Chlorinated Water Samples Research Articles

Leaching of organic matter from cigarette butt filters as a potential disinfection by-products precursor

The study aimed to evaluate cigarette butt filters (CBFs) as a potential source of dissolved organic carbon (DOC) in water leading to the formation of disinfection by-products. Two different forms of CBFs – intact (I) and disintegrated (D), as they occur in the environment, were selected for leaching in chlorinated (CI, CD), non-chlorinated (NI, ND), and highly chlorinated (HCD) water samples. The UV absorbance profiles of the leachate samples showed that intact CBFs exhibited higher DOC leaching compared to the disintegrated ones, which was further accentuated in chlorinated samples (CI > CD > NI > ND). The Fourier Transform Infrared spectra of the leachates revealed the presence of characteristic functional groups of cellulose acetate and its chlorinated derivatives, indicating the potential degradation of the polymer. Moreover, trihalomethane (THM) formation in chlorinated samples was relatively higher in CI samples (2 – 11.5 times) compared to CD, consistent with the DOC leaching trends. Further, the speciation characteristics of different THMs in both CI and CD samples were similar. Although spectral and morphological analyzes of CI and CD samples revealed negligible variation, HCD samples depicted significant surface roughness characterized by the formation of pits and holes, along with the evolution of crystallinity. This suggested accelerated degradation of CBFs and disruption of acetyl groups as a factor of elevated chlorine concentrations.

Formation of halogenated forms of bisphenol A (BPA) in water: Resolving isomers with ion mobility – mass spectrometry and the role of halogenation position in cellular toxicity

Halogenated BPA (XBPA) forms resulting from water chlorination can lead to increased toxicity and different biological effects. While previous studies have reported the occurrence of different XBPAs, analytical limitation have hindered the analysis and differentiation of the many potential isomeric forms. Using online solid-phase extraction - liquid chromatography - ion-mobility - high-resolution mass spectrometry (OSPE-LC-IM-HRMS), we demonstrated a rapid analysis method for the analysis of XBPA forms after water chlorination, with a total analysis time of less than 10 min including extraction and concentration and low detection limits (∼5–80 ng/L range). A multi in-vitro bioassay testing approach for the identified products revealed that cytotoxicity and bioenergetics impacts were largely associated with the presence of halogen atoms at positions 2 or 2’ and the overall number of halogens incorporated into the BPA molecule. Different XBPA also showed distinct impacts on oxidative stress, peroxisome proliferator-activated receptor gamma - PPARγ, and inflammatory response. While increased DNA damage was observed for chlorinated water samples (4.14 ± 1.21-fold change), the additive effect of the selected 20 XBPA studied could not explain the increased DNA damage observed, indicating that additional species or synergistic effects might be at play.

Analysis of Antibiotic Resistant Gene from Microbial Isolates of Chlorinated Water

Background: Chlorination is commonly used to disinfect water as it efficiently kills the microbe by destroying its membrane enzyme. Although some gram positive bacteria that are antibiotic resistant also show resistance against chlorine. This resistance may be due to some unique protein or maybe confer by the antibiotic resistant genes. Aim: To analyze the relationship between antibiotic and chlorine resistance to verify the role of antibiotic resistant genes in chlorine resistance. Methodology: VAN-A and TET-O genes were amplified from a chlorinated water sample and computation analysis was carried out to analyze these proteins. Docking was performed to quantify binding affinity between resistant genes and hypochlorite ligand. Results: Low binding energy confirmed the incompetency of chlorine and antibiotics against resistant genes. Expression analysis of PET-28 GFP recombinant plasmid under antibiotic and chlorine stress indicated successful expression by J express. Conclusion: Computational study proves that antibiotic resistant gene has a role in conferring resistance against chlorine. Keywords: Antibiotic resistance, chlorine resistance, molecular modeling, recombinant plasmid, hypochlorite

Concentration and reduction efficiency of vancomycin-resistant heterotrophic bacteria and vanA and vanB genes in wastewater treatment unit processes

