Advective Flow and Floc Permeability

Tsou, G.W.; Wu, Rome-Ming; Yen, Pei-Shan; Lee, D.J.; Peng, Xiaofeng

doi:10.1006/jcis.2002.8317

Cited by 34 publications

(32 citation statements)

References 19 publications

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“…Hence, the floc permeability could not be accurately determined. Tsou et al (2002) employed a bubble-tracking technique to observe the flow field to investigate floc permeability. This technique had the great advantage of being able to observe the fluid flow directly.…”

Section: Discussionmentioning

confidence: 99%

“…However, these experiments just predicted the floc permeability from the floc terminal velocity and could not provide detailed information about the hydrodynamics in the creeping flow field. A bubble-tracking technique was utilized to visualize the flow field near the settling floc (Tsou et al, 2002;Wu and Lee, 1998;Wu et al, 2002;Pietsch et al, 2002). However, this technique does not follow the motions of water molecules induced by the falling particle.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry

Xiao

Lam

et al. 2012

Journal of Environmental Sciences

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The hydrodynamic behavior of diatom aggregates has a significant influence on the interactions and flocculation kinetics of algae. However, characterization of the hydrodynamics of diatoms and diatom aggregates in water is rather difficult. In this laboratory study, an advanced visualization technique in particle image velocimetry (PIV) was employed to investigate the hydrodynamic properties of settling diatom aggregates. The experiments were conducted in a settling column filled with a suspension of fluorescent polymeric beads as seed tracers. A laser light sheet was generated by the PIV setup to illuminate a thin vertical planar region in the settling column, while the motions of particles were recorded by a high speed charge-coupled device (CCD) camera. This technique was able to capture the trajectories of the tracers when a diatom aggregate settled through the tracer suspension. The PIV results indicated directly the curvilinear feature of the streamlines around diatom aggregates. The rectilinear collision model largely overestimated the collision areas of the settling particles. Algae aggregates appeared to be highly porous and fractal, which allowed streamlines to penetrate into the aggregate interior. The diatom aggregates have a fluid collection efficiency of 10%-40%. The permeable feature of aggregates can significantly enhance the collisions and flocculation between the aggregates and other small particles including algal cells in water.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry

Xiao

Lam

et al. 2012

Journal of Environmental Sciences

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“…Biological flocs produced in activated sludge reactors are highly porous and fractal (Li and Ganczarczyk, 1990;Lee et al, 1996;Li and Yuan, 2002), but the flow through the floc is not large enough to affect their settling behavior. However, floc permeability can affect mass transport rates to bacteria inside the floc, even under conditions where it does not affect settling velocity (Logan and Hunt, 1988;Li and Ganczarczyk, 1992;Tsou et al, 2002;Li et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Physical and hydrodynamic properties of flocs produced during biological hydrogen production

Zhang¹,

Li²,

Oh³

et al. 2004

Biotech & Bioengineering

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Dense flocs readily form in continuous culture bioreactors used for hydrogen production, but the fractal and hydrodynamic properties of these flocs have not been previously analyzed. We therefore examined the size distribution, fractal dimension, and hydrodynamic properties of flocs formed in a continuous flow, well-mixed reactor treating synthetic wastewater at a fixed condition of a 4.5 h hydraulic detention time (23jC, pH 5.5). The reactor was operated for a total of 3 months at three different organic loading rates (27, 53, and 80 g-COD/L-d) with influent glucose concentrations of 5, 10, and 15 g-COD/L. At all three loading rates the removal of glucose was nearly complete (98.6 -99.4%) and biomass was produced in proportion to the organic loading rate (0.86 F 0.11, 2.40 F 0.26, and 4.59 F 1.55 g/L of MLVSS in the reactor). Overall conversion efficiencies of glucose to hydrogen, evaluated on the basis of a maximum of 4 mol-H 2 /molglucose, increased with organic loading rates in the order 17.7%, 23.1%, and 25.6%. The gas contained 56.1 F 4.9% hydrogen, with the balance as carbon dioxide. No methane gas was detected. Under these conditions, flocs were produced with mean sizes that increased with organic loading, in the order 0.12 cm (5 g-COD/L), 0.35 cm (10 g-COD/L), and 0.58 cm (15 g-COD/L). As the average floc size increased, the flocs became on average denser and less fractal, with fractal dimensions increasing from 2.11 F 0.17 to 2.48 F 0.13. Floc porosities ranged from 0.75 -0.96, and resulted in aggregate densities that allowed little intra-aggregate flow through the floc. As a result, average settling velocities were not appreciably larger than those predicted by Stokes' law for spherical, impermeable flocs. Our results demonstrate that dense, relatively impermeable flocs are produced in biohydrogen reactors that have settling properties in reasonable agreement with Stokes' law. B 2004 Wiley Periodicals, Inc.

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“…A semilog plot of (C 0 -C)/[2(C 0 -C 1 )] versus time is a straight line that passes through the origin with a slope of (-4π 2 …”

Section: Methodsmentioning

confidence: 99%

Microscale Hydrodynamic Analysis of Aerobic Granules in the Mass Transfer Process

Liu

Sheng

et al. 2010

Environ. Sci. Technol.

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The internal structure of aerobic granules has a significant impact on the hydrodynamic performance and mass transfer process, and severely affects the efficiency and stability of granules-based reactors for wastewater treatment. In this study, for the first time the granule complex structure was correlated with the hydrodynamic performance and substrates reactions process. First, a series of multiple fluorescence stained confocal laser scanning microscopy images of aerobic granules were obtained. Then, the form and structure of the entire granule was reconstructed. A three-dimensional computational fluid dynamics study was carried out for the hydrodynamic analysis. Two different models were developed on the basis of different fluorescence stained confocal laser scanning microscopy images to elucidate the roles of the granule structure in the hydrodynamic and mass transfer processes of aerobic granules. The fluid flow behavior, such as the velocity profiles, the pathlines and hence the hydrodynamic drag force, exerted on the granule in a Newtonian fluid, was studied by varying the Reynolds number. Furthermore, the spatial distribution of dissolved nutrients (e.g., oxygen) was acquired by solving the convection-diffusion equations on the basis of the reconstructed granule structure. This study demonstrates that the reconstructed granule model could offer a better understanding to the mass transfer process of aerobic granules than simply considering the granule structure to be homogeneous.

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Advective Flow and Floc Permeability

Cited by 34 publications

References 19 publications

Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry

Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry

Physical and hydrodynamic properties of flocs produced during biological hydrogen production

Microscale Hydrodynamic Analysis of Aerobic Granules in the Mass Transfer Process

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