• Journal of Korean Society of Water and Wastewater
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• v.24 no.1
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• pp.103-108
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• 2010

Until now, research reports that it is difficult for brokenup floc after coagulation to reaggregate and settling efficiency of reaggregated floc is relatively low have dominated in water treatment process. In contrast, from recent study conducted by the French researcher, because the density of the reaggregated floc was higher than the previous floc, the settling efficiency of reaggregated floc increased. In this study, 15 times wet test were carried out and the removal efficiency of reagrregated floc was considerably increased. Moreover, this result was explained using the turbulent model for the flow occurred around the floc. Consequently, in the case of suitable hydrodynamic condition for the reaggregation, the characteristics of the reaggregated floc was changed into the favorable condition for improvement of settling efficiency. Also, the most important factor for reaggregation of floc was governed by hydrodynamic shear stress.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.33 no.3
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• pp.9-17
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• 2001

The floc characteristics of base paper stock for coating by the retention aid system consisting of polyacrylamide (high molecular weight low charge density, HMLC) and PEI without and with anionic inorganic oxide (IO) were investigated under various shear conditions of MDDA (modified dynamic drainage analyzer). The floc size was increased with cationic electrolytes dosage whatever inorganic oxide is applied or not. The effect of inorganic oxide on the floc size showed the different result between PAM and PEI. The smaller floc was obtained by PAM without inorganic oxide, but larger floc was obtained by PAM with inorganic oxide. However, the effect of shear force was not observed. Floc formation index was decreased by the addition of cationic electrolytes with or without inorganic oxide. Floc formation index had better correlation format formation index than floc size. The relationships between wet web permeability and mat air permeability showed the significant linear correlation ($R^2$=0.97~0.98) for HML PAM and PEI. Floc formation index gave more useful information than the retention measurement when the performance of retention aids is evaluated at the laboratory before applying at the paper mill.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.485-493
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• 2010

Chemical coagulation destabilizes colloidal particles so that particles grow to larger flocs. Solid particles are then removed by solid-liquid separation after typical precipitation. Rapid precipitation enhances the separation by reducing the precipitation time with larger and denser particles. Conventionally, polyelectolyte compounds (polymers) function as a flocculant aid by introducing a interparticle binding, which increases the particle size and density. And more recent ballasted flocculation adds a ballasting agent (microsand) to form denser particles with its high-density(sp gr=2.65). The current research was to evaluate the manner in which ballasted flocs are formed under different injection timings of microsand and to recognize the effects on floc formation. $FeCl_3$ as a coagulant, anionic polymer for a flocculation aid and microsand were used for the floc formation. Floc size (diameter) was widely ranged with the highest mean value when microsand was injected between $FeCl_3$ and polymer. Mean floc density was larger when the floc formed smaller. Settling velocity increased with larger floc size, whilst not significantly affected by the timing of microsand injection. The additional slow mixing on floc formation increased floc size to some extent.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.107-113
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• 2009

This paper considers the influence of floc on the sedimentation rate for the cohesive material. The effects of floc density and size changes were also taking into consideration during the experiment. The settling velocity of a discrete floc was measured in a quiescent water column. Floc diameter and density were investigated using a modified Stokes equation with some constants such as water density, viscosity, material density and the floc fractal dimension $n_f$ obtained from the relationship between the floc diameter and the floc settling. The floc diameter of quartz and alumina increased at increasing initial concentrations. The floc size of quartz with increasing NaCl concentration varied between approximately 0.8 um to $10{\mu}m$. Floc density decreased as floc size increased. The floc settling velocity and the floc diameter have a straight line relationship on a logarithm. The floc fractal dimension nf was 2.65 with increasing of initial concentration and 2.93 with increasing of NaCl. The exponent n to predict the settling velocity was proposed and varied from 1 to 1.93.

