Optimizing ozone treatment for pathogen removal and disinfection by-product control for potable reuse at pilot-scale.

Reclaimed water poses environmental and human health risks due to residual organic micropollutants and pathogens. Ozonation of reclaimed water to control pathogens and trace organics is an important step in advanced water treatment systems for potable reuse of reclaimed water. Ensuring efficient pathogen reduction while controlling disinfection byproducts remains a significant challenge to implementing ozonation in reclaimed water reuse applications. This study aimed to investigate ozonation conditions using a plug flow reactor (PFR) to achieve effective pathogen removal/inactivation while minimizing bromate and N-Nitrosodimethylamine (NDMA) formation. The pilot scale study was conducted using three doses of ozone (0.7, 1.0 and 1.4 ozone/total organic carbon (O3/TOC) ratio) to determine the disinfection performance using actual reclaimed water. The disinfection efficiency was assessed by measuring total coliforms, Escherichia coli (E. coli), Pepper Mild Mottle Virus (PMMoV), Tomato Brown Rugose Fruit Virus (ToBRFV) and Norovirus (HNoV). The ozone CT values ranged from 1.60 to 13.62 mg min L-1, resulting in significant reductions in pathogens and indicators. Specifically, ozone treatment led to concentration reductions of 2.46-2.89, 2.03-2.18, 0.46-1.63, 2.23-2.64 and > 4 log for total coliforms, E. coli, PMMoV, ToBRFV, and HNoV, respectively. After ozonation, concentrations of bromate and NDMA increased, reaching levels between 2.8 and 12.0 µg L-1, and 28-40.0 ng L-1, respectively, for average feed water bromide levels of 86.7 ± 1.8 µg L-1 and TOC levels of 7.2 ± 0.1 mg L-1. The increases in DBP formation were pronounced with higher ozone dosages, possibly requiring removal/control in subsequent treatment steps in some potable reuse applications.

Efficient trihalomethane quantification in drinking water for minimally-equipped water treatment plants labs.

Chlorine is a common disinfectant used in water treatment. However, its reaction with organic matter can lead to the formation of harmful byproducts, such as trihalomethanes (THMs), which are potentially carcinogenic. To address this issue, the aim of this work was to enhance a colorimetric method capable of quantifying THMs in drinking water through UV/Vis Spectrophotometry, using cost-effective equipment, and validate this methodology for the first time according to established validation protocols. The method's innovation involved replacing the solvent pentane with the more common hexane, along with adjusting the heating ramp, elucidating the mechanisms involved in the process. This method involves the reaction between THMs, pyridine, and NaOH to produce a colored compound, which is then monitored through molecular absorption spectroscopy in the visible region. The method was thoroughly validated, achieving a limit of detection of 13.41 µg L-1 and a limit of quantification of 40.65 µg L-1. Recovery assays ranged from 86.1 % to 90.7 %, demonstrating high accuracy. The quality of the linear fit for the analytical curve exceeded R2 > 0.98. The method was applied to real samples, revealing concentrations ranging from 13.58 to 55.46 µg L-1, all way below the legal limit in Brazil (Maximum Contaminant Levels (MCL) = 100 µg L-1). This cost-effective and straightforward method is suitable for integration into water treatment plant laboratories.

Use of tannin-based coagulant and chlorine dioxide in treating brewing water: reduction of trihalomethanes and impact on physicochemical and sensory quality.

This study aimed to evaluate an alternative to reduce trihalomethane (THM) formation in brewing water. THM affects the organoleptic properties of water and, consequently, the produced beer. Water treatment based on common chemicals such as alum and free chlorine could potentially form THM. Therefore, we studied the replacement of chemicals used in water treatment: aluminum sulfate by a tannin-based coagulant and sodium hypochlorite by chlorine dioxide. Experimentally, jar tests were conducted, and the role of coagulants and oxidizing agents was evaluated for: the removal of apparent color, turbidity, natural organic matter (NOM) and microorganisms; the formation of trihalomethanes (THM); and the sensory quality of the water. Using tannin-based coagulant with chlorine dioxide was associated with the lowest THM in treated water (1.7 µg/L) and higher satisfaction in the sensory analysis. However, using these chemicals make the water treatment more expensive than the current strategy. Overall, using the tannin-based coagulant and chlorine dioxide treatment is an alternative to produce water with a lower THM concentration, better physical-chemical, and sensory quality. These findings motivate further brewing experiments and a deeper economics evaluation considering the process's sustainability.

