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1.
Braz. j. biol ; 84: e255755, 2024. tab, graf
Artículo en Inglés | MEDLINE, LILACS, VETINDEX | ID: biblio-1355898

RESUMEN

Abstract The present study involves the chemical and bacteriological analysis of water from different sources i.e., bore, wells, bottle, and tap, from Peshawar, Mardan, Swat and Kohat districts of Khyber Pakhtunkhwa (KP) province, Pakistan. From each district, 50 water samples (10 samples from each source), regardless of urban and rural status, were collected from these sources and analysed for sulphates, nitrates, nitrites, chlorides, total soluble solids and coliforms (E. coli). Results indicated that majority of the water sources had unacceptable E. coli count i.e.> 34 CFU/100mL. E. coli positive samples were high in Mardan District, followed by Kohat, Swat and Peshawar district. Besides this, the some water sources were also chemically contaminated by different inorganic fertilizers (nitrates/nitrites of sodium, potassium) but under safe levels whereas agricultural and industrial wastes (chloride and sulphate compounds) were in unsafe range. Among all districts, the water quality was found comparatively more deteriorated in Kohat and Mardan districts than Peshawar and Swat districts. Such chemically and bacteriologically unfit water sources for drinking and can cause human health problems.


Resumo O presente estudo envolve a análise química e bacteriológica de água de diferentes fontes, ou seja, furo, poços, garrafa e torneira, dos distritos de Peshawar, Mardan, Swat e Kohat da província de Khyber Pakhtunkhwa (KP), Paquistão. De cada distrito, 50 amostras de água (10 amostras de cada fonte), independentemente do status urbano e rural, foram coletadas dessas fontes e analisadas para sulfatos, nitratos, nitritos, cloretos, sólidos solúveis totais e coliformes (E. coli). Os resultados indicaram que a maioria das fontes de água tinha uma contagem inaceitável de E. coli, ou seja, > 34 UFC / 100 mL. As amostras positivas para E. coli foram elevadas no distrito de Mardan, seguido por Kohat, Swat e distrito de Peshawar. Além disso, algumas fontes de água também foram contaminadas quimicamente por diferentes fertilizantes inorgânicos (nitratos/nitritos de sódio, potássio), mas em níveis seguros, enquanto os resíduos agrícolas e industriais (compostos de cloreto e sulfato) estavam em níveis inseguros. Entre todos os distritos, a qualidade da água foi considerada comparativamente mais deteriorada nos distritos de Kohat e Mardan do que nos distritos de Peshawar e Swat. Essas fontes de água química e bacteriologicamente impróprias para beber podem causar problemas à saúde humana.


Asunto(s)
Humanos , Agua Potable , Calidad del Agua , Pakistán , Escherichia coli
2.
Sci Total Environ ; 838(Pt 3): 156406, 2022 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-35660589

RESUMEN

Granular activated carbon (GAC) was harvested from six filter-adsorbers that are used for taste and odour control in three drinking water treatment plants in Ontario, Canada, and evaluated for the removal of perfluorooctanic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) using minicolumn tests under different operational conditions. Parallel column tests were conducted using unsterilized GAC and sterilized GAC to distinguish adsorption from potential biodegradation of PFOA and PFOS across the GAC. It was observed that the GAC could achieve approximately 20% to 55% of PFOA and PFOS removal even after a long period of GAC operation (e.g., 6 years). There was no evidence of PFOA and PFOS biodegradation, so the removal in GAC can be attributed solely to adsorption under the conditions tested. However, in one location, there was evidence suggesting both removal and formation of PFOS and PFOA across the GAC, with the formation presumably due to the biotransformation of pre-existing precursors in the source water. Additionally, GAC service time and empty bed contact time (EBCT) were identified to be important factors that could affect the removal of PFOA and PFOS. Based on this information, an empirical model was proposed to predict PFOA and PFOS removal in GAC filter-adsorbers as a function of GAC service time and EBCT. This study provides useful information for utilities that have installed GAC for taste and odour control but may consider per- and polyfluoroalkyl substances (PFAS) removal as an additional voluntary objective or due to more stringent guidelines.


