Free Chlorine Levels Research Articles

Overview of the low-cost technologies for household water treatment in developing countries

ABSTRACT This study explored various low-cost water treatment technologies that are used to minimize levels of pathogens and contaminants in raw water. The paper focused on techniques such as cloth filtration, boiling, chlorination, and solar water disinfection. In the communities, cloth filtration is applied as the initial step of treating raw water with the proper choice of cloth fabrics followed by either boiling, chlorination or solar water disinfection. In low-income communities with unclean burning fuel sources, boiling was found to be the preferred method. Chlorination was also a popular technique associated with the challenges of low or high levels of free chlorine at the point of use and disinfection by-products. Solar water disinfection required optimal residence time and detection sensors for microorganism inactivation. Overall, the paper provided valuable insights into the different low-cost water treatment techniques that are commonly used for household applications, particularly in developing countries.

Quality Control of Tap Water and Factors Determining Bacterial Contamination of Households’ Stored Drinking Water in the Town of Aboisso (Côte d’Ivoire)

Piped water must inspire consumer confidence in health and organoleptic terms. In the event of a food poisoning, consumers who have a poor perception of its quality may incriminate it, without taking into consideration that the fact of passing it through a drinking water storage container before consuming it can also cause contamination. The present study carried out in the town of Aboisso aimed to assess the role of water storage in the deterioration of microbiological quality of drinking water, and to identify the predictive factors of the presence of bacteria in stored water. To do this, physicochemical parameters (temperature, pH, conductivity, turbidity and free chlorine) and microbiological parameters (total coliforms, thermotolerant coliforms and <i>E. coli</i>) were measured on water samples taken from taps and storage containers in 94 households. The storage conditions of drinking water were also the subject of a brief household survey. The identification of predictive factors for the presence of total coliforms and <i>E. coli</i> in stored water was done using bivariate analysis and multivariate analysis by binary logistic regression through two models. The first model included the use of a transport container and the storage conditions as independent variables. The second included besides that the values of turbidity and free chlorine. As results, the waters were weakly mineralized and acidic. Free chlorine levels, temperature values, and bacterial loads in tap water were significantly (p < 0.05) higher than those in stored water. While 13.83% of samples taken at the taps were contaminated with total coliforms and 1.06% with <i>E. coli</i>, 50% and 18.09% of those taken in containers were contaminated with total coliforms and <i>E. coli</i>, respectively. In the first model, only the storage duration and the method used to draw water from storage container were statistically associated with the presence of total coliforms while no variable was statistically associated with the presence of <i>E. coli</i>. In the second model, the drawing method and the free chlorine level were significantly associated with the presence of total coliforms while only the free chlorine level was associated with <i>E. coli</i>. These results motivate the need to raise awareness and train populations in drinking water hygiene.

Depletion of Free Chlorine and Generation of Trichloromethane in the Presence of pH Control Agents in Chlorinated Water at pH 6.5

Chlorine is commonly used by the fresh produce industry to sanitize water and minimize pathogen cross-contamination during handling. The pH of chlorinated water is often reduced to values of pH 6–7, most commonly with citric acid to stabilize the active antimicrobial, hypochlorous acid (a form of free chlorine). Previous studies have demonstrated that citric acid reacts with chlorine to form trichloromethane, a major chlorine by−product in water and a potential human carcinogen. However, it is unclear if other pH control agents could be used in the place of citric acid to minimize the formation of trichloromethane. The objective of the present study was to determine the reactivity of organic and inorganic pH control agents, with chlorine, to generate trichloromethane. Free chlorine (∼100 mg/L) was mixed with 10 mM of each of twelve organic acids and two inorganic pH control agents (i.e., sodium acid sulfate and phosphoric acid) to effect a pH level of 6.5. Free chlorine and trichloromethane levels were measured over 3 h at 3 and 22°C. Results demonstrated that ascorbic acid, dehydroascorbic acid, citric acid, and malic acid rapidly depleted free chlorine concentrations at both 22°C and 3°C, while tartaric acid and lactic acid decreased chlorine concentrations more slowly. Other pH control agents did not significantly reduce free chlorine either at 22 or 3°C. Citric acid led to the generation of significantly higher concentrations of trichloromethane than did other acids. Chloroacetone was also found in chlorinated water in the presence of citric acid and ascorbic acid. Taking buffering capacity and pKa values into account, phosphoric acid and some organic acids may be used to replace citric acid as pH control agents in chlorinated water for washing fresh produce, to stabilize free chlorine level and reduce the generation of trichloromethane.

