• Journal of Environmental Science International
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• v.5 no.1
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• pp.35-41
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• 1996

For studying of coagulation and sedimentation in estuarine clay, we obtained several flow curves with various concentrations of sea water by using Coutte type rotational rheometer. The initial shear stress on high concentration of sea water was observed big, but after this, its value is decreasing with increasing shear rate. The maximum pick of shear stress is decreasing with the decreasing of concentration of sea water The trend is same totally above for viscosity. The sedimentation times with the concentration of sea water vary in $\infty$ ~ 5 minutes. The zeta potential is changed dramatically between 114 and 118 concentration of sea water. That is consistent with the sedimentation graph. From these results, the phenomena of coagulation and sedimentation can be explained with viscoelastic terms on structual formation among particles by the changes of surface potential affected from contacting sea water to dispersed particles.

• Journal of the Korean Ceramic Society
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• v.45 no.2
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• pp.99-104
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• 2008

Zeta potential, sedimentation bulk density and rheology in the dispersion system have been studied in terms of solid loading (40-55 vol%), and types of additives. Ammonium polymethacrylate, glycerol, ethoxylated acetylenic diol, and polyvinyl alcohol have been used as the dispersant, cryo-protectant, surfactant, and binder, respectively. Sedimentation density greatly increased upon adding dispersant; the effect was more pronounced with ionic alumina suspension compared with covalent silicon carbide. With further addition of cryo-protectant and surfactant to dispersant, the sedimentation density increased somewhat. The suspension viscosity generally behaviored in an opposite manner to the sedimentation density, i.e., high sedimentation gave low high-shear viscosity, indicative of low order structure formation in the suspended particles. Shear rate rheology in shear rate of $2-300\;sec^{-1}$ showed a shear thinning and its onset began at similar shear rate (${\sim}100\;sce^{-1}$), regardless of solid loading.

• Journal of the korean society of oceanography
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• v.38 no.4
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• pp.157-165
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• 2003

In order to understand the characteristics of sedimentary environments in Ulleung Basin of the East Sea (Sea of Japan), three sediment cores were taken with a box corer during R/V Tamyang cruise in October 1999. Activities of $^{7}Be,{\;}^{210}Pb,{\;}^{226}Ra,{\;}^{234}Th,{\;}^{238}{\;}and{\;}^{137}Cs$ in sediment samples were determined by non-destructive gamma-ray spectrometry. Rates of sedimentation and particle mixing were estimated by best fitting an advection­diffusion particle mixing model to the data of $^{7}Be,{\;}^{234}Th,{\;}and{\;}^{210}Pb$. Estimated sedimentation rates were 0.06-0.08 cm/yr and particle mixing rates were $0.13-0.65{\;}\textrm{cm}^2/yr$. The use of multiple tracers in our study prevented us from probable up to 38% overestimation of sedimentation rates.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.6
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• pp.713-722
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• 2010

This paper has assessed the flow patterns and settling efficiency in the sedimentation basin using the particle tracking method of the CFD code and has reached the following conclusions: In the original design where no baffle is installed in the sedimentation basin, a large recirculating area where the flow stagnates is created in the right side of the sedimentation basin, with most of the particles moving to the left side of the sedimentation basin following the flow. This biased flow structure in the sedimentation basin reduces the residence time of particles and thereby undermines settling efficiency. The biased flow toward the left side of the sedimentation basin is alleviated by installing a baffle in the sedimentation basin, promptly reducing the fast flow of over 0.7 m/s in the inlet of the sedimentation basin to the rate below 0.2 m/s. In this paper's simulation conditions, if a one-sided baffle is to be installed in the sedimentation basin, placing it 15 meters away from the basin's inlet leads to the best settling efficiency; it has also been analyzed that installing a two-sided baffle-rather than a one-sided one-is a better option in terms of settling efficiency. The highest settling efficiency of 96.2% is achieved when the underwater length of the two-sided baffle is set at 8 meters.

• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.109-114
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• 2012

In this study, both sedimentation and thickening experiments were conducted for residuals produced from an advanced water treatment plant for more accurate and practical design of residual treatment train. In order to design a backwashed residual sedimentation basin (SRSB) in the filter backwash water recycle system, two kinds of backwash waters, one from sand filter (SFBW) and the other from GAC adsorption bed (GACBW), were separately collected and their surface loading rate measured. In addition, in order to design a gravity thickener, batch thickening tests were conducted for concentrated residuals taken from sedimentation basin and their limiting solid flux ($SF_{L}$) measured. From the experimental results and consideration of the seasonal characteristics of the residual, surface loading rate of $70m^{3}/m^{2}{\cdot}d$ was proposed as a design parameter for SRSB and solid loading rate of 20 kg $TS/m^{2}{\cdot}d$ was proposed as a design parameter for gravity thickeners. Finally, the material mass-balance was made for the design of each unit process in the residual treatment train.

