Experimental analysis of coagulation of particles under low-shear flow

Colomer, Jordi; Peters, Francesc; Marrasé, Cèlia

doi:10.1016/j.watres.2005.04.076

Cited by 62 publications

(49 citation statements)

References 44 publications

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“…Similar results have been found by Serra et al (2008) and Colomer et al (2005), who observed that the mean floc size increases with G at low shear. They used a mixing jar similar to ours and latex particles with the same density as the suspension (not affected by settling).…”

Section: Influence Of Shear Ratesupporting

confidence: 91%

Influence of shear rate, organic matter content, pH and salinity on mud flocculation

et al. 2009

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The purpose of this paper is to establish a relation between a few measurable quantities (the socalled ζ potential, organic matter content, and shear rate) and the flocculation behavior of mud. The results obtained with small-scale flocculation experiments (mixing jar) are compared to results of large-scale experiments (settling column). The mud used for all experiments has been collected in October 2007 in the lower Western Schelde, near Antwerp, Belgium. From this study, it was found that the mean floc size and the Kolmogorov microscale vary in a similar way with the shear rate for suspensions with different pH and salt concentrations. The size of flocs at a given shear rate depends on the properties of the suspension, which affect the electrokinetic properties of the sediment; these can be described by means of the ζ potential. The main findings of this paper are: (1) In saline suspensions at pH = 8, the mean floc size increases when the salt concentration and the ζ potential increase. (2) For a given ζ potential, the mean floc size at low pH is larger than observed at pH = 8 for any added salt. (3) The mean floc size increases with increasing organic matter content. (4) Mud with no organic matter at pH = 8 and no added salt flocculates very little. The response of mud suspensions to variations in salinity and pH is similar to that of kaolinite. This suggests that a general trend can be established for different and complex types of clays and mud. This systematic study can therefore be used for further development of flocculation models.

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Section: Influence Of Shear Ratesupporting

confidence: 91%

Influence of shear rate, organic matter content, pH and salinity on mud flocculation

et al. 2009

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“…The 2-L system has been described in Colomer et al (2005). Containers were cylinders of 129 mm inner diameter and 170 mm height.…”

Section: Guadayol Et Al Turbulence In Laboratory Containersmentioning

confidence: 99%

“…They have been used with planktonic organisms ranging from bacteria (Moeseneder and Herndl 1995) to copepods (e.g., Saiz and Alcaraz 1992) and have been especially important in studies with dinoflagellates (e.g., Pollingher and Zemel 1981, Berdalet 1992, Zirbel et al 2000. They have also been used to study exopolymer particles (Stoderegger and Herndl 1999) and aggregation dynamics Colomer et al 2005). In most of these studies, turbulence was not determined, or estimates were based on theoretical approaches that have not been validated with data.…”

Section: Guadayol Et Al Turbulence In Laboratory Containersmentioning

confidence: 99%

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Evaluation of oscillating grids and orbital shakers as means to generate isotropic and homogeneous small‐scale turbulence in laboratory enclosures commonly used in plankton studies

Guadayol

Peters

Stiansen

et al. 2009

Limnology & Ocean Methods

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The effects of turbulent motion on planktonic organisms have mainly been studied in the laboratory with devices capable of generating controlled turbulent conditions. Owing to technical and logistical difficulties, thorough assessments of hydrodynamics in such experiments are not routinely made. In this study, we examined the suitability of two widely used systems to generate isotropic, homogeneous, and stationary turbulence in laboratory containers: oscillating grid devices with large stroke length and relatively low frequencies of oscillation and orbital shaker tables. Turbulent kinetic energy dissipation rates were estimated from velocity measurements made with acoustic Doppler velocimeters. Both systems were shown to generate isotropic conditions in a relatively broad range of dissipation rates. Grid-stirred tanks produce homogeneous turbulence in both the horizontal and vertical dimensions, as long as stroke length is comparable to the height of the container. Turbulence in orbital shakers is not completely homogeneous, as it depends on the distance to the wall and to the surface. Empirical models are derived as a tool for the calculation of dissipation rates in the two systems within the ranges and conditions examined in this study.

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“…Design and operational parameters for coagulation/flocculation and DAF were studied by Edzwald (1995). Some researchers studied rapid mixing (Amirtharajah and Mills, 1982;Muyibi and Evison, 1995) and slow mixing (Colomer et al, 2005) with the objective of finding the optimal conditions of velocity gradient and mixing time.…”

Section: Introductionmentioning

confidence: 99%

Coagulation and Flotation Conditions of Humic Acid by Dissolved Air Flotation

Lee

2012

Journal of Environmental Science International

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Coagulation, flocculation, and dissolved air flotation (DAF) experiments were performed with humic acid to evaluate the influence of operational conditions on removal efficiencies. We investigated coagulation, flocculation, and flotation conditions of humic acid removal using a laboratory-scale DAF system. This paper deals with coagulant type (aluminum sulfate and PSO-M) and the most relevant operational conditions (velocity gradients for coagulation and flocculation, retention time and recycle ratio and flotation time). Results showed that optimal conditions for removing humic acid, yielding CHA removal efficiencies of approximately 85 %, are a recycle ratio of 40 %, coagulant dosages of 0.15 -0.20 gAl/gHA as aluminum sulfate and 0.03 -0.12 gAl/gHA as PSO-M, coagulation(400s -1 and 60s), flocculation(60s -1 and 900s or more), and flotation(490 kPa or more and at least 10 min).

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Experimental analysis of coagulation of particles under low-shear flow

Cited by 62 publications

References 44 publications

Influence of shear rate, organic matter content, pH and salinity on mud flocculation

Influence of shear rate, organic matter content, pH and salinity on mud flocculation

Evaluation of oscillating grids and orbital shakers as means to generate isotropic and homogeneous small‐scale turbulence in laboratory enclosures commonly used in plankton studies

Coagulation and Flotation Conditions of Humic Acid by Dissolved Air Flotation

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