Modeling the formation of trihalomethanes in rural and semi-urban drinking water distribution networks of Costa Rica.

Chlorination is one of the most important stages in the treatment of drinking water due to its effectiveness in the inactivation of pathogenic organisms. However, the reaction between chlorine and natural organic matter (NOM) generates harmful disinfection by-products (DBPs), such as trihalomethanes (THMs). In this research, drinking water quality data was collected from the distribution networks of 19 rural and semi-urban systems that use water sources as springs, surfaces, and a mixture of both, in three provinces of Costa Rica from April 2018 to September 2019. Twelve models were developed from four data sets: all water sources, spring, surface, and a mixture of spring and surface waters. Linear, logarithmic, and exponential multivariate regression models were developed for each data set to predict the concentration of total trihalomethanes (TTHMs) in the distribution networks. Concentrations of TTHMs were found between < 0.20 and 91.31 µg/L, with chloroform being the dominant species accounting for 62% of TTHMs on average. Turbidity, free residual chlorine, total organic carbon (TOC), dissolved organic carbon (DOC), and ultraviolet absorbance at 254 nm (UV254) showed a significant correlation with TTHMs. In all the data sets the linear models presented the best goodness-of-fit and were moderately robust. Four models, the best of each data set, were validated with data from the same systems, and, according to the criteria of R2, standard error (SE), mean square error (MSE), and mean absolute error (MAE), spring water and mixed spring/surface water models showed a satisfactory level of explanation of the variability of the data. Moreover, the models seem to better predict TTHM concentrations below 30 µg/L. These models were satisfactory and could be useful for decision-making in drinking water supply systems.

Measured and Modeled Comparisons of Chemical and Microbial Contaminants in Tap and Bottled Water in a US-Mexico Border Community.

Tap water quality concerns and advertisements often drive increased bottled water consumption, especially in communities with historical tap water quality problems (e.g., Nogales, Arizona). The study objective was to assess contamination of municipal tap and bottled water in Nogales, Arizona. Bottled (sealed, open/partially consumed bottles, and reusable containers for vended water) and tap water samples were collected from 30 homes and analyzed for chemical and microbial contaminants. Fisher exact tests and Wilcoxon rank sum tests were used to compare proportions of positive samples and contaminant concentrations between tap and bottled water samples. While none of the chemical contaminants were above MCLs, there were statistically significantly greater concentrations and proportions of positive samples for some contaminants, including arsenic, in tap vs. bottled water. E. coli concentrations were >0 CFU/100mL in some unsealed bottled water samples but not for sealed bottles. This study demonstrates that 1) the measured concentrations in tap and bottled water likely pose low risks, as they are below the MCLs, 2) more education in this community on hygiene maintenance of refillable or opened bottled water containers is needed, and 3) using tap water over bottled water is advantageous due to likely lower E. coli risk and lower cost.

Pilot-scale expanded assessment of inorganic and organic tapwater exposures and predicted effects in Puerto Rico, USA.

A pilot-scale expanded target assessment of mixtures of inorganic and organic contaminants in point-of-consumption drinking water (tapwater, TW) was conducted in Puerto Rico (PR) to continue to inform TW exposures and corresponding estimations of cumulative human-health risks across the US. In August 2018, a spatial synoptic pilot assessment of than 524 organic and 37 inorganic chemicals was conducted in 14 locations (7 home; 7 commercial) across PR. A follow-up 3-day temporal assessment of TW variability was conducted in December 2018 at two of the synoptic locations (1 home, 1 commercial) and included daily pre- and post-flush samples. Concentrations of regulated and unregulated TW contaminants were used to calculate cumulative in vitro bioactivity ratios and Hazard Indices (HI) based on existing human-health benchmarks. Synoptic results confirmed that human exposures to inorganic and organic contaminant mixtures, which are rarely monitored together in drinking water at the point of consumption, occurred across PR and consisted of elevated concentrations of inorganic contaminants (e.g., lead, copper), disinfection byproducts (DBP), and to a lesser extent per/polyfluoroalkyl substances (PFAS) and phthalates. Exceedances of human-health benchmarks in every synoptic TW sample support further investigation of the potential cumulative risk to vulnerable populations in PR and emphasize the importance of continued broad characterization of drinking-water exposures at the tap with analytical capabilities that better represent the complexity of both inorganic and organic contaminant mixtures known to occur in ambient source waters. Such health-based monitoring data are essential to support public engagement in source water sustainability and treatment and to inform consumer point-of-use treatment decision making in PR and throughout the US.

