• Journal of the Mineralogical Society of Korea
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• v.20 no.3
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• pp.213-222
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• 2007

Changes of turbidity and suspended solid concentration of inflow tend to be very similar in Andong and Imha dam, and show significant effect on the amount of rainfall. Concentrations of suspended solid and turbidity in Imha are higher than these of Andogn dam, and Banbyon have higher values than that of Yongjeon stream in Imha dam. There is no difference in size distribution and mineral composition of the suspended particles in Andong and Imha dam. The turbidity-causing materials are composed of vermiculite. illite, kaolinite, quartz and albite. X-ray diffraction analysis shows that turbidity-causing materials are have similar mineralogy between Andong and Imha Dam, but they have different abundance.

• Journal of Environmental Science International
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• v.20 no.6
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• pp.711-719
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• 2011

This study was conducted to estimate the distribution characteristics and budget of organic matter in the Lake Hapcheon. In the dry season, the concentration ranges of organic carbons were similar, but in the rainfall season, it showed about double concentrations. Changes of vertical water quality in the lake, there were no big differences with the concentration by the depth. However, it tends to be relatively high on the surface, a little low on the mid-depth and high in the lake bottom. DOC rate at TOC, it was lower than POC rate at inflow and DOC rate was higher than POC rate in the lake and discharging water. R-DOC accounted for more 80% of DOC rate in all investigated areas, therefore we judge that this R-DOC is to increase the organic carbon pollution gradually. As the result of the calculated organic carbon budget in the Lake Hapcheon, the amount of allochthonous, autochthonous and release were 3,552, 3,288, 228 tonC/year, respectively. the amount of discharge, decomposition and sedimentation were 504, 1,344, 5,520 tonC/year, respectively. According to this investigation, the changed amount of organic matter in the Lake Hapcheon recorded -300 tonC/year with the increase of 7,068 tonC/year and the decrease of 7,368 tonC/year.

• Korean Journal of Ecology and Environment
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• v.49 no.2
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• pp.67-79
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• 2016

Cyanotoxins in aquatic ecosystems have been investigated by many researchers worldwide. Cyanotoxins can be classified according to toxicity as neurotoxins (anatoxin-a, anatoxin-a(s), saxitoxins) or hepatotoxins (microcystins, nodularin, cylindrospermopsin). Microcystins are generally present within cyanobacterial cells and are released by damage to the cell membrane. Cyanotoxins have been reported to cause adverse effects and to accumulate in aquatic organisms in lakes, rivers and oceans. Possible pathways of microcystins in Lake Suwa, Japan, have been investigated from five perspectives: production, adsorption, physiochemical decomposition, bioaccumulation and biodegradation. In this study, temporal variability in microcystins in Lake Suwa were investigated over 25 years (1991~2015). In nature, microcystins are removed by biodegradation of microorganisms and/or feeding of predators. However, during water treatment, the use of copper sulfate to remove algal cells causes extraction of a mess of microcystins. Cyanotoxins are removed by physical, chemical and biological methods, and the reduction of nutrients inflow is a basic method to prevent cyanobacterial bloom formation. However, this method is not effective for eutrophic lakes because nutrients are already present. The presence of a cyanotoxins can be a potential threat and therefore must be considered during water treatment. A complete understanding of the mechanism of cyanotoxins degradation in the ecosystem requires more intensive study, including a quantitative enumeration of cyanotoxin degrading microbes. This should be done in conjunction with an investigation of the microbial ecological mechanism of cyanobacteria degradation.

• Spatial Information Research
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• v.10 no.2
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• pp.301-316
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• 2002

Soil Loss by outflow of water or rainfall has caused many environmental problems as declining agricultural productivity, damaging pasture and preventing flow of water. Also, validity pondage of reservoir or dam is decreased by rivers inflow of eroded soil. Revised Universal Soil Loss Equation(RUSLE) is mainly used to presume soil loss amount of basin using GIS. But, because comparison with survey data is difficult, it is no large meaning that estimate calculated soil loss amount as quantitative. This research used unit sediment deposit survey data of Bo-seong basin for quantitative conclusion of soil loss amount that calculate on RUSLE. Through comparison examination with unit sediment yield that calculate on RUSLE and unit sediment deposit survey data, we can estimate resolution far RUSLE Model. As a result, cell size of 150m was estimated by thing which is most suitable.

• Journal of Korean Society on Water Environment
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• v.32 no.4
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• pp.367-374
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• 2016

In this study, the RDII impact on sewer designing in the upstream monitoring area (A site) was considered. Based on the long-term (1/1/2011~12/31/2011) rainfall and flow data consisting of 10-min interval sampling in the nearby design area (B site), the maximum RDII/DWF ratio was selected. The sewer network system at B site was evaluated by the Manning equation. Scenario 1 considering the hourly maximum flow with respect to the flow velocity showed that none of the sewer pipes satisfied the minimum flow velocity condition (0.6 m/s), and 40 pipes did not achieve half of the velocity condition. In scenario 2 considering I/I, 1 the pipes satisfied 0.6 m/s, and 35 pipes showed 0.3 m/s. Scenario 3 reflected the effect of RDII. Velocities in 26 pipes were less than 0.3 m/s, and 4 pipes satisfied the velocity condition. With respect to the allowance rate, 17 pipes were shown to have more than 99%, and none of the pipes satisfied less than 95% of the allowance rate in scenario 1. In scenario 2, 17 Ed: Per the Table pipes showed more than 99% and one pipe showed less than 95%. In scenario 3, 16 pipes showed more than 99% of the allowance rate, and 19 pipes showed less than 95%. Based on these results, it is predicted that deposition would occur due to the slow flow velocity; however, capacity would not be a problem.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.6
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• pp.819-826
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• 2005

