• Journal of Korean Society of Environmental Engineers
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• v.31 no.12
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• pp.1135-1142
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• 2009

This study was carried out to investigate of aerobic granulation by using aerobic granular reactor. To make aerobic granular sludge in short period of time, we used polymer. In reactor, we have studied on physicochemical characteristics of particle size, density, and microbial secreting polymer depending on aerobic particle's formation. The results of running aerobic granular reactor with 3, 6, 9 $kg{\cdot}COD/m^3{\cdot}d$ of COD loading rate and 35 days reaction time showed that particle size were 3.6 mm, 4.3 mm, and 3.4 mm respectively. The settling velocities were 1.5 cm/s, 1.6 cm/s, and 1.2 cm/s respectively. The microbic growth rates were 0.12 $d^{-1}$, 0.135 $d^{-1}$, and 0.133 $d^{-1}$ respectively. The overall result of aerobic granular reactor showed that $6kg{\cdot}COD/m^3{\cdot}d$ of COD loading rate had optimal physicochemical characteristics.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.727-733
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• 2009

Effects of $Ca(OH)_2$ concentration(0.16~0.64 wt%), total volumetric flow rate(3~6 L/min) and $CO_2$ volume fraction(0.3~0.6) on morphology of the precipitated $CaCO_3$ and the mean particle size of the precipitated $CaCO_3$ were investigated in the slurry bubble column reactor. Experiments were carried out in acrylic reactor($0.11m-ID{\times}1.0m-high$) with a internal tube($0.04m-ID{\times}1.0m-high$). The calibration curve on the mass ratio of $CaCO_3$ to $Ca(OH)_2$ was obtained by FT-IR for the conversion of $Ca(OH)_2$ with the reaction time. The reaction rate of $Ca(OH)_2$ increased with increasing the volumetric flow rate of $CO_2$. From SEM images, the crystal size of $CaCO_3$ increased with increasing the reaction rate in the saturated concentration of $Ca(OH)_2$ (0.16 wt%). In addition, the crystal size of precipitated $CaCO_3$ decreased with increasing the concentration of $Ca(OH)_2$, but the mean particle size of precipitated $CaCO_3$ increased with increasing the concentration of $Ca(OH)_2$.

• Journal of Korea Water Resources Association
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• v.49 no.10
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• pp.887-901
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• 2016

Cohesive sediments form flocs through the flocculation process. The size and density of floc are variable whereas those of a fine sediment are always assumed to be constant. The settling velocity, one of main factors of sediment transport, is determined by size and density of particle. Therefore, the flocculation process plays an important role in transport of cohesive sediment. It is of great difficulty to directly measure the density of floc in the field due to technical limitation at present. It is a popular approach to estimate the density of floc by applying the fractal theory. The main assumption of fractal theory is the self-similarity. This study aims to examine the applicability of fractal theory to cohesive sediment in small rivers of Korea. Sampling sediment has been conducted in two different basins of Geum river and Yeongsan river. The results of settling experiments using commercial camera show that the sediment in Geum river basin follows the main concept of fractal theory whereas the sediment in Yeongsan river basin does not have a clear relationship between floc size and fractal dimension. It is known from this finding that the fractal theory is not easily applicable under the condition that the cohesive sediment includes the high content of organic matter.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.830-836
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• 1997

The surface modification of iron oxide particle produced from steel-pickled acid by sodium-contained materials was studied. The molar ratio of $SiO_2$ to $Na_2O$ of sodium silicate was 1, 2, 3.5, respectively. The dispersion stability of iron oxide suspension as functions of amount of silica and pH was evaluated by surface charge and sedimentation velocity of iron oxide particle. Then the amount of sodium silicate was determined to provide a dispersion stability of iron oxide particle above pH 7. Finally, the surface modification of iron oxide particle with sodium silicate as silica-contained materials was done by wet ball milling. In the results of study, the dispersion stability of silica modified iron oxide particle was largely depended on amount of silica and pH together. The untreated iron oxide was unstable at pH 8, i.e. isoelectric point, but, the surface modified iron oxide particle with 0.8wt% silica was stable above pH 5. The dispersion stability was enhanced with 0.2wt% of anionic polyelectrolyte.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1C
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• pp.7-15
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• 2010

In case that the seepage of contaminants into the subsurface has been generated from the waste impoundment by demage of geomembrane liner, it is necessary to repair the leaks of geomembrane liner for minimizing the environmental contamination by electrophoresis method. However, when electrophoresis method is applied to leachate electrolyte system, the phenomenon of clay particles flocculation would be accelerated by the interaction between clay particles and specific chemicals in leachate. In addition, the gravitational settling behaviour would be induced superior to the electrophoretic migration behaviour. Eventually, the limitations of field applicability for using the electrophoresis method are appeared. Therefore, 1-D enhanced electrophoresis method is conducted to prevent the clay flocculation and accelerate the migration of clay particles separately. After the 1-D enhanced electrophoresis experiment, we can get the results that the deflocculation effect of clay particles is increased by electrical repulsion of polymer, which adsorbed in clay particle edge, in case of using PAA dispersing agent.

