The Experts below are selected from a list of 78 Experts worldwide ranked by ideXlab platform
Roger Alexande Falcone - One of the best experts on this subject based on the ideXlab platform.
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appraisal of chlorine Contact Tank modelling practices
Water Research, 2012Co-Authors: William Bonino Raue, Athanasios Angeloudis, Roger Alexande FalconeAbstract:Abstract With new water directives imposing strict regulations to reduce the footprint of treatment operations and contaminant levels, a performance review of water treatment facilities, including Chlorine Contact Tanks (CCTs) is required. This paper includes a critical appraisal of the international literature on CCT modelling practices to date, aiming to assist the identification of areas requiring further development, in particular, relating to the computational modelling capability and availability of tools to assist hydraulic design and optimisation studies of CCTs. It notes that the hydraulic optimisation practice of poorly designed Tanks commenced with experimental studies undertaken in the 1960s and 1970s, which involved mainly two types of studies, namely in situ tracer tests and laboratory physical modelling. The former has traditionally been conducted to diagnose the hydraulic performance of existing CCTs, typically based on results such as Residence Time Distribution (RTD) curves and values of the Hydraulic Efficiency Indicators (HEIs). The latter has been useful in trial and error testing of the impact of certain design modifications on those results, with suggestions for later improvements of the field scale unit. In the 1980s mathematical and numerical modelling studies started to be used to assist CCT investigations, offering a greater level of detail in a more cost-effective manner than equivalent experimentally based investigations. With the growth of computing power and the popularisation of computational models, the 1990s saw the development and application of Computational Fluid Dynamics (CFD) tools to simulate the hydraulic performance of CCTs, sometimes independently of experimentation, other than by using available data to calibrate and validate modelling predictions. This has led to the current scenario of CFD models being invaluable assistive tools in optimisation studies of CCTs, with the experimentation practice continuing to allow for specific diagnostics and to supply data for the calibration and validation of CFD modelling results. The vast majority of CCT modelling studies published to date have focused on simulating CCT hydrodynamic and conservative solute transport processes. The chlorination kinetics and Disinfection By-Product (DBP) formation have rarely been contemplated in computer modelling studies of CCTs. Commercially available CFD models have not traditionally been applied with this purpose, while research studies undertaken using open source codes to produce tailor-made applications are rare. Aspects that could benefit from further understanding and/or development include the impact of scale when conducting experimentation with prototypes, adequate turbulence closure for a given situation, adequate numerical schemes vis-a-vis CFD model complexity vis-a-vis cost–benefit ratio of simulations and the inclusion of state of the art chlorination kinetics and DBP formation modelling in the CFD tools that can assist modern design and retrofit studies of CCTs.
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flow and transport simulation models for prediction of chlorine Contact Tank flow through curves
Water Environment Research, 2003Co-Authors: Hong Wang, Xueju Shao, Roger Alexande FalconeAbstract:Turbulent flow, solute transport, and chemical and biological decay are some of the basic processes encountered in water treatment plants. This paper presents recent developments in the numerical simulation of turbulent flow and disinfection processes in disinfection Contact Tanks. Simulation runs have been conducted for various Tank design alternatives and in different grid resolutions. The accuracy of simulated Contact Tank flow and the disinfection process depends largely on calculations of the hydrodynamic and solute transport characteristics in the Tanks. A key factor of this is the accuracy of advection and shear stress term computations, which can be affected by the use of different hydrodynamic submodels and numerical schemes. The performance of a simulation model relies to a great extent on the right combination of such submodels and numerical schemes. In this study, a number of simulation models were tested against realistic Tank configurations and measurements to evaluate the various combinations of turbulence models and difference schemes by analyzing predicted flow and solute transport patterns, as well as the corresponding flow-through curves. Models for disinfection Tank simulations are recommended based on comparisons of simulation results with measurements. These models may also be applied to other water treatment processes such as wastewater treatment.
