Characterization of micro-bubble size distribution and flow configuration in DAF contact zone by a non-intrusive image analysis system and tracer tests

2010 ◽  
Vol 61 (1) ◽  
pp. 253-262 ◽  
Author(s):  
R. B. Moruzzi ◽  
M. A. P. Reali
Keyword(s):  
Size Distribution ◽  
Contact Zone ◽  
Bubble Size ◽  
Bubble Size Distribution ◽  
Image Analysis System ◽  
Particle Removal ◽  
Air Concentration ◽  
Dissolved Air Flotation ◽  
Micro Bubble ◽  
Dissolved Air

This paper aims to investigate the influence of some dissolved air flotation (DAF) process variables (specifically: the hydraulic detention time in the contact zone and the supplied dissolved air concentration) and the pH values, as pretreatment chemical variables, on the micro-bubble size distribution (BSD) in a DAF contact zone. This work was carried out in a pilot plant where bubbles were measured by an appropriate non-intrusive image acquisition system. The results show that the obtained diameter ranges were in agreement with values reported in the literature (10–100 μm), quite independently of the investigated conditions. The linear average diameter varied from 20 to 30 μm, or equivalently, the Sauter (d3,2) diameter varied from 40 to 50 μm. In all investigated conditions, D50 was between 75% and 95%. The BSD might present different profile (with a bimodal curve trend), however, when analyzing the volumetric frequency distribution (in some cases with the appearance of peaks in diameters ranging from 90–100 μm). Regarding volumetric frequency analysis, all the investigated parameters can modify the BSD in DAF contact zone after the release point, thus potentially causing changes in DAF kinetics. This finding prompts further research in order to verify the effect of these BSD changes on solid particle removal efficiency by DAF.

scholarly journals Numerical Simulation Study on Distribution of Bubble in Flow near Aerator Based on CFD-PBM Coupled Model in Tunnel

2021 ◽  
Vol 2021 ◽  
pp. 1-24
Author(s):  
Jiaming Lei ◽  
Jianmin Zhang ◽  
Lifang Zhang
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Numerical Models ◽  
Coupled Model ◽  
Bubble Size Distribution ◽  
Balance Model ◽  
Main Process ◽  
Air Bubbles ◽  
Air Concentration ◽  
Aerated Flow

The aerator can reduce erosion by mixing a large amount of air into the water in the solid wall area. The effectiveness of erosion reduction is mainly based on air concentration and its bubble size distribution. However, simultaneous simulation of the air concentration and its bubble size distribution in numerical simulations is still a hot and difficult area of research. Aiming at the downstream aerated flow of hydraulic aeration facilities, several numerical models, such as VOF, mixture, Euler, and Population Balance Model (PBM), are compared and verified by experiments. The results show that the CFD-PBM coupled model performs well compared to other conventional multiphase models. It can not only obtain the evolution law of the bubble distribution downstream of the aerator but also accurately simulate the recombination and evolution process of bubble aggregation and breakage. The Sauter mean diameter of the air bubbles in the aerated flow decreases along the way and eventually reaches a stable value. The bubble breakage is the main process in the development of the bubbles. It reveals the aeration law that the small air bubbles are closer to the bottom plate, while the large bubbles float up along the aerated flow, which provides a powerful support for the basic research on the mechanism of aeration and erosion reduction.

Dissolved air flotation model for drinking water treatment

2000 ◽  
Vol 27 (2) ◽  
pp. 373-382 ◽  
Author(s):  
Ayman R Shawwa ◽  
Daniel W Smith
Keyword(s):  
Water Treatment ◽  
Kinetic Model ◽  
Contact Zone ◽  
Removal Rate ◽  
Particle Removal ◽  
Dissolved Air Flotation ◽  
First Order ◽  
Air Flotation ◽  
Particle Attachment ◽  
Dissolved Air

In this study, a kinetic model that describes bubble-particle transport and attachment in the contact zone of dissolved air flotation (DAF) process is presented. The kinetic model, which is based on the assumption that the contact zone is analogous to a chemical reactor, describes the particle removal rate as a first-order reaction with respect to the concentration of particles. It identified important parameters, such as the bubble-particle attachment efficiency (αPB). The theoretical first-order particle removal rate constant (kP), based on the mathematical model, was determined by varying αPB from 0.1 to 1.0. On the other hand, the experimental kP value was determined by measuring the mean residence time, the degree of mixing of particles, and the particle removal efficiency of the contact zone by conducting pilot-scale DAF experiments at different hydraulic loading rates and recycle ratios. The experimentally determined first-order particle removal rate constant was equal to the theoretical kP value when the bubble-particle attachment efficiency (αPB) was in the range of 0.35 to 0.55, which is considered typical for water treatment applications. The kinetic model can be used to predict DAF removal efficiencies provided that αPB is determined for the system under investigation and that the operating conditions applied in this research are used. However, independent experiments are required to verify the applicability of the proposed model.Key words: algae, bubble, coagulation, dissolved air flotation, flocculation, kinetic model, particle size distribution, water treatment.