Asunto(s)
Agua Potable , Fluorocarburos , Contaminantes Químicos del Agua , Purificación del Agua , Adsorción , Ácidos Alcanesulfónicos , Caprilatos , Carbón Orgánico , Fluorocarburos/análisis , Ontario , Contaminantes Químicos del Agua/análisis
3.
Sci Total Environ ; 838(Pt 3): 156465, 2022 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-35660623

RESUMEN

The release of vanadium (V) from drinking water distribution systems (DWDS) can endanger water quality and human health. Therefore, in this study, the physicochemical characteristics of old steel pipe scales were analyzed, and dynamic pipeline devices were constructed. Subsequently, static release experiments were conducted to find an optimum scale-water ratio and investigate the release behaviors of V in lumpy pipe scales. Besides, the release behaviors of V from layered pipe scales to bulk, steady, and occluded water under the combined effect of multiple water quality conditions were studied for the first time. Computational fluid dynamics (CFD) was adopted to explain the release behaviors of V in the dynamic pipeline. Results revealed that the adsorption performance of the layered scales decreased in the order of surface layer > porous core layer > hard shell-like layer. The release behaviors of V in the lumpy pipe scales were mainly divided into rapid desorption and colloidal agglomeration stages. The Double constant and Weber-Morris models can suitably describe release stage I (R2 > 0.919) and release stage II (R2 > 0.948), respectively. Notably, the release of V was aggravated by low pH, high temperature, and high SO42- concentration, and the release amount of V in the pipeline was more significant than the layered pipe scales. Steady water in the gaps of scales contained more V than bulk water, and the malignant occluded water encased in scales contained relatively low V concentrations. In short, the main mechanism of V release was competitive adsorption in the early stage, and pH was the main influencing factor in the later stage. The above results are of great significance for revealing the release behaviors of V and reducing its release in DWDS.


Asunto(s)
Agua Potable , Contaminantes Químicos del Agua , Corrosión , Humanos , Hierro , Acero , Vanadio , Contaminantes Químicos del Agua/análisis , Abastecimiento de Agua
4.
Sci Total Environ ; 838(Pt 3): 156500, 2022 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-35675884

RESUMEN

Risk-informed decision making permits a more effective water safety management. In this framework, this article introduces the rationale and proposes a new approach to carry out a quantitative risk assessment along the water chain, from river source to tap water, by integrating predictive modelling combined with event-tree and fault-tree techniques. The model developed by this approach could not only account for normal but also for abnormal process conditions in the water treatment plant, as well as assess the real impact of the applied safety controls, such as turbidity control. A sensitivity study was conducted to determine the effect of considering a typical drinking water treatment plant (DWTP), i.e. coagulation, sedimentation and filtration with two turbidity controls (on intake and after filtration) on the risk of infection due to exposure to Cryptosporidium in tap water. The results showed that, with the current effectiveness of turbidity reduction in the DWTP, the first control did not minimise the annual risk of Cryptosporidium infection (3.6E-04) and only limiting turbidity after filtration to below 0.01NTU provided a clear reduction in risk (7.7E-05) at the cost of rejecting 60 % of the water after the control. The lowest risk was found when turbidity reduction was set at 4 logs (8.48E-06), although this means that the effectiveness of turbidity reduction should be greatly improved. It was therefore concluded that supplementing the current treatment with alternative barriers such as UV or ozone disinfection and/or implementing direct control of Cryptosporidium concentration should be considered.


Asunto(s)
Criptosporidiosis , Cryptosporidium , Agua Potable , Purificación del Agua , Humanos , Medición de Riesgo , Abastecimiento de Agua
5.
Sci Total Environ ; 838(Pt 3): 156541, 2022 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-35679920

RESUMEN

Dissolved oxygen (DO) dynamics of a temperate drinking water reservoir in the Harz Mountains (Germany) were investigated over a time period of 18 months. Via depth profiles in a fortnightly sampling resolution we were able to trace DO and temperature dynamics including the formation and breakdown of a Metalimnetic Oxygen Minimum (MOM) by means of DO concentration, saturation patterns and stable isotope ratios of dissolved oxygen (expressed as δ18ODO). Over the evaluation period, 19.4 % of the samples collected had δ18ODO values compatible with atmospheric equilibration (+24.6 ‰ ± 0.4 ‰). With values smaller and larger than this threshold, the remaining δ18ODO values showed that 40.8 % of our samples were dominated by photosynthesis and 39.8 % by respiration. From December to April the reservoir was mixed and DO consumption by respiration exceeded production via photosynthesis. During stratification period, quantification of respiration/photosynthesis rates (R/P) confirmed the epilimnion as a photosynthetic (i.e. net-autotrophic) environment while the hypolimnion was heterotrophic and dominated by respiration at various degrees. Samples of the MOM zone showed the highest R/P ratios and had among the most positive δ18ODO signals caused by respiration. This study showed that combinations of DO concentrations and their isotope ratios are promising to quantify critical zones of respiration and photosynthesis in aquatic environments.


