Free Residual Chlorine Concentration Research Articles

Effects of Chlorinated Water on Neurite Length of Cultured Dorsal Root Ganglion Neurons and Semaphorin 3A Content of Cultured Epidermal Keratinocytes

The tap water that we normally use contains certain concentrations of free residual chlorine to kill microorganisms and viruses and make it safe for use. Water containing free residual chlorine not only dries out our hair and skin but can also cause irritation and itching in some people—especially those with sensitive skin or reduced skin barrier function. We investigated the effects of free residual chlorine on cultured dorsal root ganglion neurons and cultured epidermal keratinocytes. First, we measured neurite length in cultured rat dorsal root ganglion neurons. Next, to evaluate the effects of chlorine on semaphorin 3A (Sema3A) and nerve growth factor (NGF) levels in cultured human epidermal keratinocytes, we used an enzyme-linked immunosorbent assay to measure NGF in the supernatant and polymerase chain reaction and Western blot to determine Sema3A and NGF levels. Chlorine elongated the neurite length and increased the number of projections in cultured rat dorsal root ganglion neurons. Although there were no changes in NGF mRNA or protein levels in the supernatant of cultured human epidermal keratinocytes in the presence of chlorine, Sema3A mRNA and protein levels decreased, and the ratio of Sema3A to NGF was also reduced.

Modeling the Chlorine Series from the Treatment Plant of Drinking Water in Constanta, Romania.

Ensuring good drinking water quality, which does not damage the population's health, should be a priority of decision factors. Therefore, water treatment must be carried out to remove the contaminants. Chlorination is one of the most used treatment procedures. Modeling the free chlorine residual concentration series in the water distribution network provides the water supply managers with a tool for predicting residual chlorine concentration in the networks. With regard to this idea, this article proposes alternative models for the monthly free chlorine residual concentration series collected at the Palas Constanta Water Treatment Plant, in Romania, from January 2013 to December 2018. The forecasts based on the determined models are provided, and the best results are highlighted.

Drinking water chlorination in dairy beef fattening bulls: water quality, potential hazards, apparent total tract digestibility, and growth performance

The first study aimed to evaluate the effect of drinking water disinfection (chlorination: NaClO 15%) and conditioning (acidification: H3PO4 diluted 1:5 in water) on water quality, water and feed consumption, apparent total tract digestibility, and its potential hazardous effects on Holstein bulls fed high-concentrate diets. Twenty-four animals (221 ± 20.9 kg of BW, and 184 ± 9.9 days of age) were individually assigned to one of four treatments according to a 2 × 2 factorial arrangement: conditioning (with or without acidification) and disinfection (with or without chlorination). The entire study lasted 210 days. Physicochemical and microbiological water quality, water and feed consumption, haematological and biochemical blood parameters, and apparent total tract digestibility were measured; data were analysed via a mixed-effects model. Chlorination and acidification increased (P = 0.02) free residual chlorine in water, and chlorination reduced (P = 0.01) total coliform and Clostridium perfringens counts in water. Treatment did not affect water consumption, total DM intake, or blood parameters. At the beginning of the study, NDF digestibility decreased (P = 0.04) with acidification, however, this was restored at the end of the study. The second study evaluated the potential benefit of drinking water chlorination and acidification on the performance of crossbred Holstein bulls fed high-concentrate diets under commercial conditions. Ninety-six animals (322 ± 35.0 kg of BW, and 220 ± 14.2 days of age) were allocated into six pens assigned to one of the two treatments: untreated drinking water or drinking water treated with chlorination and acidification for a total of 112 days. Physicochemical and microbiological water quality, water and concentrate consumption, eating behaviour, growth performance, and carcass quality were analysed via a mixed-effects model. Water conditioning and disinfection increased (P = 0.01) free residual chlorine concentration and reduced (P = 0.04) total coliform count in water. Although water consumption and eating behaviour were similar between treatments, water conditioning and disinfection increased average daily weight gain (P = 0.03), BW before slaughter (P = 0.01), and hot carcass weight (P = 0.01). In conclusion, drinking water chlorination and acidification in fattening dairy beef bulls is recommended as it improves growth performance without any detrimental side effects on health or nutrient digestibility.

