Free Residual Chlorine Research Articles

Inactivation kinetics of gram-negative bacteria in the presence of residual free chlorine

Inactivation kinetics of gram-negative bacteria in the presence of residual free chlorine

Application of Water Quality Index in Assessment of Swimming Pools Water Quality in Hotels in Emerging Africa Littoral Metropolis of Warri, Delta State, Nigeria

Swimming pools in guest houses and hotels in many cities in sub-Saharan Africa have been labelled ‘beautiful irritation’ or hazard zones for public health issues due to the unwholesomeness of water. Pollution in swimming pools is therefore, not uncommon and it is a serious public health issue both at the global, regional, national and local levels. This study focused on application of water quality index in assessment of swimming pools water quality in hotels in emerging Africa littoral metropolis of Warri, Delta State, Nigeria. It used stratified random sampling technique to select five hotels with swimming pool in Warri for assessment. Temperature, pH, turbidity, free (residual) chlorine, total heterotrophic bacteria, total heterotrophic fungi, Escherichia coli and Staphylococcus aureus tested in the laboratory using scientific method of sampling. Water quality index (WQI) was computed using Weighted Arithmetic Water Quality Index (WAWQI) to evaluate in general, the quality of water in each of the five sampled swimming pools. A five-point scale (excellent, good, poor, very poor and unsuitable) was used to rank each swimming pool quality. Result showed that Wellington Hotel had the value of 2.52 and considered excellent in terms of water quality index value. Also, Brook View and Best Western Plus Hotels were classified as good water based on water quality index values of 36.9 and 39.9 respectively while BB swimming pool was ranked poor due to water quality index of 51.4. In contrast, Oasis Place Hotel swimming pool was declared unsuitable for recreational purpose due to a water quality index of 102.1. The study recommended routine and periodic surveillance of swimming pools and other recreational water sources to guarantee optimum health and wellbeing of users.

Measurement of free chlorine levels in water using potentiometric responses of biofilms and applications for monitoring and managing the quality of potable water

Residual free chlorine is not monitored continuously at scale in drinking water distribution systems because existing real-time sensor technologies require frequent maintenance, cleaning, and calibration, which makes these products too costly to be used throughout a distribution system. As a result, current measurement approaches require manual sampling, which is not feasible for the consistent monitoring of free chlorine because chlorine concentrations vary significantly throughout pipeline distribution and over time and space. This research presents an alternative and cost-effective method of predicting free chlorine levels in drinking water using graphite electrodes coated with naturally grown microbial biofilms. This Microbial Potentiometric Sensor (MPS) array was installed in a Continuously Mixed Batch Reactor (CMBR), and drinking water containing variable free chlorine concentrations. The chlorine concentrations were introduced in a controlled manner, and the MPS signals were monitored over time. MPS signals were measured from the change in Open Circuit Potential (OCP) across the MPS array in real-time. An empirically derived relationship between the normalized change in OCP and free chlorine was established by fitting individual and average MPS data to a decaying exponential growth function in order to predict free chlorine levels. The results show that free chlorine can be predicted with reasonable accuracy, with model validation showing an average absolute error of ±0.09 ppm below 1.1 ppm and ±0.30 ppm between 1.1 and 2.7 ppm. However, the accuracy of predictions was reduced at higher free chlorine levels. The researchers conclude that MPS systems may benefit drinking water distribution systems by measuring free chlorine. These advantages of the MPS are especially pronounced in the developing world because this system is inexpensive and does not require routine maintenance or cleaning. The system relies on a naturally forming and regenerating biofilm and an inexpensive potentiometric meter to produce stable measurements.

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).

Evaluation of Dialysis Water Quality at Hospitals in Baghdad, Iraq.