Asunto(s)
Agua Potable , Oxígeno , Isótopos de Carbono/análisis , Isótopos , Oxígeno/análisis , Consumo de Oxígeno , Isótopos de Oxígeno/análisis , Temperatura
6.
J Hazard Mater ; 436: 129011, 2022 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-35643007

RESUMEN

Microplastics detected in potable water sources and tap water have led to concerns about the efficacy of current drinking water treatment processes to remove these contaminants. It is hypothesized that drinking water resources contain nanoplastics (NPs), but the detection of NPs is challenging. We, therefore, used palladium (Pd)-labeled NPs to investigate the behavior and removal of NPs during conventional drinking water treatment processes including ozonation, sand and activated carbon filtration. Ozone doses typically applied in drinking water treatment plants (DWTPs) hardly affect the NPs transport in the subsequent filtration systems. Amongst the different filtration media, NPs particles were most efficiently retained when aged (i.e. biofilm coated) sand was used with good agreements between laboratory and pilot scale systems. The removal of NPs through multiple filtration steps in a municipal full-scale DWTP was simulated using the MNMs software code. Removal efficiencies exceeding 3-log units were modeled for a combination of three consecutive filtration steps (rapid sand filtration, activated carbon filtration and slow sand filtration with 0.4-, 0.2- and 3.0-log-removal, respectively). According to the results from the model, the removal of NPs during slow sand filtration dominated the overall NPs removal which is also supported by the laboratory-scale and pilot-scale data. The results from this study can be used to estimate the NPs removal efficiency of typical DWTPs with similar water treatment chains.


Asunto(s)
Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , Carbón Orgánico , Filtración , Microplásticos , Plásticos , Arena , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos
7.
Sci Total Environ ; 839: 156228, 2022 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-35643141

RESUMEN

AC-supported nanoscale zero-valent iron composites (nZVI/AC) exhibit significant environmental implications for trihalomethanes (THMs)-contaminated water remediation. To improve the adsorption and degradation capability of AC, herein, a composite (nZVI/Ag@AC-RGO) consisting of AC, reduced graphene oxide (RGO), nanoscale zero-valent iron (nZVI), and silver (Ag) was synthesized and characterized using several techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption-desorption isotherms, and X-ray photoelectron spectroscopy (XPS). The analysis of textural and morphological structures showed that a tightly-attached RGO film, amorphous iron, and weak crystal silver nanoparticles with a size of 20-30 nm were evenly immobilized on the support. Specific surface area increased by 19.12% after supporting RGO, while it decreased after supporting nZVI and Ag due to the partial blockage of micropores. The Fe surface was concurrently coated by iron oxides (Fe2O3, FeOOH) and Ag. THMs were eliminated through multilayer reaction processes. The values of the adsorption constant (KF) of chloroform (CHCl3), dichlorobromoethane (CHBrCl2), dibromochloroethane (CHBr2Cl), and tribromomethane (CHBr3) adsorbed by nZVI/Ag@AC-RGO increased by 34.4, 33.7, 81.6, and 67.3%, respectively, compared to pristine AC. THMs with more Br atoms exhibited better removal efficiency and adsorption capacity, along with a higher oxidation degree of the Fe surface. CHBrCl2 and CHBr2Cl mainly decomposed into chloromethane (CH3Cl) and dichloromethane (CH2Cl2), and CHBr3 and CHCl3 primarily degraded into dibromomethane (CH2Br2) and CH2Cl2, respectively, along with generating Cl- and Br-. Conclusively, THMs-contaminated water could be remediated by coupling AC pre-enrichment and the reactivity of nZVI/Ag.


Asunto(s)
Agua Potable , Nanopartículas del Metal , Contaminantes Químicos del Agua , Adsorción , Carbón Orgánico/química , Grafito , Hierro/química , Plata , Trihalometanos , Contaminantes Químicos del Agua/análisis
8.
Chemosphere ; 303(Pt 3): 135208, 2022 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-35667500