ObjectivesThis study elucidated the distribution and fate of vancomycin (VCM)-resistant heterotrophic bacteria (HTB) and resistance genes, vanA and vanB, during each treatment unit process of a wastewater treatment plant (WWTP). MethodsSeveral bacterial counts as well as copy numbers of vanA and vanB genes were determined in each wastewater and sludge sample. In addition, HTB strains isolated from wastewater and sludge were analyzed for VCM susceptibility. Then, the fate and reduction ratios of each bacterial count, copy number of vanA and vanB genes, and the existence ratio of VCM-resistant HTB strains in the wastewater treatment unit process were evaluated. ResultsVCM-resistant HTB were detected in all wastewater and sludge samples, and their existence ratio decreased along the treatment process (92.9% in influent wastewater to 39.4% in chlorinated water). Notably, most of the HTB isolated from the influent wastewater were resistant to 8.0 µg/mL of VCM, strongly suggesting that a significant number of antibiotic-resistant bacteria are flowing into the WWTP from urban areas through the sewage system. The vanA and vanB genes were also detected in all wastewater and sludge, with high copy numbers (102-104 copies/mL) even in chlorinated water samples. ConclusionsResults revealed that residual VCM-resistant HTB, and resistance genes, which could not be completely removed, were ubiquitously released into the aquatic environment. Furthermore, a high existence ratio of VCM-resistant HTB and high copy numbers of resistance genes were also detected in the sludge, indicating that they are constantly circulating in the WWTP via the returned sludge.

A multistep enrichment process with custom growth medium improves resuscitation of chlorine-stressed coliforms from secondary sewage effluents

Resuscitation and detection of stressed total coliforms in chlorinated water samples is needed to assess and prevent health effects from adverse exposure. In this study, we report that the addition of a growth enhancer mix consisting of trehalose, sodium pyruvate, magnesium chloride, and 1× trace mineral supplement improved growth of microorganisms from chlorinated secondary effluent in the base medium with Colilert-18. Improving growth of chlorine stressed microorganisms from secondary effluent is crucial to decreased detection time from 18 to 8 h.

Water quality assessment of Raw and Chlorinated drinking water of a Residential University

The safety of water is essential for life on earth. Drinking contaminated water can give rise to many health issues. Tohighlight the major causes of contamination in water, this study was carried out to determine the physicochemical andbacteriological quality of raw and chlorinated water. Raw and chlorinated water samples were obtained from three locations (zones) of a residential university (National University of Sciences and Technology, NUST). Ten physicochemicalparameters were analyzed (pH, Electrical conductivity, Turbidity, Dissolved oxygen, Hardness, Alkalinity, Total suspendedsolids, Total dissolved solids, Total organic carbon, and Chlorine (free & total)). Bacteriological analysis was performedthrough the MPN technique. The results showed that all the physicochemical parameters were found within the permissible limits set by WHO and PSDWQ for raw and chlorinated water, except TSS and Chlorine (free & total). The TSS of raw and chlorinated water ranged from 3.3-14.3mg/L and 8.7-12.7mg/L, greater than the permissible limits. The free Chlorine for both raw and chlorinated water ranged from 0.04-0.09mg/L and 0.06-0.07mg/L and total Chlorine for both raw and chlorinated water in the range 0.10-0.09mg/L and 0.22-0.24mg/L, respectively, which were far below the recommended limit required for water disinfection. The MPN index for raw and chlorinated water ranged from 23 to >23MPN/100ml and 16 to >23MPN/100ml, exceeding the permissible limits. The results concluded that the water, whether raw or chlorinated, was not fit for drinking purposes. Proper dosages of Chlorine and filtration techniques are required to make the water fit for consumption.

Microbial Reduction Potential of Chlorine and its Contribution to Incidence of Stress Response Genes in Antibiotic-Resistant Bacteria

