Chlorine Decay Coefficient Research Articles

Identifying key pipe attributes and locations to best determine chlorine decay coefficients within a water distribution system

Abstract Water distribution system (WDS) characteristics can impact drinking water quality. Kinetic reaction coefficients of residual disinfectant associated with bulk water (kb) and pipe wall (kw) during water distribution can lead to water quality degradation. Determining these coefficients can be expensive and time-consuming. The main objective of this study is to determine the most relevant pipe characteristics and locations to best determine chlorine decay coefficients in a WDS. This article aims to evaluate various scenarios of kb and kw values and compare them to measured data in a full-scale WDS. The most accurate scenario is also compared with the lowest-cost scenario to identify the most effective information needed to determine these coefficients, in terms of location within the WDS and pipe characteristics (age, diameter, and material). Results showed that the scenario with the highest kw and kb values corresponds best to the field-measured data. Moreover, determining specific kinetic coefficients was shown to be more accurate for gray cast iron pipes, pipes installed in a period before 1960, and vulnerable zones for residual chlorine decay.

Wall Decay Coefficient Estimation in a Real-Life Drinking Water Distribution Network

Injection of chlorine as a disinfectant and the correct prediction of the residual amount in water distribution networks are key points and important principles in the quality management of these networks. It is necessary to determine and measure some parameters to develop an effective model in this field. In this study, for the first time, the Simple Hybrid of Genetic Algorithm and Particle Swarm Optimization (SHGAPSO) method along with GA and PSO algorithms are used for qualitative calibration of a real-life water distribution network in Iran to minimize the difference between observed chlorine concentrations at measurement points and the concentrations simulated by the EPANET2.0 hydraulic-qualitative simulation model. The objective functions in this study are Mean Absolute Error (MAE) and Mean Square Error (MSE). The decision variables include bulk (kb) and wall (kw) chlorine decay coefficients are estimated by SHGAPSO, GA, and PSO methods during 4 scenarios. In this study, the amount of residual chlorine in the network was measured by a digital chlorine meter in different days of the year 2018. The results show that SHGAPSO method enhanced the performance of GA and PSO algorithms in the scenarios studied. In scenario 3, this difference was noticeable. Also, scenario 4 with the lowest values of objective functions is selected to estimate the coefficients kw and kb as the best scenario, and finally the qualitative calibration of the network.

Analysis of water quality characteristic for water distribution systems

Abstract Since governments all over the world are paying more attention to water quality in water distribution systems (WDS), a method based on mass balance and first-order chlorine decay model was proposed to assess the efficiency of WDS involving water quality (represented by residual chlorine). The concepts of surplus chlorine factor (S) for nodes in individual pipes and comprehensive surplus chlorine factor (CS) for nodes in WDS were put forward to represent the water quality characteristic of nodes in WDS based on the assumption that the structure of the pipe network and quantity of chlorine dose are definite. The proposed method was applied to two examples of WDS and sensitivity analysis regarding chlorine decay coefficient (k0) was discussed. The results indicated that values of CS for nodes in WDS are affected by the inflow of nodes, which is determined by water demand and pipe length from water sources to nodes. In addition, the value of CS increases with k0 when the inflow of the node is larger than the optimized inflow. The results verified that the deduction of S for a single pipe can be generalized to WDS, and can measure the water quality characteristics for nodes in WDS easily.

Integrating booster chlorination and operational interventions in water distribution systems

Abstract Booster chlorination reduces the risks associated with conventional disinfection such as high chlorine residuals near water treatment plants and low chlorine residuals at remote parts of water distribution systems (WDSs). Network operational interventions have a significant influence on water age and chlorine decay in WDSs. In this study, an integrated booster chlorination method is developed to obtain optimal designs that reduce the risks associated with conventional disinfection in WDSs. The method integrates booster chlorination with network operational interventions to reduce water age and improve chlorine residuals in WDSs. A multi-objective booster optimisation problem is formulated based on risks associated with chlorine disinfection and solved using a non-dominated sorting genetic algorithm (NSGA-II) and the EPANET hydraulic and water quality solver. The proposed methodology was tested in the Phakalane WDS in Botswana. The integrated booster disinfection method significantly improves chlorine residuals in a WDSs with lower mass and cost of chlorine than conventional disinfection. Furthermore, the study indicates that integrated booster chlorination designs are influenced by changes in network conditions such as water demand and chlorine decay coefficients. Therefore, periodic monitoring of these parameters is required to ensure that the acceptable performance of chlorine boosters in WDSs is maintained.

