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James K. Edzwald - One of the best experts on this subject based on the ideXlab platform.
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Adapting Dissolved Air Flotation for the clarification of seawater
Desalination, 2013Co-Authors: Johannes Haarhoff, James K. EdzwaldAbstract:Abstract The high ionic strength of seawater affects the performance of the Dissolved Air Flotation (DAF) clarification process in a number of ways. At a reference temperature of 20 °C, the density of seawater is 3% higher than freshwater; the dynamic viscosity 8% higher; and the surface tension 1% higher. These differences cause very small changes in the rates of movement of particles and bubbles in both the contact and separation zones of the DAF reactor, that can be ignored for practical design purposes. Much more important are the differences in the solubility of Air in seawater (controlled by Henry's constant) and the Air transfer efficiency in pressure saturators or other Air saturation devices (largely controlled by the molecular diffusivities of the Air gases in water). At 20 °C, a typical Air saturator only transfers 74% of the Air to seawater relative to freshwater. This shortfall can be corrected by either increasing the recycle rate, or by operating the saturator at a higher pressure. The paper presents design charts for both these options.
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Dissolved Air Flotation For Water Clarification
2011Co-Authors: James K. Edzwald, Johannes HaarhoffAbstract:Dissolved Air Flotation for water clarification , Dissolved Air Flotation for water clarification , کتابخانه دیجیتال جندی شاپور اهواز
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Dissolved Air Flotation and me.
Water Research, 2010Co-Authors: James K. EdzwaldAbstract:This paper is mainly a critical review of the literature and an assessment of what we know about Dissolved Air Flotation (DAF). A few remarks are made at the outset about the author's personal journey in DAF research, his start and its progression. DAF has been used for several decades in drinking water treatment as an alternative clarification method to sedimentation. DAF is particularly effective in treating reservoir water supplies; those supplies containing algae, natural color or natural organic matter; and those with low mineral turbidity. It is more efficient than sedimentation in removing turbidity and particles for these type supplies. Furthermore, it is more efficient in removing Giardia cysts and Cryptosporidium oocysts. In the last 20 years, fundamental models were developed that provide a basis for understanding the process, optimizing it, and integrating it into water treatment plants. The theories were tested through laboratory and pilot-plant studies. Consequently, there have been trends in which DAF pretreatment has been optimized resulting in better coagulation and a decrease in the size of flocculation tanks. In addition, the hydraulic loading rates have increased reducing the size of DAF processes. While DAF has been used mainly in conventional type water plants, there is now interest in the technology as a pretreatment step in ultrafiltration membrane plants and in desalination reverse osmosis plants.
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Dissolved Air Flotation modelling insights and shortcomings
Journal of Water Supply Research and Technology-aqua, 2004Co-Authors: Johannes Haarhoff, James K. EdzwaldAbstract:The use of relatively simple but conceptually sound mathematical models is a powerful tool to identify and understand variables that affect the performance of a process. Such models have been used to better understand the many and complex Dissolved Air Flotation (DAF) variables that are in play when water, flocs and Air bubbles are mixed in the contact zone and then removed in the separation zone. The first purpose of this paper is to examine critically models that have been previously developed, primarily by the authors, for the contact and separation zones, and to summarize the insights gained from these efforts. During the past 5–10 years, significant strides were made towards more efficient designs that allow reduced flocculation time and much higher hydraulic loading rates. These developments have also exposed some fundamental weaknesses in the traditional modelling approaches, as some systems are now working beyond the theoretical limits of feasibility. The second purpose of the paper, therefore, is to probe these weaknesses and to suggest some directions for future modelling efforts.
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Effects of Dissolved Air Flotation hydraulic loading rate on water treatment performance
Environmental engineering, 1999Co-Authors: John E. Tobiason, James K. Edzwald, Tony Amato, Lawrence J. MaggiAbstract:The performance of Dissolved Air Flotation (DAF) followed by granular media filtration for water treatment was evaluated via pilot-scale studies for two water sources. The study focused on short flocculation times (5--8 minutes), high DAF hydraulic loading rates (17--44 m/hr (7--18 gpm/ft{sup 2})) and rapid rate filtration (10--20 m/hr (4--8 gpm/ft{sup 2})). Excellent treatment performance was achieved in terms of DAF clarified water turbidity, filtered water turbidity, organic matter removal and filtered water production. Bubble carryover from the DAF tank was mitigated by employing either internal or external Air removal strategies. Overall, the results demonstrate the effectiveness of an integrated, high rate flocculation/DAF/filtration water treatment strategy.
Pascal Guiraud - One of the best experts on this subject based on the ideXlab platform.