Background: The quest for potability of drinking water in various homes led to the widely use of chlorine or chlorine compound in treatment of water. Which however has contributed to increasing incidences of antibiotic resistance in the environment.
 Aim: This study aimed to investigate the microbial reduction potential and contribution of Sodium hypochlorite, NaOCl, to incidence of stress response genes in antibiotic-resistant bacteria.
 Study Design: Experimental Design was adopted in this study
 Place and Duration of the Study: The study was carried out at the Department of Microbiology, Faculty of Science, Ekiti State University between October, 2019 and February, 2020.
 Methodology: Sixteen (16) different water samples were randomly collected from various homes in Ajilosun, Ado-Ekiti and were chlorinated following manufacturer’s instruction. Microbial load of both raw and chlorinated water was determined using standard pour plate technique. Standard streaking method was used to isolate bacteria from chlorinated water samples. Standard CLSI technique was used to test the sensitivity of isolates to different antibiotics and PCR technique was employed to detect stress response genes (RpoS, RpoN, KatF genes) in multiple antibiotic-resistant bacterial isolates.
 Results: The result showed 24% and 52% reduction in the microbial load of well and pipe-borne water samples respectively following treatment with NaOCl for 180 sec. The different identified bacterial isolates recovered from chlorinated water samples included Enterobacter aerogenes (7.14 %), Proteus vulgaris (10.71 %), Escherichia coli (25 %), Bacillus cereus (32.14 %), Bacillus licheniformis (14.29 %) and Staphylococcus aureus (10.70 %). The bacterial isolates demonstrated varying resistance pattern to the different antibiotics. RpoS, RpoN and KatF genes encoding stress responses were detected in some of the tested antibiotic-resistant isolates.
 Conclusion: The study therefore stresses the importance of chlorination in contributing to increasing incidence of resistance of bacteria to stressors in the environment. Hence, subverting chlorination efficacy in treatment of water.

Antibiotic Resistance Patterns of Bacteria Isolated from Dechlorinated Water Samples

Chlorination has been the method of choice for disinfecting water used for drinking purposes. However, some stressed bacteria during chlorination are able to recover and alter the potability of water. This study assessed the recovery of stressed bacteria in dechlorinated water. Ten chlorinated water samples were collected from different points within Ilorin metropolis, Kwara, Nigeria. The samples (100ml) were dechlorinated with 0.1ml of 11.4mM sodium thiosulphate solution. The physicochemical characteristics of the chlorinated water samples were determined while bacteriological analyses were carried out on both chlorinated and dechlorinated water samples. The antibiotic susceptibility pattern of the isolates was determined using disc diffusion method. The physicochemical characteristics of the water samples ranged as follow: pH 7.3-8.4, chloride content 4.37-6.85 mg/l, suspended solids 0.004-0.017 g/100ml, and total hardness 30-72mg/l. The chlorinated water samples had bacterial, total, and faecal coliform counts ranging from 1.0 × 101 – 1.9 × 104cfu/ml, 0 – 480 MPN/100ml, and zero, respectively. The dechlorinated water sample had corresponding counts of 5.4 × 102 – 7.36 × 104cfu/ml, 6 - 1100 MPN/100ml, and 0 – 380 MPN/100ml. A total of eleven bacterial species belonging to the genera Bacillus, Burkholderia, Citrobacter, Enterobacter, Enterococcus, Escherichia, Staphylococcus, Serratia, and Streptococcus were isolated. Not lower than 60% of the bacterial isolates were susceptible to ofloxacin and ciprofloxacin. All the isolates exhibited multiple antibiotic resistances. The antibiotic resistance pattern of an isolate of Citrobacter freundii to cefuroxime, cefixime, and gentamycin changed remarkably and was plasmid-mediated, while that of E. coli and Enterobacter agglomerans remained unchanged to all the antibiotics and was non-plasmid mediated. Chlorination of water at the point of use is recommended. It is concluded that chlorination is essential in order to prevent reactivation of stressed bacteria during distribution and prevent infection by bacteria with high multiple antibiotic resistance index.

Quantification of Legionella pneumophila by qPCR and culture in tap water with different concentrations of residual disinfectants and heterotrophic bacteria

Legionellosis prevalence is increasing in the United States. This disease is caused primarily by the bacterium Legionella pneumophila found in water and transmitted by aerosol inhalation. This pathogen has a slow growth rate and can “hide” in amoeba, making it difficult to monitor by the traditional culture method on selective media. Tap water samples (n = 358) collected across the United States were tested for L. pneumophila by both culture and quantitative Polymerase Chain Reaction (qPCR). The presence of other bacteria was quantified by heterotrophic plate counts (HPC). Residual disinfectant concentrations (free chlorine or monochloramine) were measured in all samples. Legionella pneumophila had the highest prevalence and concentration in the chlorinated water samples that had a free‑chlorine value of less than 0.2 mg Cl2/L. In total, 24% (87/358) of the samples were positive for L. pneumophila either by qPCR or 3% (11/358) were positive by culture. In chloramine-treated samples, L. pneumophila was detected by qPCR in 21% (31/148) and 1% (2/148) by culture, despite a high monochloramine residual >1 mg Cl2/L. Despite the presence of a high disinfectant residual (>1 mg Cl2/L), HPC counts were substantial. This study indicates that both culture and qPCR methods have limitations when predicting a potential risk for disease associated with L. pneumophila in tap water. Measuring disinfectant residuals and quantifying HPC in water samples may be useful adjunct parameters for reducing Legionellosis' risk from public water supplies at high-risk locations.