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numerical modeling of tracer transport in a Contact Tank
Environment International, 1997Co-Authors: Roger Alexande Falcone, Ahmad Izani Md IsmailAbstract:Abstract Chlorine is extensively used to disinfect the drinking water supply. However, the inefficient use of chlorine as a disinfectant can result in the formation of chemical compounds which can have adverse health effects. Numerical models are increasingly being used in the design of efficient chlorine Contact Tanks. In this paper, details are given of the application of a two-dimensional semi-time-centred implicit QUICK scheme to model the transport of a tracer in a scaled physical model of a serpentine chlorine Contact disinfection Tank. The model is shown to give good agreement with laboratory measurements in the compartments of the Tank where the flow is relatively uniform over the depth.
And E. Aral - One of the best experts on this subject based on the ideXlab platform.
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Efficiency enhancement of chlorine Contact Tanks in water treatment plants: A full-scale application
'MDPI AG', 2019Co-Authors: M.a. And Demirel, And E. AralAbstract:The mixing and disinfection performance of a full-scale chlorine Contact Tank (CCT) is thoroughly investigated by means of numerical simulations for seasonal water supply variations in the water treatment plant (WTP) of Eskisehir in Turkey. Velocity measurements and tracer studies are carried out on a 1:10 scale laboratory model of the CCT to validate the numerical model. A good agreement between numerical and experimental results shows that the numerical model developed can be reliably used for the simulation of turbulent flow and solute transport in the full-scale CCT. Tracer studies indicate that the hydraulic performance of the CCT is classified as "average" according to the baffling factor, while the Morrill, Aral-Demirel (AD), and dispersion indexes indicate low mixing due to the recirculating and short-circuiting effects inside the chambers of the CCT.With respect to the first order modeling of chlorine decay and pathogen inactivation, chlorine concentrations are found to be significantly distinct for seasonal variations in water supply to maintain 3-log inactivation of Giardia cysts. A recently developed and patented slot-baffle design (SBD) is then applied to the full-scale CCT. It is found that the hydraulic efficiency of the CCT is improved to "high" and the Morrill index approaches 2, which identifies the system as a perfect mixing Tank. Using the SBD, the chlorine demand has been successfully decreased by 19% while providing equivalent inactivation level. The novel SBD design also reduces energy loses in the turbulent flow through the Tank and increases the energy efficiency of the CCT by 62%, which is significant for energy considerations in modern cities. © 2019 by the authors
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An efficient Contact Tank design for potable water treatment
'Teknik Dergi', 2018Co-Authors: And E. AralAbstract:In this study, a second order accurate Large Eddy Simulation (LES) model is used to simulate three-dimensional turbulent flow and disinfectant transport in a Contact Tank. The hydraulic and mixing indexes of the Tank are evaluated based on computational tracer studies. It is shown that the energy consumption rates of the Contact Tank can be reduced by the use of the proposed slot-baffle design instead of the conventional baffle system that is used in these facilities. The proposed slot-baffle design improves the hydraulic efficiency by 44%, mixing efficiency by 42% and reduces the energy required to drive the flow through the system by 43%. The outcome reported in this study shows that the energy consumption in water treatment plants can be significantly reduced when the novel baffle design is implemented on existing Contact Tanks without expensive infrastructure modifications. © 2018 tur Chamber of Civil Engineers.All right reserved
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Performance of Efficiency Indexes for Contact Tanks
'American Society of Civil Engineers (ASCE)', 2018Co-Authors: And E. AralAbstract:Hydraulic and mixing efficiencies of Contact Tanks are evaluated using several indexes that are used in the literature. These indexes emphasize different aspects of flow and mixing processes in the mixing Tank at different scales. Uniformity of the evaluations obtained from these indexes is necessary for unified characterization of the overall performance of Contact Tanks, which is very difficult to achieve. In this study, several Contact Tanks with different baffling configurations were studied using computational fluid dynamics (CFD) analysis in which three-dimensional hydrodynamic analysis of flow and transport of a conservative tracer within the flow field were studied. The performance data developed were extended by including the outcome of some of the earlier studies that are reported in the literature. The most common indexes that are used in the literature were used to evaluate the performance of these cases. The results indicate that the performance evaluation obtained for these cases was not consistent for all indexes. An analysis was performed to identify the suitability of the performance indexes for a specific performance parameter. Performance of the newly introduced AD index, which yields more consistent evaluations for both short-circuiting and dispersion evaluation in the Contact Tank, was compared with the performance of the Morrill index. A dimensionless energy-efficiency index was also proposed for the evaluation of the efficiency of the flow-through system in the Tank. © 2018 American Society of Civil Engineers
Mustafa M. - One of the best experts on this subject based on the ideXlab platform.
