• Journal of computational fluids engineering
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• v.21 no.3
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• pp.24-30
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• 2016

In the water purification plant, the mixture of water and chemical from the mixing basin enters the flocculation basin. The rotating flocculators are generally used for the efficient flocculation of dregs. In this paper, the performance of flocculators of a vertical paddle type, widely used in the typical flocculation basins, and a hydro-foil type, recently disseminated in the field, are compared with each other by use of the numerical method. Also the characteristics and the efficiency are analyzed with CFD techniques. The strain rate and the eddy viscosity are compared for two types to predict the mixing efficiency, and the maximum speed and its location are pursued from the computed data. The hydrofoil type shows that the eddy viscosity is enhanced 1.66 to 3.03 times larger than that of vertical paddle type, and also produced 1.87 to 1.95 times larger flocs for each stage. However, the rapid rotation of hydrofoil may chop the floc to small size due to the higher turbulence intensity. From the result of computation, the strong and weak points of each type have been analyzed for the decision making.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.1
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• pp.53-62
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• 1982

This study was attempted to find best fitted distribution and the equations for probable maximum flow with the evaluation of parameters by the method of moment for the rat- ional design of hydraulic structures in the annual exceedance series. Six subwatersheds were selected as studying basins along Geum River basin. The results obtained through this study were analyzed and summarized as follows. 1. Fitted probability distribution was showed in the order of Three Parameter Lognorm al, Type 1 Extremal, Exponential, Pearson Type III, and Log Pearson Type I distribu- tion as the results of x$^2$ goodness of fit test. 2. Kolmogorov-Smirnov test showed in the order of Three Parameter Lognormal, Exp- onential' Pearson Type III, Log Pearson Type III and Type 1 Extremal distribution for the fitted probability distribution. 3. It can be concluded that Three parameter Lognormal distribution is a best fitted one among some other distributions out of respect for each both tests. An Exponential distribution was proposed as a suitable one by Chow, V.T. showeci lower fittness than that of Three Parameter Lognormal in Geum River basin. 5. Probable flood flow equations followins the return periods for each station were obt- ained by Three Parameter Lognormal distribution. 6. It is urgently essential that best fitted probability distribution should be established for the annual exceedance series in the main river systems of Korea.

• Journal of Wetlands Research
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• v.11 no.1
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• pp.1-13
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• 2009

The influence of moving rainstorms to runoff was analysed for the nonsymmetric shaped basins using kinematic wave theory. The distribution types of moving rainstorms are uniform, advanced, delayed and intermediate type, the nonsymmetric shaped basins are square, oblong and elongated shape. The runoff hydrographs were simulated and the characteristics were compared with the symmetric shaped basins for the rainstorms moving up, down and cross the basins with various velocities. The smallest differences of peak runoff of symmetric and nonsymmetric basins are appeared in the case of elongated basin, and the largest differences are shown at the oblong basin for the downstream direction. The identical results are shown for the upstream direction. The greatest peak runoff differences are shown in the delayed type rainstorm and the smallest differences are in the advanced type rainstorm for the crossstream direction. The oblong shaped basin generates the longest peak time and shortest peak time for the elongated shape basin.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.493-503
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• 2014

The NRCS-CN method is generally applied for estimating effective rainfalls in practice, in which the basin-averaged CN is normally used. In order to develop a more appropriate method for estimating effective rainfalls in a basin, this study compared estimated effective rainfalls from two distinct methods with the observed direct runoff. The first method is to estimate the basin-representative effective rainfall using the basin-averaged CN (hereafter, effective rainfall I), whereas the second method to estimate the basin-averaged effective rainfall through areal-averaging sub-area effective rainfalls corresponding to the soil type and landuse type (hereafter, effective rainfall II). The overall results indicated that the effective rainfall II was higher than the effective rainfall I and closer to the observed direct runoff. The study also performed error analyses to verify that the effective rainfall II can be applied in practice in a basin as more accurate estimate of basin-representative effective rainfall.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.3
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• pp.240-250
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• 2000

In this study, DWTP Advisor developed from U.S. EPA was adapted for performance assessment in small water treatment plant and studied for improvement advice about the problem. From results of performance assessment, the ability of each major unit process meets to Peak Instantaneous Flow(PIF) as Type I (above 95% of PIF) in N WTP. But, outlet condition in the sedimentation basin are permitting the loss of solids from the basin and the lack of proper solids removal is degrading the performance in N WTP. From results of the hydraulic analysis using fluoride tracer, flow rate in sedimentation basin is rapidly more lower than upper. The Reynolds number, Re, and Froude number, Fr which are used to predict flow condition in sedimentation basin is calculated to be 3159.98 and $2.06{\times}10^{-7}$, respectively. There is possibility of occurrence of short-circuiting and turbulence. Also, the different type of effluent trough makes unstable flow in sedimentation basin and increases carry-overing of sedimented solids.

