423, 2021 Mar 06.
Artigo em Chinês | MEDLINE | ID: mdl-33730838

RESUMO

Haloacetaldehydes (HALs), as emerging disinfection by-products in drinking water, are the third largest group by weight of identified disinfection by-products (DBPs) in drinking water. The formation of HALs is associated with the level of natural organic matter and halide in the source water, the treatment process of drinking water and the type of disinfectant. Recent studies have shown that HALs are more cytotoxic and genotoxic than regulated trihalomethanes and halo-acetic acids in drinking water. Currently, only a few countries and regions have set limit values for trichloroacetaldehyde with high detection rate in drinking water. However, there is growing evidence that unregulated HALs have a higher potential risk to human health compared to regulated HALs. This paper reviews the current research progress on the formation and transformation, cytotoxicity and genotoxicity of HALs in drinking water, and looks forward to the problems that should be paid attention in the future toxicological research of HALs in order to support the development of scientific drinking water standards.


Assuntos
Desinfetantes , Água Potável , Poluentes Químicos da Água , Purificação da Água , Desinfetantes/toxicidade , Desinfecção , Água Potável/análise , Humanos , Trialometanos , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade
10.
Water Res ; 193: 116851, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-33540343

RESUMO

This study investigated the mechanisms of mixed IO3-/I- system under UV irradiation in drinking water and compared the iodinated trihalomethanes (I-THMs) formation of a mixed IO3-/I- system to that of single I- and IO3- systems during subsequent chloramination. The effects of initial I-/IO3- molar ratio, pH, and UV intensity on a mixed IO3-/I- system were studied. The introduction of I- enhanced the conversion rate of IO3- to reactive iodine species (RIS). Besides, IO3- degradation rate increased with the increase of initial I- concentration and UV intensity and the decrease of pH value. In a mixed IO3-/I- system, IO3- could undergo direct photolysis and photoreduction by hydrated electron (eaq-). Moreover, the enhancement of I-THM formation in a mixed IO3-/I- system during subsequent chloramination was observed. The I-THM yields in a mixed IO3-/I- system were higher than the sum of I-THMs produced in a single IO3- and I- systems at all the evaluated initial I- concentrations and pH values. The difference between I-THM formation in a mixed IO3-/I- system and the sum of I-THMs in a single IO3- and I- systems increased with the increase of initial I- concentration. As the initial pH decreased from 9 to 5, the difference of I-THM yields enhanced, while the total I-THM yield of a mixed IO3-/I- system and single I- and IO3- systems decreased slightly. Besides, IO3--I--containing water with DOC concentration of 2.5-4.5 mg-C/L, which mainly contained humic-acid substances, had a higher risk in I-THMs formation than individual I--containing and IO3--containing water.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Desinfecção , Halogenação , Iodatos , Iodetos , Fotólise , Trialometanos/análise , Água , Poluentes Químicos da Água/análise
11.
Sci Total Environ ; 774: 145297, 2021 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-33611000

RESUMO

Dissolved organic matter (DOM) is the precursor of disinfection by-products (DBPs) which is widely found in the aquatic environment. The analysis of DOM in raw water is helpful to evaluate the formation potentials of DBPs. However, there is relatively little research on the DOM identification of raw water in northern China. In this study, the variation in DOM in M reservoir water in one year by fluorescence excitation-emission matrix-parallel factor analysis (EEM-PARAFAC) was investigated to evaluate the DBP formation potential (DBPFP). The results suggested that five components, namely, two humic-like substances (C2, C3), two fulvic-like substances (C1, C4) and one protein-like substance (C5), were identified in the DOM of M reservoir water. The content of DOM in autumn and winter was higher than that in spring and summer. The source of DOM in the water body of M reservoir was mainly from terrestrial source, but less from aquatic source. The source, types and humification degree of DOM affect the formation of DBPs. The formation potential of DBPs had the following order: trihalomethanes (THMs) > dichloroacetic acid (TCAA) > trichloroacetic acid (DCAA) > chloral hydrate (CH). The formation potentials of THM and TCAA were strongly correlated with C2 (rTHM = 0.805, rTCAA = 0.857). The formation potential of CH has a good correlation with C1 (r = 0.722). The formation of DCAA has a good correlation with C4 (r = 0.787). DOM and DBPFP were negatively correlated with the biological index (BIX) and fluorescence index (FI) of the raw water, and positively correlated with the humification index (HIX).