• Journal of Industrial Technology
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• v.33 no.A
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• pp.89-92
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• 2013

The characteristics of floc formation of the iron(Fe) ions was studied for developing the process treating the acid mine drainage. The metal ions in aqueous solution oxidized with oxygen in air, which generated hydrogen ion and lowered the pH of the aqueous solution. The iron(Fe) ions were formed into flocs by the acid-base reaction with the added $Ca(OH)_2$ for the neutralizing the solution. There were several variables affecting the formation, size and color of floc; whether air was present or not, air feeding rate, oxidizing time, concentration of $Ca(OH)_2$, the acid-base reaction time of the $iron(Fe)-Ca(OH)_2$. For proper formation of the $iron(Fe)-Ca(OH)_2$ flocs and developing the floc treating system, the control variables mentioned above should be considered.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.2
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• pp.10-16
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• 2004

Structures and strengths of paper have been studied by analyzing fibers characteristics depending on refining methods. Mixing ratio of softwood and hardwood fibers and fibers characteristics have been analyzed for paper quality improvement. In this study flocculation and drainage of fibers were analyzed to improve the production efficiency and paper product's quality. Floc size and drainage rate depending on stock consistency and fines content were analyzed. Total amount of drainage during drainage process was measured quantitatively by using DI(drainage index). Floc size, viscosity of floc and dewatering times were also measured. In the case of refining load $2.8 kg_f$ , drainage was occurred by filtration mechanism rather than thickening mechanism because drainage resistance increased by fibrillation of fibers. Therefore, the drainage rate of $2.8 kg_f$ refining load stock was slower than that of $5.6 kg_f$.

• Environmental Engineering Research
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• v.17 no.3
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• pp.139-144
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• 2012

In this study, the effects of starvation on floc characteristics when treating saline wastewater using a sequencing batch reactor (SBR) were investigated. The effectiveness over 5 days of starvation for aerobic and non-aerobic strategies for maintaining the physical characteristics of floc-forming sludge and the recovery period needed to regain the initial pollutant removal efficiency were investigated. Experiment results revealed that the sludge volume index (SVI) increased and the floc size and fractal dimension decreased after starvation under both aerobic and non-aerobic conditions. Sludge settleability deteriorated faster under aerobic conditions compared to non-aerobic conditions. Under non-aerobic conditions, the SBR required less time to return to its initial pollutant removal efficiency and settleability. Floc size, fractal dimension, and SVI were observed to be fairly correlated with each other. The results demonstrated that it was better to maintain the sludge under non-aerobic rather than aerobic starvation, because it adapted to, resisted starvation and had a quicker re-start afterward.

• Journal of Wetlands Research
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• v.20 no.3
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• pp.227-234
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• 2018

This paper was examined the physical characteristics of floc density of suspended fine particles with varying cohesiveness. The analysis of floc density was performed in a small annular flume with a free water surface under different bed shear stresses and ion addition. Fine-grained silica was used as model material, as it is the main mineral components of clay that affects sedimentation. It was concluded that floc density depended on increasing the bed shear stress, the salinity and pH value. Floc density decreased with increasing the salinity in still water and floc size, whereas the opposite was true when increasing the bed shear stress. Also, it increased at pH6.8 more than at pH4.2 when increasing the bed shear stress in the range from 0.0086 to $0.0132N/m^2$.

• Journal of Korea Water Resources Association
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• v.32 no.2
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• pp.177-184
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• 1999

In this paper, the characteristics of the flow and the movement of the floc were analyzed through the experiments in the sedimentation basin using the redioisotope. Tc-99m radioisotope was used for the experiments for the characteristics of the flow, and the bentonite absorbing Tc-99m radioisotope was used in the experiments for the movement of the floc. Through the experiments of the flow, it was found that the velocities of flow in the sedimentation basin were different depending upon the position and the depth. The distance of the moving trajectories of the floc is increased by increasing the discharge. By increasing the discharge, the settling point is farther from the inlet, and the turbidity removal efficiencies in the sedimentation basin are decreased. The moving velocities of the floc and the density are changed in the different depths in the sedimentation basin.

• Journal of Korean Society on Water Environment
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• v.16 no.4
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• pp.459-468
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• 2000

This study is to investigate the floc structure and removal of turbidity and organic matter by PACI coagulation. The turbidity removal by PACI coagulation was obtained at larger pH range than alum coagulation. And the removal of organic matter was obtained at smaller pH range than that of turbidity. The organic matter was removed by the adsorption of $Al(OH)_3$ precipitates. Floc structure was characterized by measuring fractal dimension and volume diameter using AIA and SALLS. Fractal dimension measured by AIA did not show the different characteristics of floc produced in sweep floe and charge neutralization region. Using SALLS, floes in sweep floc region were found to be larger size and fractal dimension than flocs in charge neutralization region. As pollutant removal increased. larger fractal dimension and size of floc were measured. SALLS method was found to be more useful method to characterize flocs in coagulation than AIA method.