• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.157-161
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• 2007

Nutrients were investigated for surface water, bottom sediment and ground water in a rural watershed from January 2006 to March 2007. The concentrations of TN and $NO_3-N$ in ground water were higher than those in surface water due to fertilization on cabbage upland neighboring a river during March to August, but lower than those in surface water during September to February. However, the concentrations TP and $PO_4-P$ in ground water were lower than those in surface water. The concentrations of TP and $PO_4-P$ in surface water was lower than those in bottom sediment. The TP concentration in the bottom greatly decreased during rainy season. due to flush sediment of bottom, and then gradually increased.

• Korean Journal of Ecology and Environment
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• v.39 no.2 s.116
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• pp.236-244
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• 2006

Water quality fluctuation of Gyeongan water area in Paldang reservoir, which measured from the downstream sampling point of Gyeongan stream (G1) to dam sampling point (P), was examined in the light of seasonal rainfall and regional difference in the year of 2002. Annual COD, T-P and T-N concentration dropped conspicuously at the point P (in front of dam) although concentration of Gl point was high. Concentration variation of COD, T-P and T-N from Gl to P point in Gyeongan area was small in August and September. And at G l point showed relatively low concentration. Chlorophyll-a concentration varies less during the autumn season (October to December) than spring season (March to June). Water temperature of Bughangang (north Han-river) area was relatively lower in August and higher in November compared with that of other areas. COD and SS concentration showed big regional difference except in November when the concentrations of which were relatively low. The high Chlorophyll-a concentration of April fell conspicuously in rainy season. Gyeongan area, where the water depth is relatively shallow, indicated steep temperature gradient in April compared with that in August or November. High 55 concentration in April at P point characterized surface layer while the opposite was recorded in August. Mixing of upper and lower layers had taken place causing dilution of COD, T-N and T-P concentration in August. This condition was maintained throughout November. Therefore, spring-summer seasons needed more attention for water management countermeasure than summer-autumn seasons.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.4
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• pp.73-86
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• 1995

The propriety of the numerical model application was examined on Paldang resevoir and its inflow tributaries located in the center of the Korean peninsula and the long term water quality forecast of the oxygen profile was carried out in this syduy. The input data of the model was the capacity of the reservoir, catchment area, percolation, diffusion rate, vertical mixing rate, dissolution rate from the bottom of the reservoir, outflow of the resevoir, water quality measurement and meteorology data of the drainage basin, and the output result was the annual estimation value of the dissolved oxygen concentration and the biochemical oxygen demand. The modeling method is based on the measured or calculated boundary condition dividing the water area into several blocks from the macorscopic aspect and considering the mass balance in these blocks. As the result of the water quality forecast, it was expected that the water quality in Northern Han River and Paldang reservoir would maintain the recent level, but that the water quality in the Southern Han River and its inflow tributary would worsen below the grade 4 of the life environmental standard from around 2000 owing to the decrease of DO concentration and the increase of BOD concentration.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.2
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• pp.107-113
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• 2018

Maintaining adequate residual chlorine concentration is an important criteria to provide secure drinking water. The chlorine decay can be influenced by unstable flow due to the transient event caused by operation of hydraulic devices in the pipeline system. In order to understand the relationship between the transient event and the chlorine decay, the probability density function based on the water demand curve of a hypothetical water distribution system was used. The irregular transient events and the same number of events with regular interval were assumed and the fate of chlorine decay was compared. The chlorine decay was modeled using a generic chlorine decay model with optimized parameters to minimize the root mean square error between the experimental chlorine concentration and the simulated chlorine concentration using genetic algorithm. As a result, the chlorine decay can be determined through the number of transients regardless of the occurrence intervals.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.5
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• pp.547-554
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• 2013

Chlorine has strong oxidizing power, also it is many advantages over other disinfectants such as the residual characteristic and economic feasibility. However, chlorine also has disadvantages such as creating disinfection by-products of chlorine as THMs. In particular, the most deadly disadvantage of chlorine is that it is extremely poisonous toxins about all alive lives. Disinfection with electrolysis water can be a very useful way Because you do not have to worry about chlorine's dangerous. In this study, we evaluated the potential as a disinfectant, across the evaluating disinfection effect and generating characteristic of by-products. The electrolyzed water could be obtained removal efficiencies of over 99.9 % the coliform by operating condition such as residence time, current density (voltage), the electrode gap. The residual chlorine be generated 10,000 mg/L in current density $1.0A/dm^2$ and residence time of 10 minutes. The residual chlorine concentration was possible to maintain a stable. The by-products generated by high concentration residual chlorine in the reactor such as trihalomethanes, haloaceticacid, chloralhydrate, haloacetonitrile were detected in less than a water quality standards. At the concentration of less than residual chlorine of 1 ppm, the chlorine disinfection by-products be generated most below the detection limit.