Assuntos
Água Potável , China , Desinfecção , Água Potável/análise , Análise Fatorial , Substâncias Húmicas/análise , Espectrometria de Fluorescência , Trialometanos/análise
12.
Environ Sci Technol ; 55(5): 2908-2918, 2021 03 02.
Artigo em Inglês | MEDLINE | ID: mdl-33594894

RESUMO

Swimming pools are commonly treated with chlorine, which reacts with the natural organic matter and organic matter introduced by swimmers and form disinfection byproducts (DBPs) that are associated with respiratory-related issues, including asthma, in avid swimmers. We investigated a complementary disinfectant to chlorine, copper-silver ionization (CSI), with the aim of lowering the amount of chlorine used in pools and limiting health risks from DBPs. We sampled an indoor and outdoor pool treated with CSI-chlorine during the swimming season in 2017-2018 and measured 71 DBPs, speciated total organic halogen, in vitro mammalian cell cytotoxicity, and N-acetyl-l-cysteine (NAC) thiol reactivity as a cytotoxicity predictor. Controlled, simulated swimming pools were also investigated. Emerging DBP concentrations decreased by as much as 80% and cytotoxicity decreased as much as 70% in the indoor pool when a lower chlorine residual (1.0 mg/L) and CSI was used. Some DBPs were quantified for the first time in pools, including chloroacetaldehyde (up to 10.6 µg/L), the most cytotoxic haloacetaldehyde studied to date and a major driver of the measured cytotoxicity in this study. Three highly toxic iodinated haloacetic acids (iodoacetic acid, bromoiodoacetic acid, and chloroiodoacetic acid) were also quantified in pools for the first time. We also found that the NAC thiol reactivity was significantly correlated to cytotoxicity, which could be useful for predicting the cytotoxicity of swimming pool waters in future studies.


Assuntos
Desinfetantes , Piscinas , Poluentes Químicos da Água , Animais , Cloro , Cobre/toxicidade , Desinfetantes/toxicidade , Desinfecção , Prata , Trialometanos/análise , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade
13.
Environ Sci Technol ; 55(7): 4103-4114, 2021 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-33523638

RESUMO

Intensified efforts to curb transmission of the Severe Acute Respiratory Syndrome Coronavirus-2 might lead to an elevated concentration of disinfectants in domestic wastewater and drinking water in China, possibly resulting in the generation of numerous toxic disinfection byproducts (DBPs). In this study, the occurrence and distribution of five categories of DBPs, including six trihalomethanes (THMs), nine haloacetic acids (HAAs), two haloketones, nine nitrosamines, and nine aromatic halogenated DBPs, in domestic wastewater effluent, tap water, and surface water were investigated. The results showed that the total concentration level of measured DBPs in wastewater effluents (78.3 µg/L) was higher than that in tap water (56.0 µg/L, p = 0.05), followed by surface water (8.0 µg/L, p < 0.01). Moreover, HAAs and THMs were the two most dominant categories of DBPs in wastewater effluents, tap water, and surface water, accounting for >90%, respectively. Out of the regulated DBPs, none of the wastewater effluents and tap water samples exceeded the corresponding maximum guideline values of chloroform (300 µg/L), THM4 (80 µg/L), NDMA (100 ng/L), and only 2 of 35 tap water samples (67.6 and 63.3 µg/L) exceeded the HAA5 (60 µg/L) safe limit. HAAs in wastewater effluents showed higher values of risk quotient for green algae. This study illustrates that the elevated use of disinfectants within the guidance ranges during water disinfection did not result in a significant increase in the concentration of DBPs.


