• Journal of Environmental Science International
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• v.25 no.2
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• pp.231-238
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• 2016

In this study, we have investigated to find optimal pre-treatment flocculation condition by analyzing the floc growth rate with mixing conditions and the membrane permeation flux for pre-treatment step of the membrane process. The higher mixing intensity showed a constant floc size index (FSI) values, and lower mixing intensity increased the degree of dispersion of the FSI values. Results of comparing the distribution characteristics of the FSI value and the permeation flux were more effective in increasing flux when the FSI values were 0.2 or higher. The degree of dispersion of FSI was relatively large in 40 rpm mixing condition compared to 120 rpm. In 40 rpm mixing condition, it decreased the permeation flux compared to 120 rpm because various sizes of flocs were distributed. Coagulation-UF membrane process enhanced 30%~40% of the flux rate compare to UF alone process, and the coagulation-MF process increased up to 5% of the flux rate compare to MF alone process. Pre-treatment, that is, coagulation process, has been found to be less effects on relatively larger pore size for MF membrane. For UF membrane, the flux was a little bit same when applying only the rapid mixing process or rapid mixing with slow mixing processes together. In case of MF membrane, the flux was improved when rapid mixing process applied with slow mixing process together.

• 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 Environmental Science International
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• v.18 no.3
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• pp.289-298
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• 2009

The blue-green algae which caused odor problem in the tap water are difficult to precipitate in sedimentation basin and clogged the filter void rapidly. The studies of this paper were not only oxidation, coagulation and sedimentation processes for effectively removing blue-green algae but yellow clay and polyamine for verification as coagulants aids. The results of this research are summarized as follows: Higher ozone dose(C) and longer contact time(T) were needed for a high degree of removing blue-green algae efficiency. the removal rate of blue-green algae was proportional to the $C\times T$ value. The removal percent of chlorophyll-a by sedimentation and filter without pre-ozonation was about 75% but 1 mg/L pre-ozonation could increase the removal percent of chlorophyll-a to 99% and more pre-ozonation could remove completely. Though the removal efficiency of turbidity could increased by high dose of chlorination, the dissolved organic carbon was increased. More chlorine dose from 4 to 10 mg/L dissolved organic carbon was decreased. Using yellow clay as coagulant aids increased density of floc so the settling velocity of floc become rising but polyamine could not increase settling velocity of floc though it could formated large floc.

• Journal of Korea Water Resources Association
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• v.53 no.10
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• pp.917-928
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• 2020

The purpose of this study is to find the appropriate probability distribution representing the size distribution of suspended cohesive sediment. Based on goodness-of-fit test for a significance level of 5% using the Kolmogorov-Smirnov test, it is found that the floc size distributions measured in laboratory experiment and field study show different results. In the case of sample data collected from field experiments, the Gamma distribution is the best fitting form. In the case of laboratory experiment results, the sample data shows the positively-skewed distribution and the GEV distribution is the best fitted. The lognormal distribution, which is generally assumed to be a floc size distribution, is not suitable for both field and laboratory results. By using 3-parameter lognormal distribution, it is shown that similar size distribution with floc size distribution can be simulated.

• 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.

• Journal of Environmental Science International
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• v.23 no.4
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• pp.715-722
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• 2014

Effects of coagulation types on flocculation were investigated by using a photometric dispersion analyzer (PDA) as an on-line monitoring technique in this study. Nakdong River water were used and alum and ferric chloride were used as coagulants. The aim of this study is to compare the coagulation characteristics of alum and ferric chloride by a photometric dispersion analyzer (PDA). Floc growing rates ($R_v$) in three different water temperatures ($4^{\circ}C$, $16^{\circ}C$ and $30^{\circ}C$) and coagulants doses (0.15 mM, 0.20 mM and 0.25 mM as Al, Fe) were measured. The floc growing rate ($R_v$) by alum was 1.8~2.8 times higher than that of ferric chloride during rapid mixing period, however, for 0.15 mM~0.25 mM coagulant doses the floc growing rate ($R_v$) by ferric chloride was 1.1~2.3 times higher than that of alum in the slow mixing period at $16^{\circ}C$ water temperature. Reasonable coagulant doses of alum and ferric chloride for turbidity removal were 0.1 mM (as Al) and 0.2 mM (as Fe), respectively, and the removal efficiency of those coagulant doses showed 94% for alum and 97% for ferric chloride. The appropriate coagulant dose of alum and ferric chloride for removing dissolved organic carbon (DOC) showed about 0.3 mM (as Al, Fe) and at this dosage, DOC removal efficiencies were 36% and 44%, and ferric chloride was superior to the alum for removal of the DOC in water.

• Clean Technology
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• v.6 no.1
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• pp.27-38
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• 2000

A physicochemical process called Ultra Rapid Coagulation(URC) can dramatically remove organics, metals, and phosphates in wastewater by adding weighted coagulation additive(WCA) and recycling sludge into the coagulation basin to increase the growth rate and adsorption ability of floc. Also this process can improve floc settling rate than conventional coagulation process and reduce the pollutants loaded into the receiving water for securing water source. It was evaluated that WCA and sludge added have effects on the removal efficiency and estimated the possibilities of reusing the effluent from this process.

• Journal of Forest and Environmental Science
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• v.22 no.1
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• pp.27-31
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• 2006

Sedimentation characteristics such as SS, COD removal efficiency of wastewater in the toilet paper mill using recycled paper were examined by zeta potential. Optimum dosage of coagulant were determined by turbidity, SS, COD and then equation for treatment efficiency was suggested. Mechanical strength of floc was determined by turbidity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.2
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• pp.137-145
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• 1990

In this research, biological uptake of heavy metals(Cd(II), Cu(II), Zn(II)) was measured under various conditions ; pH, initial heavy metal concentration, temperature, contact time and the amount of biomass through batch test. From this research, it was found that heavy metals might be removed through adsorption and accumulation in activated sludge process. Heavy metals were highly concentrated by microbial floc in activated sludge. Also, the removal efficiency was reached up to 80~90% within and after 1 hour the increase of removal efficiency was minimal. The order of accumulation efficiency was Cu(II)>Zn(II)>Cd(II), and the bonding strength between heavy metals and microbial floc may be expressed in order of Cu(II)>Zn(II)>Cd(II).

• Journal of Korean Society of Water and Wastewater
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• v.25 no.2
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• pp.231-240
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• 2011

The objectives of this research are to investigate coagulation efficiencies of two coagulants l.e., alum and polyaluminum chloride and to understand effects of the coagulants on membrane fouling in microfiltration. The turbidity of supernatant from alum coagulation was increased with increasing doses whereas the turbidity from PACl coagulation was maintained at the low values. The observed injection volume of PACl for the same removal was approximately 30 percent less than alum, which produced a low sludge volume. The settling velocity of PACl flocs was greater than alum flocs. The results corresponded well with floc size measurements. Flux decline from alum coagulation was significant due in part to small sizes of flocs. At the low dose, alum floc had less specific cake resistance than PACl floc. However, as the dosage was increased, the increases in specific cake resistances of alum was substantial. Alum coagulation pretreatment needs careful operation to reduce membrane fouling by flocs. In general, PACl coagulants were more effective than alum coagulants for pretreatment of membrane processes because PACl showed the better performance in coagulation and membrane fouling.