Assessment of Physicochemical and Microbiological Qualities of Drinking Water in Ahmedabad Slum, India: A Cross-Sectional Study

ntroduction: The quality of drinking water is a public health concern, especially in urban slum areas. Drinking water quality and contamination are seriously threatened by the growing slum population and irregular water supply. Objective: To examine the physicochemical and microbiological quality of drinking water in the field practice area of one of the Tertiary-care hospital in Ahmedabad a part of PG teaching activity. Method: A cross-sectional study was carried out for water quality assessment using stratified random sampling. A total of 139 water samples were collected; samples were collected from different households in different areas of the Asarwa ward of Ahmedabad Corporation. From each ASHA worker’s area, according to population of that area, 6 to 10 samples were selected. The samples were analysed using standard methods and compared with WHO and BIS water quality standards. Results: TDS and alkalinity are above permissible levels in 42.4% and 46.7% samples respectively. pH, turbidity, conductivity, total hardness, and magnesium were found altered in a few samples. The mean free residual chlorine was 0.05 mg/L. Microbiological analysis of water samples revealed the presence of coliform in 5 (3.6%) samples. Conclusion: Except for total alkalinity and TDS, most physicochemical parameters of drinking water were acceptable. By storing water, a low level of free residual chlorine can be justified. A few samples (3.6%) with coliform bacteria indicate water contamination somewhere in the distribution system or at the consumer level.

Microbial and physicochemical water quality changes within distribution and premise plumbing systems during a chlorine conversion

A strategy for nitrification control within chloraminated drinking water systems (CDWSs) is to temporarily switch from chloramine secondary disinfection to free chlorine, also known as a free chlorine conversion (FCC). However, the long-term and beneficial effects of FCCs are unclear, especially regarding opportunistic pathogen occurrence. In this study, the impacts to microbial and physicochemical parameters were monitored throughout a CDWS implementing a FCC. Water samples were collected weekly for 4–6 weeks before, during, and after a FCC at eight locations: four distribution system and four residential sites. Monochloramine residual (mean±standard deviation) before and after the FCC averaged 1.8±0.9 and 1.6±1.0 parts per million (ppm) for all sites, respectively. Free chlorine levels averaged 2.3±0.9 ppm. There were no significant differences in turbidity and hardness at each location during the three time periods, but some were noted for pH, temperature, and orthophosphate levels across various sites and sampling periods. For all locations, heterotrophic plate count levels were lower during the FCC compared to the periods before and after. All samples from one residence were culture positive for P. aeruginosa which exhibited high levels before the FCC, decreasing levels during, and steadily increasing levels after. Additionally, one week prior to the FCC, sediment samples from two elevated storage tanks, ET-1 and ET-2, were analyzed with ET-1 displaying higher levels of culturable heterotrophic bacteria and molecularly detected total bacteria, Legionella spp., and nontuberculous mycobacteria (NTM), as well as presence of culturable P. aeruginosa and total coliforms compared to ET-2. Fourteen P. aeruginosa and total coliform isolates were whole genome sequenced with genetic differences observed depending on the sampling location and timepoint. Collectively, the observed differences in chemical and microbial parameters advocates for a better understanding of the effects associated with implementing FCCs to determine both their effectiveness and potential risks/rewards to water quality.

ПРОБЛЕМЫ ЭКСПЛУАТАЦИИ ПЛАВАТЕЛЬНЫХ БАССЕЙНОВ И МЕТОДЫ ИХ РЕШЕНИЯ

The article provides an analysis of pollutants entering the water of swimming pools. We identified the main factors affecting the quality of water filtration and circulation in swimming pools. Based on extensive practical experience, we considered the main methods of water disinfection using chemical reagents with the formation of disinfection by-products as well as commonly used methods of their removal. We also analyzed additional water disinfection methods using specialized equipment, with a description of the harmful substances formed during their application. We described possible options for determining free and combined chlorine levels. We as well discussed water analyzers for swimming pools, focusing on the types of sensors that determine the free chlorine content and the impact of external factors on the final readings. Finally, we recommended ways to improve the operation of swimming pools.