RESUMEN

The primary source of heavy metal discharge into the water is human activity and urbanization near water bodies. Contamination of drinking water sources with heavy metals has a harmful impact on the environment and human health. The most commonly used heavy metals are Zinc (Zn), Copper (Cu), Nickel (Ni), Lead (Pb), Cadmium (Cd), Chromium (Cr), Arsenic (As), Mercury (Hg), etc. The heavy metal ions are easily absorbed by living things via water and spread throughout the food chain, posing a threat to humans, plants, and animals (Zhang et al., 2018; Lu et al., 2019; Ma et al., 2020; Gao et al., 2018; Wen et al., 2018; Saranya et al., 2021). Colorimetric sensing is a simple and cost-effective method for the detection of heavy metal ions. Moreover, the results can be analysed with naked eye. In this work, Ag doped ZnO nanoparticles synthesized via co-precipitation method are used for the colorimetric detection of heavy metal ions. The nanoparticles are characterized for their morphology, structural, and chemical analysis using XRD, SEM, EDS, and XPS techniques. The synthesized nanoparticles are used for the colorimetric detection of heavy metal ions. The heavy metal ions such as Ni2+, Cu2+, Cr3+, Cr6+, Fe2+, and Fe3+ are successfully detected and the color change is visible from the naked eye. The minimum concentration detected is found to be 100 µM. The results are analysed via UV-vis spectroscopy. In addition to detection, the nanoparticles are further used as catalyst during the degradation of above detected heavy metal ions using NaBH4. All the heavy metal ions are degraded with in the duration of 30 min. Thus, the Ag doped ZnO nanoparticles successfully detected the heavy metal ions in aqueous solution and also acted as a catalyst during their degradation.


Asunto(s)
Agua Potable , Mercurio , Nanopartículas del Metal , Metales Pesados , Nanopartículas , Óxido de Zinc , Animales , Cromo/análisis , Colorimetría/métodos , Agua Potable/análisis , Iones , Mercurio/análisis , Nanopartículas del Metal/química , Metales Pesados/análisis , Níquel/análisis , Análisis Espectral
9.
Chemosphere ; 303(Pt 3): 135256, 2022 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-35679981

RESUMEN

Contamination of drinking water by carcinogen arsenic (As) is of worldwide concern as its exposure poses potential threat to human health. As such, it is important to understand the mechanisms associated with As-induced toxicity to humans. The Nrf2/Keap1 signal pathway is one of the most important defense mechanisms in cells to counter oxidative stress; however, limited information is available regarding its role in countering As-induced stress in model animal mouse. In this study, we assessed the responses of Nrf2/keap1 pathway in mice after chronic exposure to As at environmentally-relevant concentrations of 10-200 µg L-1 for 30 days via drinking water. Our results indicate that chronic As exposure had limited effect on mouse growth. However, As induced oxidative stress to mice as indicated by increased content of malondialdehyde (MDA; 52-90%), an index of lipid peroxidation. Further, arsenic exposure reduced the activity of superoxide dismutase (SOD; 14-18%), an indication of reduced anti-oxidative activity. Besides, arsenic exposure increased MnSOD mRNA transcription by 25-66%, and decreased the mRNA transcriptions of Cu/ZnSOD by 72-83% and metallothionein by 16-75%, a cysteine-rich protein involved in metal detoxification. To counter arsenic toxicity, the expression of transcription factor for Nrf2 and Keap1 was increased by 2.8-8.9 and 0.2-8.1 fold in mice. To effectively reduce As-induced oxidative stress, the Nrf2/Keap1 transcription factor upregulated several downstream anti-oxidative genes, including heme oxygenase-1 (0.9-2.5 fold), glutamate-cysteine ligase catalytic subunit (0.6-1.7 fold), and NADH quinone dehydrogenase 1 (2.1-4.8 fold). This study shows the importance of Nrf2/Keap1 signaling pathway and associated anti-oxidative enzymes in countering As-toxicity in mice, possibly having implication for human health.


Asunto(s)
Arsénico , Agua Potable , Animales , Arsénico/metabolismo , Agua Potable/metabolismo , Proteína 1 Asociada A ECH Tipo Kelch/genética , Proteína 1 Asociada A ECH Tipo Kelch/metabolismo , Ratones , Factor 2 Relacionado con NF-E2/metabolismo , Estrés Oxidativo , ARN Mensajero/metabolismo
10.
J Infect Dev Ctries ; 16(5): 843-849, 2022 05 30.
Artículo en Inglés | MEDLINE | ID: mdl-35656956

