Booster Chlorination Research Articles

Optimal location and scheduling of booster chlorination stations for drinking water distribution system

The optimum location of booster chlorination stations is worked out along with the scheduling of booster chlorination stations for the steady-state flow conditions for drinking water distribution system (DWDS). Linear programming in Excel is utilized for the formulation of the model by coupling the simulation results of EPANET software for residual chlorine at critical nodes and optimal location of booster chlorination stations, using different combinations of booster stations. The combination of booster stations gives a minimum applied dose of chlorine at the same time satisfying the constraint of residual chlorine of 0.2 mg/l (IS 10500-2012) at all the locations within the DWDS. The optimal location of booster chlorination stations, in combination with optimal scheduling of booster stations using optimization method, can serve as an important decision-making tool for any water supply authority for the selection of appropriate location, number of booster stations, application of optimum chlorine mass rate and overall cost reduction.

Optimal use of chlorine in water distribution networks based on specific locations of booster chlorination: analyzing conditions in Mexico

Water distribution networks (WDNs) could present problems of pathogen intrusion that affect the health of consumers. One solution to diminish this risk is to add more disinfectant to the water at the drinking water treatment plant (DWTP). However, this increases the cost of water treatment and may also cause the formation of trihalomethanes. Mexico has the largest bottled water market in the world. Also, most houses are built with individual storage containers due to intermittent service, which generates a greater residence time of the water before use. This paper shows an alternative to guarantee minimum disinfection along WDNs and diminish the use of disinfectant at the DWTP considering the conditions of water consumption and use in Mexico. We propose a model based on Genetic Algorithms to obtain scenarios where free chlorine is maintained at the minimum permissible concentration throughout the day. In addition, Water Managers could optimize the use of disinfectant by implementing booster chlorination stations (BCSs). The results show that chlorine use could be reduced by 38%, therefore guaranteeing the chlorine concentration limits along the WDN.

Chance Constrained Optimization of Booster Chlorination in Water Distribution Networks

AbstractQuality of municipal water is sustained by addition of disinfectant, generally chlorine, to the water distribution network. Because of health problems, chlorine concentration in the network is limited between maximum and minimum limits. Carcinogenic disinfectant by‐products start to occur at high concentrations so it is desired to have minimum amount of chlorine without violating the limit. In addition to the health issues, minimum injection amount is favorable concerning cost. Hence, an optimization problem which covers all of these considerations should be modeled. However, there are uncertain factors as chlorine is reactive and decays both over time and space. Thus, probabilistic approach is necessary to obtain reliable and realistic results from the model. In this study, a linear programming model is developed for the chance constrained optimization of the water distribution network. The objective is to obtain minimum amount of injection mass subjected to maintaining more uniformly distributed chlorine concentrations within the limits, while considering the randomness of chlorine concentration by probability distributions. Network hydraulics and chlorine concentration are computed by the network simulation software, EPANET.

Analysis of residual chlorine in simple drinking water distribution system with intermittent water supply

Knowledge of residual chlorine concentration at various locations in drinking water distribution system is essential final check to the quality of water supplied to the consumers. This paper presents a methodology to find out the residual chlorine concentration at various locations in simple branch network by integrating the hydraulic and water quality model using first-order chlorine decay equation with booster chlorination nodes for intermittent water supply. The explicit equations are developed to compute the residual chlorine in network with a long distribution pipe line at critical nodes. These equations are applicable to Indian conditions where intermittent water supply is the most common system of water supply. It is observed that in intermittent water supply, the residual chlorine at farthest node is sensitive to water supply hours and travelling time of chlorine. Thus, the travelling time of chlorine can be considered to justify the requirement of booster chlorination for intermittent water supply.

Optimal design and operation of booster chlorination stations layout in water distribution systems

This study describes a new methodology for the disinfection booster design, placement, and operation problem in water distribution systems. Disinfectant residuals, which are in most cases chlorine residuals, are assumed to be sufficient to prevent growth of pathogenic bacteria, yet low enough to avoid taste and odor problems. Commonly, large quantities of disinfectants are released at the sources outlets for preserving minimum residual disinfectant concentrations throughout the network. Such an approach can cause taste and odor problems near the disinfectant injection locations, but more important hazardous excessive disinfectant by-product formations (DBPs) at the far network ends, of which some may be carcinogenic. To cope with these deficiencies booster chlorination stations were suggested to be placed at the distribution system itself and not just at the sources, motivating considerable research in recent years on placement, design, and operation of booster chlorination stations in water distribution systems. The model formulated and solved herein is aimed at setting the required chlorination dose of the boosters for delivering water at acceptable residual chlorine and TTHM concentrations for minimizing the overall cost of booster placement, construction, and operation under extended period hydraulic simulation conditions through utilizing a multi-species approach. The developed methodology links a genetic algorithm with EPANET-MSX, and is demonstrated through base runs and sensitivity analyses on a network example application. Two approaches are suggested for dealing with water quality initial conditions and species periodicity: (1) repetitive cyclical simulation (RCS), and (2) cyclical constrained species (CCS). RCS was found to be more robust but with longer computational time.

