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1.
Environ Sci Technol ; 55(8): 5547-5558, 2021 04 20.
Artículo en Inglés | MEDLINE | ID: mdl-33788559

RESUMEN

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.


Asunto(s)
Bromatos , Trihalometanos , Sulfuros
2.
Zhonghua Yu Fang Yi Xue Za Zhi ; 55(3): 418-423, 2021 Mar 06.
Artículo en Chino | MEDLINE | ID: mdl-33730838

RESUMEN

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.


Asunto(s)
Desinfectantes , Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , Desinfectantes/toxicidad , Desinfección , Agua Potable/análisis , Humanos , Trihalometanos , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidad
3.
Water Res ; 194: 116964, 2021 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-33652228

RESUMEN

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.


Asunto(s)
Desinfectantes , Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , Cloro , Desinfectantes/análisis , Desinfección , Halogenación , Aguas del Alcantarillado , Trihalometanos , Contaminantes Químicos del Agua/análisis
4.
Sci Total Environ ; 771: 144885, 2021 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-33736131

RESUMEN

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.


Asunto(s)
Desinfectantes , Contaminantes Químicos del Agua , Purificación del Agua , Cloro , Desinfección , Halogenación , Fenilalanina , Trihalometanos , Contaminantes Químicos del Agua/análisis
5.
Sci Total Environ ; 770: 144767, 2021 May 20.
Artículo en Inglés | MEDLINE | ID: mdl-33736400

RESUMEN

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.


Asunto(s)
Desinfectantes , Agua Potable , Ozono , Contaminantes Químicos del Agua , Purificación del Agua , Desinfectantes/análisis , Desinfección , Halogenación , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis
6.
Sci Total Environ ; 774: 145297, 2021 Jun 20.
Artículo en Inglés | MEDLINE | ID: mdl-33611000

RESUMEN

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).


Asunto(s)
Agua Potable , China , Desinfección , Agua Potable/análisis , Análisis Factorial , Sustancias Húmicas/análisis , Espectrometría de Fluorescencia , Trihalometanos/análisis
7.
Environ Sci Technol ; 55(5): 2908-2918, 2021 03 02.
Artículo en Inglés | MEDLINE | ID: mdl-33594894

RESUMEN

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.


Asunto(s)
Desinfectantes , Piscinas , Contaminantes Químicos del Agua , Animales , Cloro , Cobre/toxicidad , Desinfectantes/toxicidad , Desinfección , Plata , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidad
8.
Environ Sci Technol ; 55(7): 4103-4114, 2021 04 06.
Artículo en Inglés | MEDLINE | ID: mdl-33523638

RESUMEN

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.


Asunto(s)
Desinfectantes , Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , China , Desinfectantes/análisis , Desinfección , Agua Potable/análisis , Humanos , Pandemias , Trihalometanos/análisis , Aguas Residuales , Agua , Contaminantes Químicos del Agua/análisis
9.
Water Res ; 193: 116851, 2021 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-33540343

RESUMEN

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.


Asunto(s)
Contaminantes Químicos del Agua , Purificación del Agua , Desinfección , Halogenación , Yodatos , Yoduros , Fotólisis , Trihalometanos/análisis , Agua , Contaminantes Químicos del Agua/análisis
10.
Environ Sci Technol ; 55(3): 1545-1554, 2021 02 02.
Artículo en Inglés | MEDLINE | ID: mdl-33449615

RESUMEN

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.


Asunto(s)
Fracking Hidráulico , Contaminantes Químicos del Agua , Halogenación , Halógenos , Compuestos Orgánicos , Trihalometanos
11.
Environ Sci Technol ; 55(3): 1790-1799, 2021 02 02.
Artículo en Inglés | MEDLINE | ID: mdl-33492937

RESUMEN

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.


Asunto(s)
Desinfectantes , Contaminantes Químicos del Agua , Purificación del Agua , Cloro , Desinfección , Halogenación , Histidina , Péptidos , Trihalometanos , Contaminantes Químicos del Agua/análisis
12.
Chemosphere ; 272: 129568, 2021 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-33476791

RESUMEN

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.


