• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.131-140
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• 2008

The application of magnetic ion exchange resin($MIEX^{(R)}$) is effective for natural organic matter(NOM) removal and for control of the formation of disinfection byproducts(DBPs). NOM removal is also enhanced by adding $MIEX^{(R)}$ with coagulant such as polyaluminium chloride(PACl) in conventional drinking water treatment systems. In the application of $MIEX^{(R)}$, it is important to understand changes of NOM characteristics such as hydrophobicity and molecular weight distributions with $MIEX^{(R)}$ or $MIEX^{(R)}$+coagulant treatment.To observe characteristics of NOM by treatment with $MIEX^{(R)}$ or $MIEX^{(R)}$+coagulant, four major drinking water sources were employed. Results showed that the addition of $MIEX^{(R)}$ to coagulation significantly reduced the amount of coagulant required for the optimum removal of dissolved organic matter(DOC) and turbidity in the all four waters. The DOC removal was also increased approximately 20%, compared to coagulant treatment alone. The process with $MIEX^{(R)}$ and coagulant showed that complementary removal of hydrophobic and hydrophilic fraction of DOC. The combined processes preferentially removed the fractions of intermediate (3,000-10,000 Da) and low (< 500 Da) molecular weight. The microfiltration test showed that membrane cake resistance was decreased for waters with flocs from $MIEX^{(R)}$+coagulant. A porous layer was formed to $MIEX^{(R)}$ on the membrane surface and the layer consequently inhibited settling of coagulant flocs, which could act on a foulant.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.3
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• pp.359-366
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• 2007

Slow sand filtrations have been widely used for water treatment in small communities, however their capacity is often limited by high turbidity in the raw water. For this reason, several pre-treatment facilities were required for a slow sand filter. Turbidity removal from the highly turbid raw water was investigated in roughing filters as a pre-treatment process. The roughing filters followed by rapid mixing tank were operated in the form of a contact filtration. In several jar tests, the predetermined optimum aluminium sulfate (alum) doses for turbid water of 30 and 120NTU were 30 and 50mg/L, respectively. At the optimum alum dose, physically optimum parameters including G value of $220sec^{-1}$ and rapid mixing time of 3 minutes were applied to the contact filtration system. Without addition of alum, the filtrate turbidity from the roughing filters, packed respectively with different media such as sand, porous diatomite ball and gravel, was in the range of 5~30NTU at filtration velocities of 30 and 50m/day. However, the application of a contact filtration to roughing filters showed stably lower filtrate turbidity below 1.0NTU at filtration velocity of 30 m/day. Although the filtration velocity increased to 50m/day, filtrate turbidity was still below 1.0NTU in both single and double layer roughing filters. At influent turbidity of 120NTU, the filtrate turbidity was over 5 NTU in the triple layer roughing filter, which shortened the filter run time. The flocs larger than $10{\mu}m$, formed in the rapid mixing tank, were almost captured through the roughing filter bed, while the almost flocs smaller than $10{\mu}m$ remained in filtrate.

• Membrane Journal
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• v.17 no.3
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• pp.191-196
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• 2007

In the study, excess of lime-soda ash(L-S) was added to groundwater for chemical precipitation of hardness ions. After formation of the coagulated flocs, sedimentation step was replaced with crossflow ultrafiltration(UF) process using tubular ceramic membrane. As results, our treated water was below total hardness(TH) 10 mg/L as $CaCO_3$ from groundwater using washing water in a soymilk factory. Then, we investigated the change of permeat flux(J) and dimensionless permeate flux($J/J_0$) during experiments for variations of TMP(Trans-membrane pressure) or flow rate, to see effect of TMP or flow rate on membrane fouling by the coagulated Inorganic flocs. In the result, membrane fouling and rejection rate of total hardness were not affected by TMP and flow rate variations in the range of our experiments.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.3
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• pp.267-276
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• 2010

Many plants have been improved to adapt the target of the biological treatment processes changed from organics to nutrients since the water quality criteria of effluent was reinforced and included T-N and T-P for the municipal wastewater treatment plant. To meet the criteria of T-N and T-P, the conventional biological reactor such as aeration tank in activated sludge system is changed to the BNR (biological nutrient removal) processes, which are typically divided into three units as anaerobic, anoxic and oxic tank. Therefore, the solid separation process should be redesigned to fit the BNR processes in case of the application of the DAF (dissolved air flotation) process as an alternatives because the solid-liquid separation characteristics of microbial flocs produced in the BNR processes are also different from that of activated sludge system as well. The results of this study revealed that the microbial floc of the anaerobic tank was the hardest to be separated among the three steps of the unit tanks for the BNR processes. On the contrary, the oxic tank was best for the removal efficiency of nutrients as well as suspended solid. In addition, the removal efficiency of nutrients was much improved under the chemical coagulation treatment though coagulation was not indispensable with a respect to the solid separation. On the other hand, in spited that the separation time for the microbial floc from the BNR processes were similar to the typical particles like clay flocs, over $2.32{\times}10^3$ ppm of air volume concentration was required to keep back the break-up of the bubble-floc agglomerates.

• Journal of Korea Water Resources Association
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• v.48 no.3
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• pp.233-243
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• 2015

The bimodal flocculation of cohesive sediments in water environments describes the aggregation and breakage process developing a bimodal floc size distribution with dense flocculi and floppy flocs. A two class population balance equation (TCPBE) was tested for simulating the bimodal flocculation by a model-data fitting analysis with two sets of experimental data (low and high turbulent flows) from 1-D flocculation-settling column tests. In contrast to the Single-Class PBE (SCPBE), the TCPBE could simulate interactions between flocculi and flocs and the flocculation mechanism by differential settling in a low turbulent flow. Also, the TCPBE could perform the same quality of simulation as the elaborate Multi-Class PBE (MCPBE), with a small number of floc size classes and differential equations. Thus, the TCPBE was proven to be the simplest model that is capable of simulating the bimodal flocculation of cohesive sediments in water environments and water, wastewater treatment systems.