Optimizing booster chlorination in water distribution networks: a water quality index approach

The optimization of chlorine dosage and the number of booster locations is an important aspect of water quality management in distribution networks. Booster chlorination helps to maintain uniformity and adequacy of free residual chlorine concentration, essential for safeguarding against microbiological contamination. Higher chlorine dosages increase free residual chlorine concentration but generate harmful by-products, in addition to taste and odor complaints. It is possible to address these microbial, chemical, and aesthetic water quality issues through free residual chlorine concentration. Estimating a water quality index (WQI) based on regulatory chlorine thresholds for microbial, chemical, and aesthetics criteria can help engineers make intelligent decisions. An innovative scheme for maintaining adequate residual chlorine with optimal chlorine dosages and numbers of booster locations was established based on a proposed WQI. The City of Kelowna (BC, Canada) water distribution network served to demonstrate the application of the proposed scheme. Temporal free residual chlorine concentration predicted with EPANET software was used to estimate the WQI, later coupled with an optimization scheme. Preliminary temporal and spatial analyses identified critical zones (relatively poor water quality) in the distribution network. The model may also prove useful for small or rural communities where free residual chlorine is considered as the only water quality criterion.

Research Database of Water Distribution System Models

AbstractSince the 1960s, researchers have continued to develop new methodologies and algorithms in support of the planning, design, and management of water distribution systems. While initial research focused on modeling the hydraulics of such systems, the 1980s gave rise to additional research focus on water quality issues. More recent research has expanded into issues of system reliability and resilience, energy management, and sensor and chlorine booster station placement. In most cases, researchers have relied on either hypothetical water distribution systems or a handful of actual systems for use as benchmark test systems. Some of the more widely used actual systems include the New York tunnel system and the Hanoi water distribution system. This paper describes the development of a database of several water distribution systems synthesized from a statewide database of systems originally developed by the Kentucky Infrastructure Authority. The developed models include both small and medium networks, as...

Small Water Distribution System Operations and Disinfection By Product Fate

The Stage-2 Disinfectant and Disinfection By-Product (D/DBP) regulations force water utilities to be more concerned with their finished and distributed water quality. Compliance requires changes to their current operational strategy, which affect the formation of DBPs over time. This study quantifies changes in DBP formation and chlorine decay kinetics under different operational conditions and pipe materials found at many small-scale water utilities. A physical model (Pipe Loop) of a distribution system was used to evaluate the change in water quality from conditions such as having a high chlorine dosage entering the distribution system, using a chlorine booster system in the distribution system, and operation of clearwells/storage tanks. The High Chlorine Run (HC) is least favorable option with approximately 64% and 30% higher TTHMs than Normal Run (NR) and Chlorine Booster Run (CB), respectively. High Chlorine conditions also minimize the wall effects. The location of Boosters should always be after the storage systems to avoid extra contact time that can produce approximately 23% - 78% higher TTHMs. The following trends are discovered from the data analysis: Chlorine residual HC > CB > NR and TTHM NR > CB > HC.

Resolving Problematic Biofilms in Buildings and Compounds

Biofilm problems persist in water distribution systems and, as a result, have been the focus of remediation strategy development. However, there have been limited reports of investigations of problematic biofilms in individual buildings and groups of buildings where biofilms may grow and affect a defined population. The authors have investigated three sites in subtropical areas—a school, a resort, and a condominium development. Each situation created different effects that were detected by the occupants and resulted in a water quality assessment. The common connection was problematic biofilm growth in the potable water distribution system resulting from site-specific incidents. In one case, the biofilm was formed as the system was not used for a long period. Another was a result of operational issues with the on-site water treatment process. The third case was caused by the water quality issues in the water delivered to the site. In each situation, solutions were sought to address the biofilm problem while keeping the buildings in service and reducing the potential for future recurrence. Applied control strategies included superchlorination and flushing, and were demonstrated to be effective. Operational strategies, including periodic pipe flushing and installation of a chlorine booster station, were recommended on a site-specific basis to prevent the return of problematic biofilms.