Asunto(s)
Desinfectantes , Contaminantes Químicos del Agua , Purificación del Agua , Cloraminas , Desinfección , Halogenación , Yopamidol , Hierro , Trihalometanos , Agua , Contaminantes Químicos del Agua/análisis
13.
J Environ Manage ; 282: 111951, 2021 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-33461088

RESUMEN

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.


Asunto(s)
Contaminantes Químicos del Agua , Purificación del Agua , Desinfección , Halogenación , Nitrógeno/análisis , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis
14.
Chemosphere ; 263: 127862, 2021 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-32814132

RESUMEN

Haloacetic acids (HAAs) are a group of disinfection by-products formed by the reaction of dissolved organic matter (DOM) in source water and disinfectants in the drinking water treatment process. The formation of HAAs is known to be affected by several factors (e.g., pH, temperature, concentration, and DOM components in source water). However, the effects of coexisting substances, such as metal ions, on HAA formation are not well understood. In this study, HAA formation potentials (FPs) of model compounds of DOM and environmental waters in the presence or absence of manganese ion upon chlorination were compared. The results of experiments with model compounds of DOM showed that manganese ion promoted the formation of HAA from citric acid, trans-aconitic acid, and cis-aconitic acid. Even for a manganese concentration of less than 50 µg/L, which is the standard value of manganese in drinking water in the USA, EU, and Japan, manganese had great influence on the dichloroacetic acid FPs of these compounds. However, the manganese ion did not enhance the HAAFPs of the environmental waters tested. Nevertheless, manganese may have an effect on HAAFPs of environmental waters collected at the occurrence of an unusual growth of microorganisms, such as algal bloom.


Asunto(s)
Desinfectantes , Contaminantes Químicos del Agua , Purificación del Agua , Desinfección , Halogenación , Iones , Japón , Manganeso , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis
15.
Chemosphere ; 263: 128094, 2021 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-33297090

RESUMEN

Both organic and inorganic precursors play important roles in the formation and speciation of disinfection by-products (DBPs). This study aimed to investigate the efficacy of three different anion exchange resins for removing both organic and inorganic DBP precursors simultaneously in a single treatment system. Resins in the single (Purolite®-Br, MIEX®-Br, and MIEX®-Gold) and mixed (Purolite®-Br with MIEX®-Gold and MIEX®-Br with MIEX®-Gold) application modes were tested and compared for the removal of dissolved organic carbon (DOC), bromide (Br-), and iodide (I-) from a raw source water and a treated wastewater effluent. Uniform formation condition (UFC) tests were conducted to measure the concentrations of trihalomethanes (THM4), haloacetic acids (HAA9), haloacetonitriles (HAN6), and total organic halides (TOX): total organic chlorine (TOCl), total organic bromine (TOBr), and total organic iodine (TOI) before and after the anion exchange resin treatments. The anion exchange treatment substantially lowered the DOC, UV254 absorbing matter, dissolved nitrogen (DN), Br-, and I-. Consequently, the formation of THM4, HAA9, HAN6, and TOX in the examined chlorinated water samples were reduced significantly. The maximum reduction in THM4 and TOX (66-69% and 61%, respectively) from wastewater effluent was achieved by the mixed resin system, which also reduced the THM4 and TOX by 77% and 77%, respectively, from raw source water. Overall, mixed resin systems (a DOC-selective and a Br-selective resin) resulted in lower amounts of THM4 and HAA9 formation during subsequent chlorination with lower bromine incorporation as compared to single resin systems. Furthermore, they exhibited lower TOBr formation, while TOI formation was not detected.


Asunto(s)
Desinfectantes , Contaminantes Químicos del Agua , Purificación del Agua , Resinas de Intercambio Aniónico , Desinfección , Halogenación , Trihalometanos/análisis , Aguas Residuales , Contaminantes Químicos del Agua/análisis
16.
Sci Total Environ ; 752: 141470, 2021 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-32889255