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Efficiency Enhancement of Chlorine Contact Tanks in Water Treatment Plants: A Full-Scale Application
'MDPI AG', 2019Co-Authors: Anil And M. Demirel, Ender And Aral, Mustafa M.Abstract:The mixing and disinfection performance of a full-scale chlorine Contact Tank (CCT) is thoroughly investigated by means of numerical simulations for seasonal water supply variations in the water treatment plant (WTP) of Eskisehir in Turkey. Velocity measurements and tracer studies are carried out on a 1:10 scale laboratory model of the CCT to validate the numerical model. A good agreement between numerical and experimental results shows that the numerical model developed can be reliably used for the simulation of turbulent flow and solute transport in the full-scale CCT. Tracer studies indicate that the hydraulic performance of the CCT is classified as ``average{''} according to the baffling factor, while the Morrill, Aral-Demirel (AD), and dispersion indexes indicate low mixing due to the recirculating and short-circuiting effects inside the chambers of the CCT. With respect to the first order modeling of chlorine decay and pathogen inactivation, chlorine concentrations are found to be significantly distinct for seasonal variations in water supply to maintain 3-log inactivation of Giardia cysts. A recently developed and patented slot-baffle design (SBD) is then applied to the full-scale CCT. It is found that the hydraulic efficiency of the CCT is improved to ``high{''} and the Morrill index approaches 2, which identifies the system as a perfect mixing Tank. Using the SBD, the chlorine demand has been successfully decreased by 19\% while providing equivalent inactivation level. The novel SBD design also reduces energy loses in the turbulent flow through the Tank and increases the energy efficiency of the CCT by 62\%, which is significant for energy considerations in modern cities
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Performance of Efficiency Indexes for Contact Tanks
'American Society of Civil Engineers (ASCE)', 2018Co-Authors: Ender And Aral, Mustafa M.Abstract:Hydraulic and mixing efficiencies of Contact Tanks are evaluated using several indexes that are used in the literature. These indexes emphasize different aspects of flow and mixing processes in the mixing Tank at different scales. Uniformity of the evaluations obtained from these indexes is necessary for unified characterization of the overall performance of Contact Tanks, which is very difficult to achieve. In this study, several Contact Tanks with different baffling configurations were studied using computational fluid dynamics (CFD) analysis in which three-dimensional hydrodynamic analysis of flow and transport of a conservative tracer within the flow field were studied. The performance data developed were extended by including the outcome of some of the earlier studies that are reported in the literature. The most common indexes that are used in the literature were used to evaluate the performance of these cases. The results indicate that the performance evaluation obtained for these cases was not consistent for all indexes. An analysis was performed to identify the suitability of the performance indexes for a specific performance parameter. Performance of the newly introduced AD index, which yields more consistent evaluations for both short-circuiting and dispersion evaluation in the Contact Tank, was compared with the performance of the Morrill index. A dimensionless energy-efficiency index was also proposed for the evaluation of the efficiency of the flow-through system in the Tank
Athanasios Angeloudis - One of the best experts on this subject based on the ideXlab platform.