Monitoring seasonal variations of haloacetic acids (HAAS) in low-TOC and low-chlorine networks and assessing risk to public health: Muş, Türkiye case

Chlorine not only removes parasitic pathogenic microorganisms in water, but also causes the formation of disinfection by-products (DBPs) that can be carcinogenic to humans, due to reacting with natural organic matter (NOMs) in raw water sources. Haloacetic acids (HAAs) are one of the most well-known and common disinfection by-product groups (DBPs) in the literature. In the risk definitions of the EPA, some of its components have been identified as carcinogenic. Therefore, determination of HAA concentration in water and execution of a risk analysis are very important in terms of determining the possible effects on public health. This study aimed to monitor the seasonal and spatial variations of haloacetic acids (HAAs) in 2 different water supplies (surface and groundwater) serving the city center of Muş Province, Türkiye, and to demonstrate their public health implications. In this context, an analytical study was conducted covering 4 seasons. According to the results, although the amount of NOM in water bodies was less than 1 mg‧L−1, the HAA5 content may occasionally exceed the USEPA limits of 60 µg‧L−1, but did not exceed the Canadian 80 µg‧L−1 limit. When the WHO limit values were examined on a component basis, it was determined that the MCAA concentrations in both water sources sometimes exceeded the limit of 20 µg‧L−1 in the July and October sampling periods. The risk level related to maximum DCAA level in the main network by means of ingestion pathway was found to be 18.7 times higher for women and 16.5 times higher for men when compared with USEPA risk criteria. Also, in the Muratpaşa water network, risk from DCAA exceeds the USEPA risk level 15.2-fold in women and 13.4-fold in men. However, since it was also found that the level of free chlorine in the network does not meet the required level, it should be noted that there may be an increase in the risk level if there is adequate chlorination in the supply.

Carbon‐Based Electrochemical‐Free Chlorine Sensors

AbstractSodium hypochlorite is a widely used additive in water used to disinfect and remove any disease‐causing bacteria that can be found in sources of water, and is used to wash contaminants from meats, fruits, and vegetables. Many free chlorine sensors exist which monitor free chlorine levels such as the use of colorimetric or electrochemical methods, ensuring that the free chlorine is within safe and regulated levels. However colorimetric sensing methods are irreversible and often use toxic compounds, and electrochemical sensors, although reversible, are made with materials which are not suitable to be used near drinking water or food products. By developing sensors which are made using alternative materials and methods, the sensors can be used in and around drinking water and food products. This review article discusses various electrochemical‐free chlorine sensors made with various carbon‐based materials and methods resulting in sensors that are biodegradable, relatively inert, and resilient in the presence of harsh chemicals, making them safe to use near and around food and still maintain competitive performance parameters. This review article showcases some of the recent progress, the importance, preconditions, and the various future needs and potentials of carbon‐based electrochemical‐free chlorine sensors.

Evaluation of Drinking Water Quality and Treatment from Coolers in Public Places in Madinah City, Saudi Arabia

The aim of this work is to prevent the public drinking from water coolers, by using an auto-detection process, if the quality of water is low. Therefore, the proposed water treatment management system for allows the activation of dispensers to provide the best-quality water coolers. The objective is to investigate the quality of the drinking water from coolers in public places in Madinah and to provide clean, safe, and healthy drinking water for the general public. The methodology consisted of performing different analyses, tests, and water treatments, such as physicochemical analyses of the water samples, measurements of the different concentrations of anions, measurements of the concentrations of heavy metals, and bacteriological tests of the water samples. Therefore, 66 water samples were tested, and the experimental values were compared with the reference values given by the World Health Organization (WHO) and Saudi Standards, Metrology, and Quality Organization (SASO) for drinking water. The tests revealed that the physicochemical parameters (pH, EC, TDS, and TH) of different water sources (95.5%) were in accordance with the SASO and WHO values. In addition, all the analyzed water samples (100%) contained permissible levels of nitrates, sulfates, nitrites, and free residual chlorine, as indicated by the results. However, 68.2% of the samples studied had fluoride concentrations below the standard limits. Furthermore, heavy metals such as lead, iron, and others were tested for all water coolers. The measured findings indicated that just one cooler exceeded the permissible limit of 0.3 mg/L for Fe, and the biological contamination testing revealed that 4.5% of the coolers were infected with coliforms. Finally, this research suggests that water coolers should be regularly maintained. Additionally, using the best design for the water desalination process is very important to give the best drinking water quality.