Framework for optimizing chlorine dose in small- to medium-sized water distribution systems: A case of a residential neighbourhood in Lahore, Pakistan

To maintain desirable residual chlorine for a groundwater source, optimizing the chlorine dose in small- to medium-sized water distribution systems (SM-WDS) is a daunting task in developing countries. Mostly, operators add a random chlorine dose without recognizing the smaller size of their distribution network. In this research, a modelling framework for optimizing chlorine dose in SM-WDS is developed. In order to evaluate its practicality, the proposed framework has been applied in a case study of a residential neighbourhood in Lahore (Pakistan) with a small network spanning over 0.35 km 2 . Three datasets for residual chlorine were monitored at 6 locations spread over the study area. EPANET 2.0 software was used for hydraulic and residual chorine modelling. The bulk decay coefficient (K b ) was determined in the laboratory, whereas the wall decay coefficient (K w ) was estimated by calibrating the simulation results with the residual chlorine determined in the field. Based on the calibrated EPANET simulations, a fuzzy rule-based model was developed for pragmatic application of the proposed framework. Scenario analyses for different situations have also been carried out for achieving residual chlorine required at the consumer end. This exercise revealed that much lower chlorine doses than the existing practice can generate detectable chlorine residuals. Moreover, the model can be used to deal with emergency situations, which may arise in developing countries due to viral outbreaks and cross-contamination events in SM-WDS. Keywords : small- to- medium-sized water distribution systems, residual chlorine modelling, water quality, chlorine decay coefficients, fuzzy rule-based modelling, EPANET

DRINKING WATER QUALITY SIMULATION IN ALMONSHA DISTRIBUTION NETWORK

Water quality in distribution systems has become a prominent issue in the study of water networks. This study concentrates on chlorine disinfection as an indicator of water quality. The model discussed in this work is based on laboratory and field collected data. The model is applied on a real network which exists in Almonsha city in Upper Egypt. The experimental set-up and procedure of measuring bulk (Kb) and wall (Kw) chlorine decay coefficients are described. The collected field data together with experimental results are used for calibrating the model using extended period simulation. The aim of this study is to find a solution for the absent of the free residual chlorine in several sections of Almonsha water distribution network. The diurnal variations of domestic water consumption are taken into consideration. Also, different values have been assigned for the daily water consumption for both rural and urban zones of the network. Different water resources (surface and underground water) have been involved in the model. Underground water reservoirs and high elevated tanks are included in the simulation. The water level in the high elevated tanks and water table in the feeding wells are studied. The free residual chlorine concentrations (FRCCs) were measured at different sections of the network and used for the model calibration. FRCCs have been simulated in different locations of the network at several times using extended period simulation. The results of the field and experimental works have shown that, the initial chlorine concentration (C0) has an effect on Kb, an equation is derived to express the relation between them. Also, another equation is derived for the relation between C0 and Kw. The simulation process was extended for several months to dispose the effect of the initial conditions. It is found that, with the existing system of chlorine injection, some parts of the network keep nil values of FRCC even with an injected free residual chlorine dose reaching to 5 mg/L at the feeding point. A new technique is proposed. This technique is based on superposition method for chlorine disinfection. Finally, with the superposition method, it is found that, the minimum injected chlorine dose which should be injected at the feeding points ranges between 0.83 mg/L to 2 mg/L. This dose is found to be sufficient to keep the minimum FRCC with values not less than 0.3 mg/L for the whole parts of the concerned network at all day hours

Simulation Of Chlorine Concentrations In Mosul University's Distribution Network Using EPANET Program

The objective of this study was to demonstrate a real-time chlorine decay with enhancement of simulation program (EPANET 2.0) developed for drinking water supply networks. Periodically samples, two runs/week at various time intervals, were tested at (20) locations in water distribution system of Mosul University and analyzed in site with chlorinator instrument. First the system hydraulic model (EPANET) was used with the entire pipe and junction data which was obtained from university’s records, while chlorine decay coefficients (both bulk and wall) were used from previous literatures and some model runs. A value of the bulk decay coefficient of (-1.0 d-1) was chosen, as for the wall decay coefficient, it was set to zero. The study demonstrated that most of the highly water consumption nodes have a residual chlorine concentration within (0.25 -1.2) mg/l. Moreover, the simulation program shows that from (12 – 5 A.M) chlorine concentration has nil values .However, due to the lack of maintenance works in both storage tank and piping network, about 93% of the reaction rates of the chlorine were happened in, so it is recommended to add an adequate dosing of chlorine with appropriate mixing in the high elevated tank. KEYWORDS: simulation, chlorine decay, water quality, distribution networks, EPANET

Keeping residual chlorine and decreasing unpleasant odor caused by disinfection of tap water