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Contact Tank Design Impact on Process Performance
Environmental Modeling & Assessment, 2016Co-Authors: Athanasios Angeloudis, Thorsten Stoesser, Carlo Gualtieri, Roger Alexander FalconerAbstract:In this study three-dimensional numerical models were refined to predict reactive processes in disinfection Contact Tanks (CTs). The methodology departs from the traditional performance assessment of Contact Tanks via hydraulic efficiency indicators, as it simulates directly transport and decay of the disinfectant, inactivation of pathogens and accumulation of by-products. The method is applied to study the effects of inlet and compartment design on Contact Tank performance, with special emphasis on turbulent mixing and minimisation of internal recirculation and short-circuiting. In contrast to the conventional approach of maximising the length-to-width ratio, the proposed design changes are aimed at addressing and mitigating adverse hydrodynamic structures, which have historically led to poor hydraulic efficiency in many existing Contact Tanks. The results suggest that water treatment facilities can benefit from in-depth analyses of the flow and kinetic processes through computational fluid dynamics, resulting in up to 38 % more efficient pathogen inactivation and 14 % less disinfection by-product formation.
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appraisal of chlorine Contact Tank modelling practices
Water Research, 2012Co-Authors: William Bonino Raue, Athanasios Angeloudis, Roger Alexande FalconeAbstract:Abstract With new water directives imposing strict regulations to reduce the footprint of treatment operations and contaminant levels, a performance review of water treatment facilities, including Chlorine Contact Tanks (CCTs) is required. This paper includes a critical appraisal of the international literature on CCT modelling practices to date, aiming to assist the identification of areas requiring further development, in particular, relating to the computational modelling capability and availability of tools to assist hydraulic design and optimisation studies of CCTs. It notes that the hydraulic optimisation practice of poorly designed Tanks commenced with experimental studies undertaken in the 1960s and 1970s, which involved mainly two types of studies, namely in situ tracer tests and laboratory physical modelling. The former has traditionally been conducted to diagnose the hydraulic performance of existing CCTs, typically based on results such as Residence Time Distribution (RTD) curves and values of the Hydraulic Efficiency Indicators (HEIs). The latter has been useful in trial and error testing of the impact of certain design modifications on those results, with suggestions for later improvements of the field scale unit. In the 1980s mathematical and numerical modelling studies started to be used to assist CCT investigations, offering a greater level of detail in a more cost-effective manner than equivalent experimentally based investigations. With the growth of computing power and the popularisation of computational models, the 1990s saw the development and application of Computational Fluid Dynamics (CFD) tools to simulate the hydraulic performance of CCTs, sometimes independently of experimentation, other than by using available data to calibrate and validate modelling predictions. This has led to the current scenario of CFD models being invaluable assistive tools in optimisation studies of CCTs, with the experimentation practice continuing to allow for specific diagnostics and to supply data for the calibration and validation of CFD modelling results. The vast majority of CCT modelling studies published to date have focused on simulating CCT hydrodynamic and conservative solute transport processes. The chlorination kinetics and Disinfection By-Product (DBP) formation have rarely been contemplated in computer modelling studies of CCTs. Commercially available CFD models have not traditionally been applied with this purpose, while research studies undertaken using open source codes to produce tailor-made applications are rare. Aspects that could benefit from further understanding and/or development include the impact of scale when conducting experimentation with prototypes, adequate turbulence closure for a given situation, adequate numerical schemes vis-a-vis CFD model complexity vis-a-vis cost–benefit ratio of simulations and the inclusion of state of the art chlorination kinetics and DBP formation modelling in the CFD tools that can assist modern design and retrofit studies of CCTs.
Ahmad Izani Md Ismail - One of the best experts on this subject based on the ideXlab platform.
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numerical modeling of tracer transport in a Contact Tank
Environment International, 1997Co-Authors: Roger Alexande Falcone, Ahmad Izani Md IsmailAbstract:Abstract Chlorine is extensively used to disinfect the drinking water supply. However, the inefficient use of chlorine as a disinfectant can result in the formation of chemical compounds which can have adverse health effects. Numerical models are increasingly being used in the design of efficient chlorine Contact Tanks. In this paper, details are given of the application of a two-dimensional semi-time-centred implicit QUICK scheme to model the transport of a tracer in a scaled physical model of a serpentine chlorine Contact disinfection Tank. The model is shown to give good agreement with laboratory measurements in the compartments of the Tank where the flow is relatively uniform over the depth.