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Role of humic acid in enhancing Dissolved Air Flotation for the removal of TiO2 nanoparticles
Industrial & Engineering Chemistry Research, 2017Co-Authors: Ming Zhang, Jean-luc Trompette, Pascal GuiraudAbstract:The particle separation efficiency by Flotation sharply decreases or even completely fails when the diameter of dispersed particles falls into the nanoscale. In the present laboratory work, humic acid was used to enhance the removal of TiO2 nanoparticles from suspension in a chemical coagulant-free Dissolved Air Flotation process. Without humic acid, merely 63.8% of TiO2 nanoparticles were removed. For the humic acid-assisted Dissolved Air Flotation, the pH of humic acid solution significantly influenced the removal efficiency: more than 90% of nanoparticles could be separated when the pH of the humic acid stock solution was acidic; however, the basic solutions resulted in rather poor performance. In the acidic solution, the fiberlike humic acid might form colloids through the attraction between hydrophobic moieties. They possibly acted as a fishnet and trapped nanoparticles, leading to the great measured bubble–particle attachment efficiency. In all the effluents, a low residual Dissolved organic carbon ...
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Role of humic acid in enhancing Dissolved Air Flotation for the removal of TiO2 nanoparticles
Industrial and engineering chemistry research, 2017Co-Authors: Ming Zhang, Jean-luc Trompette, Pascal GuiraudAbstract:The particle separation efficiency by Flotation sharply decreases or even completely fails when the diameter of dispersed particles falls into the nanoscale. In the present laboratory work, humic acid was used to enhance the removal of TiO2 nanoparticles from suspension in a chemical coagulant-free Dissolved Air Flotation process. Without humic acid, merely 63.8% of TiO2 nanoparticles were removed. For the humic acid-assisted Dissolved Air Flotation, the pH of humic acid solution significantly influenced the removal efficiency: more than 90% of nanoparticles could be separated when the pH of the humic acid stock solution was acidic; however, the basic solutions resulted in rather poor performance. In the acidic solution, the fiberlike humic acid might form colloids through the attraction between hydrophobic moieties. They possibly acted as a fishnet and trapped nanoparticles, leading to the great measured bubble–particle attachment efficiency. In all the effluents, a low residual Dissolved organic carbon was observed, revealing a good participation of humic acid in Flotation. Moreover, a higher Air-to-solid ratio could improve the nanoparticle elimination by offering a larger surface area of Air bubbles. The fractal dimension of Flotation flocs demonstrated that the aggregates with compact structure took greater advantage in the Flotation separation of nanoparticles.
Ming Zhang - One of the best experts on this subject based on the ideXlab platform.
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Role of humic acid in enhancing Dissolved Air Flotation for the removal of TiO2 nanoparticles
Industrial & Engineering Chemistry Research, 2017Co-Authors: Ming Zhang, Jean-luc Trompette, Pascal GuiraudAbstract:The particle separation efficiency by Flotation sharply decreases or even completely fails when the diameter of dispersed particles falls into the nanoscale. In the present laboratory work, humic acid was used to enhance the removal of TiO2 nanoparticles from suspension in a chemical coagulant-free Dissolved Air Flotation process. Without humic acid, merely 63.8% of TiO2 nanoparticles were removed. For the humic acid-assisted Dissolved Air Flotation, the pH of humic acid solution significantly influenced the removal efficiency: more than 90% of nanoparticles could be separated when the pH of the humic acid stock solution was acidic; however, the basic solutions resulted in rather poor performance. In the acidic solution, the fiberlike humic acid might form colloids through the attraction between hydrophobic moieties. They possibly acted as a fishnet and trapped nanoparticles, leading to the great measured bubble–particle attachment efficiency. In all the effluents, a low residual Dissolved organic carbon ...
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Role of humic acid in enhancing Dissolved Air Flotation for the removal of TiO2 nanoparticles
Industrial and engineering chemistry research, 2017Co-Authors: Ming Zhang, Jean-luc Trompette, Pascal GuiraudAbstract:The particle separation efficiency by Flotation sharply decreases or even completely fails when the diameter of dispersed particles falls into the nanoscale. In the present laboratory work, humic acid was used to enhance the removal of TiO2 nanoparticles from suspension in a chemical coagulant-free Dissolved Air Flotation process. Without humic acid, merely 63.8% of TiO2 nanoparticles were removed. For the humic acid-assisted Dissolved Air Flotation, the pH of humic acid solution significantly influenced the removal efficiency: more than 90% of nanoparticles could be separated when the pH of the humic acid stock solution was acidic; however, the basic solutions resulted in rather poor performance. In the acidic solution, the fiberlike humic acid might form colloids through the attraction between hydrophobic moieties. They possibly acted as a fishnet and trapped nanoparticles, leading to the great measured bubble–particle attachment efficiency. In all the effluents, a low residual Dissolved organic carbon was observed, revealing a good participation of humic acid in Flotation. Moreover, a higher Air-to-solid ratio could improve the nanoparticle elimination by offering a larger surface area of Air bubbles. The fractal dimension of Flotation flocs demonstrated that the aggregates with compact structure took greater advantage in the Flotation separation of nanoparticles.
