Separation characteristics in dissolved air flotation - pilot and full-scale demonstration

2003 ◽  
Vol 48 (3) ◽  
pp. 89-96
Author(s):  
M. Ljunggren ◽  
L. Jönsson
Keyword(s):  
Particle Size ◽  
Contact Zone ◽  
Separation Efficiency ◽  
Particle Separation ◽  
Full Scale ◽  
Particle Sizes ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Practical Implications ◽  
Dissolved Air

This study presents practical implications for particle separation in Dissolved Air Flotation (DAF). The objectives were to localise where particles are separated from the water phase and to determine what particles, in terms of size, are removed by the DAF-process. Both pilot- and full-scale plants were investigated. Particle sizes were analysed with a light-blocking particle counter and an optical borescope was used for visualisation of particle-bubble aggregates. It was found that particles are preferably separated upstream in the process, i.e. close to the contact zone. Furthermore, separation efficiency for particles increased with increasing particle size.

Parameters Influencing Sludge Thickening by Dissolved Air Flotation

1993 ◽  
Vol 28 (1) ◽  
pp. 87-90 ◽  
Author(s):  
M. Sugahara ◽  
S. Oku
Keyword(s):  
Particle Size ◽  
Particle Sizes ◽  
Dissolved Air Flotation ◽  
Flotation Process ◽  
Sludge Characteristics ◽  
Factors Influencing ◽  
Air Flotation ◽  
Sludge Particle ◽  
Sludge Thickening ◽  
Dissolved Air

The purpose of this study was to investigate factors influencing sludge thickening in the dissolved air flotation process. Attention focused on the alteration of sludge characteristics as a result of coagulation and aeration. Batch thickening experiments showed that both coagulation and aeration enhanced sludge thickening. The most important parameter influencing sludge thickening appeared to be sludge particle size; larger particle sizes produced higher sludge solids concentrations in the float.

Effect of pressure on bubble size in dissolved air flotation

2002 ◽  
Vol 2 (5-6) ◽  
pp. 41-46 ◽  
Author(s):  
M. Han ◽  
Y. Park ◽  
J. Lee ◽  
J. Shim
Keyword(s):  
Bubble Size ◽  
Critical Pressure ◽  
Theoretical Work ◽  
Particle Sizes ◽  
Water And Wastewater Treatment ◽  
Dissolved Air Flotation ◽  
Recent Theoretical Work ◽  
Water And Wastewater ◽  
Air Flotation ◽  
Dissolved Air

Although dissolved air flotation (DAF) has been successfully adopted for water and wastewater treatment, the fundamental characteristics of the process have not been fully investigated. According to recent theoretical work on DAF, bubble size is one of the most important factors that affect the efficiency of the process, with better removal efficiency when the sizes of both bubbles and particles are similar. In this study, a newly developed particle counter method (PCM) was introduced to measure particle sizes. To confirm its usefulness, the results were compared with those from image analysis. Then, using PCM, the size of bubbles in DAF was measured under various pressure conditions which are known to affect the bubble size the most (from 2 to 6 atmospheres). The bubble size decreased as the pressure increased up to a pressure of 3.5 atmospheres. Above this critical pressure, the bubble size did not decrease with further increases in pressure. According to these experimental results, it is not only costly, but also unnecessary, to maintain a pressure above 3.5 atmospheres if the goal is only to generate smaller bubbles.

Research on the CFD numerical simulation and process optimization of countercurrent–cocurrent dissolved air flotation

2019 ◽  
Vol 68 (5) ◽  
pp. 325-336
Author(s):  
Yonglei Wang ◽  
Wei Liu ◽  
Liping Tian ◽  
Ruibao Jia ◽  
Zhenqi Du ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Contact Zone ◽  
Process Optimization ◽  
Operating Conditions ◽  
Cocurrent Flow ◽  
Dissolved Gas ◽  
Dissolved Air Flotation ◽  
Simulation Results ◽  
Air Flotation ◽  
Dissolved Air