• Journal of Environmental Health Sciences
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• v.7 no.1
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• pp.1-7
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• 1981

During 20 days from November 4 to 28, 1980, the quantities of grease and oil, BOD (biological oxygen demand), COD (chemical oxygen demand), SS (suspended solid) were measured at Grit Chamber, Primary Sedimentation Tank, Secondary Sedimentation Tank in Chung Gye Chun sewage treatment plant. The results were as follows. 1. The average of grease and oil quantities were 251mg/l at Grit Chamber, 185mg/l at Primary Sedimentation Tank, 47mg/l at Secondary Sedimentation Tank. 2. In the secondary treatment for the removal of grease and oil, the removed quantities of grease and oil were increased according to increasing the quantities of influent grease and oil. The regression equation were as follows G.O.removed=0.731 G.O. influent+3.235 (r=0.887) 3. The average of grease and oil removal rate was 76.4% and the standard deviation of grease and oil removal rate daily was 10.6%. 4. G.O. (grease and oil) and BOD, COD, SS showed significant correlationship at Grit Chamber, Primary Sedimentation Tank, Secondary Sedimentation Tank. (P<0.05). 5. In the secondary treatment, effluent grease & oil and other parameters were analyzed by means of Stepwise multiple regression. Multple regression equation for estimates of effluent grease and oil were as follows. $GO_E=-9.1637+2.0380 SS_E+0.068 SS_I$ (r=0.778) 6. The correlative parameters for the effluent grease and oil seem to be the influent SS and the effluent SS. 7. It was estimated that the removal of grease and oil would be improved by means of improvement of suspended solids removal efficiency but it is necessary to inquire further into the study.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.1183-1189
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• 2009

The sedimentation rate of particles in a suspension is a function of particle size, initial slurry water content and salinity. Many researches conducted on the behavior of dredged soils have centered on such factors. However, there have been few attempts to assess another important influence factor of seasonal water temperature on designing the placement of dredged materials. In this paper, the effect of seasonal water temperature on sedimentation characteristics of dredged clay was investigated with consideration of three different water temperatures, that are $5^{\circ}C$, $15^{\circ}C$, $35^{\circ}C$, which represent critical water temperatures in winter, spring or fall, and summer, respectively. A series of experimental results reveal that the sedimentation rates for the water temperature of $15^{\circ}C$ and $35^{\circ}C$ are very similar each other, but that of $5^{\circ}C$ that represents a winter season leads to a considerably delayed sedimentation compared to the others. This may be attributable to the retardation of ion-leaching from clay particles at low water temperature.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.36-36
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• 2023

Sedimentation is a natural process that occurs in all reservoirs. Sedimentation problem reduces the storage capacity of the reservoir and limits its ability to provide water for various uses, such as irrigation, hydropower generation, and flood control. Therefore, predicting reservoir sedimentation is important for ensuring the efficient operation and sedimentation management of a reservoir and . In this study, the HECRAS model was applied to predict longitudinal distribution of deposited sediment in the Pleikrong reservoir to 2050. Different scenarios was considered: (i) no climate change, (ii) climate change (under two emissions scenarios, RCP4.5 and RCP8.5), and (iii) climate change and land use change (followed land use planning of the watershed). The computation results with different scenarios were analyses and compared. The results show that the reservoir reduced storage volume's rate and sedimentation proceed toward to the dam in the case of climate change is faster than in the case of no climate change. Analyses also indicates that following the land used planning could also improve the long-term problem of the reservoir sedimentation. The outcomes of this study will be helpful for a sustainable plan of sediment management for the Pleikrong reservoir.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.1 no.1
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• pp.69-76
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• 1981

The predictive equations for reservoir sedimentation rate now in use are extensively reviewed, and the equation of multiple regression type, in which the reservoir sedimentation rate is related with the watershed area and the trap-efficiency, is proposed based on the 113 irrigation reservoir resurvey data. The predictive relation so obtained proved to be a reasonable measure for the estimation of reservoir sedimentation rate. The relationship of sediment yield with the watershed area and with the reservoir trap efficiency is also analyzed. The variations of sedimentation rate and of the annual reservoir capacity loss rate was shown to heavily depend on the trap-efficiency of a reservoir. Besides, the effect of sedimentation on stream channels is confirmed and quantified based on the predictive equation derived in the present study.

• Water for future
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• v.17 no.2
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• pp.107-112
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• 1984

It si presented here that in order to estimate reservoir sedimentation rate through the use of reservoir survey data of 66 irrigation reservoir in 3 major watersheds in this country, the correlation between reservoir sedimentation rate and the following factors; watershed area, trap-efficiency, watershed slope, shape factor of water shed, and reservoir deposition age in two models simple regression model and multiple regression model. Appropriatness of the proposed models have been calibrated from the survey data and as a result, it has been determined that the multiple regression model is much more accurate than the simple regression model. The annual sediment yield is correlated with watershed area and reservoir trap efficiency. It has been found that variation of the annual average sedimentation rate and the annual reservoir capacity loss rate are influenced by the trap efficiency of reservoir.