Impact of Booster Chlorination on Chlorine Decay and THM Production: Simulated Analysis

The effect of conventional and booster chlorination on chlorine residuals and trihalomethane (THM) formation in drinking water distribution systems was modeled using the EPANET hydraulic modeling software. The model results suggest that booster chlorination may allow utilities to meet disinfection goals better by carrying chlorine residuals to remote points in the distribution system while lowering the total mass of chlorine applied to the system. The model results suggest that booster chlorination may provide the greatest advantages to points in the distribution system located near storage tanks by providing a more consistent chlorine residual and possibly reducing THM formation. A new version of the EPANET model, the EPANET Multispecies model, was also used to compare chlorine decay due to reactions in the bulk fluid and reactions occurring at the pipe wall. The results suggest that chlorine decay due to wall reactions can be very significant at remote points in the distribution system. Additionally, if THMs are assumed to form primarily through reactions in the bulk fluid, use of the new EPANET Multispecies software allows for calculation of THM formation based solely on chlorine reactions in the bulk fluid rather than on overall chlorine decay.

Assessing water quality of drinking water distribution system in the South Taiwan

This investigation conducted a full-scale survey the drinking water distribution system in Kaohsiung city, Taiwan. The aim was to investigate whether the distribution system was capable of maintaining high water quality from the water treatment facilities through to the end user. The results showed that the distribution system can maintain high water quality, except for suitable chlorine residuals. The authors plotted chlorine residual contour maps to identify areas with low chlorine residuals, helping them prioritize sections that must be flushed or renewal. The contour maps also provide sufficient and clear information for locating booster chlorination stations. Contour maps enable water facilities to identify how water quality decays in the distribution systems and the locations of such decay. Water quality decay can be caused by properties of pipeline materials, hydraulic conditions, and/or biofilm thickness. However, understanding the exact reasons is unnecessary because the contour maps provide sufficient information for trouble-shooting the distribution systems.

Conjunctive optimal scheduling of pumping and booster chlorine injections in water distribution systems

This article extends previous work on optimal booster chlorination injection design and operation in water distribution systems by solving the scheduling problem of pumping units in conjunction with the design and operation problem of booster chlorination stations. Two models are formulated and solved using a genetic algorithm scheme tailor-made to EPANET: Min Cost—for minimizing the costs of pumping and the chlorine booster design and operation, and Max Protection—for maximizing the system protection by maximizing the injected chlorine dose. An example application is explored through a base run and sensitivity analysis showing that the algorithm proposed is robust and reliable, and that the pump and chlorine injection scheduling are mutually connected.

OPTIMISED ALLOCATION OF CHLORINATION STATIONS BY MULTI-OBJECTIVE GENETIC OPTIMISATION FOR QUALITY CONTROL IN DRINKING WATER DISTRIBUTION SYSTEMS

Providing water meeting strict quality conditions is now a number one priority for the water authorities. Water chlorination only at water treatment plants forced the usage of high concentration of disinfectant which resulted in bad taste of water near them and still did not solve the quality issues at the far points of the network. The answer to this problems is booster chlorination - placing booster station throughout the network allowing a significant reduction of chlorine concentration and at the same time ensuring proper water quality in the network. The booster chlorination is highly dependent from the demand scenarios.

Control of DBPs in water distribution systems through optimal chlorine dosage and disinfection station allocation

Two different procedures, respectively aiming at the best allocation and managing of disinfection stations along water distribution systems, are presented, with the main objective of proposing a criterion to limit chlorine and disinfection by-product concentrations in the drinking water supplied to users without compromising its agreeableness and safety characteristics. The procedures are based on the evaluation of two different indexes obtained through the analysis of several operating conditions related to changes of water demands in both space and time and to the random behaviour of users: the Presence Index and the Efficiency of Allocation Index. The proposed procedures have been applied to a case study in order to determine, respectively, (1) the number and the allocation of chlorine booster stations according to minimum and maximum values of chlorine concentration indicated in drinking water standards and to minimum chlorine dosage allowed for each station; and (2) the optimal dosage of chlorine according to the number and allocation of chlorine disinfection stations and to the changes of water demand from users.

Success of booster chlorination for water supply networks with genetic algorithms

The chlorination of drinking water distribution networks is usually carried out at the supply source. However, chlorine may disappear in some portions or at distant points within a network. In this case, one or more booster chlorination stations must be built in the network in order to observe detectable chlorine residual at all levels of branching. Network hydraulic values, tank water levels and chlorine concentrations may vary over the course of one day because of changes in consumer demand. For this reason, the optimal location of a booster chlorination station, injection rates-and scheduling must be considered together. In this research, the locations, injection rates and scheduling of chlorine booster stations were studied using genetic algorithms. The results indicate that booster disinfection can significantly increase the desired residual concentrations above the minimum limit while helping to reduce variability in nodal concentrations. The objective of the study is to satisfy minimum and maximum required chlorine residual at every point in the network while minimizing chlorine consumption as much as possible. In order to find a hydraulic solution and chlorine concentration distribution in a network, EPANET software was used. In the solution phase, genetic algorithms and EPANET software were run interactively. The algorithm developed was used on an existing network given in the literature and solutions were compared with the current status of the network.