Drinking water nitrosamines in a large metropolitan region in Brazil.

Nitrosamines are a concerning group of carcinogens, which have gained increasing attention over the last years, frequently found in drinking and recycled water systems. In this work, an analytical method was developed for the detection and quantification of seven nitrosamines (NDMA, NMEA, NPYR, NDEA, NPIP, NDPA, and NDBA) in drinking water. The method is based on gas chromatography coupled with a single quadrupole mass spectrometer (GC-MS) with electron ionization (EI) mode. Sample enrichment and matrix cleanup by solid-phase extraction (SPE) were performed using the US EPA Method 521 cartridge packed with coconut-based charcoal. The simple method allowed reliable identification and quantification of nitrosamines in the water at nanogram per liter levels. The optimized method was validated at three concentration levels (20, 100, and 200 ng L-1) in ultrapure and drinking water samples. Average recoveries were 63-87% for ultrapure water and 38-79% for drinking water with relative standard deviations (RSD) below 10% for both matrices. Method detection limits were 1.23-3.14 ng L-1. The described method was applied to eighteen drinking water samples collected from 13 cities of the Metropolitan Region of Campinas (São Paulo, Brazil). NDMA was the most frequent nitrosamine detected (89% of samples) and had the highest concentration level found (67 ng L-1). The levels of nitrosamines found in drinking water samples are of considerable relevance since the selected area is a major urban center that has amply expanded industrial and agricultural activities over the last few decades. To the best of our knowledge, this is the first evaluation of nitrosamines in drinking water conducted in Brazil to date.

Preliminary assessment of antimicrobial activity and acute toxicity of norfloxacin chlorination by-product mixture.

Among drugs and personal care products, antibiotics arouse interest since they are widely used in human and veterinary medicine and can lead to the development of bacterial resistance. Usually, sewage treatment does not remove most of these compounds. So, these drugs can reach water treatment plants (WTP), where disinfection with chlorine compounds is common. This work aimed to evaluate the antimicrobial activity and preliminary toxicity of the mix of by-products forming due to the chlorination of norfloxacin. This is a fluoroquinolone antibiotic indicated for the treatment of urinary infection and gonorrhea, with sodium hypochlorite (NaClO). The drug was subjected to chlorination tests, on a bench scale, with several reaction times (from 5 min to 24 h). Analyses of high-resolution mass spectrometry (MS) were performed for the characterization of the by-products. The MS results showed five peaks attributed to the by-products' formation, of which four were identified. The antibiogram results indicated that the solution that contained the mixture of the by-products lost antibacterial activity against the E. coli strain studied. The acute toxicity tests for the Artemia salina microcrustacean showed that the blend of the by-products exhibited higher toxicity than pure norfloxacin.

Aqueous chlorination of herbicide metribuzin: Identification and elucidation of "new" disinfection by-products, degradation pathway and toxicity evaluation.

A widely used herbicide, metribuzin, was evaluated for degradation, mineralization and disinfection by-products (DBPs) formation during aqueous chlorination. In addition, to assess the toxicity effects of chlorination on metribuzin solution the following tests were performed: acute toxicity using Artemia salina nauplii; cell viability using MTT assay; estrogenicity using a re-engineered Bioluminescent Yeast Estrogen Screen (BLYES) and a constitutively bioluminescent strain (BLYR); mutagenicity and developmental toxicity using Q(SAR) methodology. Metribuzin at 10 mg·L-1 was degraded by chlorination, achieving 93% of removal at 30 min of reaction. TOC analysis showed that the herbicide does not suffer complete mineralization, even after 24 h of contact with free chlorine. Seventeen DBPs were detected and their structural formulae were elucidated by high resolution mass spectrometry. Toxicity effects for chlorinated solutions increased when compared to the unreacted metribuzin solution. DBPs were more toxic to Artemia salina nauplii, increasing around 20% on nauplii mortality. It was also observed high estrogenicity to human receptors in BLYES assays and mutagenic and developmental toxicant effects to animals and humans in Q(SAR) methodology, suggesting that DBPs are potentially more toxic than the precursor metribuzin. Metribuzin solutions at 10 mg·L-1 showed equivalent 17-ß-estradiol values ranged from 0.061 to 6.71 µg·L-1 after to be chlorinated at different reaction times.

