scholarly journals Comparison between constant and variable chlorine decay models applied to urban water supply network

2020 ◽  
Author(s):  
Ababu T. Tiruneh ◽  
Tesfamariam Y. Debessai ◽  
Gabriel C. Bwembya ◽  
Stanley J. Nkambule
Keyword(s):  
Water Quality ◽  
Water Supply ◽  
Decay Rate ◽  
Distribution System ◽  
Distribution Systems ◽  
Residual Chlorine ◽  
Quality Model ◽  
Residual Concentration ◽  
Chlorine Residual ◽  
Significant Difference

Abstract. Monitoring of chlorine residual in water distribution systems is necessary not only for ensuring potable water quality but also prevent emergence of disinfection by-products due to excess chlorination. Modelling work for chlorine residual was carried out for water supply distribution network of a town using both second order and first order reaction rate models. For the development of the model, the bulk reaction decay rate was determined in the laboratory using bottle testing while the wall decay rate was determined by calibration of the water quality model using field residual chlorine concentration measurements. The model results show that there is no significant difference in the residual chlorine between the two models or the cost saving that result in terms chlorine usage for the range of initial chlorine dosages anticipated. Constant rate chlorine model is more conservative and offers additional safety in terms of chlorine residual present. Significant differences only occur at excess chlorine residual concentration within the distribution system above the intended maximum residual to be attained. Further research that relates the chlorine dose with the water quality characteristics is necessary to make a more general evaluation.

Determination of cast iron pipe wall decay coefficient for combined chlorine in a municipal water distribution system

2015 ◽  
Vol 42 (4) ◽  
pp. 250-258 ◽  
Author(s):  
Megan J. Liu ◽  
Stephen Craik ◽  
David Z. Zhu
Keyword(s):  
Water Quality ◽  
Cast Iron ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Distribution System ◽  
Water Quality Model ◽  
Quality Model ◽  
Decay Coefficient ◽  
Municipal Water

Predicting disinfectant concentrations in water distribution systems using water quality models requires the input of the wall decay coefficient of the disinfectant. In this study, field water sampling data was integrated with network hydraulic and water quality model simulations of a section of the municipal water distribution system in the City of Edmonton, composed of predominantly cast iron piping, to determine a wall decay coefficient for combined chlorine (chloramine). Unique combined chlorine wall decay coefficients that provided the best fit of model-predicted chlorine concentrations to the field data were determined at two temperatures. Using the determined wall decay coefficients, the water quality model can be used to predict combined chlorine concentrations.

Poor efficacy of residual chlorine disinfectant in drinking water to inactivate waterborne pathogens in distribution systems

1999 ◽  
Vol 45 (8) ◽  
pp. 709-715 ◽  
Author(s):  
Pierre Payment
Keyword(s):  
Escherichia Coli ◽  
Drinking Water ◽  
Clostridium Perfringens ◽  
Water Samples ◽  
Distribution System ◽  
Distribution Systems ◽  
Treatment Plant ◽  
Epidemiological Studies ◽  
Residual Chlorine ◽  
Residual Concentration

To evaluate the inactivating power of residual chlorine in a distribution system, test microorganisms (Escherichia coli, Clostridium perfringens, bacteriophage phi-X 170, and poliovirus type 1) were added to drinking water samples obtained from two water treatment plants and their distribution system. Except for Escherichia coli, microorganisms remained relatively unaffected in water from the distribution systems tested. When sewage was added to the water samples, indigenous thermotolerant coliforms were inactivated only when water was obtained from sites very close to the treatment plant and containing a high residual chlorine concentration. Clostridium perfringens was barely inactivated, suggesting that the most resistant pathogens such as Giardia lamblia, Cryptosporidium parvum, and human enteric viruses would not be inactivated. Our results suggest that the maintenance of a free residual concentration in a distribution system does not provide a significant inactivation of pathogens, could even mask events of contamination of the distribution, and thus would provide only a false sense of safety with little active protection of public health. Recent epidemiological studies that have suggested a significant waterborne level of endemic gastrointestinal illness could then be explained by undetected intrusions in the distribution system, intrusions resulting in the infection of a small number of individuals without eliciting an outbreak situation.Key words: drinking water, chlorine, disinfection, pathogens, distribution system.