RESUMEN

INTRODUCTION: Outbreaks of acute watery diarrhoea are common in developing countries having poor access to safe drinking water and sanitation. An outbreak of acute watery diarrhoea in a village in North India was investigated with the aim to initiate and recommend necessary actions to control it. METHODOLOGY: A house to house survey using a specially designed case record form was conducted covering all the households. Stool samples of some of the affected individuals and twenty water samples during and after the outbreak from various sites were collected for laboratory analysis. RESULTS: Out of 624 inhabitants surveyed, 118 were found to be suffering from acute watery diarrhoea (Overall attack rate of 18.9%) with two suspected deaths following diarrhoea. Males and females were affected equally and the age group of 15-44 years was affected predominantly. A peculiar epidemic curve with single peak was noted. One of the stool samples collected during the outbreak grew Vibrio Cholera O1(Ogawa) and twelve out of the twenty water samples including the samples from both the tube wells had high coliform counts indicating fecal contamination. Chlorine levels in all the water samples were found to be inadequate. CONCLUSIONS: Local cultural practices such as indiscriminate defecation in public places, using tullu pumps to extract water from the public supply line, poor engineering design and maintenance of the water supply system having leakages at many sites along with inadequate chlorination of the supply water from the tube wells were the risk factors that could have contributed to this outbreak.


Asunto(s)
Cólera , Agua Potable , Adolescente , Adulto , Cólera/epidemiología , Diarrea/epidemiología , Brotes de Enfermedades , Femenino , Humanos , India/epidemiología , Masculino , Adulto Joven
11.
Environ Monit Assess ; 194(7): 502, 2022 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-35704104

RESUMEN

Twelve major hydro-geochemical parameters derived from about 1134 water samples were studied to understand spatial variation of groundwater quality in the coastal state of Odisha. Multivariate statistical analysis techniques, i.e., cluster analysis and principal component analysis (PCA), and varimax rotation were used to classify various types of groundwater, and plausible sources that control the quality of water in the region. The concentration of major ions varies in the order of Na+ > Ca2+ > Mg2+ > K+ and HCO3- > Cl- > SO42- > F-. Out of the three clusters identified, the 2nd cluster is having more mineralization and relatively poor quality of groundwater as compared to the first and the third cluster. Furthermore, estimates of the Water Quality Index (WQI) indicate that the groundwater in the area can be classified from excellent to medium quality. Furthermore, the sodium absorption ratio (SAR) and Kelly's ratio (KR) suggest that about 70% of groundwater samples are of low to medium salinity, whereas about 30% show higher salinity. The Wilcox diagram reveals that almost 90% of the groundwater is suitable for irrigation. The mining activity appears less likely to be affecting the quality of subsurface water. Water-rock interactions and evaporation-crystallization may be the two dominant factors that appear to control the groundwater away from the coastal areas. Results of this study may be useful to identify the suitable sites for groundwater extraction for drinking and irrigation purposes, besides being useful to the policy-makers in formulating effective plans for preventing further contamination of groundwater aquifers.


Asunto(s)
Agua Potable , Agua Subterránea , Contaminantes Químicos del Agua , Agua Potable/análisis , Monitoreo del Ambiente/métodos , Agua Subterránea/química , India , Salinidad , Contaminantes Químicos del Agua/análisis , Calidad del Agua
12.
Environ Int ; 165: 107321, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-35691095

RESUMEN

Pesticides, which are associated with endocrine dysfunction, immunological dysregulation, and cancer, are widespread sources of drinking water contamination. The state of Paraná has a population of 11 million, is the second largest grain producer in Brazil and is a leading consumer of pesticides. In this study, we analyzed the extent of drinking water contamination from 11 proven, probable, or potentially carcinogenic pesticides (alachlor, aldrin-dieldrin, atrazine, chlordane, DDT-DDD-DDE, diuron, glyphosate-AMPA, lindane-γ-HCH, mancozeb-ETU, molinate, and trifluralin) in 127 grain-producing municipalities in the state of Paraná. Extensive contamination of drinking water was found, including legacy pesticides such as aldrin-dieldrin (mean 0.047 ppb), DDT-DDD-DDE (mean: 0.07), chlordane (mean: 0.181), and lindane-HCH (mean: 2.17). Most of the municipalities were significantly above the maximum limits for each one of the currently allowed pesticides (67% for alachlor, 9.44% for atrazine, 96.85% for diuron, 100% for glyphosate-AMPA, 80.31% for mancozeb-ETU, 91.33% for molinate, and 12.6% for trifluralin). Ninety-seven percent of municipalities presented a sum of all pesticides at levels significantly above (189.84 ppb) the European Union preconized limits (<0.5 ppb). Using the mean pesticide concentration in water (ppb), the exposed population for each municipality, and the benchmark cancer risk for pesticides, we estimated the minimum number of cancer cases attributable to pesticide-contaminated drinking water during the period (total of 542 cases). More than 80% were attributed to mancozeb-ETU and diuron. Glyphosate-AMPA and diuron-attributable cases strongly correlated with the total cancer cases in the same period (R = 0.8117 and 0.8138, respectively) as well as with breast cancer cases (R = 0.7695 and 0.7551, respectively). Water contamination was significantly correlated with the sum of the estimated cancer cases for all 11 pesticides detected in each city (R = 0.58 and p < 0.0001). These findings reveal extensive contamination of drinking water in the state of Paraná and suggest that contamination may increase the risk of cancer in this region.