Linear Least-Squares Formulation for Operation of Booster Disinfection Systems

Maintaining a disinfectant residual in drinking water distribution networks is a challenge for water utilities. These challenges arise from the spatial and temporal distribution of water usage, and from chemical reactions that cause disinfectants to decay. A potential solution is booster chlorination, a strategy where disinfectant is reapplied within the network. Here, a linear least-squares problem is formulated to determine the optimal disinfectant injection rates that minimize variation in the system residual space-time distribution. Locations of booster stations are assumed known. The solution is simple and can be analytically derived in some cases. The problem formulation allows an arbitrary weight on the contribution of each consumer node disinfectant residual to the overall objective function; two possible weighting schemes are suggested. In a planning context, the method is shown to apply to network flows whose first and second moments are stationary. In contrast to previous approaches, the number...

A reactive species model for chlorine decay and THM formation under rechlorination conditions

Chlorine is typically used within drinking water distribution systems to maintain a disinfectant residual and minimize biological regrowth. Typical distribution system models describe the loss of disinfectant due to reactions within the water matrix as first order with respect to chlorine concentration, with the reactants in excess. Recent work, however, has investigated relatively simple dynamic models that include a second, hypothetical reactive species. This work extends these latter models to account for discontinuities associated with rechlorination events, such as those caused by booster chlorination and by mixing at distribution system junction nodes. Mathematical arguments show that the reactive species model will always represent chlorine decay better than, or as well as, a first-order model, under single dose or rechlorination conditions; this result is confirmed by experiments on five different natural waters, and is further shown that the reactive species model can be significantly better under some rechlorination conditions. Trihalomethane (THM) formation was also monitored, and results show that a linear relationship between total THM (TTHM) formation and chlorine demand is appropriate under both single dose and rechlorination conditions. This linear relationship was estimated using the modeled chlorine demand from a calibrated reactive species model, and using the measured chlorine demand, both of which adequately represented the TTHM formation.

Study of transport of contaminants in a pipe network using the model EPANET

A rural water supply system having two probable water sources, with an elevated tank, required to serve three schools and a hospital, was selected for this study. The model EPANET was used to study the variation of concentrations within the network of conservative and non-conservative substances introduced into the water at the source node and at other nodes. This paper discusses the findings of four scenario analyses undertaken in order to study the behaviour of the contaminants, and to develop strategies for management of some difficult situations encountered in water supply schemes. In the two source supply situation, it was observed that the water quality at the critical points in the system could be maintained below the permissible fluoride concentration, while maintaining the water requirements, by changing the pump operation cycles. When the behaviour of residual chlorine in the system was studied, it was observed that the model can be used to discover the chlorine booster points to maintain the required minimum residual chlorine content at the distribution terminal points. The results need to be verified by field-testing, once the water supply scheme, which is still under construction, is commissioned.

Booster chlorination for managing disinfectant residuals

Booster chlorination allows disinfection in the treatment plant and maintenance of a residual in the distribution system to be viewed as separate treatment objectives.Booster chlorination is an approach to residual maintenance in which chlorine is applied at strategic locations within the distribution system. Situations in which booster chlorination may be most effective for maintaining a residual are explained informally in the context of a conceptual distribution system. To form the basis of a quantitative analysis of booster chlorination, experiments simulated chlorine decay under booster conditions. These experiments suggested a conceptual model for bulk chlorine decay, which is used to analyze an example representing a header pipe serving two distinct zones in a distribution system. The chlorine mass savings associated with booster chlorination in this example are derived and used to show the influence of flow rates, residence times, and decay kinetics on the effectiveness of booster chlorination. The role of booster chlorination is also discussed as part of coordinated treatment efforts meant to manage the risks associated with biological regrowth and disinfection by‐products.

Study of transport of contaminants in a pipe network using the model EPANET

A rural water supply system having two probable water sources, with an elevated tank, required to serve three schools and a hospital, was selected for this study. The model EPANET was used to study the variation of concentrations within the network of conservative and non-conservative substances introduced into the water at the source node and at other nodes. This paper discusses the findings of four scenario analyses undertaken in order to study the behaviour of the contaminants, and to develop strategies for management of some difficult situations encountered in water supply schemes. In the two source supply situation, it was observed that the water quality at the critical points in the system could be maintained below the permissible fluoride concentration, while maintaining the water requirements, by changing the pump operation cycles. When the behaviour of residual chlorine in the system was studied, it was observed that the model can be used to discover the chlorine booster points to maintain the required minimum residual chlorine content at the distribution terminal points. The results need to be verified by field-testing, once the water supply scheme, which is still under construction, is commissioned.