Keeping residual chlorine at a certain level in tap water is effective not only in improving sanitary conditions but also in suppressing the regrowth of microorganisms and preventing the formation of biofilms on the internal surface of distribution pipelines. However, in our recent survey about customer satisfaction, over 50% of the customers were not satisfied with tap water for drinking. One of the main reasons for the dissatisfaction was the odor or taste caused by the disinfection process. We therefore investigated the behavior of residual chlorine in the water distribution network by estimating the chlorine decay coefficients, and discussed measures to decrease the unpleasant odor while maintaining the effect of disinfection. The effective measures are shortening of retention time, replacement of aged pipes, corrosion control of distribution and service pipes, removal of organic substances in water, additional chlorination at water-supply stations, and improvement in water supply facilities with receiving tanks. By adopting these measures, and setting the target value of residual chlorine at representative water taps, we successfully controlled residual chlorine at the outlets of purification plants or water-supply stations by application of the decay coefficient of chlorine in each water distribution system.

Modelling chlorine residuals at Jabal Amman water supply

The purpose of the study presented in this paper is to test the ability of WaterCad, which simulates chlorine concentrations throughout water supplies, in predicting chlorine concentrations in the Jabal Amman distribution system and hence provide a tool to water supply operators in Jordan that helps them to better manage chlorine concentrations throughout distribution systems. To achieve this goal a sampling programme that aimed at measuring chlorine concentrations throughout Jabal Amman over time was conducted over a 2-year period. Half of the data collected was used for model calibration and the other half was used for model verification. Results showed good agreement between measured and simulated chlorine concentrations. An important input for WaterCad is bulk chlorine decay coefficient. So, bulk chlorine decay coefficient for Zai Water Treatment Plant effluent, which supplies water to Jabal Amman, was modelled in terms of initial chlorine concentration, total organic carbon and temperature based on laboratory experiments. The developed mathematical model was used to determine bulk chlorine decay coefficient for the conditions of initial chlorine concentration, total organic carbon and temperature observed at the time of sampling, the determined bulk chlorine decay coefficient was then input into WaterCad.

Discussion of “Unsteady-State Inverse Chlorine Modeling in Pipe Networks” by A. S. Al-Omari and M. Hanif Chaudhry

The writers, have presented an interesting inverse modeling technique as applicable to the estimation of source concentrations and chlorine decay coefficients in the pipe networks. The parameters estimated are very useful in water quality modeling in distribution systems. The application of the model is carried out in two stages: 1. The unsteady-state nodal chlorine concentrations are generated by the forward simulation. These are considered as measured concentrations in the inverse simulation. 2. In the second stage, some of these measurements are used as input to the inverse simulation to estimate either source concentrations or chlorine-decay coefficients. The number of measurements used are less than, equal to, or more than the unknowns to be computed leading to under, even- or overdetermined cases, respectively. Also, an error analysis, which relates sensitivity of measurement node and percentage error in computed chlorine-decay coefficients, is done based on these measurements.

Water quality decay modelling in hydraulic pressure systems

A mathematical model able to evaluate water quality variations in complex hydraulic pressure systems has been developed. The model consists of a set of mass balance equations for tanks, pipes and nodes. It has been applied to predict chlorine concentration inside a case-study water network described in literature by using different expressions of chlorine decay coefficients, obtained in laboratory tests and expressed as a function of the residence time of water in pipes, the initial chlorine concentration, the history and temperature of water. The results showed little variations of the chlorine concentrations and the need to calibrate the parameters of chlorine decay coefficients expressions on full scale hydraulic systems.

Estimation of Bench-Scale Chlorine Decay in Drinking Water Using nth-Order Kinetic and Back Propagation Neural Network Models

Abstract This paper presents the development of two models for simulating residual chlorine decay in raw and treated waters collected from six different utilities of the Quebec City area. The data for modelling was generated by means of several bench-scale chlorination assays undertaken with chlorine doses that varied according to the content of natural organic matter in the water. The first model is a classical kinetic model in which chlorine decay is represented by a first or a second order function, according to the contact time of chlorine. A decay coefficient is estimated based on water quality and operational parameters, using linear regression. The second is a non-linear back propagation neural network model in which all the parameters responsible for chlorine decay are processed within a single model. The performances of both models were evaluated and compared using the database for model development and an independent database for validation. Both models demonstrated acceptable abilities for simulating residual chlorine decay. However, the back propagation neural network model gave significantly better results for conditions involving high chlorine dosage, high organic matter content and long reaction times during chlorination experiments. In the other cases, the performance of the kinetic model was slightly superior. Back propagation neural networks are also advantageous because they do not require assumptions about model order or the estimation of a chlorine decay coefficient. Also included in the paper is a discussion of possible strategies for use in future research work in order to generalize the results obtained.

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

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.

Application of two approaches to model chlorine residuals in severn trent water ltd (STW) distribution systems

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 fast 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 succes 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.