Residual-chlorine concentration impacts the ecology of biofilms in drinking water pipes and their water quality response

2020 ◽  
Author(s):  
Katherine Fish ◽  
Paul Gaskin ◽  
Joby Boxall
Keyword(s):  
Water Quality ◽  
Drinking Water ◽  
Distribution Systems ◽  
Water Disinfection ◽  
Test Facility ◽  
Residual Chlorine ◽  
Internal Diameter ◽  
Shear Stresses ◽  
Chlorine Residual ◽  
The Impact

<p>Drinking water distribution systems (DWDS) are an engineered system designed to protect water quality during delivery from treatment works to consumers’ taps. Biofilms form on the vast internal surfaces of DWDS, impacting water quality by their activity and/or mobilisation into the bulk-water. Disinfection-residuals are often maintained in drinking water to mitigate planktonic microbial contamination (and associated water quality/health risks). However, the impact of residual-disinfection upon biofilms, and the subsequent unintended risk they may present to water quality, is unclear.</p> <p>To address this, an internationally-unique, temperature-controlled, full-scale DWDS test facility, fed with water from the local DWDS, was used to grow biofilms (for 28 days). The facility enables three simultaneous conditions to be run in replicate pipe loops (each ~200m long, 79mm internal diameter, PE100 pipe). Conditions studied were Low-, Medium- and High-chlorine regimes. Various water quality parameters were monitored throughout, biofilms were sampled every two weeks (n=5). Physical, chemical and molecular analyses were applied to characterise the matrix (structure and composition) and microbial communities (via analysis of bacterial 16S rRNA and fungal ITS genes) of biofilms developed under the different chlorine regimes. After growth, a “mobilisation” test was conducted simulating hydraulic changes that occur in DWDS. Biofilms from each chlorine regime were exposed to increasing shear stresses to determine any water quality degradation as a consequence of biofilm mobilisation.</p> <p>High-chlorine residual concentration during development reduced biofilm bacterial concentrations but increased inorganics and selected for unique bacterial and fungal communities. Ultimately the biofilms developed under a High-chlorine residual resulted in the greatest decrease in water quality, in response to mobilisation, and the Low-chlorine regime resulted in biofilms which had the lowest impact on water quality. These unanticipated findings suggest chlorine-boosting should be considered carefully and may actually exacerbate water quality issues. The derived understanding could impact the long-term management of DWDS water quality and biofilm, whilst challenging the current mind-set of continuous residual-disinfection control strategies.</p>

scholarly journals Investigating the occurrence of algae in the drinking water supply system of Harare, Zimbabwe

2020 ◽  
Vol 10 (2) ◽  
pp. 179-190
Author(s):  
Pardon Dandadzi ◽  
Zvikomborero Hoko ◽  
Tamuka Nhiwatiwa
Keyword(s):  
Water Quality ◽  
Drinking Water ◽  
Water Treatment ◽  
Water Supply ◽  
Distribution System ◽  
Quality Parameters ◽  
Supply System ◽  
Water Quality Parameters ◽  
Residual Chlorine ◽  
Raw Water

Abstract This study assessed the quality of drinking water in the water supply system for the City of Harare (Zimbabwe) by investigating the occurrence of algae and other water quality parameters that affect its growth. At Morton Jaffray Water Treatment Works (MJWTWs), samples were collected from the raw water inlet and treated water outlet points. In the distribution system, samples were collected from selected sites and grouped into four zones (1, 2, 3 and 4). The algal taxonomic groups that were found in both raw and treated water comprised of Cyanophyceae, Chlorophyceae, Bacillariophyceae, Euglenophyceae and Dinophyceae. It was found out that Microcystis aeruginosa followed by Anabaena were the most abundant species in both raw water and in the distribution system. All measured water quality parameters were within the Standards Association of Zimbabwe and WHO guideline values except for chlorine which had an average residual chlorine concentration that was lower than the WHO recommended lower value of 0.2 mg/L in parts of Zone 2. Morton Jaffray Water Treatment Works does not completely remove algae, and there is a carry-over of algae into the distribution system. Boosting of chlorine is recommended for Zone 2 that had residual chlorine less than the WHO minimum threshold of 0.2 mg/L.