Flow-based green ceramics microdevice with smartphone image colorimetric detection for free chlorine determination in drinking water

The residual free chlorine concentration is an important parameter to evaluate the potability of water and the efficiency of disinfection in the water treatment system. As a restricted range of residual free chlorine concentration at all points of the distribution network is needed to ensure efficiency and to avoid deleterious effects, fast and in situ quantification of this specie is important. This work deals with the development and validation of two procedures based on DPD (N,N-diethyl-p-phenylenediamine) and OT (ortho-tolidine, 3,3-dimethylbenzidine) for the determination of residual free chlorine in water by exploiting a flow-based microdevice built with Low Temperature Co-Fired Ceramic (LTCC) technology. The analytical signal was monitored by a smartphone camera through RGB values obtained by a free application (Color Grab®). Under optimized conditions, linear ranges within 0.6–2.5 mg/L and 0.1–2.3 mg/L were obtained for DPD and OT methods, with limits of detection and quantification of 0.023 and 0.077 mg/L (DPD) and 0.026 and 0.089 mg/L (OT). Precision expressed as RSD (2.0 mg/L free chlorine, n = 10), was 1.3 % and 0.7 %, respectively. Both procedures were successfully applied to the analysis of samples from a water treatment plant. The flow-based microdevice coupled to digital-image colorimetry is an innovative, sustainable, and cost-effective analytical tool for in-field chemical analysis.

Analysis of Factors Involving Drinking Water Contamination by Glyphosate and/or Nitrate in Urban Areas

This study investigated factors that could be related to drinking water contamination in urban areas in order to obtain quality profiles that characterized presence of the glyphosate and nitrate contaminants. Thus, in a period of one year, 4,853 tap water samples from 89 cities in the northeastern region of the State of São Paulo, Brazil, were analyzed in 21 physicochemical and 2 microbiological parameters. Additionally, 4 demographic variables were also included in multivariate data analysis. Principal Component Analysis of physicochemical and microbiological data showed that glyphosate concentration is positively correlated with nitrate concentration, especially in cities that make exclusive use of groundwater, besides correlating with conductivity and with concentrations of calcium, magnesium, fluoride, chloride, phosphate and free residual chlorine. The inclusion of demographic variables in Principal Component Analysis did not significantly change waters physicochemical profiles, but in cities that exclusive use groundwater for public supply the number of hospitalizations for diarrhea correlated positively with glyphosate, nitrate and chloride concentrations, in addition to conductivity. Linear Discriminant Analysis models involving 5 variables (conductivity and concentrations of calcium, magnesium, chloride and nitrate) were able to predict the cities vulnerability to groundwater contamination by nitrate.

Bacterial community structure and metabolic activity of drinking water pipelines in buildings: A new perspective on dual effects of hydrodynamic stagnation and algal organic matter invasion

Eutrophication and algal blooms have become global issues. The drinking water treatment process suffers from pollution by algal organic matter (AOM) through cell lysis during the algal blooms. Nevertheless, it remains unclear how AOM invasion affects water quality and microbial communities in drinking water, particularly in the stagnant settings. In this study, the addition of AOM caused the residual chlorine to rapidly degrade and below the limit of 0.05 mg/L, while the NO2−-N concentration ranged from 0.11 to 3.71 mg/L. Additionally, total bacterial counts increased and subsequently decreased. The results of Biolog demonstrated that the AOM significantly improved the utilization capacity of carbon sources and changed the preference for carbon sources. Full-length 16S rRNA gene sequencing and network modeling revealed a considerable reduction in the abundance of Proteobacteria, whereas that of Bacteroidetes increased significantly under the influence of AOM. Furthermore, the species abundance distributions of the Microcystis group and Scenedesmus group was most consistent with the Mandelbrot model. According to redundancy analysis and structural equation modeling, the bacterial community structure of the control group was most positively regulated by the free residual chlorine concentrations, whereas the Microcystis group and Scenedesmus group were positively correlated with the total organic carbon (TOC) concentration. Overall, these findings provide a scientific foundation for the evolution of drinking water quality under algae bloom pollution.