Cancer risk assessment from exposure to trihalomethanes in showers by inhalation.

In many countries water disinfection for human consumption is still carried out via chlorination which generates by-products such as trihalomethanes (THM). Exposure to THM constitutes a public health risk as such substances are known to be carcinogenic. This study evaluated exposure to THMs by inhalation in showers and assessed the carcinogenic risk for lifetime exposure. The study population involved students at Universidad de los Andes residing in Bogotá, Colombia. The risk assessment was performed stochastically and the exposure parameters were taken as probability distributions. Most variables were measured in relation to the chosen population. The risk was calculated using two different methodologies but no significant variations were obtained. The average risk calculated for men and women was 56 cases in a million (5.6 × 10-5). A sensitivity analysis was carried out where it was found that the parameters that increase risk the most are the concentration of chloroform in the water, exposure time, and the volume of the shower cubicle.

Estudo do potencial de formação de trihalometanos na lagoa de Extremoz (RN) / Study of trihalomethanes potencial formation in Extremoz-RN pond

RESUMO O potencial de formação de trihalometanos (PFTHM) é uma metodologia utilizada para avaliar a possibilidade de formação de subprodutos da desinfecção (SPD) por cloração durante o processo de tratamento da água. Trihalometanos (THM) são compostos organoclorados e representam a soma de clorofórmio, diclorobromometano, dibromoclorometano e bromofórmio, sendo a principal classe de SPD formados a partir da reação entre o cloro residual livre e a matéria orgânica natural (MON) presente na água bruta de mananciais de superfície. Esta pesquisa teve como objetivo avaliar o PFTHM resultante da aplicação de cloro na água bruta da lagoa de Extremoz, cuja tecnologia de tratamento utilizada é a filtração direta, seguida de desinfecção com cloro. Os resultados obtidos indicaram presença de matéria orgânica natural hidrofílica com predominância de ácidos fúlvicos na água bruta do manancial. A concentração média de TTHM7 (4,22 mg.L-1) revelou que a água do manancial possui forte potencialidade para formação de compostos orgânicos halogenados. O clorofórmio representou cerca de 80% da concentração total de THM nos ensaios realizados. Foram observadas correlações fortes e significativas entre as variáveis dureza (R = 0,90 e p = 0,005) e cor aparente (R = -0,93 e p = 0,002) da água bruta, resultados que indicaram que íons Ca2+ e Mg2+ podem promover a formação de THM, assim como a cor aparente.

ABSTRACT Trihalomethanes formation potential (THMFP) has been used to evaluate the possibility of disinfection byproduct (DBP) formation by chlorination during the water treatment process. Trihalomethanes (THM) are organochlorine compounds and represents the sum of chloroform, dichlorobromomethane, dibromochloromethane, and bromoform, and is the main class of DBP formed from the reaction between free residual chlorine and natural organic matter (NOM) present in the source waters of surface fountains. This research evaluates the THMFP on the source water from the Extremoz Pond (Natal-RN, Brazil), which is treated by direct filtration followed by chlorine disinfection. Results indicated the presence on source water of hydrophilic natural organic matter with the predominance of fulvic acids. The mean concentration of TTHM7 (4.22 mg.L-1) showed that the source water has a strong potential for halogenated organic compounds formation. Chloroform represented about 80% of the total THM concentration in the assays performed. Significant and strong correlations were observed between hardness (R = 0.90 and p = 0.005) and apparent color (R = -0.93 and p = 0.002) attesting that Ca2+ and Mg2+ ions can promote the formation of THM, as well as the apparent color.

Removal of both N-nitrosodimethylamine and trihalomethanes precursors in a single treatment using ion exchange resins.