Non-target screening of dissolved organic matter in raw water, coagulated water, and chlorinated water by Orbitrap mass spectrometry

This study aimed to classify the possible molecular formulas of precursors for disinfection by-products (DBPs) in raw, coagulated, and chlorinated water samples from the U-Tapao Canal, Songkhla, Thailand. The molecular formulas of DBPs in chlorinated water were investigated. Polyaluminum chloride (PACl) was employed as a coagulant. Orbitrap Fourier transform-mass spectrometry was able to estimate the composition of dissolved organic matter (DOM) with the carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S) elements contained and DBPs at the molecular level. The molecular formulas of the DOM in the raw water primarily consisted of CHO and CHON when extracted by lichrolut EN. The CHO and CHON species were rich in lignin-, tannin-, and condensed aromatic-like substances. The DOM with high-molecular-weight from 300 to 500 Da were preferentially removed by coagulation. The PACl coagulation decreased the abundances of lignin-, tannin-, and condensed aromatic-like substances in the CHO formulas, while lignin- and condensed aromatic-like substances in the CHON formulas remained. The remaining precursors corresponded to CHON molecules in the coagulated water, which may result in the formation of some chlorine (Cl)-containing molecules. Several DBPs among the CHOCl and CHONCl species were produced in the chlorinated water through the addition reaction of chlorine. New chlorinated N-DBPs of 21 formulas were detected.

Removal of the precursors of regulated DBPs and TOX from surface waters and wastewater effluents using mixed anion exchange resins

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.

Non-volatile disinfection byproducts are far more toxic to mammalian cells than volatile byproducts

Water is often chlorinated to protect public health, but chlorination causes harmful disinfection byproducts to form. Currently available in vitro assays generally determine non-volatile disinfection byproduct (NVDBP) toxicities because of the limitation of pretreatments used, but chemical analyses and regulations are focused on volatile disinfection byproducts (VDBPs) such as trihalomethanes. The gap of VDBP toxicities have been of concern for some time. In this study, we extracted VDBPs from two chlorinated effluent organic matters and one chlorinated natural organic matter, using a helium aeration–liquid nitrogen condensation system, and systematically assessed the VDBP and NVDBP toxicities to mammalian cells. VDBPs accounted for 10%–20% of the total organic halogen concentrations in three chlorinated water samples. VDBPs were much less cytotoxic, caused fewer DNA double-strand breaks, induced less reactive oxygen species and DNA/RNA oxidative damage marker of 8-hydroxyl(deoxy)guanosine in cells than did NVDBPs. Moreover, by collecting the VDBPs, toxicity measurement of the full range of DBPs was achieved. Cytotoxicity, reactive oxygen species and 8-hydroxyl(deoxy)guanosine levels were significantly higher for cells exposed to the mixture of VDBPs and NVDBPs than only NVDBPs, but not by large percentages (20%–30% for cytotoxicity), suggesting NVDBPs mainly contributed to the toxicity of chlorinated water. Our study suggested that future research should focus more on NVDBP toxicity and identifying toxicity drivers from NVDBPs.

Assessment of regulated halo-acetic acids disinfection by-products and their concomitant risks in Ahmadu Bello University Zaria drinking water supply