Environmental, social, and WASH factors affecting the recurrence of cholera outbreaks in displacement camps in Northeast Nigeria: a rapid appraisal

Abstract In 2021, Nigeria witnessed a severe cholera outbreak that affected Borno state, in which more than 1,600,000 internally displaced persons (IDPs) resided at the time. This rapid appraisal explored factors that facilitate the recurrence of cholera outbreaks in sites hosting IDPs in Northeast Nigeria. Semi-structured interviews were conducted with water, sanitation, and hygiene (WASH), management, and healthcare personnel working in ten displacement camps in Borno state. The interviews were complemented by transect walks and field observations, measurements of free residual chlorine levels, and publicly available data published by the International Organization for Migration Displacement Tracking Matrix. The recurrence of cholera outbreaks appears to be facilitated by substantial interactions between IDPs and host communities, and suboptimal WASH services in camps. Of particular concern, IDP camps are exposed to extreme weather-related events that damage facilities and subsequently affect WASH practices. WASH services in camps may likewise be severely hindered by an influx of new arrivals. In conclusion, we emphasize the importance of expanding WASH activities to host communities and developing site-specific WASH interventions and chlorination targets. Practical recommendations are needed for the prevention and control of outbreaks following extreme weather-related events and population influxes.

Formation of Dichlorine Monoxide for Organic Pollutant Degradation by Free Chlorine in High Chloride-Containing Water

Several ppm levels of free chlorine in high chloride-containing water of no less than 0.20 M show remarkably high degradation rate constants toward carbamazepine (kCBZ′). Dichlorine monoxide (Cl2O) was identified to be responsible for the high kCBZ′. Cl2O degrades aromatic pollutants connected to more electron-donating functional groups faster when comparing kCl2O to 1,4-dimethoxybenzene, bisphenol A, benzoic acid, and CBZ. However, its formation at low free chlorine levels in high chloride-containing water cannot be explained by our current knowledge. We proposed an alternative Cl2O formation mechanism, in which chloride transforms hypochlorous acid/hypochlorite (HOCl/ClO–) to dichlorine (Cl2) and polychloride monoanions (Cln–), which then react with HOCl/ClO– to form Cl2O. Decreasing pH from 8.60 to 4.33 increases Cl2 concentrations and thus generates about 600× higher Cl2O concentrations. Weak acid anions, for example, phosphate and bicarbonate, are strong nucleophiles assisting the Cl2O hydrolysis, but their presence at the testing conditions does not much affect kCBZ′. The proposed alternative Cl2O formation mechanism reveals the roles of chloride in shifting the equilibrium toward the Cl2O formation, allowing the simple chlorine addition strategy to degrade recalcitrant organic pollutants in high chloride-containing wastewater. It may also change our understanding of the speciation of different free chlorine species and their impacts on the DBP formation in high chloride-containing wastewater.

Poly(caffeic acid) Redox Couple Decorated on Electrochemically Reduced Graphene Oxide for Electrocatalytic Sensing Free Chlorine in Drinking Water

Regular water quality measurements are essential to the public water supply. Moreover, selective free chlorine (disinfectant) level monitoring without an interfering agent is necessary. The present work aimed to fabricate poly(caffeic acid) (p-CFA) coated on an electrochemically reduced graphene oxide (ERGO) surface for the selective detection of free chlorine. Electron microscopy and various spectroscopic techniques confirmed the p-CFA@ERGO/glassy carbon (GC) electrode. The p-CFA@ERGO/GC coated probe surface coverage was calculated to be 4.75 × 10-11 mol cm-2. The p-CFA@ERGO/GC showed superior catechol/o-quinone oxidation/reduction peaks for electrocatalytic free chlorine determination. The performance of the developed sensor electrode was outstanding, with an extensive range of free chlorine detection (20 μM to 20 mM), high sensitivity (0.0361 µA µM-1), and low detection limit (0.03 µM). The p-CFA@ERGO/GC capability of the realist water samples, such as the tested commercial and tap water, yielded a good range of recovery (from 98.5% to 99.9%). These values align with the standard N,N'-diethyl-p-phenylenediamine reagent method results.