Background.Dialysis water quality is one of the most important factors for ensuring the safe and effective delivery of hemodialysis. It has been known for over a decade that there might be hazardous contaminants in the water and concentrates used to prepare dialysis fluid. Rigorous international standards for the purification of dialysis fluids have been established, which were used in the present study to compare the quality of dialysis water as there is no national standard for dialysis water quality in Iraq.Objectives.There are more than 20 dialysis centers in Iraq, most of which contain similar units for the processing of dialysis water. The present study evaluated the quality of water used for dialysis in four dialysis centers located within Baghdad hospitals.Methods.Physical and chemical tests were carried out in the laboratory after sampling water from each dialysis center. Water samples were collected from three locations in each dialysis center. Hospital municipal water samples were collected from the tanks feeding dialysis units; samples of dialysis water were collected from the dialysis water treatment unit outlets; and samples of dialysis water were collected from the distribution network in dialysis rooms.Results.The results showed a fluctuation in the quality of the dialysis water (dialysis water and water from the dialysis distribution network), indicating that it is unacceptable compared to international standards. Chemical analysis showed that 75% of the dialysis water had elevated aluminum concentrations. Chemical analysis also found that dialysis water had elevated concentrations of free residual chlorine at some dialysis centers.Conclusions.All hemodialysis centers need careful monitoring and preventive maintenance to ensure good water quality. In addition, it is important to revise the design of the water treatment units according to water quality.Competing Interests.The authors declare no competing financial interests

Evidence-based chlorination targets for household water safety in humanitarian settings: Recommendations from a multi-site study in refugee camps in South Sudan, Jordan, and Rwanda

The current Sphere guideline for water chlorination in humanitarian emergencies fails to reliably ensure household water safety in refugee camps. We investigated post-distribution chlorine decay and household water safety in refugee camps in South Sudan, Jordan, and Rwanda between 2013-2015 with the goal of demonstrating an approach for generating site-specific and evidence-based chlorination targets that better ensure household water safety than the status quo Sphere guideline. In each of four field studies we conducted, we observed how water quality changed between distribution and point of consumption. We implemented a nonlinear optimization approach for the novel technical challenge of modelling post-distribution chlorine decay in order to generate estimates on what free residual chlorine (FRC) levels must be at water distribution points, in order to provide adequate FRC protection up to the point of consumption in households many hours later at each site. The site-specific FRC targets developed through this modelling approach improved the proportion of households having sufficient chlorine residual (i.e., ≥0.2 mg/L FRC) at the point of consumption in three out of four field studies (South Sudan 2013, Jordan 2014, and Rwanda 2015). These sites tended to be hotter (i.e., average mid-afternoon air temperatures >30°C) and/or had poorer water, sanitation, and hygiene (WASH) conditions, contributing to considerable chlorine decay between distribution and consumption. Our modelling approach did not work as well where chlorine decay was small in absolute terms (Jordan 2015). In such settings, which were cooler (20 to 30°C) and had better WASH conditions, we found that the upper range of the current Sphere chlorination guideline (i.e., 0.5 mg/L FRC) provided sufficient residual chlorine for ensuring household water safety up to 24 hours post-distribution. Site-specific and evidence-based chlorination targets generated from post-distribution chlorine decay modelling could help improve household water safety and public health outcomes in refugee camp settings where the current Sphere chlorination guideline does not provide adequate residual protection. Water quality monitoring in refugee/IDP camps should shift focus from distribution points to household points of consumption in order to monitor if the intended public health goal of safe water at the point of consumption is being achieved.

Assessing the factors affecting the water chemistry parameters in the auxiliary water system of a nuclear power plant

Cooling towers are used as a final heat sink which cools the reactor auxiliary systems and transfers the heat energy to the atmosphere. The reliability endowed upon the cooling tower operation in a nuclear power plant is considerably high when compared to other power plants since the proper functioning of auxiliary systems is crucial for the decay heat removal from the core. Hence, appropriate chemistry control is mandatory in the operation of cooling towers for corrosion control, scale prevention, and control of biological growth. The operating data and water chemistry parameters like conductivity, turbidity, free residual chlorine, pH, cycles of concentration, chlorides, hardness, and alkalinity are analyzed for a typical nuclear power plant. The effect of the individual water quality parameter is correlated by the Pearson matrix to find its influence on the system water chemistry parameter. It is observed that the build-up of chloride ions in the cooling water is the major contributing factor for the cooling tower feed and bleed operations. The aspect of reducing the feed and bleed operation is analyzed, and suitable modifications are suggested to reduce water consumption.