Asunto(s)
Atrazina , Agua Potable , Neoplasias , Plaguicidas , Aldrín , Brasil , Clordano , DDT , Diclorodifenil Dicloroetileno , Dieldrín , Diurona , Hexaclorociclohexano/análisis , Neoplasias/epidemiología , Plaguicidas/análisis , Trifluralina , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiónico
13.
Water Res ; 220: 118515, 2022 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-35700645

RESUMEN

Chlorine dioxide (ClO2) applications to drinking water are limited by the formation of chlorite (ClO2-) which is regulated in many countries. However, when ClO2 is used as a pre-oxidant, ClO2- can be oxidized by chlorine during subsequent disinfection. In this study, a kinetic model for the reaction of chlorine with ClO2- was developed to predict the fate of ClO2- during chlorine disinfection. The reaction of ClO2- with chlorine was found to be highly pH-dependent with formation of ClO3- and ClO2 in ultrapure water. In presence of dissolved organic matter (DOM), 60-70% of the ClO2- was transformed to ClO3- during chlorination, while the in situ regenerated ClO2 was quickly consumed by reaction with DOM. The remaining 30-40% of the ClO2- first reacted to ClO2 which then formed chlorine from the DOM-ClO2 reaction. Since only part of the ClO2- was transformed to ClO3-, the sum of the molar concentrations of oxychlorine species (ClO2- + ClO3-) decreased during chlorination. By kinetic modelling, the ClO2- concentration after 24 h of chlorination was accurately predicted in synthetic waters but was largely overestimated in natural waters, possibly due to a ClO2- decay enhanced by high concentrations of chloride and in situ formed bromine from bromide. Understanding the chlorine-ClO2- reaction mechanism and the corresponding kinetics allows to potentially apply higher ClO2 doses during the pre-oxidation step, thus improving disinfection byproduct mitigation while keeping ClO2-, and if required, ClO3- below the regulatory limits. In addition, ClO2 was demonstrated to efficiently degrade haloacetonitrile precursors, either when used as pre-oxidant or when regenerated in situ during chlorination.


Asunto(s)
Compuestos de Cloro , Desinfectantes , Agua Potable , Purificación del Agua , 2,5-Dimetoxi-4-Metilanfetamina , Cloruros , Cloro , Desinfección , Halogenación , Cinética , Oxidantes , Óxidos
14.
J Environ Public Health ; 2022: 9336247, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35712041

RESUMEN

In Uganda, tap water is always ensured to be potable. However, people are not sure whether tap water is generally safe for drinking without being boiled. Conversely, bottled water consumption is on the increase in Uganda. The main problem lies in the cost of energy for boiling tap water or purchasing bottled water. This study analyzed results of laboratory tests and consumers' perception for comparison of tap and bottled water in Nakawa division, Kampala. Tap water was sampled at four representative locations. At least 16 different brands of bottled water were considered. The top four most consumer-preferred bottled water brands were selected for further analysis. In our study, 28.8%, 6.06%, and 13.64% of the 142 respondents indicated that bottled water had taste, color, and smell, respectively. However, 27.5%, 25.4%, and 34.5% of the respondents agreed that tap water had taste, color, and smell, respectively. Both tap and bottled water met the World Health Organization (WHO) guidelines for pH, total dissolved solids, chloride, copper, sodium, sulfate, and nitrate. However, a tap water sample was found to contain Coliform bacteria. In this line, affected communities need to thoroughly boil the raw tap water to kill the pathogens. All tap water samples yielded iron concentrations above the WHO recommended limit. Student's t-tests showed that tap and bottled water samples were significantly (p<0.05) different with respect to total dissolved solids, pH, chloride, calcium, magnesium, iron, sodium, sulfate, and nitrate. We emphasize the need for routine maintenance of the water distribution system to check for leakages which can be potential source of contaminations.