Tunable functionalization of poly(ethylene terephthalate) with short-chained quaternary ammonium salt and N-chloramine to enhance conversion of N-H to N-Cl and the antibacterial activity of the resulting N-Cl

Cross-contamination mediated by fomites such as textiles has been identified as one of the major pathways of infectious disease transmission. It is therefore critical to endow those substrates with rechargeable potent antimicrobial activity. N -chloramines, compounds with N-Cl bonds, are a typical group of broad-spectrum effective antimicrobials. Once immobilized onto a substrate, N -chloramines can attain repeated cycles of killing pathogens (loss of active chlorine) and regeneration (recovery of the original N -chloramine structure). However, relatively high levels of free chlorine are needed to recharge the biocidal function on N -chloramine containing textile substrates especially on such hydrophobic ones such as poly(ethylene terephthalate) (PET). We found the introduction of a short-chained quaternary ammonium group to N -chloramines could lead to higher conversion rate of surface bound N-H to N-Cl. Here, we separately clicked an azido N -chloramine precursor (AzH) and a short chain QAS (AzQAS) onto a previously established clickable PET platform to explore the effect of such surface bound QAS on the conversion of surface N-H to N-Cl and the antibacterial activity of the resulting N-Cl. Despite not being covalently bonded to hydantoin, the source of a cyclic N-H, the positive charge center dramatically facilitates the conversion of the hydantoin N-H to N -chloramine in dilute chlorine bleach (<250 ppm Cl 0 ). At a 5 0 :50 ratio to the cyclic N -chloramine precursor (hydantoin), the surface bound QAS enables the PET substrate, after being activated with dilute chlorine bleach (100 ppm Cl 0 ), to achieve 5.81 log reduction of MDR- E. coli within 10 minutes of contact. • A new way to achieve tunable functionalization of poly(ethylene terephthalate) (PET) with short-chained quaternary ammonium salt (QAS) and N-chloramine at varying ratios • Despite being separately bonded to PET surface with an N-chloramine precursor hydantoin, a quaternary ammonium molecule can dramatically facilitate the conversion of the hydantoin N-H to N-chloramine in dilute chlorine bleach (<250 ppm Cl0). • At a 50:50 ratio to the cyclic N-chloramine precursor (hydantoin), the surface bound QAS enables the PET substrate, after being activated with dilute chlorine bleach (100 ppm Cl0), to achieve 5.81 log reduction of MDR-E. coli within 10 minutes of contact. • Positive charge contributes to faster killing of MDR-E. coli by N-chloramine immobilized on PET.

Synergistic nanowire-assisted electroporation and chlorination for inactivation of chlorine-resistant bacteria in drinking water systems via inducing cell pores for chlorine permeation

The widespread use of chlorination (Cl2) in drinking water systems causes the selection of chlorine-resistant bacteria commonly with dense extracellular polymeric substance (EPS) against chlorine permeation, posing significant threat to public health. Herein, a nanowire-assisted electroporation (EP) via locally enhanced electric field was combined with Cl2 to construct the synergistic EP/Cl2 disinfection, with the purposes of inducing cell pores for chlorine permeation and bacterial inactivation. The synergistic effects of EP/Cl2 were observed for inactivation of chlorine-resistant Bacillus cereus (G+, 304 μg DOC-EPS/109 CFU) and Aeromonas media (G-, 35.8 μg), and chlorine-sensitive Escherichia coli (G-, 5.1 μg) that were frequent occurrence in drinking water systems. The EP/Cl2 enabled above 6 log B. cereus inactivation (undetectable live bacteria) at 1.5 V-EP and 0.9 mg/L-Cl2, which was much higher than the individual EP (1.11 log) and Cl2 (1.13 log) disinfection. The cell membrane integrity, intracellular free chlorine levels, and morphology analyses revealed that the electroporation-induced pores on cell wall/membrane destructed the bound EPS barrier for chlorine permeation, and the pore sizes were further enlarged by chlorine oxidation, hence facilitating bacterial inactivation via destroying the cell structures. The excellent disinfection performance for tap water and lake water also suggested its sound application potentials.

Shift to remote learning degrades water quality in buildings

AbstractCommercial and institutional buildings now experience weeks and even months with below‐normal occupancy due to remote work/learning, which results in reduced water use and has the potential to adversely impact water quality. This study monitored the variations in water quality in multiple university buildings during several months of below‐normal occupancy followed by several months of normal occupancy. The levels of free chlorine, copper, and cellular ATP in water varied within buildings and between buildings. Using Wi‐Fi activity as a surrogate for building occupancy, the free chlorine concentration in water increased as Wi‐Fi counts increased. The copper concentration in building water was higher when the occupancy was below‐normal compared with normal occupancy, and the copper concentration decreased as Wi‐Fi counts increased. Throughout the study, flushing a fixture at the time of use decreased the concentrations of copper and cellular ATP and increased the concentration of free chlorine.