Water as Source of Salmonella Species Contamination in Jordanian Broiler Farms

Broiler chickens are a major meat product worldwide. Maintaining the health of flocks is essential for poultry farming and it is critical to minimize exposure to waterborne pathogens. This study determined the extent of Salmonella spp. infections and identified sources of waterborne disease transmission at representative Jordanian broiler farms. We investigated 10 broiler farms located in five Jordanian Governorates; Amman, Irbid, Karak, Zarqa, and Madaba. Cloacal swabs were collected from chickens and water samples were collected from farm tanks, broiler house tanks, and drinking apparatus (drinkers) over three rearing cycles. Water was tested for pH and residual free chlorine. Salmonella spp. was isolated from the cloacal and water samples using biochemical methods and confirmed as Salmonella enterica serovar Enteritidis by PCR. Salmonella enterica serovar Enteritidis was detected at sampled farms at different percentages and the pathogen was found in 16.6% (15/90) of drinkers and 20% (30/150) of cloacal samples. The total and free residual chlorine concentrations in the water were lower than the recommended levels. The average pH was within the recommended values. This study concluded that S. Enteritidis is prevalent in broiler farms in Jordan. Thus, improved hygienic practices at broiler farms and the establishment of national water quality guidelines are necessary to decrease S. Enteritidis transmission in boiler farmers and thus enhance food safety in Jordan.

Decay process of free residual chlorine concentration affected by travel time in water distribution systems

Chlorination is the most widely used method for disinfecting water for human consumption. While the chlorinated water travels through a distribution system, the concentration of free residual chlorine (FRC) declines depending on the natural water characteristics. This study investigated FRC decay in two types of water sources – ground and surface water – with varied concentrations of organic compounds. The travel time variable depended on water consumption patterns of both distribution systems which attend low density populations and their initial project needs. Based on mathematical simulation techniques of water quality models, the study also investigated the effects of water temperature and total organic carbon (TOC) on the kinetic constants (kb) of chlorine decay. Results show that travel time in the most critical locations in the water networks and the minimum disinfectant concentrations required at the entry points were 40 hours and 0.27-0.28 mg L-1 at Vale dos Pássaros housing complex, and 144 hours and 0.30-0.36 mg L-1 at Terras Alphaville housing complex.
 Keywords: disinfection, TOC, water quality.

Solar-powered electrocoagulation treatment of wet flue gas desulfurization wastewater using dimensionally stable anode and induced electrode

Solar-powered electrocoagulation (EC) process is proven to be an alternative option for wet flue gas desulfurization (WFGD) wastewater treatment, due to simultaneous removal of multiple pollutants efficiently and reduce the operation costs significantly. Rapid and stable photoelectricity response is necessary for the removal efficiency of pollutants (eg. COD and turbudity), especially in low solar irradiation intensity. In this paper, dimensionally stable anode (DSA) and operation voltages in EC process driven by solar cells were investigated, for the purpose of the optimized removal of pollutants, including COD, turbidity, (free residual chlorine and chlorine dioxide). The results show that the removal efficiency of COD and turbidity can respectively reach 59.12% and 39.11% within 30 min of illumination time (the enhanced solar radiation = 915.8 W m-2), when Ti-based plates were adopted. The concentration of free residual chlorine and chlorine dioxide can reach 2.70 and 5.31 mg L-1, indicating that chlorine ions present in WFGD wastewater have been converted into active chlorine partly. Solar-powered EC equipped with Ti-based plates have a potential prospect in EC process for WFGD wastewater treatment.