Impact of community health promoters on awareness of a rural social marketing program, purchase and use of health products, and disease risk, Kenya, 2014–2016

Abstract The Safe Water and AIDS Project (SWAP), a non-governmental organization in western Kenya, opened kiosks run as businesses by community health promoters (CHPs) to increase access to health products among poor rural families. We conducted a baseline survey in 2014 before kiosks opened, and a post-intervention follow-up in 2016, enrolling 1,517 households with children <18 months old. From baseline to follow-up, we observed increases in reported exposure to the SWAP program (3–11%, p = 0.01) and reported purchases of any SWAP product (3–10%, p < 0.01). The percent of households with confirmed water treatment (detectable free chlorine residual (FCR) >0.2 mg/ml) was similar from baseline to follow-up (7% vs. 8%, p = 0.57). The odds of reported diarrhea in children decreased from baseline to follow-up (odds ratios or OR: 0.77, 95% CI: 0.64–0.93) and households with detectable FCR had lower odds of diarrhea (OR: 0.53, 95% CI: 0.34–0.83). Focus group discussions with CHPs suggested that high product prices, lack of affordability, and expectations that products should be free contributed to low sales. In conclusion, modest reported increases in SWAP exposure and product sales in the target population were insufficient to impact health, but children in households confirmed to chlorinate their water had decreased diarrhea.

The assessment of environmental health status in the route of Arbaeen pilgrims at Shalamcheh border in southwestern Iran

The negligence of health regulations in the preparation of the foods, services, and sanitary and welfare facilities provided in religious borders could increase the risk of waterborne infectious intestinal diseases. Therefore, the continuous monitoring and control of health indicators is essential in mourning borders. This descriptive, cross-sectional study was conducted on the Mawkebs of Shalamcheh border (n=267). In total, 186 samples were evaluated in terms of the microbial quality of water, and 66 samples were evaluated in terms of the microbial quality of food. The studied parameters in drinking water included the residual free chlorine, pH, turbidity, total coliform, and fecal coliform, and the studied parameters in foodstuffs included the total count and fecal coliform (Escherichia coli). According to the findings, these indicators were appropriate in terms of accommodation hygiene and preparation and distribution of crew hygiene by 99.9%. On the other hand, there were zero cases where the food sampling results were undesirable for the measurement of the total count and fecal coliform. The number of the contaminated water samples was 46 (24.7%) out of 186 water samples. Therefore, the proper implementation and continuous control of health instructions seem critical for these borders, and it is suggested that special regulations and indicators be enacted for the crew in charge, so that they would attend training courses, obtain medical examination cards, and practice personal hygiene.

Radial basis function artificial neural network (RBF ANN) as well as the hybrid method of RBF ANN and grey relational analysis able to well predict trihalomethanes levels in tap water

Many models have been developed in previous studies for predicting the formation of disinfection by-products (DBPs) in drinking water. However, most of them were linear or log-linear regression models, and generated based on simulated disinfection of source water or treated water in a laboratory other than real tap water, which shows low application potential in practice. In this study, a radial basis function artificial neural network (RBF ANN) as well as the hybrid method of RBF ANN and grey relational analysis (GRA) was proposed to predict trihalomethanes (THMs) levels in real distribution systems. A total of 64 sets of data including THMs levels (trichloromethane (TCM), bromodichloromethane (BDCM) and total-THMs (T-THMs)) and 8 water quality parameters (temperature, pH, UV absorbance at 254 (UVA254), dissolved organic carbon, bromide, residual free chlorine, nitrite and ammonia) were used to train and verify the proposed model. As compared to linear and log-linear regression models (rp = 0.254–0.659; N25 = 46–78%), RBF ANNs for THMs (TCM, BDCM and T-THMs) prediction consistently show higher regression coefficients (rp = 0.760–0.925) and prediction accuracy (N25 = 92–98%), which indicates the high capability of RBF ANN to learn the complex non-linear relationships involved THMs formation. Further analysis shows that RBF ANNs using fewer water quality parameters based on GRA still make excellent performance in THMs prediction (rp = 0.760–0.946; N25 = 92–98%). This result demonstrates that GRA can be an effective technique to facilitate the generation of sound RBF ANN models with fewer factors.

