Method for quantitative analysis of flocculation performance

Tse, Ian C.; Swetland, Karen A.; Weber‐Shirk, Monroe L.; Lion, Leonard W.

doi:10.1016/j.watres.2011.03.021

Cited by 16 publications

(12 citation statements)

References 10 publications

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“…Flow rate inside the flocculator was 3.6 mL/s, and the hydraulic residence time was 300 s. Sedimentation occurred in a 1.37 m tube settler (whose inner cross-sectional dimensions were 2.22 · 2.22 cm and angle of inclination was 60°) with a capture velocity (also In laminar flow, there is no turbulence to resuspend particles that may settle in the flocculator. As a result, the experimental flocculator tubing was coiled in a figure-eight configuration to create a secondary flow circulation to prevent floc sedimentation (Tse et al, 2011).…”

Section: Experimental Methodsmentioning

confidence: 99%

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Characterization of Flocs and Floc Size Distributions Using Image Analysis

Sun

Weber‐Shirk

Lion

2016

Environmental Engineering Science

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A nonintrusive digital imaging process was developed to study particle size distributions created through flocculation and sedimentation. Quantification of particle size distributions under different operating conditions can be of use in the understanding of aggregation mechanisms. This process was calibrated by measuring standardized polystyrene particles of known size and was utilized to count and measure individual kaolin clay particles as well as aggregates formed by coagulation with polyaluminum chloride and flocculation. Identification of out-of-focus flocs was automated with LabVIEW and used to remove them from the database that was analyzed. The particle diameter of the test suspension of kaolinite clay was measured to be 7.7 -3.8 lm and a linear relationship was obtained between turbidity and the concentration of clay particles determined by imaging. The analysis technique was applied to characterize flocs and floc particle size distribution as a function of coagulant dose. Removal of flocs by sedimentation was characterized by imaging, and the negative logarithm of the fraction of turbidity remaining after settling had a linear relationship with the logarithm of aluminum dose. The maximum floc size observed in the settled water was less than 120 lm, which was in accordance with the value predicted by a model for the capture velocity of the experimental tube settler of 0.21 mm/s.

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Section: Experimental Methodsmentioning

confidence: 99%

“…The average velocity gradient (G c ) in the coiled figureeight flocculator that accounts for the secondary flow was calculated as described by Tse et al (2011):…”

Section: Experimental Methodsmentioning

confidence: 99%

Characterization of Flocs and Floc Size Distributions Using Image Analysis

Sun

Weber‐Shirk

Lion

2016

Environmental Engineering Science

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“…Tse et al [59] developed a flocculation residual turbidity analyzer (FReTA) that monitors the turbidity of floc suspensions undergoing quiescent settling and records the residual turbidity. From the data, the sedimentation velocity distribution characterized by the mean value and the variance can be determined.…”

Section: Feed-backward Control Based On Dosed Water Qualitymentioning

confidence: 99%

State of the Art of Online Monitoring and Control of the Coagulation Process

Ratnaweera

Fettig

2015

Water

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Abstract:Coagulation is an essential process for the removal of suspended and colloidal material from water and wastewater. However, no comprehensive or universally accepted mathematical description of the process has been developed so far. Therefore, process optimization and control is usually based on data from jar tests and simple flow-proportional dosing concepts, while more accurate concepts based on water quality parameters that can be measured online are emerging. In addition, there have been attempts to develop software sensors and control schemes that involve advanced mathematical analyses of these parameters. The paper presents an overview of the parameters and physical sensors that are used for feed-forward and feed-backward control schemes and the experiences that have been made with their implementation. Moreover, the development and use of software sensors is described. Finally, the practical applications of different control techniques are given in order to illustrate the state of the art of coagulation control. Some thoughts about research needs conclude this review.

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“…In this model, Van der Waals interactions are responsible for the attractive energy between particles; V A $V A is inversely proportional to separation distance between particles and is, therefore, effective at small separation distances [Eq. (1)] (van Oss et al, 1990).…”

Section: Derjaguin-landau-verwey-overbeek Theory and Modelmentioning

confidence: 99%

Influence of Polymeric Aluminum Oxyhydroxide Precipitate-Aggregation on Flocculation Performance

Swetland

Weber‐Shirk

Lion

2013

Environmental Engineering Science

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Polyaluminum chloride (PACl) is a commonly used coagulant for water treatment. One mode of action of PACl [(AlO 4 Al 12 (OH) 24 (H 2 O) 12 ) 7þ ] is reported to be through the formation of polymeric Al-oxyhydroxide precipitate aggregates that bridge between colloids. Although many studies have considered the effectiveness of PACl under a spectrum of conditions for influent suspensions, little is known about the effect of precipitate aggregate size on the subsequent formation of flocs that can be readily removed by sedimentation. Self-aggregation of polymeric Al-oxyhydroxide precipitate and the rate at which this occurs may be used to guide the designs used for the mixing of coagulant with the raw water. In this research, a novel kinetic aggregation model was developed and validated to give the precipitate aggregate size before mixing with a colloidal suspension and entering a flocculator. Granular PACl, a form commonly marketed and used in the developing world, was used for experiments. Efficacy of polymeric Al-oxyhydroxide precipitates of varying aggregate size in flocculation and sedimentation of a kaolin suspension was experimentally observed. These data, in combination with modeling results and geometric analysis, show that under the experimental conditions tested in this research, polymeric Al-oxyhydroxide self-aggregation consistently lowers attachment efficiency of the colloidal suspension, reduces the effectiveness of the flocculator, and reduces turbidity removal. Generally, minimization of aggregate size and maximum turbidity removal is best accomplished by immediate, rapid, and efficient mixing of PACl with the influent water. The relationship between residual turbidity and PACl dose is consistent with results from a geometric adhesive model of coagulation in which surface coverage of colloids by polymeric Al-oxyhydroxide aggregates governs the effectiveness of collisions.

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Method for quantitative analysis of flocculation performance

Cited by 16 publications

References 10 publications

Characterization of Flocs and Floc Size Distributions Using Image Analysis

Characterization of Flocs and Floc Size Distributions Using Image Analysis

State of the Art of Online Monitoring and Control of the Coagulation Process

Influence of Polymeric Aluminum Oxyhydroxide Precipitate-Aggregation on Flocculation Performance

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