Asunto(s)
Agua Potable , Cloruros/análisis , Agua Potable/análisis , Humanos , Hierro/análisis , Nitratos/análisis , Percepción , Sodio/análisis , Sulfatos/análisis , Uganda , Calidad del Agua , Abastecimiento de Agua
16.
J Environ Sci (China) ; 117: 119-128, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-35725064

RESUMEN

Drinking water utilities are interested in upgrading their treatment facilities to enhance micropollutant removal and byproduct control. Pre-oxidation by chlorine dioxide (ClO2) followed by coagulation-flocculation-sedimentation and advanced oxidation processes (AOPs) is one of the promising solutions. However, the chlorite (ClO2-) formed from the ClO2 pre-oxidation stage cannot be removed by the conventional coagulation process using aluminum sulfate. ClO2- negatively affects the post-UV/chlorine process due to its strong radical scavenging effect, and it also enhances the formation of chlorate (ClO3-). In this study, dosing micromolar-level ferrous iron (Fe(II)) into aluminum-based coagulants was proposed to eliminate the ClO2- generated from ClO2 pre-oxidation and benefit the post-UV/chlorine process in radical production and ClO3- reduction. Results showed that the addition of 52.1-µmol/L FeSO4 effectively eliminated the ClO2- generated from the pre-oxidation using 1.0 mg/L (14.8 µmol/L) of ClO2. Reduction of ClO2- increased the degradation rate constant of a model micropollutant (carbamazepine) by 55.0% in the post-UV/chlorine process. The enhanced degradation was verified to be attributed to the increased steady-state concentrations of HO· and ClO· by Fe(II) addition. Moreover, Fe(II) addition also decreased the ClO3- formation by 53.8% in the UV/chlorine process and its impact on the formation of chloro-organic byproducts was rather minor. The findings demonstrated a promising strategy to improve the drinking water quality and safety by adding low-level Fe(II) in coagulation in an advanced drinking water treatment train.


Asunto(s)
Compuestos de Cloro , Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , Cloratos , Cloruros , Cloro , Desinfección/métodos , Compuestos Ferrosos , Hierro , Oxidación-Reducción , Óxidos , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos
17.
J Environ Sci (China) ; 117: 129-140, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-35725065

RESUMEN

Halobenzoquinones (HBQs) are emerging disinfection byproducts (DBPs) with a widespread presence in drinking water that exhibit much higher cytotoxicity than regulated DBPs. However, the developmental neurotoxicity of HBQs has not been studied in vivo. In this work, we studied the neurotoxicity of HBQs on zebrafish embryos, after exposure to varying concentrations (0-8 µmol/L) of three HBQs, 2,5-dichloro-1,4-benzoquinone (2,5-DCBQ), 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ), and 2,5-dibromo-1,4-benzoquinone (2,5-DBBQ) for 4 to 120 hr post fertilization (hpf). HBQ exposure significantly decreased the locomotor activity of larvae, accompanied by significant reduction of neurotransmitters (dopamine and γ-aminobutyric acid) and acetylcholinesterase activity. Furthermore, the expression of genes involved in neuronal morphogenesis (gfap, α1-tubulin, mbp, and syn-2α) were downregulated by 4.4-, 5.2-, 3.0-, and 4.5-fold in the 5 µmol/L 2,5-DCBQ group and 2.0-, 1.6-, 2.1-, and 2.3-fold in the 5 µmol/L 2,5-DBBQ group, respectively. Transcriptomic analysis revealed that HBQ exposure affected the signaling pathways of neural development. This study demonstrates the significant neurotoxicity of HBQs in embryonic zebrafish and provides molecular evidence for understanding the potential mechanisms of HBQ neurotoxicity.


Asunto(s)
Agua Potable , Pez Cebra , Acetilcolinesterasa/metabolismo , Animales , Benzoquinonas/análisis , Agua Potable/análisis , Transcriptoma , Pez Cebra/metabolismo
18.
J Environ Sci (China) ; 117: 161-172, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-35725068