Effect of chloramine residual on iron release in drinking water distribution systems

2009 ◽  
Vol 9 (4) ◽  
pp. 349-355 ◽  
Author(s):  
Y. Wang ◽  
X. J. Zhang ◽  
Z. B. Niu ◽  
C. Chen ◽  
P. P. Lu ◽  
...  
Keyword(s):  
Drinking Water ◽  
Cast Iron ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Iron Release ◽  
Residual Concentration ◽  
Drinking Water Distribution Systems ◽  
Chlorine Residual ◽  
Drinking Water Distribution

Iron release from scale brought about serious problems such as noticeable increases in turbidity and colour of the water in distribution system and taps. Field study and bench scale experiment on iron release from corrosion scale were carried out. In old cast iron pipe, higher iron release occurred with lower chlorine residual concentration, while lower iron release occurred with higher chlorine residual concentration. The reason lay in the structure of scale and the electro-chemical reactions occurring on the scale and in the bulk. The passivated-out-layer of scale was formed by ferric oxide. It could be broken down by reductive reaction in an atmosphere of low chlorine residual concentration. In contrast, the situation was quite different with new cast iron pipe, the age of which was only half a year. Iron release was considered as the product of the iron matrix and chlorine since the passivated-out-layer of scale had not formed yet. This iron release was consistent with chlorine residual concentration. It is suggested that maintaining a high chlorine residual concentration in a drinking water distribution system is beneficial to controlling both microorganism' regrowth and iron release.

Application of two approaches to model chlorine residuals in Severn Trent Water Ltd (STW) distribution systems

1997 ◽  
Vol 36 (5) ◽  
pp. 317-324 ◽  
Author(s):  
M.J. Rodriguez ◽  
J.R. West ◽  
J. Powell ◽  
J.B. Sérodes
Keyword(s):  
Distribution System ◽  
Distribution Systems ◽  
Treatment Plant ◽  
Residual Chlorine ◽  
Ann Model ◽  
Order Model ◽  
First Order ◽  
Chlorine Decay ◽  
Artificial Neural Network Ann ◽  
Key Parameter

Increasingly, those who work in the field of drinking water have demonstrated an interest in developing models for evolution of water quality from the treatment plant to the consumer's tap. To date, most of the modelling efforts have been focused on residual chlorine as a key parameter of quality within distribution systems. This paper presents the application of a conventional approach, the first order model, and the application of an emergent modelling approach, an artificial neural network (ANN) model, to simulate residual chlorine in a Severn Trent Water Ltd (U.K.) distribution system. The application of the first order model depends on the adequate estimation of the chlorine decay coefficient and the travel time within the system. The success of an ANN model depends on the use of representative data about factors which affect chlorine evolution in the system. Results demonstrate that ANN has a promising capacity for learning the dynamics of chlorine decay. The development of an ANN appears to be justifiable for disinfection control purposes, in cases when parameter estimation within the first order model is imprecise or difficult to obtain.

Sensory aspects of drinking water in contact with epoxy lined copper pipe

2007 ◽  
Vol 55 (5) ◽  
pp. 161-168 ◽  
Author(s):  
T.H. Heim ◽  
A.M. Dietrich
Keyword(s):  
Water Quality ◽  
Drinking Water ◽  
Organic Compounds ◽  
Sensory Analysis ◽  
Water Samples ◽  
Distribution System ◽  
Distribution Systems ◽  
Free Chlorine ◽  
Copper Pipe

Pipe relining via in situ epoxy lining is used to remediate corroded plumbing or distribution systems. This investigation examined the effects on odour, TOC, THM formation and disinfectant demand in water exposed to epoxy-lined copper pipes used for home plumbing. The study was conducted in accordance with the Utility Quick Test, a migration/leaching method for utilities to conduct sensory analysis of materials in contact with drinking water. The test was performed using water with no disinfectant and levels of chlorine and monochloramines representative of those found in the distribution system. Panelists repeatedly and consistently described a “plastic/adhesive/putty” odour in the water from the pipes. The odour intensity remained relatively constant for each of two subsequent flushes. Water samples stored in the epoxy-lined pipes showed a significant increase in the leaching of organic compounds (as TOC), and this TOC was demonstrated to react with free chlorine to form trichloromethane. Water stored in the pipes also showed a marked increase in disinfectant demand relative to the water stored in glass control flasks. A study conducted at a full scale installation at an apartment demonstrated that after installation and regular use, the epoxy lining did not yield detectable differences in water quality.

