Free Residual Chlorine Research Articles

Surveillance of Legionella pneumophila: Detection in Public Swimming Pool Environment.

The bacterium Legionella pneumophila is a ubiquitous microorganism naturally present in water environments. The actual presence of this opportunistic premise plumbing pathogen in recreational swimming pools and hot tubs in the northwestern part of Croatia has not been investigated. This study aimed to analyze the presence of the opportunistic pathogen L. pneumophila in public swimming pool water in Primorje-Gorski Kotar County (N = 4587) over a four-year period (2018-2021). Additionally, the second aim was to investigate the connection between the presence of L. pneumophila and pool water physicochemical parameters using mathematical predictive models. The presence of L. pneumophila was detected in six pool samples. Five positive samples were found in the water of indoor hot tubs filled with fresh water, and one positive sample in an outdoor recreational saltwater pool. A predictive mathematical model showed the simultaneous influence of chemical parameters dominated by the temperature in saltwater and freshwater pools, as well as the significant influence of free residual chlorine and trihalomethanes. Our results pointed out that keeping all physicochemical parameters in perfect harmony is necessary to reach the best disinfection procedure and to avoid the optimum conditions for L. pneumophila occurrence.

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.

Physicochemical and microbial quality of drinking water in slum households of Hawassa City, Ethiopia

Drinking water quality and its public health effect are ignored in urban slum households of Ethiopia. The aim of this study was to assess physicochemical and microbial quality of drinking water stored in slum households of Hawassa City, Ethiopia. Cross-sectional study was conducted and a total of 120 water samples were collected from 60 households (60 tap, 60 households) to test the quality. Wagtech Potalab + PTW − 1000 was used to test the parameters. Physicochemical parameters—temperature, turbidity, pH and residual free chlorine were measured. Presence of total and faecal coliform bacteria was tested using the Wagtech membrane filtration procedure. Heads of the households were asked about the case of diarrhoeal diseases in any of their family members. Data were statistically analysed and compared with World Health Organization (WHO) standards. Paired t test was used to analyse the mean difference between tap and household water samples. Binary logistic regression was used to investigate any significant association between presence of faecal coliform in the water samples and occurrence of diarrhoeal diseases. Eight (13.3%) tap and 28 (46.7%) household water samples were found positive for total coliform; five (8.3%) tap and 19 (31.7%) household water samples were positive for faecal coliform. Eleven (18.3%) household water samples had faecal coliform 10–100 CFU/100 ml, which falls under high-risk category based on WHO standard. The paired t test (p < 0.05) showed significant mean difference between faecal coliform count of the tap and household water samples. The binary logistic regression analysis implied the odds for occurrence of diarrhoeal disease is 17.33 more in households with positive faecal coliform results (p < 0.05). It is concluded that there was a significant level of faecal contamination of drinking water at the household level. Therefore, it is recommended that continuous health education on drinking water handling should be given to slum households.

A case study: Comparison of disinfection by-product formations between LEED-certified and non-certified buildings

In a few studies focusing on premise plumbing, water quality parameters were compared between LEED-certified and non-certified buildings. However, in those studies, the building characteristics were different, which can cause variations in comparison attempts. This study's purpose is to identify the effects of building type on premise plumbing water quality. For this purpose, temperature, pH, free chlorine residuals, total organic carbon, and trihalomethanes (THMs) were sampled from four drinking fountains of a combined LEED-certified and non-certified building. Although some influential factors on water quality (e.g., location of buildings, distributed water quality) were isolated for a better comparison, variations in parameters and total THMs were observed resulting from the plumbing age differences in the buildings. The findings of this study point out the impacts of the plumbing pipe age on water chemistry and emphasize the consideration of piping age as a factor in water quality comparisons between LEED-certified and non-certified buildings.

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.

PSXIV-2 Effect of Drinking Water Disinfection Treatments on Water Quality, Water and Feed Consumption, Apparent Total Tract Digestibility and Health in Holstein Bulls fed High-Concentrate Diets