Chlorine Efficiency in the Reducing Coliforms in the Sanitary Effluent of Septic Tank Treatment Systems with Anaerobic Filter

The lack of basic sanitation is still a problem in Brazil, only about half of all sewage produced undergoes treatment, due to difficulties in introducing sanitary effluent treatment plants considering that most Brazilian cities do not have financial resources for implementation and maintenance of these stations. In this way, many cities have been adopting different methods for treating sewage before discarding into the rain network. Thus, this work aimed to analyze the efficiency of chlorine in the reduction of coliforms in the sanitary effluent of a treatment system with septic tank, anaerobic filter and disinfection. Six sanitary sewage treatment systems were evaluated from different condominiums from august to december 2019. To check its efficiency, the following parameters were analyzed: pH, thermotolerant coliforms, free residual chlorine and chemical oxygen demand (COD). The results showed that of the six stations evaluated, only one (16,78%) presented the amount of thermotolerant coliforms within the permissible standards. Furthermore, of these only three stations (50%) presented the concentrations of free residual chlorine according to the required parameters. In addition, COD was high at four (66,66%) of the analyzed stations. These data allow us to conclude that the efficiency of chlorine in the reduction of coliforms in the sanitary effluent from a septic tank treatment system, anaerobic filter and disinfection unfortunately may not be happening, because this type of system needs to be well operated and inspected frequently, since the operation is mostly done by users.

Decreasing Pasteurization Treatment Efficiency against Amoeba-Grown Legionella pneumophila-Recognized Public Health Risk Factor.

Legionellae are gram-negative bacteria most commonly found in freshwater ecosystems and purpose-built water systems. In humans, the bacterium causes Legionnaires’ disease (LD) or a Pontiac fever. In this study, the different waters (drinking water, pool water, cooling towers) in which Legionella pneumophila has been isolated were studied to assess the possible risk of bacterial spreading in the population. The influence of physical and chemical parameters, and interactions with Acanthamoeba castellanii on L. pneumophila, were analyzed by Heterotrophic Plate Count, the Colony-forming units (CFU) methods, transmission electron microscopy (TEM), and Sequence-Based Typing (SBT) analysis. During the study period (2013–2019), a total of 1932 water samples were analyzed, with the average annual rate of Legionella-positive water samples of 8.9%, showing an increasing trend. The largest proportion of Legionella-positive samples was found in cooling towers and rehabilitation centers (33.9% and 33.3%, respectively). Among the isolates, L. pneumophila SGs 2–14 was the most commonly identified strain (76%). The survival of Legionella was enhanced in the samples with higher pH values, while higher electrical conductivity, nitrate, and free residual chlorine concentration significantly reduced the survival of Legionella. Our results show that growth in amoeba does not affect the allelic profile, phenotype, and morphology of the bacterium but environmental L. pneumophila becomes more resistant to pasteurization treatment.

Comparison of commercial disinfectants and an in loco-produced solution: free residual chlorine decay in human supply waters

Abstract The disinfection process is used in the treatment of water for human supply to promote sanitary safety and provide users with drinking water that meets potability standards. Thus, it is necessary to sustain a minimal concentration of free residual chlorine (FRC) throughout the entire distribution system. The present study investigated the decay process of FRC concentration in water destined for human supply. The decay was evaluated in bench-scale testing, using sodium hypochlorite, calcium hypochlorite, sodium dichloroisocyanurate (organic chlorine) as disinfectant agents, and also an alternative disinfectant solution (ADS) produced in loco, with oxidizing and disinfectant properties, which is being used in Brazilian sanitation industry. To evaluate the decay, four models were fitted: first-order, nth-order, limited first-order and parallel first-order, hence determining the corresponding parameters which describe the decay speed of the FRC concentration in water. Achieved results demonstrated that all models were statistically significant and predictive. However, the parallel first-order model produced the best fit. Regarding the evaluated disinfectants, there was preeminence of the ADS solution when compared to the others, since it imparted a higher FRC over time, a behavior indicated by lower values for reaction rate constant in all models and when compared to other disinfectants used in this study.