Biofilm growth on PVC and HDPE pipes impacts chlorine stability in the recycled water

This study investigated the effects of pipe materials on biofilm growth in full-scale recycled water (RW) distribution system. A biofilm reactor containing high-density polyethylene (HDPE) and polyvinyl chloride (PVC) pipe coupons was fed directly with chlorinated water from the storage reservoir of a full-scale RW distribution system. The reactor was operated at a variable water flow rate of 0.08−0.30 L/min and free chlorine residuals of 0.05−0.7 mg/L. Total carbohydrate, biofilm thickness, biofilm mass, and extracellular polymeric substance (EPS) measurements showed that both HDPE and PVC pipe surface materials are susceptible to biofilm formation and there was no significant difference in biofilm formation between the two pipe materials used in this study. The difference between total chlorine and free chlorine was significant even in the presence of minimal ammonia-nitrogen (<0.066 mg/L) demonstrating chlorine is largely in the form of organic chloramines. Additionally, a significant role of biofilm in decaying chlorine demonstrates the need for biofilm management strategies to maintain water quality in the RW distribution systems.

Optimization of disinfectant dosage for simultaneous control of lead and disinfection-byproducts in water distribution networks

Drinking water utilities are increasingly facing the challenges of maintaining water quality, and simultaneously complying with conflicting regulatory standards. One such challenge is the dosage of chlorine-based disinfectants which is typically regulated to prevent microbial growth in the water distribution systems, while limiting disinfection by-products (DBPs). On the other hand, chlorine residuals also influence the dissolution of lead into drinking water from corrosion scales in the pipe internals, as has been shown by previous studies. Hence, it is important to consider water lead levels (WLLs) while determining the appropriate chlorine dosage. This study proposes a multi-objective optimization framework to understand and balance the trade-offs between (i) minimizing total disinfectant dosage to reduce DBPs formation potential, and (ii) maximizing the volume of safe drinking water supply with respect to both WLLs and residual free chlorine concentrations. The approach comprises of the development of a dynamic simulation-optimization framework to account for the impact of spatial and temporal variations of network hydraulics and water chemistry on WLLs and residual free chlorine. The framework couples dynamic multi-species water quality simulations (pH, residual free chlorine, dissolved inorganic carbon, and orthophosphate concentration) with a multi-objective genetic optimization algorithm in an integrated MATLAB-EPANET-MSX platform. The application of the optimization formulation is demonstrated on a real-world distribution network case study. The resulting optimal solution set on pareto-plots are discussed for sensitivity of the trade-offs between the two objective functions, under various water chemistry conditions that have been suggested in earlier studies for minimizing lead release from plattnerite (PbO2) corrosion scales in lead service lines. The resulting optimal disinfectant dosage schedule, for pumping and booster station nodes in each case, provided insights on maintaining disinfectant residuals throughout the distribution system so as to prevent microbial growth as well as lead contamination events while limiting DBPs formation. Further, environmental implications related to the use of the proposed framework are also discussed.

Evaluation of water quality and sanitation of reservoirs used in field activities of a military unit in the state of Rio de Janeiro

In the Armed Forces' campaign activities, large troops may be exposed to serious health risks even before war itself. In 2010, for example, the Brazilian Army sent nearly 2,000 men to join the United Nations peacekeeping mission in Haiti, which was experiencing a cholera epidemic. This work therefore investigated the water quality and sanitation of the various types of reservoirs used in four field-training activities of a Brazilian Army Unit located in the state of Rio de Janeiro. Physicochemical and microbiological analyses of the water were carried out, and visual inspections and swab samples were collected from the inner surface of these reservoirs for counting coliform bacteria and counting mesophilic aerobic microorganisms. Physicochemical and microbiological analyses of water from different types of reservoirs revealed a lack of conformity with American Public Health Association and Ordinance Number 518, of 03/25/04, of the Brazilian Ministry of Health . It was observed that 50% of the collective and individual reservoirs did not have the desirable minimum levels of Free Residual Chlorine. In addition, in 35.7% of the total collective and individual reservoirs evaluated there was growth of coliform group bacteria and in 28.57% of them the number of heterotrophic bacteria exceeded the maximum recommendation. According to the swabs performed on the inner surfaces, results of the total viable mesophilic aerobic counts were above the recommended levels in 78.57% of the total evaluated reservoirs. Besides that, in the Lyster bags of activities 1 and 2, there was growth of coliforms, or 14.28% of the total evaluated reservoirs. It was concluded that there were failures in the management of multiple barriers during storage and / or distribution, as well as in the maintenance of disinfection to prevent or eliminate microbial contamination, indicating the need for corrective measures.