RESUMEN

Many traditional drinking water treatment processes have limited removal efficiencies on natural organic matter (NOM) and organic micropollutants (OMPs), and thus may lead to the production of harmful disinfection byproducts (DBPs). We examined four kinds of anion exchange resins (D205, D213, NDMP-3, and M80) in conjunction with chlorination in the treatment of drinking water. Five categories including 40 OMPs at environmentally relevant concentrations were analyzed. M80 showed the best performance to remove OMPs in water. However, it was vulnerable to the presence of humic acid (HA), indicating its limitation on removing OMPs and NOM at the same time. In contrast, D205, D213, NDMP-3 resins were less affected by HA. Besides, D205, D213 and NDMP-3 provided higher efficiencies on the reduction of DBPs than M80. The amount of trihalomethanes (THMs) lowered by 42.7%, 37.6%, 32.1%, and 0%, whereas haloacetic acids (HAAs) were decreased by 34.0%, 31.2%, 23.0%, and 17.9% by D205, D312, NDMP-3, and M80. Notably, D205 showed the highest removal effects on the bromide ion, brominated THMs, and HAAs, supporting that D205 can be a selective resin for the treatment of drinking water in high bromide-containing areas.


Asunto(s)
Desinfectantes , Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , Desinfección , Halogenación , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis
17.
Sci Total Environ ; 763: 144197, 2021 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-33383504

RESUMEN

Drinking water treatment plants (DWTPs) face changes in raw water quality, which affect the formation of disinfection by-products. Several empirical modelling approaches have been reported in the literature, but most of them have been developed with lab-scale data, which may not be representative of real water systems. Therefore, the application of these models for real-time operation of DWTPs might be limited. At the present study, multiple linear regression (MLR) and multi-layer perceptrons (MLP) were benchmarked using field-scale data for predicting the THMs formation in a case-study DWTP in Barcelona, Spain. After fitting the studied models, MLR exhibited good fit with the validation data set (R2 = 0.88 and MAE = 4.0 µg·L-1) and described the most plausible input-output relationships with field-scale data. The MLR predictive model was incorporated into an environmental decision support system (EDSS) for assessing the THMs formation at two critical points of the distribution network. A Monte Carlo scheme was applied for quantifying uncertainty of model predictions at these points, considering low and high water quality scenarios and different degrees of treatment by an electrodialysis reversal process. The results show that the use of the proposed EDSS can help in real operation of complex drinking water systems, which face important changes in water quality throughout the year.


Asunto(s)
Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , Benchmarking , Desinfección , Agua Potable/análisis , España , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis
18.
Water Res ; 190: 116712, 2021 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-33310438

RESUMEN

Controlling disinfection by-products formation while ensuring effective drinking water disinfection is important for protecting public health. However, understanding and predicting disinfection by-product formation under a variety of conditions in drinking water distribution systems remains challenging as disinfection by-product formation is a multifactorial phenomenon. This study aimed to assess the application of Bayesian Network models to predict the concentration of trihalomethanes, the dominant halogenated disinfection by-product class, using various water quality parameters. Naïve Bayesian and semi-naïve Bayesian models were constructed from Sydney and South East Queensland datasets across 15 drinking water distribution systems in Australia. The targeted variable, total trihalomethanes concentration, was discretised into 3 bins (<0.1 mg L-1, 0.1 - 0.2 mg L-1 and >0.2 mg L-1). The Bayesian network structures were built using water quality parameters including concentrations of individual and total trihalomethanes, disinfectant species (free chlorine, monochloramine, dichloramine, total chlorine), nitrogen species (free ammonia, total ammonia, nitrate, nitrite), and other physical/chemical parameters (temperature, pH, dissolved organic carbon, total dissolved solids, conductivity and turbidity). Seven performance parameters, including predictive accuracy and the rates of true and false positive and negative results, were used to assess the accuracy and precision of the Bayesian network models. After evaluating the model performance, the optimum models were selected to be Bayesian network augmented naïve models. These were observed to have the highest predictive accuracies for Sydney (78%) and South East Queensland (94%). Although disinfectant residuals are among the key variables that lead to trihalomethanes formation, potential concentrations of trihalomethanes in distribution systems can be more confidently predicted, in terms of probability associated with a wider range of water quality variables, using Bayesian networks. The modelling procedure developed in this work can now be applied to develop system-specific Bayesian network models for trihalomethanes prediction in other drinking water distribution systems.