Abstract The aim of this study was to evaluate the effect of different drinking water disinfection treatments on water quality, water and feed consumption, apparent total tract digestibility, and animal health in fattening Holstein bulls. Bulls (n=24; 176 ± 16.3 kg BW, and 149 ± 5.8 d age) were housed individually and fed ad libitum. Animals were assigned to 1 of 4 drinking water disinfection treatments: 1) CTR (n=6), no treatment; 2) ACCHL (n=6), acidification (0.65 mL/L phosphoric acid) and chlorination (0.15 mL/L sodium hypochlorite); 3) PER (n=6), 0.15 mL/L peroxide, and 4) DIO (n=6), 2.50 mL/L chlorine dioxide. Water consumption and animal health status was recorded daily. Water disinfectant capacity were analyzed weekly. Feed consumption was recorded every 2 wk. Water quality was analyzed every 4 wk. At d 0, 42, 112 and 210 blood samples were collected. At d 35 and 140 apparent total tract digestibility was estimated. Data were analyzed with a mixed effects model. Means water disinfectant capacity were pH 6.60 and 0.75 mg/L free residual chlorine in ACCHL, 10.6 mg/L peroxide in PER, and 0.52 mg/L chlorine dioxide in DIO. Water treatments did not affect physicochemical water quality; however, they reduced (P&amp;lt; 0.01) water total coliforms count compared with CTR, and ACCHL and DIO were lesser than PER (199, 0, 35, and 0 ± 0.2 UFC/100mL for CTR, ACCHL, PER, and DIO, respectively). Dry matter intake tended (P=0.06) to increase in DIO compared with CTR (8.24 vs. 7.49 ± 0.266 kg/d, respectively). Water treatments did not affect nutrient digestibility nor blood parameters. In conclusion, drinking water disinfection treatments tested had a good disinfectant efficacy without detrimental effect on health and nutrient digestibility in bulls fed high-concentrate diets. Further commercial studies with more animals are needed to evaluate the potential effect of chlorine dioxide on intake and efficiency.

Modelling point-of-consumption residual chlorine in humanitarian response: Can cost-sensitive learning improve probabilistic forecasts?

Ensuring sufficient free residual chlorine (FRC) up to the time and place water is consumed in refugee settlements is essential for preventing the spread of waterborne illnesses. Water system operators need accurate forecasts of FRC during the household storage period. However, factors that drive FRC decay after water leaves the piped distribution system vary substantially, introducing significant uncertainty when modelling point-of-consumption FRC. Artificial neural network (ANN) ensemble forecasting systems (EFS) can account for this uncertainty by generating probabilistic forecasts of point-of-consumption FRC. ANNs are typically trained using symmetrical error metrics like mean squared error (MSE), but this leads to forecast underdispersion forecasts (the spread of the forecast is smaller than the spread of the observations). This study proposes to solve forecast underdispersion by training an ANN-EFS using cost functions that combine alternative metrics (Nash-Sutcliffe efficiency, Kling Gupta Efficiency, Index of Agreement) with cost-sensitive learning (inverse FRC weighting, class-based FRC weighting, inverse frequency weighting). The ANN-EFS trained with each cost function was evaluated using water quality data from refugee settlements in Bangladesh and Tanzania by comparing the percent capture, confidence interval reliability diagrams, rank histograms, and the continuous ranked probability. Training the ANN-EFS using the cost functions developed in this study produced up to a 70% improvement in forecast reliability and dispersion compared to the baseline cost function (MSE), with the best performance typically obtained by training the model using Kling-Gupta Efficiency and inverse frequency weighting. Our findings demonstrate that training the ANN-EFS using alternative metrics and cost-sensitive learning can improve the quality of forecasts of point-of-consumption FRC and better account for uncertainty in post-distribution chlorine decay. These techniques can enable humanitarian responders to ensure sufficient FRC more reliably at the point-of-consumption, thereby preventing the spread of waterborne illnesses.

Free-Living Amoeba and Associated Pathogenic Bacteria in Well-Chlorinated Drinking Water Storage Tanks

Free-living amoebae (FLA) and amoeba-resistant bacteria (ARB) are of increasing concern for water utilities as they cause diseases in humans. To protect consumers, disinfectants are used to prevent colonization by these pathogens in drinking water; however, FLA possess inherent defence mechanisms that can protect them from disinfection. This study investigated the presence and abundance of these amoebae and bacteria in chlorinated drinking water storage tanks in Western Australia. Viability and molecular testing methods, in the form of culturing, quantitative polymerase chain reaction, and 16S rRNA gene amplicon sequencing, were employed to detect amoebae and bacteria present in bulk water and sediment samples. FLA and ARB were detected in water storage tanks that had free chlorine residuals above 0.5 mg/L. Viable Acanthamoeba spp. and Vermamoeba sp. were isolated from the tanks along with various other FLA also detected molecularly. Nontuberculous mycobacteria, a known ARB and opportunistic pathogen, was isolated from all tanks and sample types as well as in the growth fronts of the viable amoebae. This study illustrates the presence and persistence of FLA, ARB, and associated bacterial communities in well-chlorinated water storage tanks, highlighting the need for continued surveillance and risk management.