Abstract The countercurrent–cocurrent dissolved air flotation (CCDAF) process is a new type of air flotation process integrating countercurrent collision and cocurrent flow adhesion processes. The structural form of the CCDAF tank and its process parameters are the required conditions to achieve countercurrent collision and cocurrent adhesion. In this study, eight CCDAF tank process models were established with a flow rate of 0.5 m3/h. Flow field numerical simulation and process optimization of a CCDAF tank was conducted using Fluent software. The simulation results show that the optimal conditions for the CCDAF process are as follows: contact zone ascending velocity 10 mm/s, separation zone separation velocity 1.5 mm/s, dissolved gas pressure 0.45 MPa, and recirculating dissolved-gas distribution ratio R1/R2 1:1. Under these operating conditions, the flow state in the flotation tank is the most stable and the gas in the contact zone is evenly distributed. According to the simulation results, a 5 m3/h pilot plant was built. The structural dimensions were: B × L × H = 1,020 mm × 1,300 mm × 1,350 mm. The test results show that the CCDAF has a significant decontamination effect and is clearly superior to the cocurrent flow DAF process and countercurrent flow DAF process.

Significance of pressure and recirculation in sludge thickening by dissolved air flotation

1997 ◽  
Vol 36 (12) ◽  
pp. 223-230 ◽  
Author(s):  
Hak Chung Tai ◽  
Yeon Kim Doo
Keyword(s):  
Separation Efficiency ◽  
Reliable Operation ◽  
Dissolved Air Flotation ◽  
Efficient Operation ◽  
Recirculation Flow ◽  
Operating Variable ◽  
Solids Separation ◽  
Air Flotation ◽  
Sludge Thickening ◽  
Dissolved Air

An experimental study was conducted to identify the effect of each operating variable on the liquid-solids separation efficiency using a bench scale batch flotation system and waste activated sludge. Interpretation of the experimental results was performed by use of the characteristic constants of an empirical equation proposed. Minimum A/S ratio for reliable operation of dissolved air flotation should be greater than 0.009. However, unstable sludge rising took place at the initial clarification stage due to excessive shear and turbulence when the pressure was high in spite of high A/S ratio. The efficiency increased as the A/S ratio increased except a case of high pressure coupled with high A/S ratio. High recirculation flow with a saturator pressure less than 5 atm is recommended for stable and efficient operation. The pore size of a diffuser did not affect the thickening efficiency significantly. Concentration gradient of the float solids became larger as flotation continued. Skimming of a top layer or a long skimming interval is desirable for high thickening efficiency.

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.

Large batch bench-scale dissolved air flotation system (LB-DAF) for drinking water treatability tests

2020 ◽  
Vol 6 (4) ◽  
pp. 1004-1017 ◽  
Author(s):  
Juan Pablo Gonzalez-Galvis ◽  
Roberto M. Narbaitz
Keyword(s):  
Drinking Water ◽  
River Water ◽  
Full Scale ◽  
Dissolved Air Flotation ◽  
Large Batch ◽  
Bench Scale ◽  
Air Flotation ◽  
Dissolved Air

A new bench-scale batch DAF system was developed, for the river water tested it yielded better predictions of full-scale DAF turbidity removals than a commercial DAF jar tester.

A simplified method for assessing the saturation efficiency at full-scale dissolved air flotation plants

1998 ◽  
Vol 38 (6) ◽  
pp. 303-310 ◽  
Author(s):  
S. Steinbach ◽  
J. Haarhoff
Keyword(s):  
Full Scale ◽  
Dissolved Air Flotation ◽  
Atmospheric Air ◽  
Comprehensive Method ◽  
Simplified Method ◽  
Saturation Efficiency ◽  
Air Flotation ◽  
Saturation Systems ◽  
Measuring Unit ◽  
Dissolved Air

This paper proposes a simplified yet comprehensive method for measuring the efficiency of air saturation systems used in dissolved air flotation. It is based on a review of methods suggested by other researchers in this field, but several improvements to existing methods are made. A saturation air composition different than that of atmospheric air and incomplete precipitation in the measuring unit after pressure release are taken into consideration. The developed measurement and calculation procedure provide engineers and operators alike with an easy tool to assess the saturation efficiency of their system at full-scale DAF plants as well as at pilot and laboratory scale plants.

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