Residence Time Distribution Characterization of the Flow Structure in Dissolved Air Flotation

Lundh, Måns; Jönsson, Lennart

doi:10.1061/(asce)0733-9372(2005)131:1(93)

Cited by 8 publications

(6 citation statements)

References 8 publications

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“…For both the reactors, three CSTR (N) in series were found to represent the system well. Lundh & Jönsson (2005) reported that the number of CSTR in a DAF reactor ranges from two to four. Our study gives the number in this range.…”

Section: Compartment Modelmentioning

confidence: 99%

“…Lundh & Jönsson (2005), using a compartment model, presented the changes in hydraulic patterns at different operating condition of LV and recirculafion ratio of pressurized water. In this study, we showed that introducfion of baffles results in an increase in volume of the clear water zone represented by the plug flow regime in the compartment model.…”

Section: Compartment Modelmentioning

confidence: 99%

“…The hydraulic characteristics in the separation chamber of the DAF tank could be represented by two stratified zones (Lundh et al 2000) of top white water zone and bottom clecir water zone as shown in Figure 2 (left). Based on this stratification scheme, the hydraulics in DAF was modelled with a compartment model as shown in Figure 2 (right) (Levenspiel 1999;Lundh & Jönsson 2005). The contact chamber was modelled as a mixing flow vessel.…”

Section: Analysis Of Rtdmentioning

confidence: 99%

“…The RTD curves from the tracer experiments were normalized by using the following Equations (l)-(4) (Levenspiel 1999;Lundh & Jönsson 2005).…”

Section: Analysis Of Rtdmentioning

confidence: 99%

“…Lundh & Jönsson (2005) reported that the stratified flow structiu"e of a flotation tank was successfully modelled by a compartment model of the tank-in-series model for the top white water zone and the plug flow model for the bottom clear water zone. In this paper, the performance of the 'DAF reactor with flow streamlining baffles (Terashima et al 2009a) is studied using the experimental RTD curves and the compartment model.…”

Section: Introductionmentioning

confidence: 99%

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Tracer experiment and RTD analysis of DAF separator with bar-type baffles

Terashima

Iwasaki

Yasui

et al. 2013

Water Science and Technology

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This paper describes the development of a new dissolved air flotation (DAF) separator with a flow streamlining baffle to improve solid separation efficiency. The analysis of the RTD (residence time distribution) curves indicated that the parameter θ(10) (dimensionless time at which 10% of tracer has discharged) increased from 0.38 for control reactor to 0.54 for the test reactor, suggesting significant reduction in short circuit flow. The RTD curves were also used to develop a compartment model for white water (rich in micro-bubbles and water flow is turbulent) and clear water (little or no air content and water flow is quiescent) zones in the reactor using a series of CSTR (continuous stirred tank reactors) and plug flow regime respectively. The proportion of the volume occupied by the white water zone was different in control and test configurations. In the test reactor, the fraction of the clear water zone was found to increase from 6 to 37%, resulting in improvement of the suspended solid (SS) removal efficiency from 97 to 99%.

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Section: Compartment Modelmentioning

confidence: 99%

Section: Compartment Modelmentioning

confidence: 99%

Section: Analysis Of Rtdmentioning

confidence: 99%

“…The RTD curves from the tracer experiments were normalized by using the following Equations (l)-(4) (Levenspiel 1999;Lundh & Jönsson 2005).…”

Section: Analysis Of Rtdmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tracer experiment and RTD analysis of DAF separator with bar-type baffles

Terashima

Iwasaki

Yasui

et al. 2013

Water Science and Technology

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An in-depth analysis of the hydrodynamic behaviour of a high-rate lamellar DAF tank by means of CFD simulations

Hlukhov,

Larraona,

Rivas

et al. 2024

Appl Water Sci

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This research is based on computational fluid dynamics simulations of water and microbubble flow within the tank of a lamellar DAF (L-DAF) clarification system operating under high-rate DAF conditions (12–30 m/h). Firstly, performance of the DAF tank with lamellae was evaluated under two operating conditions in which the flow was either short-circuited or stratified in the absence of lamellae. In addition, the improvement in bubble removal efficiency achieved by the incorporation of lamellae in each scenario was assessed. Secondly, an in-depth analysis was conducted of the flow that develops in the separation zone as a result of placing the lamella pack in that part of the tank. The significant density difference that the lamellae cause to exist between the bubble blanket and clarified water below is responsible for the complex three-dimensional flow observed between the two regions. Analysis of this flow showed a previously undescribed mechanism in which the density gradient plays a crucial role in preventing bubbles from passing through the lamellae and ultimately escaping with the effluent. Finally, the effect of hydraulic loading on the bubble removal efficiency of the L-DAF tank under consideration was researched, and it was found that an L-DAF with a height/length ratio of 0.72 is able to operate at hydraulic loading close to 30 m/h, evidencing good debubbling performance.

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