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.

Laboratory evaluation of the efficacy of bucket chlorination guidelines at inactivating Vibrio cholerae for waters of varying quality

Abstract Bucket chlorination, where chlorine is dosed directly into water collection containers, is a point-of-source water treatment intervention commonly implemented in cholera outbreaks. There is little previous data on chlorine efficacy against Vibrio cholerae in different waters and appropriate dosage regimes. We evaluated V. cholerae reduction and free chlorine residual (FCR) in waters with four turbidities (1/5/10/50 NTU), two total organic carbon (TOC) concentrations (0.4, 1 mg/L), and two dosing schemes (fixed-dose of 2 or 4 mg/L, variable-dose based on jar testing) treated with three chlorine types (HTH, NaOCl, NaDCC). We found that chlorine was efficacious at reducing V. cholerae by ≥2.75 to ≥3.63 log reduction value (LRV); variably dosed reactors were dosed higher, met ≥0.5 mg/L FCR at 30 min, and had higher LRVs (p=0.024) than fixed doses; and low TOC reactors had more samples ≥0.2 mg/L FRC at 4 h (p=0.007). Our results are conservative, as internationally recommended additives to create test water increased chlorine demand, highlighting the challenge of replicating field conditions in laboratory testing. Overall, we found that chlorine can efficaciously reduce V. cholerae; we recommend further research on appropriate chlorine demand for test waters; and we recommend establishing appropriate chlorine doses based on source water and taste/odor acceptability in bucket chlorination programs.

Quality of rainwater drained by a green roof in the metropolitan region of Recife, Brazil

The objective of this study was to evaluate the potential non-potable uses that can be given to the water flowing from a green roof through the characterization of its quality using the parameters and reference values contained in the Brazilian Standard ABNT NBR 15527:2007. The research was carried out in the Garage Building of the Charles Darwin Business, for a period of five months. Fifteen samples were collected from three collection points (rainwater, irrigation, and drainage from the green roof) and evaluated. For the qualitative characterization of the waters, the physicochemical parameters hydrogen potential (pH), turbidity (TBD), apparent color (AC), free residual chlorine (FRC) and electrical conductivity (EC), in addition to the microbiological parameters total coliforms, Escherichia coli and number of heterotrophic bacteria (HB), were determined. Data were subjected to descriptive and multivariate statistical analysis. The results obtained show that the green roof contributed to the reduction of rainwater pH. The green roof drainage water had higher levels of AC and TBD due to the concentrations of suspended particles, which acted as a source of EC. The FRC values complied with the legislation in all treatments. Likewise, the microbiological parameters partially complied with the standards established by the legislation. Cluster analysis formed two distinct groups, G1 comprising HB and TBD, and G2 containing the variables pH, AC, EC, and FRC. Although the quality of the drainage water does not meet all the standards required by law, this water has the potential for reuse for non-potable purposes.

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.&#x0D; Keywords: disinfection, TOC, water quality.

Assessment of drinking water treatment and disinfection by-products

Water treatment plants and disinfection by-products are a worldwide problem in the provision of drinking water with disinfectants. However, in countries like Ethiopia, studies on the condition of water treatment plants and the risks they pose are scarce. Hence, this study was designed to evaluate the drinking water treatment plants of Jimma Town. The WatPro v4 simulation was used to evaluate the performance of the water treatment plant and disinfection. The results show that the treatment efficiency of the study was estimated to be 69.75%, while giardia and virus were reduced by 22.6% and 75.34%, respectively, and did not meet the requirements for surface water treatment. Furthermore, the contact time of the water system did not meet the contact time requirement (it should be great than one), but it was 0.476 for this study, and the current water distribution network and treatment plant of Jimma town were underperforming and did not provide adequate water to the various demand categories. Due to the poor performance of water treatment plants, the health and economic well-being of the majority of the population is seriously affected, and some people refuse to drink it, preferring to treat it at home instead. Disinfection of drinking water (chlorination) causes some to react with naturally occurring organic matter or waterborne diseases, while others exist as free chlorine or residual chlorine, producing the disinfection by-products (DBP), increased risk of bladder cancer and other human health effects. Therefore, the study strongly suggests that DBP and their precursors be removed following chlorination. We believe that the study provided new and updated insights on the treatment condition and DBP risk, which could aid decision-makers, planners and stakeholders in monitoring actions to reduce the health risks associated with DBPs in drinking water.