Drinking water utilities are relying more than ever on water sources impacted by wastewater effluents. Disinfection/oxidation of these waters during water treatment may lead to the formation of several disinfection by-products, including the probable human carcinogen N-nitrosodimethylamine (NDMA) and the regulated trihalomethanes (THMs). In this study, the potential of ion exchange resins to control both NDMA and THMs precursors in a single treatment is presented. Two ion exchange resins were examined, a cation exchange resin (Plus) to target NDMA precursors and an anion exchange resin (MIEX) for THMs precursors control. We applied the resins, individually and combined, in the treatment of surface and wastewater effluent samples. The treatment with both resins removed simultaneously NDMA (43-85%) and THMs (39-65%) precursors. However, no removal of NDMA precursors was observed in the surface water with low initial NDMA FP (14 ng/L). The removals of NDMA FP and THMs FP with Plus and MIEX resins applied alone were (49-90%) and (41-69%), respectively. These results suggest no interaction between the resins, and thus the feasibility of effectively controlling NDMA and THMs precursors concomitantly. Additionally, the effects of the wastewater impact and the natural attenuation of precursors were studied. The results showed that neither the wastewater content nor the attenuation of the precursor affected the removals of NDMA and THMs precursors. Finally, experiments using a wastewater effluent sample showed that an increase in the calcium concentration resulted in a reduction in the removal of NDMA precursors of about 50%.

Removal of N-nitrosodimethylamine precursors with powdered activated carbon adsorption.

The main objective of this study was to examine the roles of powdered activated carbon (PAC) characteristics (i.e., surface chemistry, pore size distribution, and surface area) in the removal of N-nitrosodimethylamine (NDMA) formation potential (FP) in surface and wastewater-impacted waters. Also, the effects of natural attenuation of NDMA precursors in surface waters, NDMA FP concentration, and carbon dose on the removal of NDMA FP by PAC were evaluated. Finally, the removal of NDMA FP by PAC at two full-scale DWTPs was monitored. Wastewater-impacted and surface water samples were collected to conduct adsorption experiments using different PACs and activated carbon fibers (ACFs) with a wide range of physicochemical characteristics. The removal efficiency of NDMA FP by PAC was significantly higher in wastewater-impacted than surface waters. Adsorbable NDMA precursors showed a size distribution in the waters tested; the adsorbable fraction included precursors accessing the pore size regions of 10-20 Å and <10 Å. Basic carbons showed higher removal of NDMA FP than acidic carbons on a surface area basis. The overall removal of NDMA FP by PAC on a mass basis depended on the surface area, pore size distribution and pHPZC. Thus, PACs with hybrid characteristics (micro and mesoporous), higher surface areas, and basic surface chemistry are more likely to be effective for NDMA precursor control by PAC adsorption. The application of PAC in DWTPs for taste and odor control resulted in an additional 20% removal of NDMA FP for the PAC doses of 7-10 mg/L. The natural attenuation of NDMA precursors through a combination of processes (biodegradation, photolysis and adsorption) decreased their adsorbability and removal by PAC adsorption.

Aplicacao da tecnica por cromatografia a gas para investigacao da formacao de sub produtos da desinfeccao em agua potavel / Application of gas chromatographic technique for investigation of the formation of by products in drinking water disinfection

O uso do cloro para a desinfecção e/ou oxidação nas estações de tratamento de água favorece a formação de subprodutos orgânicos halogenados (SOH), muitos deles carcinogênicos. O objetivo desta pesquisa foi validar uma metodologia analítica proposta para a quantificação simultânea de 12 subprodutos da desinfecção por cromatografia a gás com detector de captura de elétrons (CG-DCE). O método apresentou linearidade (r>0,998), repetibilidade menor que 0,15%, limites de detecção de 1 a 6 µg.L-1 e de quantificação de 3 a 21 Î1/4g.L-1, precisão (<10%), exatidão (93-120%) e recuperação (87-117%). Os resultados indicam que o método pode ser empregado para a investigação de SOH em água, garantindo confiabilidade analítica nos resultados.

The use of chlorine for disinfection and/or oxidation at drinking water treatment plants favors the formation of halogenated organic by-products (HOB), many of them carcinogenic. The purpose of this research was to validate an analytical method for the simultaneous quantification of 12 HOB from disinfection by gas chromatograph with electrons capture detector (GC-ECD). The method provided linearity (r>0.998), repeatability lower than 0.15%, limits of detection from 1 to 6 Î1/4g.L-1 and of quantification from 3 to 21 Î1/4g.L-1, precision (<10%), accuracy (93-120%) and recovery (87-117%). The results indicate that the method can be employed to investigate the formation of HOB in water, yielding analytically reliable results.