Jean-luc Trompette - One of the best experts on this subject based on the ideXlab platform.
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Role of humic acid in enhancing Dissolved Air Flotation for the removal of TiO2 nanoparticles
Industrial & Engineering Chemistry Research, 2017Co-Authors: Ming Zhang, Jean-luc Trompette, Pascal GuiraudAbstract:The particle separation efficiency by Flotation sharply decreases or even completely fails when the diameter of dispersed particles falls into the nanoscale. In the present laboratory work, humic acid was used to enhance the removal of TiO2 nanoparticles from suspension in a chemical coagulant-free Dissolved Air Flotation process. Without humic acid, merely 63.8% of TiO2 nanoparticles were removed. For the humic acid-assisted Dissolved Air Flotation, the pH of humic acid solution significantly influenced the removal efficiency: more than 90% of nanoparticles could be separated when the pH of the humic acid stock solution was acidic; however, the basic solutions resulted in rather poor performance. In the acidic solution, the fiberlike humic acid might form colloids through the attraction between hydrophobic moieties. They possibly acted as a fishnet and trapped nanoparticles, leading to the great measured bubble–particle attachment efficiency. In all the effluents, a low residual Dissolved organic carbon ...
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Role of humic acid in enhancing Dissolved Air Flotation for the removal of TiO2 nanoparticles
Industrial and engineering chemistry research, 2017Co-Authors: Ming Zhang, Jean-luc Trompette, Pascal GuiraudAbstract:The particle separation efficiency by Flotation sharply decreases or even completely fails when the diameter of dispersed particles falls into the nanoscale. In the present laboratory work, humic acid was used to enhance the removal of TiO2 nanoparticles from suspension in a chemical coagulant-free Dissolved Air Flotation process. Without humic acid, merely 63.8% of TiO2 nanoparticles were removed. For the humic acid-assisted Dissolved Air Flotation, the pH of humic acid solution significantly influenced the removal efficiency: more than 90% of nanoparticles could be separated when the pH of the humic acid stock solution was acidic; however, the basic solutions resulted in rather poor performance. In the acidic solution, the fiberlike humic acid might form colloids through the attraction between hydrophobic moieties. They possibly acted as a fishnet and trapped nanoparticles, leading to the great measured bubble–particle attachment efficiency. In all the effluents, a low residual Dissolved organic carbon was observed, revealing a good participation of humic acid in Flotation. Moreover, a higher Air-to-solid ratio could improve the nanoparticle elimination by offering a larger surface area of Air bubbles. The fractal dimension of Flotation flocs demonstrated that the aggregates with compact structure took greater advantage in the Flotation separation of nanoparticles.
Michael B. Kelley - One of the best experts on this subject based on the ideXlab platform.
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Removing Cryptosporidium by Dissolved‐Air Flotation
Journal American Water Works Association, 1995Co-Authors: Jeanine D. Plummer, James K. Edzwald, Michael B. KelleyAbstract:Bench-scale studies were used to investigate the effectiveness of Dissolved-Air Flotation (DAF) for the removal of Cryptosporidium parvum oocysts from a drinking water supply. Oocysts were spiked into a natural water at a concentration of 3-4 x 10 5 oocysts/L. Results indicate that DAF achieved a >2-log removal of oocysts under a variety of conditions. In addition, Flotation was a superior clarification process to sedimentation for the conditions tested. Coagulation and DAF conditions that minimize residual turbidity and maximize the removals of organic matter are conditions that produce high log removals of Cryptosporidium.
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removing cryptosporidium by Dissolved Air Flotation
Journal American Water Works Association, 1995Co-Authors: Jeanine D. Plummer, James K. Edzwald, Michael B. KelleyAbstract:Bench-scale studies were used to investigate the effectiveness of Dissolved-Air Flotation (DAF) for the removal of Cryptosporidium parvum oocysts from a drinking water supply. Oocysts were spiked into a natural water at a concentration of 3-4 x 10 5 oocysts/L. Results indicate that DAF achieved a >2-log removal of oocysts under a variety of conditions. In addition, Flotation was a superior clarification process to sedimentation for the conditions tested. Coagulation and DAF conditions that minimize residual turbidity and maximize the removals of organic matter are conditions that produce high log removals of Cryptosporidium.