Assuntos
Desinfetantes , Água Potável , Poluentes Químicos da Água , Purificação da Água , China , Desinfetantes/análise , Desinfecção , Água Potável/análise , Humanos , Pandemias , Trialometanos/análise , Águas Residuárias , Água , Poluentes Químicos da Água/análise
14.
Chemosphere ; 272: 129568, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33476791

RESUMO

Iopamidol is a commonly used iodinated X-ray contrast media in medical field, and its residue in water can react with disinfectants to form highly toxic iodinated disinfection by-products (I-DBPs). This study investigated the degradation of iopamidol and formation of DBPs, especially iodinated trihalomethanes (I-THMs), during ferrate (Fe(VI)) pre-oxidation and subsequent chlor(am)ination under raw water background. It was found that iopamidol degradation efficiency in raw water by Fe(VI) at pH 9 could reach about 80%, which was much higher than that at pH 5 and pH 7 (both about 25%). With Fe(VI) dose increasing, iopamidol removal efficiency increased obviously. During the iopamidol degradation by Fe(VI), IO3- was the dominant product among all the iodine species. After pre-treated by Fe(VI), yields of THM4 and I-THMs can be reduced in subsequent chlor(am)ination. Besides, pH was a crucial factor for Fe(VI) pre-oxidition controlling DBPs. With the pH increasing from 5 to 9, the yield of THM4 kept increasing in subsequent chlorination but showed the highest amount at pH 6 in subsequent chloramination. The yield of I-THMs increased first and then decreased with the increase of pH in both subsequent chlorination and chloramination. I-THM concentrations in chlorinated samples were lower than chloraminated ones under acidic conditions but became higher under neutral and alkaline conditions. The total CTI of THMs during Fe(VI)-chloramination was higher than that during Fe(VI)-chlorination under neutral condition, but sharply decreased under alkaline conditions. In summary, Fe(VI)-chloramination subsequent treatment under alkaline conditions should be an effective method for iopamidol removal and DBP control.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Cloraminas , Desinfecção , Halogenação , Iopamidol , Ferro , Trialometanos , Água , Poluentes Químicos da Água/análise
15.
Environ Sci Technol ; 55(3): 1545-1554, 2021 02 02.
Artigo em Inglês | MEDLINE | ID: mdl-33449615

RESUMO

In hydraulic fracturing fluids, the oxidant persulfate is used to generate sulfate radical to break down polymer-based gels. However, sulfate radical may be scavenged by high concentrations of halides in hydraulic fracturing fluids, producing halogen radicals (e.g., Cl•, Cl2•-, Br•, Br2•-, and BrCl•-). In this study, we investigated how halogen radicals alter the mechanisms and kinetics of the degradation of organic chemicals in hydraulic fracturing fluids. Using a radical scavenger (i.e., isopropanol), we determined that halogenated products of additives such as cinnamaldehyde (i.e., α-chlorocinnamaldehyde and α-bromocinnamaldehyde) and citrate (i.e., trihalomethanes) were generated via a pathway involving halogen radicals. We next investigated the impact of halogen radicals on cinnamaldehyde degradation rates. The conversion of sulfate radicals to halogen radicals may result in selective degradation of organic compounds. Surprisingly, we found that the addition of halides to convert sulfate radicals to halogen radicals did not result in selective degradation of cinnamaldehyde over other compounds (i.e., benzoate and guar), which may challenge the application of radical selectivity experiments to more complex molecules. Overall, we find that halogen radicals, known to react in advanced oxidative treatment and sunlight photochemistry, also contribute to the unintended degradation and halogenation of additives in hydraulic fracturing fluids.