Chlorine vs. Sodium Chloride Regeneration of Zeolite Column for Ammonium Removal from an Explosives Impacted Mining Wastewater

There has only been limited research on ammonium removal by zeolites followed by chlorine regeneration; these studies used batch tests and, in many cases, only dealt with single solute solutions as opposed to multi-component ones. To better simulate full-scale applications, this study used a continuous-flow ion exchange (IE) column system to assess the feasibility of chlorine regeneration of a zeolite IE column used for the removal of ammonium from synthetic explosives impacted mining wastewater (EIMWW). Multi-cycle column loading-regeneration tests were used to evaluate and compare the performance of a NaOCl (1000 ppm as free Cl2) solution with that of a standard salt regeneration solution (5% NaCl). In addition, the impact of two loading cycle durations was evaluated. After three operational cycles with 6 h loading phases, the TAN (total ammonia nitrogen) uptake after NaOCl regeneration was almost the same as that obtained with salt regeneration (0.21 meq/g vs. 0.21 meq/g). The zeolite with NaOCl regeneration showed a higher preference for TAN than with NaCl regeneration (Ca:TAN:K = 2.8:2.3:1 vs. 2.5:1.9:1 for the 6 h loading phase); however, the NaOCl regeneration took longer to complete. It was also found that effluent pH, total chlorine level, and free chlorine level during the chlorine regeneration were positively related, seemingly confirming that the ammonium is oxidized to nitrogen gas and producing hydrogen ions. Regardless of the regeneration solution, if one uses a two-column system, with one column online and the other offline, the shorter loading cycles (6 h) yield a substantially higher daily TAN removal rate.

Presence of bromide and iodide promotes the horizontal transfer of antibiotic resistance genes during chlorination: A preliminary study

Chlorination was reported to have a great potential to increase horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs), which poses a great threat to global human health. Bromide (Br−) and iodide (I−) ions are widely spread ions in water and wastewater. In chlorination, Br− and I− can be oxidized to active bromine and iodine species. The influence of the co-existing different halogen oxidants (chlorine + bromine or iodine species) on HGT of ARGs were rarely investigated. In this study, the conjugative transfer of ARGs between a donor strain E. coli K12 and a recipient strain E. coli HB101 was investigated in chlorination without/with the presence of Br− or I−. Immediately after the addition of sodium hypochlorite, 53–88 % of the dosed chlorine was rapidly consumed, 10 %–42 % fast transformed into organic combined chloramines, and only low levels of free chlorine (0.02–0.8 mg/L as Cl2) left in the diluted cultural medium. Conjugative transfer mediated by the RP4 plasmid was not significantly enhanced in chlorination without the presence of Br− or I−. With the presence of Br− (0.5–5.0 mg/L) or I− (0.05–0.5 mg/L) in chlorination, the co-existing free halogen oxidants and their organic combined ones up-regulated the mRNA expression of the oxidative stress-regulatory gene (rpoS), outer membrane protein gene (ompC), and conjugation-relevant genes (trbBp and trfAp), and caused more damage to cell entirety. As a result, the co-existing reactive halogen oxidants enhanced the HGT of ARGs probably via conjugative transfer and transformation. This study showed that the presence of Br− and I− of common levels in aquatic environment promoted HGT of ARGs in chlorination, thus accelerating the transmission and prevalence of ARGs.

Environmental surveillance of Legionella in tourist facilities of the Balearic Islands, Spain, 2006 to 2010 and 2015 to 2018.

BackgroundLegionnaires’ disease is a respiratory illness often associated with hotels and travel. Spain is a major tourist destination and one of the European countries with most cases of Legionnaires’ disease , both community- and travel-associated. However, the prevalence of Legionella in tourist facilities is unknown.AimThe present investigation aimed to survey the tourist facilities in the Balearic Islands, Spain, for Legionella prevalence.MethodsWe visited tourist facilities in the Balearic Islands in two different periods (2006–2010 and 2015–2018) and took water samples following national and international guidelines. Legionella was investigated by culture methods following international standards (ISO 11731:1998).ResultsWe evaluated 13,472 samples from 465 facilities. Bacteria of the Legionella genus were detected in 65.4% of the surveyed facilities. Contamination of the facilities was significantly higher during the second decade (54.5 vs 78.6%). The most frequent colonisers were L. pneumophila serogroup 2–14. We detected the pathogen in 15.9% and 6.9% of hot and cold water distribution systems samples, respectively. The Legionella contamination rate in cold water systems samples was higher when free chlorine levels were < 0.2 mg/L and at > 25 °C temperatures, while in the hot water systems samples, the contamination rate was higher at < 50 °C. Of the samples from hot tubs, 10.9% were contaminated.Conclusion Legionella prevalence in hotels in the Balearic Islands was high but the contamination rates depended on the installations. Corrective measures are still needed to improve Legionella control.

