• Journal of Korean Society of Water and Wastewater
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• v.28 no.1
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• pp.61-72
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• 2014

Study on effluent organic matter (EfOM) characteristic and removal efficiency is required, because EfOM is important in regard to the stability of effluents reuse, quality issues of artificial recharge and water conservation of aqueous system. UV technology is widely used in wastewater treatment. Many reports have been conducted on microbial disinfection and micro pollutant reduction with UV treatment. However, the study on EfOM with UV has limited because low/medium pressure UV lamp is not sufficient to affect refractory organics. The high intensity of pulsed UV would mineralize EfOM itself as well as change the characteristics of EfOM. Chlorine demand and DBPs formation is affected on the changed amounts and properties of EfOM. The objective of this study is to investigate the effect on EfOM, chlorine residual, and chlorinated DBPs formation with low pressure and pulsed UV treatment. The removal of organic matter through low pressure UV treatment is insignificant effect. Pulsed UV treatment effectively removes/transforms EfOM. As a result, the chlorine consumption is changed and chlorine DBPs formation is decreased. However, excessive UV treatment caused problems of increasing chlorine consumption and generating unknown by-products.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.3-32
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• 2008

The potential deep geothermal resources span a wide range of heat sources from the earth, including not only the more easily developed, currently economic hydrothermal resources; but also the earth's deeper, stored thermal energy, which is present anywhere. At shallow depths of 3,000~10,000m, the coincidence of substantial amounts heat in hot rock, fluids that heat up while flowing through the rock and permeability of connected fractures can result in natural hot water reservoirs. Although conventional hydrothermal resources which contain sufficient fluids at high temperatures and geo-pressures are used effectively for both electric and nonelectric applications in the world, they are somewhat limited in their location and ultimate potential for supplying electricity. A large portion of the world's geothermal resource base consists of hot dry rock(HDR) with limited permeability and porosity, an inadquate recharge of fluids and/or insufficient water for heat transport. An alternative known as engineered or enhanced geothermal systems(EGS), to dependence on naturally occurring hydrothermal reservoirs involves human intervention to engineer hydrothermal reservoirs in hot rocks for commercial use. Therefore EGS resources are with enormous potential for primary energy recovery using an engineered heat mining technology, which is designed to extract and utilize the earth's stored inexthermal energy. Because EGS resources have a large potential for the long term, United States focused his effort to provide 100GW of 24-hour-a-day base load electric-generating capacity by 2050.

• Economic and Environmental Geology
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• v.42 no.4
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• pp.343-356
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• 2009

SCS method was applied to make the assessments of direct runoff according to land use changes in Jeju island. Land uses were obtained from 5 year-period remote sensing time series data from 1975 to 2000 which are provided by Water Management Information System (WAMIS). Hydrologic soil groups were categorized based on soil series of National Academy of Agricultural Sciences (NAAS), and permeable geologic structures such as Sumgol, Gotzawal and so on. The land uses of Jeju island are obviously characterized by urban-agricultural areas increases, and forest areas decrease. According to land use changes, curve number (CN) for Jeju island was consistently increased from 65.3 in 1975 to 69.6 in 2000. From 1975 to 2000, the amount of direct runoff and ratios increased due to CN changes. When the rainfall data in 1995 was applied to each year, the direct runoff amounts were $299.0{\sim}351.6\;mm$, and runoff ratios were $15.1{\sim}17.7%$. In the case of the application of the rainfall data in 2000, the direct runoff amounts were $136.9{\sim}161.5\;mm$, and runoff ratios were $9.7{\sim}11.5%$. Since direct runoff can be closely related to groundwater recharge and sustainable groundwater yield, the groundwater influence caused by land use changes or district exploitations should be considered for the reasonable water management and development in Jeju island.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.375-380
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• 2013

The concept of safe yield places an emphasis on balancing groundwater withdrawal with groundwater recharge but ignores naturally occurring groundwater discharge. Because streams and their alluvial aquifers are closely linked in terms of water supply and water quality, to be properly understood and managed they must be considered together. Therefore, some districts in Kansas have reevaluated their safe-yield policies to account for natural groundwater discharge and stream-aquifer interactions by amending their safe-yield regulations to include a portion of baseflow as the minimum desirable streamflow (MDS). This study proposes a modified safe-yield policy in which the drought flow is chosen as the MDS. Baseflow separation was conducted from streamflow hydrograph and the results are presented as a flow-duration curve. The exploitable groundwater can be determined by subtracting MDS from the cumulative baseflow. This method was tested in the Musimcheon watershed, which was validated for streamflow using the SWAT-K model. The annually averaged exploitable groundwater in the whole watershed was estimated to be 86 mm. The exploitable groundwater amounts were also estimated for each subwatershed in the Musimcheon watershed.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.472-472
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• 2004