Assuntos
Fraturamento Hidráulico , Poluentes Químicos da Água , Halogenação , Halogênios , Compostos Orgânicos , Trialometanos
16.
Environ Sci Technol ; 55(3): 1790-1799, 2021 02 02.
Artigo em Inglês | MEDLINE | ID: mdl-33492937

RESUMO

The covalent modifications resulting from chlorine reactions with peptide-bound amino acids contribute to pathogen inactivation and disinfection byproduct (DBP) formation. Previous research suggested that histidine is the third most reactive of the seven chlorine-reactive amino acids, leading to the formation of 2-chlorohistidine, 2-oxohistidine, or low-molecular-weight byproducts such as trihalomethanes. This study demonstrates that histidine is less reactive toward formation of chlorine transformation products (transformation time scale of hours to days) than five of the seven chlorine-reactive amino acids, including tyrosine (transformation time scale of minutes). Chlorine targeted tyrosine in preference to histidine within peptides, indicating that chlorine reactions with tyrosine and other more reactive amino acids could contribute more to the structural modifications to proteins over the short time scales relevant to pathogen inactivation. Over the longer time scales relevant to disinfection byproduct formation in treatment plants or distribution systems, this study identified ß-cyanoalanine as the dominant transformation product of chlorine reactions with peptide-bound histidine, with molar yields of ∼50% after 1 day. While a chlorinated histidine intermediate was observed at lower yields (maximum ∼5%), the cumulative concentration of the conventional low-molecular-weight DBPs (e.g., trihalomethanes) was ≤7%. These findings support the need to identify the high-yield initial transformation products of chlorine reactions with important precursor structures to facilitate the identification of unknown DBPs.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Cloro , Desinfecção , Halogenação , Histidina , Peptídeos , Trialometanos , Poluentes Químicos da Água/análise
17.
J Hazard Mater ; 408: 124864, 2021 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-33387716

RESUMO

Algae can exhibit different disinfection by-product formation potential (DBPFP) depending on the characteristics of the algogenic organic matter (AOM) released during growth. In this study, the amount of AOM released by Microcystis aeruginosa and its DBPFP were compared between the exponential growth phase and the death phase. Moreover, the efficiency of DBPFP removal through powdered activated carbon (PAC) adsorption was evaluated. The correlations between DBPFPs and dissolved organic carbon concentration or ultraviolet absorbance at 254 nm (UV254) were also investigated to predict DBPFPs. Among DBPFPs, which were higher at the death phase, the formation potential (FP) of haloacetic acid was the highest. In addition, the high relative haloacetonitrile FP at the death phase indicated that a relevant portion of the intracellular organic matter derived from cell autolysis was converted into a large amount of haloacetonitriles. Furthermore, PAC addition reduced all DBPFPs at both growth phases. PAC was found to selectively adsorb dichloroacetic acid precursors at the death phase and dichloroacetonitrile precursors at both growth phases. Finally, UV254 showed greater correlations with the three DBPFPs at all growth phases. These results highlight the possible use of UV254 as an alternative analytical tool for fast determination of M. aeruginosa DBPFPs.


Assuntos
Microcystis , Poluentes Químicos da Água , Purificação da Água , Adsorção , Carvão Vegetal , Desinfecção , Pós , Trialometanos/análise , Poluentes Químicos da Água/análise
18.
J Environ Manage ; 282: 111951, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33461088

RESUMO

Algal organic matter (AOM) and natural organic matter (NOM) from a typical eutrophic lake were comprehensively investigated in terms of their physico-chemical property, components and disinfection byproduct formation potentials (DBPFPs). The relationships between specific chemical properties of AOM and NOM with their corresponding DBPFPs were further evaluated during chlorination. Results indicated that AOM had lower specific UV absorbance (SUVA) but richer organic nitrogen contents than NOM. Fluorescence excitation emission matrix spectroscopy further demonstrated that AOM were chiefly composed of aromatic protein-like and soluble microbial byproduct-like matters, while NOM were mainly contributed from humic acid-like and soluble microbial byproduct-like substances. Although the molecular weight (MW) distribution of AOM and NOM showed no significant difference, size-exclusion chromatography with organic carbon as well as organic nitrogen detection (LC-OCD-OND) revealed that AOM were concentrated with the fraction of building blocks and NOM had higher concentrations of biopolymers and humics (HS). Moreover, AOM displayed higher DBPFPs than NOM, especially for nitrogenous DBPFP (N-DBPFP). MW < 1 kDa fractions both in AOM and NOM contributed the largest proportion to the formation of carbonaceous disinfection byproducts (C-DBPs). In addition, Pearson correlation analysis showed that bulk parameter SUVA was significantly relevant to the formation potentials of trihalomethane both in AOM and NOM, but was ineffective for carbonaceous DBPFP (C-DBPFP) prediction. Dissolved organic nitrogen contents in biopolymer and HS characterized by LC-OCD-OND had strong correlations with N-DBPFPs from AOM and NOM, indicating that LC-OCD-OND quantitative analysis could improve the prediction accuracy of the DBP formation than bulk parameters during NOM and AOM chlorination.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Desinfecção , Halogenação , Nitrogênio/análise , Trialometanos/análise , Poluentes Químicos da Água/análise
19.
Chemosphere ; 268: 129307, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33359988