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.902-910
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• 2012

The photodegradation characteristics of 30 pharmaceuticals were investigated by batch experiments using Ultraviolet (UV) reactor. The investigated pharmaceuticals include antibiotics, analgesics and antiarrhythmic agents etc. Tested water was prepared by simultaneously spiking 30 pharmaceuticals into pure water, and each experiment was conducted using 3 types of UV lamps. As a result, batch experiments showed that reactions of all the investigated pharmaceuticals followed pseudo-first order reaction regardless of the applied UV lamps. Among the pharmaceuticals, Cyclophosphamide, 2-Quinoxaline carboxylic acid and Clarithromycin proved to be the most UV-resistant compounds. Contrarily, Ceftiofur, Diclofenac and Ketoprofen were easily degraded by all the UV lamps. Dissolved organic carbon (DOC) concentration hardly changed although the concentration of the pharmaceuticals concentration gradually decreased with time, indicating that the degradation of parent pharmaceuticals may produce their intermediates during UV treatment.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.910
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• pp.1312-1319
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• 2004

Underwear is laundered frequently and most of them is made of cotton, but a cotton fiber is more difficult to modify than a synthetic fiber. We have attempted to determine the optimum conditions necessary whereby the lowest concentration of silver solution is needed to produce the greatest antimicrobial properties of cotton fabrics. For this study, colloidal silver was made by electrolysis. The concentration of colloidal silver was increased by increasing the area of the silver plates submerged in the water, the water temperature, the water hardness and the flow time of the water per 1l. However, the colloidal silver concentration was decreased by extending a space between the silver plates and increasing the water velocity. Cotton fabrics treated in the washing machine with 1.3 ppm colloidal silver solution for 10 minutes had effective microbial properties and an unperceivable reduction of reflectance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.10
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• pp.844-853
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• 2002

A dynamic model which simulates the coupled heat and mass transfer within a vertical tube absorber was developed. The liquid film is a binary mixture of two components, and both of these components are present in the vapor phase. The pressure, concentration, temperature and mass flow rate of the vapor are obtained by assuming that the pressure is uniform within an absorber. The model was applied to an absorber for an ammonia/water absorption refrigerator. The transient behaviors of the pressure, the outlet temperature and the concentration of the solution and the cooling water outlet temperature on a step change at the absorber inlet of the cooling water temperature, the vapor mass flow rate and the concentration of the solution were shown.

• Structural Engineering and Mechanics
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• v.84 no.4
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• pp.465-477
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• 2022

The formation of biopolymer-soil matrices mainly depends on biopolymer type and concentration, soil type, pore fluid and phase transfer to influence its strengthening efficiency. In this study, the physical and mechanical properties of sodium alginate (SA) treated kaolinite are investigated through compaction test, thread rolling teat, fall cone test and unconfined compression test with considering biopolymer concentration, curing time, initial water content, mixing method. The results show that the liquid limit slightly decreases from 69.9% to 68.3% at 0.2% SA and then gradually increases to 98.3% at 5% SA. At hydrated condition, the unconfined compressive strength (UCS) of SA treated clay at 0.5%, 1%, 2% and 3% concentrations is 2.57, 4.5, 7.1 and 5.48 times of untreated clay (15.7 kPa) at the same initial water content. In addition, the optimum biopolymer concentration, curing time, mixing method and initial water content can be regarded as 2%, 28 days, room temperature water-dry mixing (RD), 50%-55% to achieve the maximum unconfined compressive strength, which corresponds to the UCS increment of 593%, compared to the maximum UCS of untreated clay (780 kPa).

• Asian Journal of Atmospheric Environment
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• v.4 no.1
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• pp.55-61
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• 2010

The sensitivity of aerosol light extinction coefficient to the aerosol chemical composition change is estimated by (1) calculating the aerosol water content and chemical concentrations by a gas/particle equilibrium model and (2) calculating the aerosol light extinction coefficient by a Mie theory based optical model. The major chemical species are total (gas and particle phase) sulfuric acid, total nitric acid, and total ammonia which are based on the measurement data at Seoul and Gosan. At Seoul, since there were enough ammonia to neutralize both total sulfuric acid and total nitric acid, the dry ionic concentration is most sensitive to the variation of the total nitric acid level, while the total mass concentration (ionic concentration plus water content) and thus, the aerosol light extinction coefficient are primarily determined by the total sulfuric acid. At Gosan, since the concentration of ambient sulfuric acid was the highest among the inorganic species, sulfate salts determined aerosol hygroscopicity. Thus, both ionic and total mass concentration, and resultant aerosol light extinction coefficient are primarily determined by the sulfuric acid level.