Abstract The conventionally treated drinking water supplied to the Ahmadu Bello University community was assessed for its levels of regulated halo-acetic acids. This is because the Ahmadu Bello University water treatment plant uses calcium hypochlorite in the chlorinated disinfection of its treated water during the treatment process. Longitudinal sampling was undertaken along the treatment and distribution stages of drinking water supply in the community. Between 2008 and 2010, 252 samples were collected and analysed for the regulated halo-acetic acids in accordance with USEPA Method 551.1 (1995) using Methyl Tert-Butyl Ether (MTBE) as extractant and a calibrated Agilent Gas Chromatograph measured their concentrations. All the regulated halo acids recorded their highest concentrations in the chlorinated water sample and these decreased towards house-level water sample except for dichloroacetic acid which increased from the booster station sample with 3.2500E-03±5.8452E-03 mg/L to the house level sample with 3.2511E-03±9.1256E-05 mg/L. The total regulated halo-acetic acid (THAAs) concentrations also decreased from the chlorinated sample concentration of 1.8324E+00±8.1252E-02 mg/L. to the house level concentration of 4.8826E-01±2.8735E-02 mg/L, a situation likely attributable to the turbulent flow during distribution resulting in the increased volatility of the acids in the distribution system. Although not specifically regulated by the Nigerian National Standards, the concentrations of these acids at house level (4.8826E-01±2.8735E-02 mg/L) drinking water is more than the maximum permissible limits of these regulated acids under the USEPA drinking water standard’s maximum contaminant level (MCL) of 0.060 mg/L. In view of their implication in increased risk of cancer and other effects including problems of the reproductive system, these acids’ concentration in household drinking water need to be rigorously monitored and regulated to minimize their risk to health.turbulent flow during distribution resulting in the increased volatility of the acids in the distribution system. Although not specifically regulated by the Nigerian National Standards, the concentrations of these acids at house level (4.8826E-01±2.8735E-02 mg/L) drinking water is more than the maximum permissible limits of these regulated acids under the USEPA drinking water standard’s maximum contaminant level (MCL) of 0.060 mg/L. In view of their implication in increased risk of cancer and other effects including problems of the reproductive system, these acids’ concentration in household drinking water need to be rigorously monitored and regulated to minimize their risk to health.

Coupling changes of disinfectant and bacteria induced by the water stagnation and disinfection strategy.

This paper studied stagnation-induced changes of disinfectant and bacteria using an orthogonal test and kinetic analysis, and then proposed a disinfection strategy. Tap water from a drinking water distribution system and ultrafiltrated water were collected and disinfected with four disinfectants (concentrations were set 0.2-1 mg/L as Cl2. The study had several findings. First, disinfectants expanded lag phases and shortened generation times of the microbiome. Reduction in culturability, substrate responsiveness, respiratory activity, membrane potential and integrity subsequently occurred with increasing disinfection concentration. Second, the disinfectant decay rate decreased with initial disinfection concentration, and the effective disinfection phase (heterotrophic plate count (HPC) was less than 100 cfu/mL) was longer in water samples with lower organic matter. Moreover, the disinfection process was divided into an effective phase and an invalid phase (HPC>100 cfu/mL). Then a disinfection efficiency model was built and the regulation of disinfection by-products (DBPs) production was studied in chlorinated water samples, which provides a general method for other disinfectant studies. The average trihalomethanes (THMs) production during the effective phase (marked as THM/th) and THMs production during the invalid phase (marked as ΔTHM) were proposed to evaluate the DBPs production. The level of THM/th and ΔTHM were lower in ultrafiltrated water than those in tap water. THM/th were negatively correlated with initial chlorine concentration while ΔTHM were positively correlated with initial chlorine concentration. Finally, for the purpose of raising disinfection efficiency and decreasing DBPs, we propose periodic pulse disinfection.

Precursors for brominated haloacetic acids during chlorination and a new useful indicator for bromine substitution factor

Brominated haloacetic acids (HAAs) are much more cytotoxic and genotoxic than chlorinated one, yet little information is available for their organic precursors. In the present study, 8 water samples were collected in East China: 2 from lakes, 2 from rivers, 2 from reservoirs, a well and a mountain spring. Dissolved organic carbon (DOC), UV absorbance at 254 (UVA), specific UVA (SUVA) and chlorophyll a (Chl-a) were determined in raw water samples; formation of 9 HAA species as well as bromine substitution factor (BSF) were measured in chlorinated water samples. Results showed that water samples located in city generally contained higher levels of DOC (6.4–12.2mg/L) and UVA (0.124–0.194/cm), while those in the country side, low DOC (2.4–5.9mg/L) and UVA (0.061–0.109/cm) levels were observed. Negative relationship (p<0.01) was found between SUVA values and Chl-a levels. Among 9 HAA species, 4 brominated HAA were detected. As for BAA and DBAA (i.e. Br-HAAs), their yields (μg/L) were significant related (p<0.05) with DOC; In terms of BCAA and BDCAA (i.e. ClBr-HAAs), they were not only related with DOC, but also with UVA. These two results were quite different from DCAA and TCAA (Cl-HAAs), whose yields (μg/mg C) were only correlated with SUVA values, suggesting that precursors of Cl-HAA, Br-HAA and ClBr-HAA were different from each other, and their aromaticity/hydrophobicity may be in the order of Br-HAA<ClBr-HAA<Cl-HAA. Interrelationship between Br/DOC, SUVA and BSF revealed that BSF can be influenced by SUVA and Br/DOC, but in comparison, Br/UVA was the best indicator to describe BSF. This pattern is not only true in di-HAAs and tri-HAAs in this study, but also valid in other water samples and other species of disinfection by-product (e.g. trihalomethanes, dihaloacetonitriles, trihalonitromethanes).