RECOMMENDATIONS FOR VISITING WATER COMPLEXES DURING COVID-19 PANDEMIC

The coronavirus pandemic has changed the usual way of life of almost every one of us, all areas have shifted to work with limited functioning and activities in quarantine. SARS-CoV-2, the causative agent of COVID-19, is mostly transmitted from person to person by close contact through small droplets (released during coughing, sneezing and talking) contaminated with the virus, or virus particles that linger in the air for several minutes to several hours, less often infection occurs through contaminated surfaces and objects. The objective was to analyze the possibility of safe operation of water complexes (water parks, swimming pools, etc.) during a pandemic COVID-19 in our country.
 Materials and methods. Since November 2019 and so far, we have been taking water samples from one private pool and from the pool of a sports complex in one University in Kyiv, in addition, because of cooperation with the Brovary Regional Department of Laboratory Research of the State Institution «Kyiv Regional Laboratory Center of the Ministry of Health of Ukraine» we have known the results of water control in one under roof water park in Brovary, which is located in Kyiv region. We explored the quality of water by sanitary chemical indices (odor, color, turbidity, pH, water hardness, concentration of ammonia and ammonium ions, chlorides, sulfates, free chlorine, etc.) and microbiological indicators (total microbial count (TMC) and coli bacterial index (index of bacteria of the group of E. coli (CBI)).
 Results of the research. In our research, we analyzed the guidelines on the possibility and conditions of the functioning of water complexes during quarantine restrictions of various countries. We found that the free chlorine level in water samples complies to those recommendation, which WHO is provided in the context of the coronavirus pandemic in private and public water complexes. Currently, there are no studies that suggest the possibility of survival of SARS-CoV-2 virus in swimming pool water or other water entertainment complexes, although experimental data obtained previously with coronaviruses (on cell cultures) other than SARS CoV-2, indicate that they are usually sensitive to strong oxidants, such as chlorine. Therefore, today, we can assume that purified water in swimming pools and other water complexes is not an environment where the SARS-CoV-2 virus can survive. The WHO states that a residual free chlorine concentration ≥ 0.5 mg / L in pool water at pH < 8,0 is sufficient to kill coronaviruses. The virus that causes COVID-19 has been found in the fecal matter of infected people, not just those with symptoms of gastrointestinal disorders. It's generally believed that the excretion of the virus may persist for several days. However, it should be noted that there are no cases of fecal-oral transmission of SARS-CoV-2 now. Therefore, to date, the risk of SARS-CoV-2 transmission by fecal-oral route is assessed as low.
 Conclusions. According to the data from lead countries regarding recommendations for visiting water complexes during the COVID-19 pandemic and because of the lack of our own research in our country, we can talk about the possibility of their implementation in Ukraine. We believe that the constant closure of swimming pools and water complexes, and, consequently, constant breaks in the training of not only professional athletes, but also amateurs, run counter to the recommendations regarding the promotion of a healthy lifestyle. It`s worth to remember that prevention is always better than treatment, and training sports is one of the key points in ensuring the effective work of the body and the immune system in particular, which is especially important during a pandemic.

Forecasting point-of-consumption chlorine residual in refugee settlements using ensembles of artificial neural networks

Waterborne illnesses are a leading health concern in refugee and internally displaced person (IDP) settlements where waterborne pathogens often spread through household recontamination of stored water. Ensuring sufficient chlorine residual is important for protecting drinking water against recontamination and ensuring water remains safe up to the point-of-consumption. We used ensembles of artificial neural networks (ANNs) to probabilistically forecast the point-of-consumption free residual chlorine (FRC) concentration and to develop point-of-distribution FRC targets based on the risk of insufficient FRC at the point-of consumption. We built ANN ensemble models using data from three refugee settlements and found that the risk-based FRC targets generated by the ensemble models were consistent with an empirical water safety evaluation, indicating that the models accurately predicted the risk of low point-of-consumption FRC despite all ensemble forecasts being underdispersed even after post-processing. This demonstrates the usefulness of ANN ensembles for generating risk-based point-of-distribution FRC targets to ensure safe drinking water in humanitarian operations.

Study of the free residual chlorine concentration in drinking water in Benin: case of Cotonou municipality