• Resources Recycling
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• v.19 no.3
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• pp.62-70
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• 2010

As the demand for paper continues to grow and the importance of recycled paper, white ledgar(WL) and old newspaper pulp(ONP), continuously increase. In addition, usage of recycled paper is essential in terms of forest conservation and environmental protection issues. However, optical and mechanical properties of recycled paper have some drawbacks than regular paper's properties that is indispensable. In order to complement these problems of recycled paper, precipitated calcium carbonate (PCC) was synthesized by the In-situ process with a recycled pulp. Depending on the size of PCC is divided into 2 types, $0.01{\mu}m{\sim}0.09{\mu}m$ colloid type ultra-fine particle and $0.1{\mu}m{\sim}0.9{\mu}m$ cubic type particles. In this study, we analyze how the different shape and size of precipitated calcium carbonate affects in the optical and mechanical properties of the recycled paper used as a filler. Furthermore, we mixed with chemical pulp for overcome reduce of mechanical properties, without using other chemicals, when we use PCC as a filler. The results has the possibility to meet in GR excellent recycling certification mark, standard was proposed.

• Ocean and Polar Research
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• v.24 no.2
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• pp.123-134
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• 2002

Seasonal variations of settling particles and metal fluxes were monitored at a nearshore site of Marian Cove, King Geroge Island, Antarctica from 28th February 1998 to 22nd January 2000. Near-bottom sediment traps were deployed at 30m water depth of the cove, and sampling bottles were recovered every month by SCUBA divers. Total particulate flux and metal concentrations were determined from the samples. Total particulate flux showed a distinct seasonality, high in austral summer and low in austral winter: the highest flux $(21.97g\;m^{-2}d^{-1})$ was found in February of 1999, and the lowest $(2.47g\;m^{-2}d^{-1})$ in September of 1998, when sea surface was frozen completely. Lithogenic particle flux accounted for 90% of the total flux, and showed a significantly negative correlation with the thickness of snow accumulation around the study site. It was suggested that the most of the lithogenic particles trapped in the bottles was transported by melt water stream from the surrounding land. Fluxes of Al, Fe, Ti, Mn, Zn, Cii, Co, Ni, Cr, Cd, and Pb showed similar seasonal variations with the total flux, and their averaged fluxes were 34000, 9000,960, 180, 13.8, 17.6, 3.0,2.1, 5.4, 0.02, and $1.5nmol\;m^{-2}d^{-1}$ respectively. Among the metals, Cu and Cd showed the most noticeable seasonal patterns. The Cd flux correlated positively with the fluxes of biogenic components while the Cu flux correlated with both the lithogenic and biogenic particle fluxes. The Cu flux peak in the late summer is likely related to a substantial amount of inflow of ice melt water laden with Cu-enriched lithogenic particles. On the other hands, the Cd flux peak in the early spring may be associated with the unusually early occurred phytoplankton bloom.

• Journal of Korea Water Resources Association
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• v.33 no.4
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• pp.461-469
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• 2000

An numerical analysis of sediment-laden flow is carried out, and results are compared with the experiments of Coleman(1981, 1986) that included the several cases varying sediment size and quantity in open channel flow. K-$\omega$ turbulence model is selected for the fully turbulent flow field, and the concentration equation considering the fall velocity is adopted for the concentration field. The model of Einstein and Chien(1955) is applied to couple the velocity field and the concentration field. Most of researches have been carried out without considering the bed-load thickness, but it is found that the bed-load thickness cannot be ignored in case of a large amount of sediment or a large size of it. The bed-load thickness and surface roughness are considered in this study. Here, $\beta$ value, which is defined by the reciprocal of turbulent Schmidt number and is related with the concentration profile, is found to be varied according to the sediment size and quantity. Even though most of researchers have insisted that $\beta$ had always larger than 1.0, it may be concluded that $\beta$ can have smaller value than 1.0, that is coincident with the report of recent research.

• Journal of the Korean Ceramic Society
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• v.41 no.7
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• pp.528-533
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• 2004

Macroporous SiC with pore size 84∼658 nm and mesoporous SiC with pore size 15∼65 nm were respectively prepared by infiltrating low viscosity preceramic polymer solutions into the various sacrificial templates obtained by natural sedimentation or centrifuge of 20∼700 nm silica sol, which were subsequently etched off with HF after pyrolysis at 1000∼140$0^{\circ}C$ in an argon atmosphere. Three-dimensionally long range ordered macroporous SiC ceramics derived from polymethylsilane (PMS) showed surface area 584.64$m^2$g$^{-1}$ when prepared with 112nm silica sol and at 140$0^{\circ}C$, whereas mesoporous SiC from polycarbosilane (PCS) exhibited the highest surface area 619.4 $m^2$g$^{-1}$ with random pore array when prepared with 20-30 nm silica sol and at 100$0^{\circ}C$. Finally, tile pore characteristics of porous SiC on the types of silica sol, polymers and pyrolytic conditions were interpreted with the analytical results of SEM, TEM, and BET instruments.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.2
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• pp.160-165
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• 1997

Three types of virus disease symptoms were observed in azuki bean plants: yellow mosaic; mosaic; severe mosaic with dwarf. The symptoms developed in the indicator plant inoculated with a virus- infected leaf of azuki bean showed similar host range with those of AMV, CMV and AzMV. In antiserum response, yellow mosaic symptom formed sediments with AMV antiserum, mosaic type with CMV antiserum, respectively, From the electron microscope observation, eclliptic particle (18~58$\times$18nm), isometric particle (30nm), and filamentous(730$\times$12nm) combined with inclusion body were observed in yellow mosaic, mosaic, and severe mosaic with leaf curling symptoms, respectively, The results demonstrate that yellow mosaic, mosaic, and severe mosaic with dwarf are caused by AMV, CMV and AzMV.