• Journal of environmental and Sanitary engineering
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• v.14 no.3
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• pp.1-9
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• 1999

In the estimation of pollution load in water basin, a data information has generally used from surveyed data. A Geographic Information System(GIS) was adopted to evaluate the amount of pollution load in Anyang stream basin which is one of the major tributaries in the Han river flows through urban area. The digital maps of administrative boundary, stream network, sub-basin, soil type, and land-use for spatial data as well as attribute data were generated. And the database of sub-basins and pollution source was structured to estimate pollution load in Anyang stream basin by an Arc/Info GIS.As the results of this investigation, the pollution load of Mokgam-chun sub-basin was the highest amount. And that of Hagi-chun sub-basin and the fourth main stream sub-basin were also high amount in Anyang stream basin. In general, it was found that the pollution load generated from the upstream area in Kyunggi province was higher than that from downstream area in Seoul. Because the point and non-point source pollution load played very significant role in the deterioration of the water quality of the Anyang stream, an integrated approach to water quality management should be required for the sub-basins of high pollution load amount.

• Journal of Korean Society of Water and Wastewater
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• v.8 no.3
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• pp.19-25
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• 1994

In this research, characteristics of nitrification and denitrification using the microorganism attached on sponge and plates were examined. The denitrification and nitrification performance were investigated under the anaerobic and aerobic condition for about 2 months. Because the basins of denitrification and nitrification were connected in series, wastewater was flowed from denitrification basin to nitrification one. The 90% of influent flowrate was returned from nitrification basin to denitrification one. Most of organic material was removed in nitrification basin, wherease the only exact amount of organics required in denitrification process was removed in denitrification one. This experiment resulted in that heterotrophic bacteria existing in aerobic basin governed the removal efficiency of organic compounds. In case the influent BOD concentration into nitrification basin was 80mg/l, it did not affect to accumulation of nitrifying bacteria, the balance of heterotrophic bacteria was proved to be an important factor in nitrification/denitrification method such as anaerobic and aerobic cycling type.

• Proceedings of the KSEEG Conference
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• 2007.04a
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• pp.255-255
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• 2007

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• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1311-1315
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• 2009

Understanding of the hydraulics of flow is very important to support the management of river. The cross-sectional area, average velocity, flow depth and discharge can be regarded as a power function each other. In this paper the flow of Bocheong stream basin is experimentally studied. The correlation analysis was performed between observed hydraulic factors by the power type function. The constants resulted from the correlation analysis were calculated by the geomorphologic characteristics of the watershed using the power type function. The correlation coefficients between the hydraulic factors were appeared close to unit having strong correlationship. The two conditions of equality of the continuity equation were analysed, and the conditions were found to be good results. From these results the observed hydraulic data of Bocheong stream basin can be concluded as a reliable data. The correlation coefficients between the parameters of the hydraulic characteristics and geomorphologic factors were found to be close to unit.

• Ocean and Polar Research
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• v.24 no.3
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• pp.215-223
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• 2002

Symbiosis of chemoautrophic bacteria with the members of hydrothermal vent and cold seep communities in the deep-sea were examined by histology using transmission electron microscopy; Bathymodiolus spp. from Sagami Bay, the Iheya Ridge and the North Fiji Basin; and Ifremeria nautilei from the North Fiji Basin. Two species of Bathymodiolus, each from Sagami Bay and the Iheya Ridge harbored methane-oxidizing symbionts within their gill tissues. Vent gastropod Ifremeria nautilei from the hydrothermal vents of the North Fiji Basin housed two types of symbionts; one sulfur-oxidizing type and the other methane-oxidizing type. The occurrence of chemosynthetic symbionts in these organisms were expected before-hand based on the ecological observations of their habit. The other members of these groups from world oceans and the recent advances in the symbiosis of the vent and seep communities were reviewed.