To guarantee the disinfection ability in clearwell, a value of CT is considered where C[mg/l] is disinfectant residual at the exit of clearwell and T[min] means $T_{10}$, the contact time when 10% of tracer is out of clearwell after introducing the tracer at the inlet. To meet a CT value required, increasing the C value is not recommended because high C value can increase potential of producing disinfection by product like THMs. Increasing the hydraulic efficiency surrogated by $T_{10}$ is thus an option widely recommended. Right now, it is widely adopted estimating $T_{10}$ considering LW ratio only due to the suggestions of previous researches. The authors think however there are other factors to consider including shape, flow rate, configuration of inlet and outlet, and the existence of intra basin. This study is initiated to closely look at the effects of two factor on hydraulic efficiency. The factors are shape and inlet flow velocity, i.e., inflow. For that, computational fluid dynamics (CFD) model is developed and pilot test is also carried out. The results show that at a L/W ratio, disinfection ability is overestimated with larger length in shape and higher inlet flow velocity. This suggests that in determining $T_{10}$, the shapes of clearwell and inlet flow velocity should also be considered as well as L/W ratio.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.2
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• pp.125-139
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• 2017

In this paper, the performance of a synthetic fiber filter aimed at high-speed operation and dosed with different coagulants or filter aids was investigated. Without a coagulant, the filter efficiency was about 62% which was greatly enhanced when three types of coagulants namely PAC, Alum, and $FeCl_3$ were used. Among the coagulants tested, PAC was the most effective, giving 91% filter efficiency, followed by Alum with 90%, and $FeCl_3$ with 78%. PAC worked effectively at a very small range of dose, but Alum was relatively effective in a wide range of concentration. Compared with PAC and Alum, $FeCl_3$ provided more or less contant efficiency regardless of its dose but gave the poorest filter efficiency. Moreover, as the inflow turbidity increased, headloss increased and the efficiency decreased at any dose and type of coagulant. The headloss recorded in this particular synthetic fiber filter is not significant as compared to that observed in typical granular filters. The recovery of solids estimated after filter cleaning was about 80% for both PAC and Alum, but poorer at 72% in the case of $FeCl_3$ due to the heavy and large floc characteristics. The recurrence of filter efficiency verified through repetitive filter runs was found to be satisfactory.

• Journal of computational fluids engineering
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• v.21 no.3
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• pp.15-23
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• 2016

In the present study, two phase flows around a projectile vertically launched from an underwater platform have been numerically investigated by using a three dimensional multi-phase RANS flow solver based on pseudo-compressibility and a homogeneous mixture model on unstructured meshes. The relative motion between the platform and projectile was described by six degrees of freedom equations of motion with Euler angles and a chimera technique. The propulsive power of the projectile was modeled as the fluid force acting on the lower surface of the body by the compressed air emitted from the underwater platform. Various flow conditions were considered to analyze the fluid-dynamics motion parameters of the projectile. The water level of platform and the current speed around the projectile were the main parametric variables. The numerical calculations were conducted up to 0.75sec in physical time scale. The dynamics tendency of the projectile was almost identical with respect to the water level variation due to the constant buoyancy term. The moving speed of the projectile along the vertical axis inside the platform decreased when the current speed increased. This is because the inflow from outside of the platform impeded development of the compressed air emitted from the floor surface of the launch platform. As a result, the fluid force acting on the lower surface of the projectile decreased, and injection time of the projectile from the platform was delayed.

• Ocean and Polar Research
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• v.25 no.4
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• pp.447-457
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• 2003

In order to understand the distribution of changes of geochemical characteristics in surface sediments according to various environmental changes around the artificial Lake Shihwa, surface sediments were sampled at $13{\sim}15$ sites form 1997 to 1999 and analyzed by C/S analyzer, ICP/MS and AAS. The average $S/C_{org}$ ratio was 0.35 in the surface sediments, which is similar to 0.36, the characteristic ratio of marine sediments. Heavy metal contents and enrichment factors in the surface sediments tended to be decreasing from the head to the mouth of the Lake Shihwa. With the deposition of fine-grained sediments in the central part of lake, anoxic water column induced the sulfides compounds with Cu, Cd and Zn. Metals such as Al, Fe, Cr, Co, Ni, Cu, Zn and Cd except for Mn and Pb showed relatively high correlation coefficients among them. The contents of Cr, Co, Ni, Cu, Zn and Cd in the surface sediments of the lake were two to five times higher than those in the lake before dike construction and also in outer part of the dike. These are mainly due to the Input of untreated industrial and municipal waste-waters into the lake, and the accumulation of heavy metals by limitation of physical mixing. Although metal contents of the surface sediments at the sites near the water-gate due to outer seawater inflow tended to be lower than those during the desalination, heavy metals were deposited in areas around the new industrial complex in the evidence of spatial distribution of heavy metals in the sediments. This is mainly due to the input of untreated waste-waters from tributaries.

• Journal of Korea Water Resources Association
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• v.42 no.9
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• pp.725-736
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• 2009

A flood event can be defined by three characteristics; peak discharge, total flood volume, and flood duration, which are correlated each other. However, a conventional flood frequency analysis for the hydrological plan, design, and operation has focused on evaluating only the amount of peak discharge. The interpretation of this univariate flood frequency analysis has a limitation in describing the complex probability behavior of flood events. This study proposed a bivariate flood frequency analysis using a Gumbel mixed model for the flood evaluation. A time series of annual flood events was extracted from observations of inflow to the Soyang River Dam and the Daechung Dam, respectively. The joint probability distribution and return period were derived from the relationship between the amount of peak discharge and the total volume of flood runoff. The applicability of the Gumbel mixed model was tested by comparing the return periods acquired from the proposed bivariate analysis and the conventional univariate analysis.