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.207-215
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• 2006

The characteristic floc growth of Al-based coagulants was investigated in the aspect of mixing intensity and visualization of generated flocs during coagulation and flocculation processes. Zeta potential of turbid particles in the artificial water nearly approached to zero at pH 8-9, in which TDS and conductivity were minimized. The removal rate of turbidity and phosphate was maximized at the optimal mixing intensity of rapid and slow mixing stages. After the rapid mixing stage of coagulation process, small particles ($3-5{\mu}m$) were abruptly generated, and higher mixing intensity made more numbers of flocs. With the progress of slow mixing stage, the number of small particles were decreased with the simultaneous increase of intermediate particles ($7-21{\mu}m$). The number of large particles (>$23{\mu}m$) were maximized at the lowest rapid mixing intensity of $95.1sec^{-1}$, whereas small particles (<$5{\mu}m$) were maximized at the highest rapid mixing intensity of $760.7sec^{-1}$.

• Water for future
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• v.27 no.3
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• pp.115-121
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• 1994

Cohesie sediment movement in estuarine systems is strongly affected by the phenomena of aggregation and flocculation. Aggregation is the process where primary particles are clustered together in tightly-packed formations; flocculation is the process where aggregates and single particles are bonded together to form large particle groups of very low specific density. The size, shape and strength of the flocculants control the rate of deposition and the processes of pollutant exchange between suspended sediments and ambient water. In estuarine waters, suspended sediments above the lutocline form the mobile suspension zone while below the lutocline they form the stationary suspension zone. Suspended particles in the mobile zone are generally in a dispersed state and the controlling forces are the Brownian motion and the turbulent flow fluctuations. In the stationary suspension zone, the driving force is the gravity. This paper discusses the settling and particle flocculation characteristics under quiescient flow conditions. Particles are entering the study domain randomly. Particles in the mobile suspension zone are simulated by using the Smoluchowski's model. Flocs created in the mobil suspension zone are moving into the stationary suspension zone where viscosity and drag effects are important. Utilizing the concepts of the maximum Feret's diameter and the Minkowski's sausage logic, the fractal dimension of the flocs within the stationary suspension is estimated and then compared with results obtained by other studies.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.2
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• pp.135-143
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• 2005

It was evaluated that the effect of turbidity removal by Pore Controllable Fiber Filter(PCF) installed in NS(Naksang) small water treatmant plant(system) using under flow water as raw water in the study. The results of the study are as the followings. Firstly, the removal efficiency of turbidity by PCF without coagulation(in operation mode not using coagulants) was mostly below 20 percent. On the other hand, when operation using proper coagulants, that of turbidity was mostly over 80 percent. Secondly, slow sand filtration after PCF, total turbidity removal efficiency of final treated water was 84.3 percent, and the contribution by PCF was 57.1 percent and that of slow sand filtration was 27.7 percent. Therefore the introduction of PCF as pre-treatment process would be helpful to reduce the loading of high turbidity of slow sand filtration. Thirdly, the results of particle counter measurements showed that when operated PCF with coagulants, fine flocs captured or adsorbed at the pore of PCF were flow out into the effluents from 120 minutes after backwashing because of the increase of headloss of PCF. Therefore the decision of backwashing time should made consideration into the outflow of fine flocs from PCF. Fourth, coagulant dosages on PCF at the same turbidity was largely variable because of the effect of the raw water characteristics and the turbidity increase velocity at rainy days, therefore flexible coagulant dosages should be considered rather than fixed coagulant dosage by the influent jar-test result.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.4
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• pp.277-284
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• 2021

The ballasted flocculation effects of the mill scale and magnetite on activated sludge were investigated. Both ballasted flocculants (BF) could remarkably improve the sludge settleability in terms of zone settling velocity (ZSV) and sludge volume index (SVI). With the BF dosage of 0.2 to 2.0 g-BF/g-SS, the magnetite particles showed better efficiency on improving settling behavior of activated sludge than the mill scale due to higher surface area and hydrophobic property. The efficiency of SVI₃₀ with magnetite injection was 2.5 to 11.3% higher than mill scale injection and that of the ZSV appreciated from 23.7% to 44.4% for magnetite injection. Averaged floc size of the BF sludge with magnetite dosage (0.5 g-BF/g-SS) was 2.3 times higher than that of the control sludge. Dewaterability of the sludge was also greatly improved by addition of the BF. The specific resistance to filtration (SRF) was reduced exponentially with increasing the dosage of BF. However, the BF's particle size effect on the SRF looks to be marginal. Consequently, for improving the dewaterability, the BF played a physical role to remove the pore water of the biological flocs by intrusive attachment and a chemical role to induce aggregation of the flocs by charge neutralization.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.4
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• pp.76-80
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• 2015

In filler loaded paper, the size of the filler affects its strength, optical and surface properties. As the size of the filler increases, tensile strength and bulk usually increases, opacity decreases, and smoothness becomes worse. Pre-flocculation of GCC (grounded calcium carbonate) makes large diameter flocs at aqueous medium that consists of multiple GCC particles, but they collapse to 2-dimensional shape in dried paper and makes low bulk paper. The hybrid calcium carbonate (HCC) that was made by in-situ $CaCO_3$ formation between GCC in aqueous medium made high bulk paper without harming tensile strength, bulk, opacity, and smoothness. The GCC that has equivalent size as HCC failed to make high opacity and smoothness as much as HCC.