Joint majorization of waterworks and secondary chlorination points considering the chloric odor and economic investment in the DWDS using machine learning and optimization algorithms

The traditional methods of increasing the chlorine disinfectant dosage in the drinking water distribution system (DWDS) to control microorganisms and improve the safety of drinking water quality are subjected to several challenges. One noticeable problem is the unpleasant odor generated by chlorine and chloramines. However, the generally proposed chlorine dosage optimization model ignores the chloric odor distribution in the DWDS. This study proposes a comprehensive multi-parameter water quality model and aims to balance the trade-offs between: (i) minimize the flavor profile analysis (FPA) degree of the chloric odor produced by chlorine and chloramines in the DWDS, and (ii) minimize the economic investment (chlorine dosage and operation cost). EPANET and back propagation (BP) network integrated with the Borg algorithm were employed as innovative approaches to simulate the chlorine, chloramines, and chloric odor intensity in the DWDS. Moreover, the application of the multi-parameter model was demonstrated in a real-world DWDS case study. 0.5 mg-Cl2/L (mg/L) chlorine at 8 secondary chlorination points was added to the DWDS as an optimized chlorine dosing scheme considering the olfactory and financial objective functions simultaneously. When switching to a superior water source, the FPA of the chloric odor in DWDS increased by a maximum of 1.4 at most if the initial chlorine dosage remained as before. To avoid the occurrence of chloric odor and also control the residual free chlorine (residual chlorine) at a suitable value, the initial and secondary chlorine dosages were optimized to 0.4 mg/L and 0.3 mg/L, respectively. Under this condition, the initial chlorine dosage was reduced by 50% compared to the original operation scheme in City J, China, the qualification rate of the residual chlorine reached 97.2%, basically consistent with that before water source switching, and the chloric odor intensity of the DWDS was controlled below FPA 3.4.

Nitrogen-Doped and Surface Functionalized CDs: Fluorescent Probe for Cellular Imaging and Environmental Sensing of ClO.

A novel nitrogen doped and surface functionalized fluorescent CDs (T1) was synthesized by one-step and green hydrothermal method, which exhibits a satisfactory fluorescence quantum yield and a series of admirable features such as good aqueous solubility, narrow particle size distribution, resistance to photobleaching as well as excitation-dependent behavior. Benefitting from above merits, T1 can be employed to serve as an outstanding sensing platform for sensitive and accurate detection of ClO- by remarkable fluorescence "on-off" process with rapid and anti-interference. More notably, the good biocompatibility and photostability can ensure enormous bioimaging potential and successful application of T1 in monitoring of exogenous ClO- in MG-63 cells. Meanwhile, T1 can also be regarded as a filter paper sensor providing a convenient and efficient analyzing technology for monitoring of free residual chlorine in practical environmental samples. All these results demonstrate that there exists promising possibility for practical applications of T1 in bioimaging systems and environmental monitoring.

Comparison of Disinfection By-Product Formation and Distribution during Breakpoint Chlorination and Chlorine-Based Disinfection in Drinking Water

Breakpoint chlorination (BC) and disinfection with chlorine-based disinfectant are widely used procedures in drinking water production. Both involve dosing chlorine into the raw water, where it can react with organic compounds, forming disinfection by-products (DBPs) of health concern. However, technological parameters (e.g., contact time, chlorine dosage, and bromide to residual free chlorine ratio) of the two chlorination procedures are different, which can lead to differences in DBP formation. To better understand this, a year-long sampling campaign was carried out at three waterworks in Hungary, where both BC and chlorine disinfection are used. To confirm the results of the field sampling, bench-scale experiments were carried out, investigating the impact of (a) bromide concentration in raw water, (b) residual free chlorine (bromide to residual chlorine ratio), and (c) contact time on DBP formation. The measured DBPs were trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and chlorate. During BC, the DBPs were formed in higher concentration, with the exception of one waterwork having elevated bromide content in the raw water. Bromine substitution factors (BSFs) were significantly higher during disinfection than BC in both field and laboratory experiments. After BC, the chlorate concentration range was 0.15–1.1 mg/L, and 96% of the samples exceeded the European Union (EU) parametric value (0.25 mg/L), whereas disinfection contributed only slightly. Granular activated carbon (GAC) filters used to remove DBPs in waterworks were exhausted after 6–8 months of use, first for those chlorinated THMs, which are generated predominantly during BC. The biological activity of the filters started to increase after 3–6 months of operation. This activity helps to remove the biodegradable compounds, such as disubstituted haloacetic acid (DHAAs) and HANs, even if the adsorption capacity of the GAC filters are low.

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.

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.