Suspended particles in the drinking water of two distribution systems

2001 ◽  
Vol 1 (4) ◽  
pp. 237-245 ◽  
Author(s):  
V. Gauthier ◽  
B. Barbeau ◽  
R. Millette ◽  
J.-C. Block ◽  
M. Prévost
Keyword(s):  
Water Quality ◽  
Drinking Water ◽  
Organic Matter ◽  
Distribution System ◽  
Distribution Systems ◽  
Suspended Solids ◽  
Suspended Particles ◽  
Raw Water ◽  
Remote Locations ◽  
Dissolved Matter

The concentrations of suspended particles were measured in the drinking water of two distribution systems, and the nature of these particles documented. The concentrations of particulate matter were invariably found to be small (maximum 350 μg/L). They are globally in the very low range in comparison with dissolved matter concentrations, which are measured in several hundreds of mg/L. Except during special water quality events, such as turnover of the raw water resource, results show that organic matter represents the most important fraction of suspended solids (from 40 to 76%) in treated and distributed water. Examination of the nature of the particles made it possible to develop several hypotheses about the type of particles penetrating Montreal's distribution system during the turnover period (algae skeleton, clays). These particles were found to have been transported throughout the distribution systems quite easily, and this could result in the accumulation of deposits if their surface charge were ever even slightly destabilised, or if the particles were to penetrate the laminar flow areas that are fairly typical of remote locations in distribution systems.

scholarly journals Hydraulic Performance Analysis and Modeling of Water Supply Distribution System of Addis Ababa Science and Technology University, Ethiopia

2020 ◽  
Author(s):  
Chalchisa Milkecha ◽  
Habtamu Itefa
Keyword(s):  
Water Supply ◽  
Water Demand ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Addis Ababa ◽  
Science And Technology ◽  
Hydraulic Performance ◽  
Alternative Methods ◽  
The University

This study was conducted generally by aiming assessment of the hydraulic performance of water distribution systems of Addis Ababa Science and Technology University (AASTU). In line with the main objective, this study addressed, (1) pinpointing problems of existing water supply versus demand deficit (2) evaluating the hydraulic performance of water distribution system using water GEMS and (3) recommended alternative methods for improving water demand scenarios. The University’s water supply distribution network layout was a looped system and the flow of water derived by both gravity and pressurized system. The gravity flow served for the academic and administrative staffs whereas the pressurized system of the network fed the students dormitories, cafeteria’s etc. The study revealed the existence of unmet minimum pressure requirement around the student dormitories which accounts 25.64% below the country’s building code standard during the peak hour consumption. The result of the water demand projection showed an increment of 2.5 liter per capita demand (LPCD) in every five years. Hence, first, the university’s water demand was projected and then hydraulic parameters such as; pressure, head loss and velocity were modeled for both the existing and the improved water supply distribution. The finding of the study was recommended to the university’s water supply project and institutional development offices for its future modification and rehabilitation works.

scholarly journals Application of model fitting technique to enhance bacterial regrowth potential (BRP) measurement for drinking water supply monitoring

2021 ◽  
Author(s):  
Wenjin Xue ◽  
Christopher W. K. Chow ◽  
John van Leeuwen
Keyword(s):  
Drinking Water ◽  
Water Supply ◽  
Water Samples ◽  
Distribution System ◽  
Distribution Systems ◽  
Tap Water ◽  
Treatment Plant ◽  
Drinking Water Supply ◽  
Water Supply Systems ◽  
Bacterial Regrowth

Abstract The bacterial regrowth potential (BRP) method was utilised to indirectly measure the assimilable organic carbon (AOC) as an indicator for the assessment of the microbial regrowth potential in drinking water distribution systems. A model using various microbial growth parameters was developed in order to standardise the experimental interpretation for BRP measurement. This study used 82 experimental BRP data sets of water samples collected from the water treatment plant to locations (customer taps) in the distribution system. The data were used to model the BRP process (growth curve) by a data fitting procedure and to obtain a best-fitted equation. Statistical assessments and model validation for evaluating the equation obtained by fitting these 82 sets of data were conducted, and the results show average R2 values were 0.987 for treated water samples (collected at the plant prior to chlorination) and 0.983 for tap water (collected at the customer taps). The F values obtained from the F-test are all exceeded their corresponding F critical values, and the results from the t-test also showed a good outcome. These results indicate this model would be successfully applied in modelling BRP in drinking water supply systems.

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