RESUMO

Reverse osmosis (RO), a promising technology for removing inorganic salts and a wide range of trace organic pollutants, is widely used in water treatment industry. In this study, the rejection of chlorinated, brominated, and iodinated trihalomethanes (THMs) by a multi-stage RO system was investigated. The results showed that the multi-stage RO system is effective in rejecting THMs, and THMs with large size, high hydrophobicity and low polarity were highly rejected. In the first stage, high percentage of THMs was adsorbed on RO membrane, and the THM rejection was dominated by both hydrophobic adsorption and size exclusion. The contribution of hydrophobic adsorption to THM rejection decreased significantly along RO stages due to decreased feed concentration, but the enhancement of size exclusion still ensured high rejection efficiencies for most THMs, indicating a compensation effect between two rejection mechanisms. Finally, to further understand the rejection in the multi-RO system from a perspective of THM property, multiple linear regression models were built. The impact of n-octanol-water partition coefficient (Log Kow) was slightly higher than that of stokes radius in the first stage, which was consistent with the rejection mechanism. But dipole moment played an increasingly important role in the second and third stage, weakening the impact of Log Kow on THM rejection.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Filtração , Osmose , Trialometanos/análise , Poluentes Químicos da Água/análise
20.
Chemosphere ; 268: 129340, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33360939

RESUMO

Bromate (BrO3-) is a predominant undesired toxic disinfection by-product (DBP) during ozonation of bromide-containing waters. The reduction of BrO3- by zero valent iron (ZVI) and its effect on formation of organic halogenated DBPs during chlorination were investigated in this study. The presence of ZVI could reduce BrO3- to bromide (Br-), and Br- formed could be transformed to free bromine (HOBr/OBr-) during chlorination, further leading to organic brominated (Br-) DBPs formation. Formation of DBPs during chlorination, including trihalomethanes (THMs) and haloacetonitriles (HANs) was detected under different conditions. The results showed that when ZVI dosage increased from 0 to 1 g L-1, the formation of Br-DBPs (e.g., TBM and DBCM) was significantly improved, while the formation of Cl-DBPs (e.g., TCM, TCAN and DCAN) reduced. Higher ZVI dosage exhibited inhibitory effect on Br-DBPs formation due to the competition between ZVI and free chlorine (HOCl/OCl-). The bromine substitution factor (BSF) of THMs significantly decreased from 0.61 ± 0.06 to 0.22 ± 0.02, as the pH was raised from 5.0 to 9.0. Besides, the increase of initial BrO3- concentration significantly improved the formation of Br-DBPs and decreased the formation of Cl-DBPs, leading to an obvious rise on the BSF of THMs. As the initial concentration of HOCl increased, all THMs and HANs gradually increased. Moreover, the analysis based on the cytotoxicity index (CTI) of the determined DBPs showed that reduction of BrO3- by ZVI during chlorination had certain risks in real water sources, which should be paid attention to in the application.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Bromatos , Brometos , Desinfecção , Halogenação , Ferro , Trialometanos , Poluentes Químicos da Água/análise
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