• Journal of Korean Society of Water and Wastewater
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• 제22권2호
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• pp.267-274
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• 2008

This study is about efficiency of pretreatment process and operating factor to membrane process at continuous coagulation/ultrafiltration process in water treatment. The capacity of pilot plant was $0.06{\beta}(C)/d$. The raw water used was from Nakdong stream which was characteristized by high organic matter and high turbidity. The result of the test was that coagulation is good process as to high removal rate to organic matter and turbidity but It caused problem to membrane pore blocking. This paper is to determine the membrane fouling potential under different membrane flux, backwash pressure and linear velocity. Backwash pressure and flux is important parameter on operation of membrane system. Those are directly affected on membrane system. When backwash pressure increased from 150 kPa to 200 kPa, the result showed that fouling (pressure increase rate) changed from 3.69 kPa/h to 0.93 kPa/h and the recovery rate changed from 90.7 % to 82.0 %. Linear velocity had slightly effect on fouling. Linear velocity increased from 0.2 m/s to 0.5 m/s, the corresponding pressure rate changed from 0.93 kPa/d to 0.77 kPa/d.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2001년도 학술발표회 논문집(I)
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• pp.52-59
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• 2001

Methods to measure and estimate transpiration of a forest composed of evergreen broad-leaved trees (Pasania edulis Makino) are studied. Heat pulse velocity has been measured along with soil moisture and micrometeorological factors at the Fukuoka Experimental Forest, the Research Institute of Kyushu University Forests in Fukuoka, Japan (33$^{\circ}$38'N, 130$^{\circ}$31'E, alt. 75m). Tree cutting measurement was conducted to convert the heat pulse velocity into sap flow and transpiration. A big leaf model to calculate transpiration and Interception loss is examined and the estimated values are compared with the measured values obtained from the heat pulse measurement. The results show that 1) Pasania edulis Makino posessing radial pore structure had relatively high water content and high heat pulse velocity even within the central part of the stem near the pith, 2) the heat pulse velocity was well correspond to the water uptake in the tree cutting measurement, 3) the estimation of sap flow based on the heat pulse velocity is accurate, and 4) the big leaf model using the parameters obtained from measurement of a portable photosynthesis system in one day in summer gives reasonable estimation of transpiration independent of seasons and weather.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.700-703
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• 2000

With respect to durability, the impotance of carbonation lies in the fact that it reduces the pH on the pore water in hardened concrete. However, the carbonation velocity is effected by the water/cement ratio, materials, unit cement weight, porosity, kinds of finishing materials, accuracy of constructing, environmental factors and so on. And the air permeability is closely related to the carbonation velocity because it represents the properties of concrete. This paper presents an experimental investigation on the carbonation effected by air permeability n mortar and concrete. As a result, it was found that the carbonation velocity of concrete is faster than that of mortar and it is possible to predict the carbonation velocity using air permeability.

• Journal of Korea Soil Environment Society
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• 제1권2호
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• pp.73-81
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• 1996

The self-diffusion coefficients of chloride and tritiated water ranged from 4.8 $\times$ 10-7 to 7.2 $\times$ 10-7 cm2/sec and 5.5 $\times$ 10-5 to 1.6 $\times$ 10-4 cm2/sec for three different depths of soil constituents at about 50% water content by volume, respectively Mobility of solute and water was conducted under steady-state flow conditions in a field soil consisting of 70 cm of clay to silty clay over a medium sand. A steady-state water flow conditions was maintained by applying irrigation water at a constant flux of 2cm per day. The water labeled with chloride and tritium was leached into the plot during the steady-state condition for 87 days. The positions of tritium and chloride as a function of soil depth and the time was measured by extracting samples of the soil solution with suction probes. Extremes in solute displacement occurred at equal and different depths within the plot. An analysis of these measurements indicated the observations of the pore-water velocity and the apparent diffusion coefficient were log normally disturbed. Twenty-four soil suction probes, used to identify the rate at which a solute was displaced in the soil, will yield an estimate of the mean pore-water velocity of this soils within a range of approximately 5% of its true value providing the effects of potential solute-soil interaction are taken into account.

• Magazine of the Korean Society of Agricultural Engineers
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• 제42권2호
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• pp.71-77
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• 2000

A multi-region model for solute transport through saturated soils has been developed to describe preferential flow. The model consists of numerous discrete pore groups, which are characterized by a discrete dispersion coefficient, flow velocity, and porosity . The hydraulic properties for each pore group are derived from a soil's hydraluic conductivity and soil water characteristic functions . Flow in pore group is described by the classical advection-disersion equation (ADE). An implict finite difference scheme was applied to the governing equation that results in a block-tridiagonal system of equations that is very efficient and allows the soil to be divided into any number of pore groups. The numerical technique is derived from methods used to solve coupled equations in fluid dynamics problems and can also be applied to the transport of interacting solutes. The results of the model are compared to the experimental data from published papers. This paper contributes on the characteristics of the method when applied to the parallel porosity model to describe preferential flow of solutes in soil.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2004년도 학술발표회
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• pp.90-101
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• 2004