Broad Diversity of Fungi in Hospital Water.

Introduction Some studies have reported the occurrence of microorganisms isolated from water. Considering these microorganisms, fungi are known to occur ubiquitously in the environment, including water, and some are pathogenic and may cause health problems, especially in immunocompromised individuals. The aim of this study was to identify fungi in hospital water samples and to correlate their presence with the concentration of free residual chlorine. Methods Water samples (100 mL) were collected from taps (n = 74) and water purifiers (n = 14) in different locations in a university hospital. Samples were filtered through a nitrocellulose membrane and placed on Sabouraud dextrose agar and incubated for 24 hours at 30°C. Fungi were identified according to established methods based on macroscopic and microscopic characteristics (filamentous) and physiological tests (yeasts). Free chlorine residual content was measured at the time of sample collection. Results Seventy species of fungi were identified in the water samples and about 56% of the water samples contained culturable fungi. Cladosporium oxysporum, Penicillium spinulosum, and Aspergillus fumigatus were the most common filamentous fungi. Aureobasidium pullulans and Candida parapsilosis were the most common yeasts. Chemical analyses revealed that free residual chlorine was present in 81.8% of the samples within recommended concentrations. Among samples from water purifiers, 92.9% showed low levels of free residual chlorine (<0.2 mg/L). There was no significant association between chlorine concentrations (either within or outside the recommended range) and the presence of filamentous fungi and yeasts. Conclusions This study showed that hospital water can be a reservoir for fungi, some of which are potentially harmful to immunocompromised patients. Free residual chlorine was ineffective in some samples.

QUEIJO MINAS ARTESANAL PRODUZIDO NA REGIÃO DE CANASTRA: CARACTERÍSTICAS DOS PARÂMETROS DE PRODUÇÃO, QUALIDADE DA ÁGUA E DOS QUEIJOS

The Serra da Canastra region is known for the production of a characteristic Minas artisanal cheese, named Canastra cheese. The objective of this study was to characterize the microbiological and physicochemical aspects of the water and cheese collected from the Minas artisanal cheese producing properties, as well as to characterize the environmental aspects of cheese manufacturing. The analyzes were carried out by private laboratories and the government in 2016 and 2017 and the results provided were tabulated and analyzed in the present study. In the physical chemical analyses of the water, the highest non-conformity was for free residual chlorine (44.69%). In the microbiological analyses of the water, 17.02% of the samples showed non-conformity for E. coli and total coliform parameters. In the microbiological analyses of the cheese, non-conformities were found in 7.84% of the samples for total coliforms at 30°C and 9.8% for coagulase-positive Staphylococcus spp. The physicochemical analyses of the cheese were all in compliance. No statistical association was found between the quality of the cheese and the water. The water sources were protected, however discard of the waste from cow pens, sanitary sewage, and garbage is still not properly handled. The study indicates that producers need to improve the quality control of the water supply for their cheese factories, fulfill the requirements of chlorine in the water and periodically verify this requirement, ensuring that the produced cheese is safe for human consumption.

Effect of household water treatment with chlorine on diarrhea among children under the age of five years in rural areas of Dire Dawa, eastern Ethiopia: a cluster randomized controlled trial

