• Journal of Korean Society of Environmental Engineers
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• v.34 no.2
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• pp.79-85
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• 2012

In this study, Application of sequencing batch reactor (SBR) process for RO retentate treatment was performed. Efficiency of treatment by load and temperature variation was tested. The SBR process was operated two types as HRT per one cycle was 8 and 12 hours, respectively. Methanol was injected for an effective denitrificaion owing to low C/N ratio of the RO retentate. TN removal efficiency of the SBR process was relatively stable at the change of flow-rate and temperature. The optimum time cycle of SBR process was 2 cycle/day for TN removal, and in the case of 3 cycle/day, the effluent TN concentration was found under the effluent quality standard. In the result of assessment, the application of SBR process for RO retentate treatment was effective and could be utilized to design for the wastewater treatment plant. The specific nitrification rate (SNR) and specific denitrification rate (SDNR) were $0.043{\sim}0.066kg\;NH_3-N/kg\;MLVSS{\cdot}day$ and $0.096{\sim}0.287kg\;NH_3^--N/kg\;MLVSS{\cdot}day$, respectively. The derived kinetic could be applied for design to the aerobic and anoxic tank in the RO retentate treatment.

• Journal of Korea Water Resources Association
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• v.51 no.8
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• pp.677-686
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• 2018

There remain numerous ungauged watersheds in Korea owing to limited spatial and temporal streamflow data with which to estimate hydrological model parameters. To deal with this problem, various regionalization approaches have been proposed over the last several decades. However, the results of the regionalization models differ according to climatic conditions and regional physical characteristics, and the results of the regionalization models in previous studies are generally inconclusive. Thus, to improve the performance of the regionalization methods, this study attaches hydrological model parameters obtained using a spatial proximity model to the explanatory variables of a regional regression model and defines it as a hybrid regionalization model (hybrid model). The performance results of the hybrid model are compared with those of existing methods for 37 test watersheds in South Korea. The GR4J model parameters in the gauged watersheds are estimated using a shuffled complex evolution algorithm. The variation inflation factor is used to consider the multicollinearity of watershed characteristics, and then stepwise regression is performed to select the optimum explanatory variables for the regression model. Analysis of the results reveals that the highest modeling accuracy is achieved using the hybrid model on RMSE overall the test watersheds. Consequently, it can be concluded that the hybrid model can be used as an alternative approach for modeling ungauged watersheds.

• Korean Journal of Ecology and Environment
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• v.36 no.1 s.102
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• pp.57-65
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• 2003

The algal growth potential test (AGPT) bioassay were conducted to assess the water quality and fertility in the Chinyang Reservoir and the lower part of the Nam River from August 2000 to July 2001, The AGPT value of the Chinyang Reservoir ranged from 0 to 23.4 mg dw $1^{-1}$, while 79% of the algae cultivation have not grown. The AGPT value was in proportion to phosphorus concentration of the water, and it was less when chlorophyll-a was high. This value was higher in the middle and lower layers than in the upper layer, and in the inflow part where the water is shallower than in the lacustrine. The AGPT value has increased in the whole reservoir in August${\sim}$September when the water volume is high. In contrast, the AGPT value in the Nam River varied greatly compared to that of the reservoir, and ranged from 0 to 252.0 mg dw $1^{-1}$ and 65% of the algae cultivation have grown. The value was less than 10 mg dw $1^{-1}$ in the upstream, over the point where the treated wastewater discharged. It was 57 mg dw $1^{-1}$ on the average in the downstream, except in March and July when the discharged water influenced greatly, exceeding the hypertrophic condition. The result of AGPT shows the differences in the time and space on the reservoir and the streams. The AGPT value has increased in July${\sim}$September, and in December in the inflow part of the reservoir; in March and August${\sim}$December in the lower part; and in January, May, and November in the streams. AGPT is useful not only in defining the influence of the limiting nutrients on the algal growth, but also in evaluating the nutrients fertility in the inland water.

• Korean Journal of Ecology and Environment
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• v.34 no.4 s.96
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• pp.267-276
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• 2001

The downstream reach of the Han River adjoining Seoul in Korea was the upper boundary of an estuary where tidal effect on the flow rate could be exerted. According to the comprehensive river regulation project, the river was channelize dand impounded by two overflow dams, which provided favorable condition for algal growth in this sewage polluted eutrophic reach. In this study primary productivity of phytoplankton was measured in the down reach and the autochthonous and allochthonous organic carbon loadings were estimated. Primary production of phytoplankton measured by C-14 uptake and P-I model method ranged from 140 to $4,890\;mgC\;m^{-2}\;d^{-1}$ (median value $1,865\;mgC\;m^{-2}\;d^{-1}$) showing the level of eutrophic lakes. Phytoplankton density that varied according to water flow rate was highest in spring. Allochthonous organic carbon loading was dominated by sewage input through tributaries in most of days except flood flow period. The average proportion of autochthonous carbon generation by phytoplankton was 40.9%, which is very high proportion for a lotic habitat.