The drinking water is very qualitatively monitored. Despite this monitoring, there is a deterioration in the Free Residual Chlorine Concentration (CCRL) along the drinking water distribution network of the commune of Cotonou. The objective of studying areas of consumer vulnerability where the CCRL reaches critical thresholds (<0.1 mg / l). To achieve this, water samples were taken from various locations in the supply network every day, from 04/30/2018. The assay method used is called N-Diethyl-P-phenylene Diamine (DPD) with the use of a DR / 890 colorimeter. This work reveal that the CCRL undergoes degradation during its delivery to the consumer's taps with average concentrations mainly above the standard in force [0.1; 0.8 mg / l] at the 5% threshold. The work made it possible to establish a linear model for predicting CCRL concentration as a function of distance and to identify areas of vulnerability in the study area.
 L’eau de consommation est très surveillée sur le plan qualitatif. En dépit de cette surveillance, on constate une dégradation de la Concentration en Chlore Résiduel Libre (CCRL) le long du réseau de distribution d’eau potable de la commune de Cotonou. L’objectif d’étudier les zones de vulnérabilité du consommateur où la CCRL atteint des seuils critiques (< à 0,1 mg /l). Pour y parvenir, des prélèvements d’échantillons d’eau ont été pris à divers endroits du réseau d’approvisionnement chaque jour, du 1er au 30/04/2018. La méthode de dosage utilisée est dénommée N-Diéthyl-P-phénylèneDiamine (DPD) avec usage d'un colorimètre DR/890. Ce travail à révéler, que la CCRL subi une dégradation lors de son acheminement vers les robinets du consommateur avec des concentrations moyennes majoritairement supérieures à la norme en vigueur [0,1 ; 0,8 mg/l] au seuil de 5%. Le travail a permis d’établir un modèle linéaire de prédiction de la concentration en CCRL en fonction de la distance et d’identifier les zones de vulnérabilité de la zone d’étude.

Bulk and pipe wall chlorine degradation kinetics in three water distribution systems

ABSTRACT This paper presents a methodology to estimate free residual chlorine concentrations (FRCC) in full-scale water distribution system (WDS) using different degradation kinetics according to pipe material, age and diameter. Intensive field sampling campaigns and laboratory-scale tests were carried out to estimate total and bulk volume FRCC in three WDS. Bulk kinetic constants were estimated for water temperatures typical of different seasons in the Quebec City area (Canada). With field-measured FRCC at all sampling sites and an estimation of travel times through the use of a hydraulic model, total, bulk and pipe wall kinetic constants were obtained with ranges of 10.2 to 130.4, 4.1 to 43.8 and 8.5 to 114.9 10−3/h, respectively. Pipe wall kinetics tend to dominate the total degradation process for older grey and ductile cast-iron pipes, followed by newer ductile iron pipes and then PVC and pre-stressed concrete pipes (mostly installed from 1990). The developed methodology and results will be useful to improve the prediction of FRCC through hydraulic and water quality modelling.

CALIDAD FISICOQUÍMICA Y ANÁLISIS DE LA CLORACIÓN PARA AGUAS DE ABASTECIMIENTO EN ESPITA, YUCATÁN

<p><strong>Background.</strong> It is undeniable the presence of many other contaminants in the food supply sources, in addition to the pathogens. <strong>Objective.</strong> The objective of this study was to analyze biogeochemical parameters to evaluate the quality of the water from the applied treatment and at the same time determine the ideal doses of chlorine for the disinfection of the supply waters in Espita, Yucatán. <strong>Methodology</strong>. The water quality was determined at sample points (i.e. houses in the areas adjacent to supply wells) during the months of August, October, November and December 2019. The biogeochemical parameters sampled were determined based on standardized methods for analysis of drinking water. <strong>Results.</strong> The free residual chlorine determined in the house-room samples presented lower elevations than necessary (0.10 to 0.25 mg / L) for a residual effect that mitigates the presence of pathogens. According to the comparative analysis, the means of the concentrations of free residual chlorine do not present statistical differences for the four supply wells, which led to a proposed sodium hypochlorite dose of 4.10 and 8.60 mg / L for 0.10 and 0.25 ppm respectively of free residual chlorine. The analysis of the results of the concentrations of ammonia nitrogen (N-NH<sub>3</sub>) showed the existence of recent contamination in the third and fourth samples; for nitrate nitrogen (N-NO<sub>3</sub>), specifically elevated concentrations were also found in the first and second sampling. <strong>Implications.</strong> This analysis is useful for local decision-makers as data-driven or proposed decisions can improve the provision of the water supply service. <strong>Conclusions.</strong> The results suggest contamination of the water by external agents, for example, from agricultural products such as fertilizers and wastewater from sumps connected to wells. No free chlorine concentrations were found that promote the residual effect, it is necessary to implement continuous verification.</p>