Asunto(s)
Desinfectantes , Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , Australia , Teorema de Bayes , Cloro , Desinfección , Agua Potable/análisis , Halogenación , Queensland , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis , Calidad del Agua
19.
Sci Total Environ ; 762: 144159, 2021 Mar 25.
Artículo en Inglés | MEDLINE | ID: mdl-33360458

RESUMEN

Field studies were conducted in a Croatian city supplied by two distinct groundwater sources (referred to as A and B) to investigate both the effects of changing water source on the water quality in the drinking water supply system, as well as to further understand discoloration events that occurred in city locations that switched water from source A to B. The water treatment processes at site A were found to alter organic matter (OM) characteristics, removing humic substances while enhancing protein-derived (tryptophan) content. Although the humic-like component predominated in raw waters, microbially/protein-derived components were found to increase throughout the distribution networks of both systems. Disinfection byproducts (DBPs) such as total trihalomethane (TTHM) and total haloacetic acid (THAA) were prevalent in water distribution system (WDS)-A, which correlated with elevated OM content as well as re-chlorination with hypochlorite (NaOCl). Our field study revealed that THMs were more readily formed than HAAs during ClO2 treatment. Unsurprisingly, chlorite concentrations were generally higher than chlorate concentrations during ClO2 treatment, whereas (secondary) NaOCl disinfection contributed to higher chlorate production. Principal component analysis indicated that variable pH values and humic-like OM could affect Mn, As and Al concentrations at the consumer's tap. Our results suggested that although Mn concentrations complied with regulations at WDS-B and were below 50 µg/L after disinfection, Mn was oxidized and formed particulate Mn oxides capable of causing discoloration events depending on prevailing network physico-chemical and hydraulic conditions. Aluminium also appears to be released during hydraulic disturbances from extensive deposits within the network. Thermodynamic calculations showed that Mn-oxidation was strongly dependent upon the ORP, and to lesser extent the pH value. Collectively, our results confirm that ensuring the provision of safe drinking waters to consumers requires an understanding of water quality across entire distribution networks in addition to any routine post-treatment monitoring.


Asunto(s)
Desinfectantes , Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , Desinfectantes/análisis , Desinfección , Agua Potable/análisis , Halogenación , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis , Calidad del Agua , Abastecimiento de Agua
20.
Water Res ; 188: 116523, 2021 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-33125996

RESUMEN

Design and operation of drinking water treatment plants and associated distribution systems with long residence times are complicated by the formation of regulated disinfection byproducts (DBPs), comprised of total trihalomethanes (TTHM) and five haloacetic acids (HAA5). Treated water dissolved organic carbon (DOC) concentrations, the unit processes required to meet those DOC concentrations, and disinfection strategies (e.g., booster chlorination) are the primary design and operational considerations that can require extensive testing or modeling to determine. In this study, twelve different treated drinking waters were generated at the bench-scale using ferric chloride coagulation and granular activated carbon adsorption from four parent raw waters collected from the San Juan River representing spring runoff, monsoon, and low flow events. Treated drinking waters with DOC concentrations of 0.9, 1.4, and 1.9 mg/L were tested for regulated DBP formation under simulated distribution system (SDS) conditions over residence times as long as 56 days and compared to 7-day formation potential (FP) testing. SDS free chlorine concentrations were maintained between 0.2 and 1.0 mg/L as Cl2 through periodic booster chlorination. Maximum SDS TTHM and HAA5 concentrations were 0.208 and 0.074 mg/L, respectively, with formation consistently varying by approximately ±20% across the four different parent raw waters despite having been treated to the same three DOC concentrations. An average of four existing TTHM models consistently underpredicted TTHM formation by approximatively 20%. Long considered a conservative measure of DBP formation, FP testing also underpredicted SDS DBP formation at 56 days by approximately 40% on average. The DBP testing approach presented in this study allowed for the development of several significant linear relationships for predicting DBP concentrations based on treated water ultraviolet light absorbance at 254 nm, water temperature, and cumulative free chlorine demand.


Asunto(s)
Desinfectantes , Contaminantes Químicos del Agua , Purificación del Agua , Cloro , Desinfección , Halogenación , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis
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