• Journal of Korea Soil Environment Society
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• v.1 no.2
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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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.1 no.1
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• pp.1-8
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• 1981

Since the estuary is a very complex place in which the sea water and the fresh water meet, it is very difficult to make a general analytical description of salinity distribution in the estuary. As an attempt to investigate the characteristics of salinity variation in the estuary of the Geum River, the field observations were continuously carried out at three points near the Gunsan New Harbor at the time intervals 1 to 1.5 hours during one tidal cycle and the data were analysed. The following results were obtained; 1. It was reconfirmed that most of the ratios of the salinity to the conductivity were widely distributed between the range of 0.5 to 1.0. 2. The salinity showed the peak at the high water, and then it began to decrease gradually and had the lowest value 0 to 2 hours after the low water. 3. The density current was generally the intense mixing type and when the river discharge was very large it was of the moderate type. 4. The vertical salinity distribution was not significantly affected by the wave height. 5. The maximum vertical salinity differences were generally less than 10 g/l and the time of the occurrence of the minimum value was 0 to 3 hours after the low water when in the spring tide and in the neap tide it occurred 2 to 3 hours after the high water.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.675-680
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• 2017

Considering that most sewage treatment facilities have a water head of less than 2.0 m and a constant flow rate, the development of a small hydro power generation device capable of maintaining stable power generation and efficiency is urgently needed. In this study, a numerical analysis using the CFD code was carried out to develop a drag force type vertical axis hydro turbine for the improvement of the production efficiency of small-scale hydro energy underlow flow velocity conditions. The blade pressure changes and internal flows were analyzed in the presence or absence of hydro turbine blade holes at a flow velocity of less than 2.0 m/s. The pressure distribution of the hydro turbine blades with holes was found to be about 5.1 % lower than that of the hydro turbine blades without holes. The analysis of the internal flow around the water tank and hydro turbine blade revealed that the flow velocity varied with the vector distribution and that the flow velocity of the hydro turbine blades with holes was 5.6 % less than that of the hydro turbine blades without holes. It is believed that forming a hole in the blade may be helpful for its structural safety.

• Journal of Korea Water Resources Association
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• v.42 no.7
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• pp.537-546
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• 2009

Determination of optimal pressure monitoring location is essential to manage water distribution system efficiently and safely. In this study, entropy theory is applied to overcome defects of previous researches about determining the optimal sensor location. The previous studies required the calibration using historical data, therefore, it was difficult to apply the proposed method in the place where the enough data were not available. Also, most researches have focused on the locations to minimize cost and maximize accuracy of the model, which is not appropriate for the purpose of maintenance of the water distribution system. The proposed method in this study quantify the entropy which is defined as the amount of information calculated from the pressure change due to the variation of discharge. When abnormal condition is occurred in a node, the effect on the entire network is presented by the entropy, and the emitter is used to reproduce actual pressure change pattern in EPANET. The optimal location to install pressure sensors in water distribution system is the nodes having the maximum information from other nodes. The looped and branched networks are evaluated using the proposed model. As a result, entropy theory provides general guideline to select the locations to install pressure sensors and the results can be used to help decision makers.

• Journal of Wetlands Research
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• v.6 no.3
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• pp.119-126
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• 2004

In recent, the critical rainfall duration concept is widely used but we do not have understandable criteria yet. However, the critical rainfall duration is usually calculated considering concentration time, runoff model using effective rainfall, and unit hydrograph for the estimation of design flood. This study is to derive the regression equations between the critical rainfall duration and hydrologic components such as the basin area, slope, length, CN, and so on. We use a GIS tool which is called the ArcView for the estimation of hydrologic components and the HEC-1 module which is provided in WMS model is used for the runoff computation. As the results, the basin area, basin slope, and basin length had a great influence on the estimations of peak runoff and critical rainfall duration. We also investigated the sensitivities for the peak runoff and critical duration of rainfall from the correlation analysis for the involved components in the runoff estimation.

• Journal of Wetlands Research
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• v.13 no.1
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• pp.105-116
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• 2011

Changes in climate have largely increased concentrated heavy rainfall, which in turn is causing enormous damages to humans and properties. Therefore, the exact relationship and the spatial variability analysis of hydrometeorological elements and characteristic factors is critical elements to reduce the uncertainty in rainfall -runoff model. In this study, radar rainfall grid resolution and grid resolution depending on the topographic factor in rainfall - runoff models were how to respond. In this study, semi-distribution of rainfall-runoff model using the model ModClark of Inje, Gangwon Naerin watershed was used as Gwangdeok RADAR data. The completed ModClark model was calibrated for use DEM of cell size of 30m, 150m, 250m, 350m was chosen for the application, and runoff simulated by the RADAR rainfall data of 500m, 1km, 2km, 5km, 10km from 14 to 17 on July, 2006. According to the resolution of each grid, in order to compare simulation results, the runoff hydrograph has been made and the runoff has also been simulated. As a result, it was highly runoff simulation if the cell size is DEM 30m~150m, RADAR rainfall 500m~2km for peak flow and runoff volume. In the statistical analysis results, if every DEM cell size are 500m and if RADAR rainfall cell size is 30m, relevance of model was higher. Result of sensitivity assessment, high index DEM give effect to result of distributed model. Recently, rainfall -runoff analysis is used lumped model to distributed model. So, this study is expected to make use of the efficiently decision criteria for configurated models.