Numerous studies on urban groundwater have been carried out in many other countries. Urban groundwater shows a unique hydrologic system because of complex urban characteristics such as road pavement, sewers and public water supply systems. These urban facilities may change the characteristics of groundwater recharge but contaminate its quality as well. There have been several researches on urban groundwater in Seoul. Seoul has been industrialized very rapidly so that the city has large population. The recent population in Seoul amounts to more than ten millions, corresponding to a very high density of about 17, 000 people/km$^2$. Therefore, many factors affect the groundwater quality and quantity in Seoul. Nowadays, groundwater in Seoul is being extracted for construction, industrial use, and drinking and so on. There are 15, 714 wells in Seoul and its annual usage is 41, 425, 977m$^3$(in 2001). Therefore, systematic studies are needed to properly manage and use the groundwater in Seoul. The purposes of this study in progress are to identify geochemical characteristics of groundwater in Seoul and to determine the extent of groundwater contamination and its relationship with urban characteristics. For this study, groundwater was sampled from more than 400 preexisting wells that were randomly selected throughout the Seoul area. For all samples, major cations together with Si, Al, Fe, Pb, Hg For 200 samples among them, TCE, PCE, BTEX were also analyzed by GC. Our study shows that groundwater types of Seoul are distributed broadly from Ca-HCO$_3$ type to Ca-Cl＋NO$_3$ type. The latter type indicates anthropogenic contamination. Among cations, Ca is generally high in most samples. In some samples, Na and K are dominant. The dominant anions change widely from HCO$_3$ to Cl＋NO$_3$. The anion composition is considered to effectively indicate the contribution of distinct anthropogenic sources. In addition, major ions are positively proportional to total dissolved solid (TDS) except K and NO$_3$. Thus, we consider that TDS may be used as an effective indicator of the extent of pollution. However, the increase of TDS may result from increased water-rock interaction. To determine the extent of groundwater contamination, it is needed to figure out the baseline water quality in Seoul. Furthermore, detailed geochemical studies are required to find out pollution sources and their corresponding hydrochemical parameters.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.4
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• pp.177-191
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• 1998

For various kinds of waters including surface water, shallow groundwater (＜70 m deep) and deep groundwater (500∼810 m deep) from the Pungki area, an integrated study based on hydrochemical, multivariate statistical, thermodynamic, environmental isotopic (tritium, oxygen-hydrogen, carbon and sulfur), and mass-balance approaches was attempted to elucidate the hydrogeochemical and hydrologic characteristics of the groundwater system in the gneiss area. Shallow groundwaters are typified as the 'Ca-HCO$_3$'type with higher concentrations of Ca, Mg, SO$_4$and NO$_3$, whereas deep groundwaters are the 'Na-HCO$_3$'type with elevated concentrations of Na, Ba, Li, H$_2$S, F and Cl and are supersaturated with respect to calcite. The waters in the area are largely classified into two groups: 1) surface waters and most of shallow groundwaters, and 2) deep groundwaters and one sample of shallow groundwater. Seasonal compositional variations are recognized for the former. Multivariate statistical analysis indicates that three factors may explain about 86% of the compositional variations observed in deep groundwaters. These are: 1) plagioclase dissolution and calcite precipitation, 2) sulfate reduction, and 3) acid hydrolysis of hydroxyl-bearing minerals(mainly mica). By combining with results of thermodynamic calculation, four appropriate models of water/ rock interaction, each showing the dissolution of plagioclase, kaolinite and micas and the precipitation of calcite, illite, laumontite, chlorite and smectite, are proposed by mass balance modelling in order to explain the water quality of deep groundwaters. Oxygen-hydrogen isotope data indicate that deep groundwaters were originated from a local meteoric water recharged from distant, topograpically high mountainous region and underwent larger degrees of water/rock interaction during the regional deep circulation, whereas the shallow groundwaters were recharged from nearby, topograpically low region. Tritium data show that the recharge time was the pre-thermonuclear age for deep groundwaters (＜0.2 TU) but the post-thermonuclear age for shallow groundwaters (5.66∼7.79 TU). The $\delta$$\^$34/S values of dissolved sulfate indicate that high amounts of dissolved H$_2$S (up to 3.9 mg/1), a characteristic of deep groundwaters in this area, might be derived from the reduction of sulfate. The $\delta$$\^$13/C values of dissolved carbonates are controlled by not only the dissolution of carbonate minerals by dissolved soil CO$_2$(for shallow groundwaters) but also the reprecipitation of calcite (for deep groundwaters). An integrated model of the origin, flow and chemical evolution for the groundwaters in this area is proposed in this study.