Investigation of the Micro Bubble Size Distribution in the Extracorporeal Blood Circulation

2006 ◽  
pp. 281-285
Author(s):  
Georg Dietrich ◽  
Klaus V. Jenderka ◽  
Ulrich Cobet ◽  
Bernhard Kopsch ◽  
Albrecht Klemenz ◽  
...  
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Blood Circulation ◽  
Bubble Size Distribution ◽  
Extracorporeal Blood ◽  
Micro Bubble ◽  
Extracorporeal Blood Circulation

Micro-bubble size distribution measurements by laser diffraction technique

2009 ◽  
Vol 22 (4) ◽  
pp. 330-335 ◽  
Author(s):  
Hudson J.B. Couto ◽  
Daniel G. Nunes ◽  
Reiner Neumann ◽  
Sílvia C.A. França
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Laser Diffraction ◽  
Bubble Size Distribution ◽  
Micro Bubble

Physiochemical properties and reproducibility of air-based sodium tetradecyl sulphate foam using the Tessari method

2016 ◽  
Vol 32 (6) ◽  
pp. 390-396 ◽  
Author(s):  
Mike R Watkins ◽  
Richard J Oliver
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Bubble Size Distribution ◽  
Foam Density ◽  
Physiochemical Properties ◽  
Significant Difference ◽  
Experienced Operator ◽  
Sodium Tetradecyl Sulphate ◽  
Foam Production ◽  
Made In

Objectives The objectives were to examine the density, bubble size distribution and durability of sodium tetradecyl sulphate foam and the consistency of production of foam by a number of different operators using the Tessari method. Methods 1% and 3% sodium tetradecyl sulphate sclerosant foam was produced by an experienced operator and a group of inexperienced operators using either a 1:3 or 1:4 liquid:air ratio and the Tessari method. The foam density, bubble size distribution and foam durability were measured on freshly prepared foam from each operator. Results The foam density measurements were similar for each of the 1:3 preparations and for each of the 1:4 preparations but not affected by the sclerosant concentration. The bubble size for all preparations were very small immediately after preparation but progressively coalesced to become a micro-foam (<250 µm) after the first 30 s up until 2 min. Both the 1% and 3% solution foams developed liquid more rapidly when made in a 1:3 ratio (37 s) than in a 1:4 ratio (45 s) but all combinations took similar times to reach 0.4 ml liquid formation. For all the experiments, there was no statistical significant difference between operators. Conclusions The Tessari method of foam production for sodium tetradecyl sulphate sclerosant is consistent and reproducible even when made by inexperienced operators. The best quality foam with micro bubbles should be used within the first minute after production.

scholarly journals Development of Bubble Characteristics on Chute Spillway Bottom

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1129
Author(s):  
Ruidi Bai ◽  
Chang Liu ◽  
Bingyang Feng ◽  
Shanjun Liu ◽  
Faxing Zhang
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Dissipation Rate ◽  
Bubble Diameter ◽  
Bubble Size Distribution ◽  
Impact Zone ◽  
Air Bubble ◽  
Air Supply ◽  
Bubble Characteristics ◽  
The Impact

Chute aerators introduce a large air discharge through air supply ducts to prevent cavitation erosion on spillways. There is not much information on the microcosmic air bubble characteristics near the chute bottom. This study was focused on examining the bottom air-water flow properties by performing a series of model tests that eliminated the upper aeration and illustrated the potential for bubble variation processes on the chute bottom. In comparison with the strong air detrainment in the impact zone, the bottom air bubble frequency decreased slightly. Observations showed that range of probability of the bubble chord length tended to decrease sharply in the impact zone and by a lesser extent in the equilibrium zone. A distinct mechanism to control the bubble size distribution, depending on bubble diameter, was proposed. For bubbles larger than about 1–2 mm, the bubble size distribution followed a—5/3 power-law scaling with diameter. Using the relationship between the local dissipation rate and bubble size, the bottom dissipation rate was found to increase along the chute bottom, and the corresponding Hinze scale showed a good agreement with the observations.

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