MODELING THE CHLORINE-CONVEYING PROCESS WITHIN A DRINKING WATER DISTRIBUTION NETWORK

The distribution network is the last component of a water supply system in which potable water must be provided to the consumer. The presence of chlorine in drinking water is a necessity and a guarantee that water is microbiologically compliant. The study was carried out by means of the Epanet 2.0 program on a future distribution network in the hilly area, in which a simulation period of 4 days was considered. The water quality analysis was performed using the flow rates resulting from the hydraulic simulation. To track the propagation of the contaminant through network pipelines, a maximum permissible value of 0.5 mg/L, entered during the entire simulation period, was considered. The reactions that occur in the bulk flow, were modeled by means of a 1st and 2nd order a decomposition law. The obtained values of the free residual chlorine concentration showed that during the 96 h of simulation, there were certain pipelines in which the chlorine concentration did not meet the minimum allowable limit of 0.1 mg/L. Modeling water quality offers the opportunity to view the decreasing of chlorine concentration, so that the free residual chlorine dosage can be optimized.

Monitoring of chlorine decay in public swimming pools in Medellín (Colombia).

The present work shows the evaluation of the decay of free residual chlorine in several public swimming pools in the city of Medellín, observing that a decrease in residual chlorine does occur. Some factors accelerate the decrease in the concentration of free residual chlorine in recreational water, such as the number of bathers in the pool, the pH, and the temperature of the water. For this reason, the concentration of the disinfectant rapidly decreases to an extent that the health of swimmers could be put at risk. The Authority of Health of Medellín carries out inspection, surveillance and quality control activities of water for recreational use. These purposes of these include guaranteeing the reduction of risk factors to the health of the users of said pools.

Keeping water from kiosks clean: Strategies for reducing recontamination during transport and storage in Eastern Uganda

Drinking water is frequently recontaminated during transport and storage when water is poured into jerrycans. To address this issue, three strategies aiming at reducing these recontamination risks were implemented at water kiosks in Eastern Uganda. In all three strategies, water at the kiosks was chlorinated to a free residual chlorine (FRC) concentration of 2 mg/L at the tap of the kiosk. In addition, water was collected in different containers for drinking water transport: a) uncleaned jerrycans, b) cleaned jerrycans, and c) cleaned improved containers with a wide mouth and a spigot. Water quality in the containers was compared to that of a control group collecting unchlorinated water in uncleaned jerrycans. Water samples were collected at the tap of the kiosk, from the containers of 135 households after they were filled at the tap, and from the same containers in the households after 24 h of water storage. The samples were analysed for counts of E. coli, total coliforms, and FRC. Household interviews and structured observations were conducted to identify confounding variables and to assess the influence of water, sanitation, and hygiene infrastructure and practices on recontamination.All three intervention strategies contributed to significantly lower E. coli recontamination levels after 24 h than in the control group (Median (Mdn) = 9 CFU/100 mL, Interquartile Range (IQR) = 25). Median E. coli counts and mean FRC consumption were higher in uncleaned jerrycans (Median = 1 CFU/100 mL, IQR = 6, ΔFRC = 1.8 mg/L) than in cleaned jerrycans (Median = 0 CFU/100 mL IQR = 2, ΔFRC = 1.6 mg/L) and the lowest in cleaned improved containers (Median = 0 CFU/100 mL, IQR = 0, ΔFRC = 1.2 mg/L). The FRC concentration at the tap of 2 mg/L was too low to protect water from E. coli recontamination in uncleaned jerrycans over 24 h. Cleaning the jerrycans was inconvenient due to their small openings, therefore, sand was used. The cleaning with sand reduced recontamination with E. coli but did not reduce the count of total coliforms. Improved containers with a larger opening allowed for cleaning with a brush and showed the lowest levels of recontamination for both E. coli and total coliforms. In addition to the intervention strategies, households receiving a higher number of WASH education visits within the previous year had lower recontamination levels of E. coli in stored water (OR = 0.54, p = 0.003).