A new approach to controlling halogenated DBPs by GAC adsorption of aromatic intermediates from chlorine disinfection: Effects of bromide and contact time

Abstract Granular activated carbon (GAC) adsorption has been traditionally used to remove natural organic matter (NOM), the major precursor of halogenated disinfection byproducts (DBPs), in drinking water treatment plants. Recently, a new approach has been developed to effectively control the formation of trihalomethanes, haloacetic acids, and total organic halogen (TOX) in chlorinated drinking water by targeting intermediate aromatic halogenated DBPs instead of NOM using GAC adsorption. However, the applicability of this new approach to different source water matrices and disinfection conditions remained unclear. In this study, the effects of bromide and contact time on the performance of the new approach for DBP control were investigated. Same source waters were also treated with the traditional approach (i.e., using GAC to remove NOM prior to chlorination) and with chlorination only for comparison. With increasing the initial bromide level from 0 to 2 mg/L, the TOX removal with the new approach increased from 52% to 74%, while the removal with the traditional approach increased from 18% to 37%. Besides, as the chlorine contact time increased from 0.5 to 3.0 h, the TOX removal with the new approach increased from 61% to 75%, while the removal with the traditional approach increased from 21% to 36%. Increasing the bromide level and chlorine contact time enhanced the halogenated DBP removal with both new and traditional approaches, but the removal with the new approach was always two times higher or more than that with the traditional approach, which justified the superiority of the new approach. Moreover, various intermediate aromatic halogenated DBPs were detected in the chlorinated water samples and their levels were significantly decreased after the GAC adsorption, which further corroborated the effectiveness of the new approach for DBP control.

Distribution and antibiotic susceptibility profiles of Aeromonas spp. from different aquatic environments in north Lebanon.

Bacteria of Aeromonas genus are ubiquitous organisms in aquatic environments. This work aims to explore the presence of four clinically relevant species in Lebanese waters and to study their susceptibility to antibiotics. One hundred water samples are collected in northern Lebanon from different sources (river, springs, wells, ponds, sea, chlorinated water and sewage) and analyzed by culture methods. The isolates were identified at genus level by a PCR assay targeting gcat gene. The presence of four species (A. hydrophila, A. caviae, A. media and A. veronii) was investigated by a multiplex PCR. The antibiotic susceptibility was also studied. Aeromonas spp. was detected in 28% of investigated samples. In total, 38 isolates were identified as Aeromonas spp (10 out of 7 river water samples, 9 out of 35 spring, 9 among 26 wells, 5 out of 4 sewage samples, 2 out of 5 ponds, 2 out of 8 seawater samples and 1 out of 15 chlorinated water samples). Aeromonas hydrophila was the predominant species (19 isolates; 50%). The 3 other species were found to a lesser extent: A. caviae (3 isolates; 7.9%), A. veronii (2 isolates; 5.3%) and A. media (2 isolates; 5.3%). 12 other isolates (31.5%) remained unidentified by the used multiplex PCR technique. All isolates were resistant to more than one antibiotic. The most common resistance concerned beta-lactams. This study has highlighted the interesting distribution of these species in aquatic biotopes in Lebanon and the threat of potential transmission of these resistant strains to humans.

Changes in Dissolved Organic Matter Composition and Disinfection Byproduct Precursors in Advanced Drinking Water Treatment Processes.