BackgroundDiarrheal disease is a leading cause of child mortality and morbidity worldwide. Household water treatment with chlorine significantly reduces morbidity due to waterborne diseases. However, the effect of point-of-use (POU) water treatment in improving the quality of water in areas where POU is not provided free of charge and the effectiveness of home visits in inspiring household members to use POU regularly have not been studied. The objective of this study was to evaluate the effectiveness of drinking water disinfection by chlorination on diarrheal disease reduction among children under the age of 5 years in rural eastern Ethiopia.MethodsA cluster randomized controlled trial was carried out in rural Dire Dawa from October 2018 through January 2019. The 405 households were randomized to intervention and control arms and intervention materials were distributed after conducting a baseline survey. This trial evaluated the effectiveness of household drinking water disinfection by chlorination in reducing incidence of diarrhea among children under the age of 5 years. Intervention households received 1.2% sodium hypochlorite with demonstration of its proper use. Participants in the control households continued with their usual habits of water collection and water storage. Generalized estimation equations (GEE) with log link Poisson distribution family and exchangeable correlation matrix was used to compute crude incidence rate ratio (IRR), adjusted IRR and the corresponding 95% confidence intervals.ResultsIn the intervention households, in total, 281 cases of diarrhea were documented (8.7 cases per 100 person-weeks observation); in the control households, in total 446 cases of diarrhea were documented (13.8 cases per 100 person-weeks observation). A 36.0% (adjusted IRR = 0.64, 95% CI: 0.57–0.73) reduction in incidence of diarrhea was observed in the intervention arm when compared with the control arm. The highest and the lowest reductions were obtained in children of age ranges 1 to 2 years and 3 to 4 years, 42.7 and 30.4%, respectively. Adherence to the intervention was 81.3% as measured by free residual chlorine test.ConclusionsIn rural areas where diarrhea is the second leading cause of morbidity, water chlorination at the household level using liquid bleach considerably reduced episodes of diarrhea among children under the age of 5 years. Therefore, chlorinating drinking water at the household level may be a valuable interim solution for reducing the incidence of diarrheal diseases until potable water is made accessible to the majority of the population in Dire Dawa Administration and other Ethiopian communities.Trial registrationPACTR, PACTR201807815961394. Registered 16 July 2018, www.pactr.org

Analysis of Free Residual Chlorine in Drinking Water Distribution Systems in Ore Processing Industry

Analysis of Free Residual Chlorine in Drinking Water Distribution Systems in Ore Processing Industry

Towards a Predictive Model for Initial Chlorine Dose in Humanitarian Emergencies

Free chlorination is a widely employed disinfection method in humanitarian water provision due to its many advantages. However, its effective application is hindered by the challenge in determining adequate initial doses to achieve free chlorine residuals that satisfy both health and aesthetic requirements. Current guidelines show varying recommended dosing strategies, and many do not adequately consider chlorine decay mechanisms that occur during water storage. Even though turbidity is commonly used as a criterion for deciding chlorine dose, it may not be an adequate proxy for the water quality in many cases. This paper addresses the fundamental relationships between chlorine decay kinetics and selected key water parameters (i.e., natural organic matter, water temperature, chlorine demand) by conducting chlorine decay tests in controlled conditions and in jerrycans (i.e., simulating humanitarian water treatment conditions). Chlorine decay constant from the Feben and Taras’s empirical model and first order model formed linear and exponential relationships with two water parameters (UVA254 and 30-min chlorine demand). With these relationships, the two chlorine decay models can be calibrated quickly and frequently in the field, allowing effective determination of initial chlorine dose. These two models calibrated based on the suggested water parameters from the study could predict chlorine decay in water having a main chlorine demand-inducing constituents as natural organic matter. However, they underpredicted chlorine decay in surface water with additional chlorine reactants. Further research on additional chlorine decay mechanisms is needed to expand the applicability of the models.

Risk Factors for Epidemic Cholera in Lusaka, Zambia-2017.

On October 6, 2017, the Zambia Ministry of Health declared a cholera outbreak in Lusaka. By December, 1,462 cases and 38 deaths had occurred (case fatality rate, 2.6%). We conducted a case-control study to identify risk factors and inform interventions. A case was any person with acute watery diarrhea (≥ 3 loose stools in 24 hours) admitted to a cholera treatment center in Lusaka from December 16 to 21, 2017. Controls were neighbors without diarrhea during the same time period. Up to two controls were matched to each case by age-group (1-4, 5-17, and ≥ 18 years) and neighborhood. Surveyors interviewed cases and controls, tested free chlorine residual (FCR) in stored water, and observed the presence of soap in the home. Conditional logistic regression was used to generate matched odds ratios (mORs) based on subdistricts and age-groups with 95% CIs. We enrolled 82 cases and 132 controls. Stored water in 71% of case homes had an FCR > 0.2 mg/L. In multivariable analyses, those who drank borehole water (mOR = 2.4, CI: 1.1-5.6), had close contact with a cholera case (mOR = 6.2, CI: 2.5-15), and were male (mOR = 2.5, CI: 1.4-5.0) had higher odds of being a cholera case than their matched controls. Based on these findings, we recommended health education about household water chlorination and hygiene in the home. Emergency responses included providing chlorinated water through emergency tanks and maintaining adequate FCR levels through close monitoring of water sources.