The present trend of disposing treated sewage water by allowing it to infiltrate the soil brings a new dimension to environmental problems. It is therefore necessary to identify the chemicals likely to be present in treated sewage water. A soil column experiment was conducted to determine the behavior of chemical species in soil columns applied with secondary treated sewage water. To predict the behavior of chemical species, a multicomponent solute transport model that includes the biochemical redox process and cation exchange process was developed. The model computes changes in concentration over time caused by the processes of advection, dispersion, biochemical reactions and cation exchange reactions. The solute transport model was able to predict the behavior of the different chemical species. The model reproduced the sequential reduction reaction. To design the safe depth of plow layer where $NO_3^-$ is totally reduced, a numerical study of $NO_3^-$ leach was done and it was found out that the pore velocity and concentration of $CH_2O$ at the inject water was found to affect $NO_3^-$ reduction in the mobile pore water phase. It is revealed that the multicomponent solute transport model is useful to design the land treatment system for $NO_3^-$ removal from wastewater.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제6권3호
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• pp.43-51
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• 1986

Triaxial compression tests were performed with control of vertical stress, confined pressure(${\sigma}_H$), and injection velocity by means of impervious soil samples with a different grain size, density and grout density. By measuring pore water pressure at the time of vertical fracturing around the bore-hole, relationships between main factors are described, and the factors are pore water pressure, confined pressure, vertical fracturing injection pressure(${\sigma}$) and the tension strength(${\sigma}_t$). The hydraulic fracturing of soft clay was occurred at the pressure which was less than the pressure obtained by the theory of elasticity. It was found that the above result was the influence of pore water pressure due to injection pressure($U_a$) and pore water pressure due to confined pressure($U_i$). Therefore, the vertical injection pressure at the time of fracturing needs to be changed as follows. $${\sigma}=2{\cdot}{{\sigma}_H}-(U_a+U_i)+{\sigma}_t$$.

• Geomechanics and Engineering
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• 제10권4호
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• pp.387-403
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• 2016

In this paper, an integrated model for the wave (current)-induced seabed response is presented. The present model consists of two parts: hydrodynamic model for wave-current interactions and poro-elastic seabed model for pore accumulations. In the wave-current model, based on the fifth-order wave theory, ocean waves were generated by adding a source function into the mass conservation equation. Then, currents were simulated through imposing a steady inlet velocity on one domain and pressure outlet on the other side. In addition, both of the Reynolds-Averaged Navier-Stokers (RANS) Equations and $k-{\varepsilon}$ turbulence model would be applied in the fluid field. Once the wave pressures on the seabed calculated through the wave-current interaction model, it would be applied to be boundary conditions on the seabed model. In the seabed model, the poro-elastic theory would be imposed to simulate the seabed soil response. After comparing with the experimental data, the effect of currents on the seabed response would be examined by emphasize on the residual mechanisms of the pore pressure inside the soil. The build-up of the pore water pressure and the resulted liquefaction phenomenon will be fully investigated. A parametric study will also be conducted to examine the effects of waves and currents as well as soil properties on the pore pressure accumulation.

• Journal of Korean Society on Water Environment
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• 제18권2호
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• pp.221-228
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• 2002

Abundant growth of algae in raw water sources caused by eutrophication brings about significant side effects on water supply, such as taste and order problem, oxygen depletion, toxic material secretion, and filter clogging problem in water treatment process, etc. The purpose of this research is to remove the algae and phosphorus compounds in the Pal-dang reservoir promptly by using the upflow filtration system with coagulant addition. The filter tower consisted of sand media and sieve filter with air back-washing process. By using coagulation and filtration with $132{\mu}m$ pore size filter, about 55% and 70% of algae and phosphorus compounds were removed respectively. The experimental conditions were as follows; head loss of 0.2m, linear velocity of 200m/day, and filtration flux of 1000($L/m^2/day$). In the case of filtration with cartridge type filter of $25{\mu}m$ pore size, the filtration flux was about 7800 LMH, and the removal ratios of COD, SS, T-P, and Chlo-a. were 61%, 99%, 54%, and 98%, respectively. However, high pressure air back-washing process with should be required for the maintenance of such high filtration flux.

• Journal of the Earthquake Engineering Society of Korea
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• 제11권2호
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• pp.81-94
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• 2007

In most experimental researches on the liquefaction phenomenon, an earthquake as a random vibration has been regraded as a sinusoidal wave or a triangular wave with an equivalent amplitude. Together with the development in the part of signal control and data acquisition, dynamic experimental equipments in the soil dynamics have also developed rapidly and further more, several real earthquakes have been simulated in the large model test such as shaking table tests and centrifuge tests. In Korea, several elementary laboratory tests to simulate the real earthquake load were performed. From these test results, it was reported that the sinusoidal wave cannot reliably reflect the soil dynamic behavior under the real earthquake motion. In this study, 4 types of dynamic motions such as the sinusoidal wave, the triangular wave, the incremental triangular wave and several real earthquake motions which were classified with shock-type and vibration-type were loaded to find something new to explain the change of the excess pore water pressure under the real earthquake load. Through the detailed investigation and comparison on all test results, it is found that the dynamic flow is generated by the soil plastic deformation and the velocity head of dynamic flow is changed the pressure head in the un-drained condition. It can be concluded that the change of the excess pore water pressure is related to the pressure head of dynamic flow. Lastly, a new hypothesis to explain such a liquefaction initiation phenomenon under the real earthquake load is also proposed and verified.