Chlorination disinfection by-products in drinking water and congenital anomalies: review and meta-analyses / Subprodutos da desinfecção com cloro em água potável e anomalias congênitas: revisão e meta-análise

This study aims to review epidemiologic evidence of the association between exposure to chlorination disinfection by-products (DBPs) and congenital anomalies. All epidemiologic studies that evaluated a relationship between an index of DBP exposure and risk of congenital anomalies were analyzed. For all congenital anomalies combined, the meta-analysis gave a statistically significant excess risk for high versus low exposure to water chlorination or TTHM (17 percent; 95 percent CI, 3-34) based on a small number of studies. The meta-analysis also suggested a statistically significant excess risk for ventricular septal defects (58 percent; 95 percent CI, 21-107), but based on only three studies, and there was little evidence of an exposure-response relationship. It was observed no statistically significant relationships in the other meta-analyses and little evidence for publication bias, except for urinary tract defects and cleft lip and palate. Although some individual studies have suggested an association between chlorination disinfection by-products and congenital anomalies, meta-analyses of all currently available studies demonstrate little evidence of such association.

O objetivo deste estudo é revisar evidências epidemiológicas da associação entre a exposição a subprodutos da desinfecção com cloro (DBPs) e anomalias congênitas. Todos os estudos epidemiológicos que avaliaram a relação entre o índice de exposição a DBPs e o risco de anomalias congênitas foram analisados. Para todas as anomalias congênitas combinadas, a meta-análise resultou em um risco de excesso estatisticamente significante para alta versus baixa exposição à cloração da água ou ao TTHM (17 por cento; 95 por cento CI, 3-34) baseado em um pequeno número de estudos. A meta-análise também sugere um excesso de risco estatisticamente significante para defeitos septais ventriculares (58 por cento; 95 por cento CI, 21-107), porém com base em apenas três estudos, nos quais se encontrou pouca evidência na relação exposição-resposta. Não foram observadas relações estatisticamente significantes em outras meta-análises e pouca evidência para uma tendência de publicação, com exceção de defeitos no trato urinário e fissura labiopalatal. Apesar de alguns estudos individuais sugerirem uma associação entre subprodutos da desinfecção com cloro e anomalias congênitas, as meta-análises de todos os estudos disponíveis atualmente demonstraram pouca evidência de tal associação.

Comportamento cinético do cloro livre em meio aquoso e formação de subprodutos da desinfecção / Kinetic behavior of free chlorine in the liquid phase and disinfection by-product (DBP) formation

Uma das formas indiretas de previsão da potencialidade de uma determinada água natural formar subprodutos da desinfecção é mediante a avaliação do comportamento cinético do cloro livre na fase líquida e determinação de sua demanda para diferentes condições de operação do processo de cloração. Desta forma, o objetivo deste trabalho foi avaliar o comportamento cinético do cloro livre em meio aquoso para diferentes tipos de água bruta, bem como investigar o impacto do processo de coagulação na redução da demanda de cloro e na formação de subprodutos da desinfecção. Observou-se que, quanto maior for à remoção de carbono orgânico total (COT) pelo processo de coagulação menor será a demanda de cloro na fase líquida. A formação de THMs apresentou relação com a demanda de cloro, tendo sido esta da ordem de 28 mg/L para cada 1 mg Cl2/L de demanda de cloro observada.

One indirect approach to predict the disinfection by-product (DBP) formation potential for a given water source is by evaluation of the kinetic behavior of free chlorine in the liquid phase and chlorine demand determination for different operation conditions of the chlorination process. The objective of this work was to evaluate the kinetic behavior of free chlorine in water or a number of different raw water sources, as well as to investigate the impact of the coagulation process on chlorine demand reduction and DBP formation. It was observed that the higher the total organic carbon (TOC) removal efficiency through coagulation, the lower the liquid phase chlorine demand. Regarding trihalomethane (THM) formation, a ratio of 28 ug/L formed per mg/L of applied chlorine was observed for the waters employed in the experimental investigation.