RESUMEN

A survey was conducted at eight U.S. drinking water plants, that spanned a wide range of water qualities and treatment/disinfection practices. Plants that treated heavily-wastewater-impacted source waters had lower trihalomethane to dihaloacetonitrile ratios due to the presence of more organic nitrogen and HAN precursors. As the bromide to total organic carbon ratio increased, there was more bromine incorporation into DBPs. This has been shown in other studies for THMs and selected emerging DBPs (HANs), whereas this study examined bromine incorporation for a wider group of emerging DBPs (haloacetaldehydes, halonitromethanes). Moreover, bromine incorporation into the emerging DBPs was, in general, similar to that of the THMs. Epidemiology studies that show an association between adverse health effects and brominated THMs may be due to the formation of brominated emerging DBPs of heath concern. Plants with higher free chlorine contact times before ammonia addition to form chloramines had less iodinated DBP formation in chloraminated distribution systems, where there was more oxidation of the iodide to iodate (a sink for the iodide) by the chlorine. This has been shown in many bench-scale studies (primarily for iodinated THMs), but seldom in full-scale studies (where this study also showed the impact on total organic iodine. Collectively, the THMs, haloacetic acids, and emerging DBPs accounted for a significant portion of the TOCl, TOBr, and TOI; however, ∼50% of the TOCl and TOBr is still unknown. The correlation of the sum of detected DBPs with the TOCl and TOBr suggests that they can be used as reliable surrogates.


Asunto(s)
Desinfectantes , Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , Bromo , Cloro , Desinfectantes/análisis , Desinfección , Halogenación , Yoduros , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis
19.
J Environ Sci (China) ; 117: 173-189, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-35725069

RESUMEN

The qualified finished water from water treatment plants (WTPs) may become discolored and deteriorated during transportation in drinking water distribution systems (DWDSs), which affected tap water quality seriously. This water stability problem often occurs due to pipe corrosion and the destabilization of corrosion scales. This paper provides a comprehensive review of pipe corrosion in DWDSs, including corrosion process, corrosion scale formation, influencing factors and monitoring technologies utilized in DWDSs. In terms of corrosion process, corrosion occurrence, development mechanisms, currently applied assays, and indices used to determine the corrosion possibility are summarized, as well as the chemical and bacterial influences. In terms of scale formation, explanations for the nature of corrosion and scale formation mechanisms are discussed and its typical multilayered structure is illustrated. Furthermore, the influences of water quality and microbial activity on scale transformation are comprehensively discussed. Corrosion-related bacteria at the genus level and their associated corrosion mechanism are also summarized. This review helps deepen the current understanding of pipe corrosion and scale formation in DWDSs, providing guidance for water supply utilities to ensure effective measures to maintain water quality stability and guarantee drinking water safety.


Asunto(s)
Agua Potable , Hierro , Corrosión , Hierro/química , Calidad del Agua , Abastecimiento de Agua
20.
J Environ Sci (China) ; 117: 209-221, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-35725072

RESUMEN

Water disinfection is an essential process that provides safe water by inactivating pathogens that cause waterborne diseases. However, disinfectants react with organic matter naturally present in water, leading to the formation of disinfection by-products (DBPs). Multi-analyte methods based on mass spectrometry (MS) are preferred to quantify multiple DBP classes at once however, most require extensive sample pre-treatment and significant resources. In this study, two analytical methods were developed for the quantification of 32 regulated and unregulated DBPs. A purge and trap (P&T) coupled with gas chromatography mass spectrometry (GC-MS) method was optimized that automated sample pre-treatment and analyzed volatile and semi-volatile compounds, including trihalomethanes (THMs), iodinated trihalomethanes (I-THMs), haloacetonitriles (HANs), haloketones (HKTs) and halonitromethanes (HNMs). LOQs were between 0.02-0.4 µg/L for most DBPs except for 8 analytes that were in the low µg/L range. A second method with liquid chromatography (LC) tandem mass spectrometry (MS/MS) was developed for the quantification of 10 haloacetic acids (HAAs) with a simple clean-up and direct injection. The LC-MS/MS direct injection method has the lowest detection limits reported (0.2-0.5 µg/L). Both methods have a simple sample pre-treatment, which make it possible for routine analysis. Hyperchlorination and uniform formation conditions (UFC) formation potential tests with chlorine were evaluated with water samples containing high and low TOC. Hyperchlorination formation potential test maximized THMs and HAAs while UFC maximized HANs. Ascorbic acid was found to be an appropriate quencher for both analytical methods. Disinfected drinking water from four water utilities in Alberta, Canada were also evaluated.


Asunto(s)
Desinfectantes , Agua Potable , Contaminantes Químicos del Agua , Purificación del Agua , Cromatografía Liquida , Desinfectantes/análisis , Desinfección/métodos , Agua Potable/análisis , Halogenación , Espectrometría de Masas en Tándem , Trihalometanos/análisis , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos
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