Prevalence of antibiotic resistance genes in drinking water of the Kathmandu Valley, Nepal

In resource-limited settings, fecal indicator bacterial analysis is the only microbiological water quality test performed, and emerging contaminants, such as antibiotic resistance genes (ARGs), are often neglected. To address this knowledge gap, water samples were collected from shallow wells (n = 24), deep wells (n = 16), stone spouts (n = 14), springs (n = 8), tanker filling stations (TFS; n = 12), water tankers (n = 12), and drinking water treatment plants (DWTPs; n = 6 each of raw and treated water) of the Kathmandu Valley, Nepal, between December 2015 and August 2016 to investigate the presence of five ARGs (blaNDM-1, blaCTX−M, tetB, qnrS, and sul1) and class one integrase gene (intI1). All ARGs were detected in water samples from shallow wells and stone spouts, whereas blaNDM-1 and blaCTX−M were not detected in deep wells and springs. tetB and intI1 were detected at a greater number of water tanker samples than TFS, indicating that water tankers were not disinfected regularly. Only sul1 and intI1 were detected in treated water of DWTPs. Persistence of intI1 throughout the water treatment process and significantly strong correlation (ρ > 0.5, p < 0.05) with the majority of ARGs included in our study suggested the suitability of intI1 to assess the contamination and fate of ARGs in drinking water of the valley. Low free chlorine levels in treated water before pipeline distribution urge water quality managers to evaluate tap water for pathogens and ARGs. Further studies are recommended on emerging contaminants, such as antibiotics, in drinking water sources that are not routinely assessed but can provide selective pressure for the spread of antibiotic resistance in the environment.

Agent‐based simulation of cross‐contamination of Escherichia coli O157:H7 On lettuce during processing with temperature fluctuations during storage in a produce facility. Part 1: Model development

AbstractA food safety agent‐based model (FS‐ABS) with discrete time event simulation using NetLogo© was developed to predict the levels of cross‐contamination in a lettuce processing facility. Visualization of the whole processing line shows different lettuce pieces around each equipment's surface. The focus was set on Romaine lettuce processing and on the impact of cross‐contamination, free‐chlorine concentration on wash‐water, and cold storage room temperature fluctuation strategies on E. coli O157:H7 growth. Microorganism decay, growth, and transfer models in the wash water, equipment, and lettuces were embedded in a discrete event simulation model to deal with the growing complexity and uncertainties occurring in processing plants. The model was developed based on literature data. Lettuces were considered agents that move through the processing line moving from patch‐to‐patch agents that have their own attributes, including levels of contamination and probability of microbial transfers. Space was represented by a 2‐D grid‐based equipment with multiple attributes. Space provides the environmental basis for movements and interactions of lettuces. The storage facility was simulated as a continuous agent‐based model, which runs parallel with the main program (processing facility). This article describes the development of the model along with assumptions and semi‐empirical models used to describe cross‐contamination during processing and pathogen growth during storage. Part 2 discusses the model verification, calibration, validation, sensitivity analysis, and results from different scenarios.Practical ApplicationsWe simulated the cross‐contamination of a common pathogen, E. coli O157:H7, in a fresh‐cut lettuce processing facility using the agent‐based model (ABM) approach. This approach captures the complex interactions between factors and emergent results based on agents' (lettuce and equipment) interactions within the model that other types of models cannot. These interactions are essential in understanding the dynamics of cross‐contamination in the post‐harvest processing chain of fresh‐cut leafy‐greens. Most of the factors that affect cross‐contamination in fresh‐cut lettuce (equipment surfaces, lettuces, wash water) were considered in this study. Wash water quality was monitored in terms of the residual free chlorine (FC) levels and the organic matter accumulation measured as chemical oxygen demand (COD). Pathogen growth due to temperature abuses during storage (post processing) were integrated into the model. Available literature data from a pilot size fresh‐cut processing facility were used to create the model.