Molecular changes in dissolved organic matter (DOM) from treatment processes at two drinking water treatment plants in Japan were investigated using unknown screening analysis by Orbitrap mass spectrometry. DOM formulas with carbon, hydrogen and oxygen (CHO-DOM) were the most abundant class in water samples, and over half of them were commonly found at both plants. Among the treatment processes, ozonation induced the most drastic changes to DOM. Mass peak intensities of less saturated CHO-DOM (positive (oxygen subtracted double bond equivalent per carbon (DBE-O)/C)) decreased by ozonation, while more saturated oxidation byproducts (negative (DBE-O)/C) increased and new oxidation byproducts (OBPs) were detected. By Kendrick mass analysis, ozone reactions preferred less saturated CHO-DOM in the same alkylation families and produced more saturated alkylation families of OBPs. Following ozonation, biological activated carbon filtration effectively removed <300 Da CHO-DOM, including OBPs. Following chlorination, over 50 chlorinated formulas of disinfection byproducts (DBPs) were found in chlorinated water samples where at least half were unknown. Putative precursors of these DBPs were determined based on electrophilic substitutions and addition reactions. Ozonation demonstrated better decomposition of addition reaction-type precursors than electrophilic substitution-type precursors; over half of both precursor types decreased during biological activated carbon filtration.

The effect of sodium thiosulfate dechlorination on fecal indicator bacteria enumeration: laboratory and field data.

In microbiological water quality testing, sample dechlorination with sodium thiosulfate is recommended to ensure that results accurately reflect the water quality at sample collection. Nevertheless, monitoring institutions in low-resource settings do not always dechlorinate samples, and there is limited research describing how this practice impacts drinking water quality results. The effect of dechlorination on indicator bacteria counts was evaluated by spiking laboratory water with five Escherichia coli (E. coli) concentrations (104-108 CFU/100 mL), chlorinating at six doses (0-0.6 mg/L), holding samples with and without sodium thiosulfate for 5-7 hours, and enumerating E. coli by membrane filtration with m-lauryl sulfate media. Additionally, sub-Saharan African water suppliers enumerated thermotolerant coliform by membrane filtration in paired chlorinated water samples collected with and without sodium thiosulfate. Across all E. coli and chlorine doses in the laboratory, and all field tests, samples held without sodium thiosulfate had lower bacteria counts (p < 0.001). Additionally, chlorinated water supply samples held without sodium thiosulfate had an 87.5% false negative rate. Results indicate the importance of dechlorinating microbiological water quality samples, discarding data from chlorinated samples collected without dechlorination, and reinforcing dechlorination recommendations in resource-limited environments to improve water safety management.

Influence of Transportation Conditions and Postharvest Disinfection Treatments on Microbiological Quality of Fresh Market Tomatoes (cv. Nemo-Netta) in a South African Supply Chain

Postharvest microbial spoilage due to suboptimal transportation and packaging conditions is a key concern for the South African tomato industry. This study investigated the influence of washing with tap water or aqueous disinfectant solutions (chlorinated and anolyte water) on the microbiological quality of tomatoes during storage after transportation in nonrefrigerated trucks along two supply routes when packaged in crates and boxes. Route 1 was 1,093 km from field to storage site, while route 2 was 1,057 km. During transport, the temperature in the trucks fluctuated between 16 and 28°C and the relative humidity between 25 and 94% for route 1, while for route 2, the temperature was between 16 and 30°C and the relative humidity between 28 and 71%. Tomatoes at the pink maturity stage were sampled, treated, and stored for 28 days (11°C). The tomato firmness before treatment was 24.8 N (box samples) and 17.4 N (crate samples) for route 1, whereas it was 22.1 N (box samples) and 20.2 N (crate samples) for route 2. Temperature fluctuation during transportation led to water condensation on tomato surfaces. Tomatoes treated with anolyte water showed the lowest microbial surface burden during storage, with mean aerobic plate counts (APC) of 2.9 log CFU/cm2, coliform counts (CC) of 1.1 log CFU/cm2, and fungal counts (FC) of 2.3 log CFU/cm2. Overall, of the total APC recorded during storage, anolyte-treated samples contributed 9% while chlorinated water-treated samples contributed 30%. Of the total CC, anolyte samples presented 3% while chlorinated water samples made up 12%, and of the total recorded FC, anolyte samples contributed 7% while chlorinated water samples made up 22%. Scanning electron microscopy imaging showed surface cracks, which enable microbial colonization in crate-transported tomatoes. A combination of anolyte treatment and box packaging during transport resulted in the best microbiological quality during storage. The findings of this investigation provide motivation for the adoption of anolyte water as a postharvest disinfection treatment in the tomato industry.