• Nuclear Engineering and Technology
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• v.46 no.6
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• pp.797-802
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• 2014

This study investigated the thermal hydraulic issues in the Containment Filtered Venting System (CFVS) for a long operating time using the MELCOR computer code. The modeling of the CFVS, including the models for pool scrubbing and the filter, was added to the input file for the OPR-1000, and a Station Blackout (SBO) was chosen as an accident scenario. Although depressurization in the containment building as a primary objective of the CFVS was successful, the decontamination feature by scrubbing and filtering in the CFVS for a long operating time could fail by the continuous evaporation of the scrubbing solution. After the operation of the CFVS, the atmosphere temperature in the CFVS became slightly above the water saturation temperature owing to the release of an amount of steam with high temperature from the containment building to the scrubbing solution. Reduced pipe diameters at the inlet and outlet of the CFVS vessel mitigated the evaporation of scrubbing water by controlling the amount of high-temperature steam and the water saturation temperature.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.113-114
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• 2022

The aim of the research is to evaluate the segregation resistivity of the mixture conditions by changing the PVA and borax solutions for thixotropic property on concrete mixture. Since the water addition caused by producing solutions of PVA and borax induces segregation of the concrete mixture, the unit water was reduced by replacing the water amount for PVA and borax solution. By replacing the water from PVA and borax solutions, the segregation was prevented with prefixed concrete mix design and thixotropic properties were also occurred.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.4
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• pp.413-420
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• 2008

In order to utilize cinder melting slag as a filter media to control the quality of early rainwater, its environmental stability was verified by heavy metal elution experiment and improved by pre-treatment. Possibilities of improving its function as an absorbent was considered. Absorption characteristics of melting slag before and after the pre-treatment were analyzed by heavy metal equilibrium and stationary-phase column experiments, which in turn were analyzed by comparison experiment with activated carbon. As a result of heavy metal elution experiment, every metal item existed in a much lower amount than the criteria or was not detected, implying that there is no problem recycling it. Absorption equilibrium experiment showed that the time for pre-treatment melting slag to reach the equilibrium was reduced, while the absorbed amount was greatly increased. Stationary-phase column experiment assures us that the elimination rate was not changed much by influx rate, pH and the change in packing volume rate, indicating that this melting slag can be used not only as a filter media to control the quality of early rainwater but also in many areas of water-processing.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.3
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• pp.261-268
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• 2018

Sludge transporting pipes in wastewater treatment plant are easy to be clogged with struvite when the digested sludge and dehydrated filtrate are transported through the pipes, which lowers the efficiency of sludge treatment system in a WWTP. pH is one of the most important factors in struvite formation, and carbon dioxide separated from biogas can be used to control pH and struvite formation. By controlling pH, the amount of dehydrating agent can be reduced by about 10%, which saves the budget for facility maintenance. As $CO_2$ is reused and dehydrating chemicals are saved, the approach can contribute to global warming gas reduction.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.689-695
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• 2004

Electrocoagulation has been suggested as a promising alternative to conventional coagulation. The process is characterized by reduced sludge production, no requirement for chemical use, and ease of operation. However, this coagulation has scarcely been studied in water purifying process. This study was performed several batch experiments to compare turbidity removal between electrocoagulation and chemical coagulation. In addition, characteristics of floe were evaluated with zeta potential and particle size distributions. Electrocoagulation showed a relatively higher removal of turbidity (approximately 5%) with the same aluminum amount than conventional chemical coagulation. In addition, turbidity removal by electrocoagulation was less sensitive to pH and was greater for more extensive pH range than chemical coagulation. The results of zeta potential and floc size distributions illustrated that electrocoagulation provided the preferable conditions for coagulation such as zeta potential close to zero millivolt and increased portions of particles in the range of 40 and $100{\mu}m$.

• Journal of Environmental Health Sciences
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• v.27 no.3
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• pp.49-56
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• 2001

The water quality simulation was carried out to predict water quality in Tan stream of the Han river using water quality model, QUAL2E. In the end, the future variations in water quality of Tan stream were simulated and the prediction of the impacts of Tan stream on water quality in the Han river was carried out by applying the Tan stream simulation results into the model. The results are as follows. The predicted results of future water quality of Tan stream suggested that the concentrations of BOD, T-N and T-P at Chungdam bridge would increase to 0.68~0.77 mg/$\ell$, 1.33~1.62 mg/$\ell$ and 0.05~0.06 mg/$\ell$, respectively in 2006 and 2011 and that with the implementation of advanced treatment in Sungnam and Tanchun sewage treatment plants, the concentration of T-N would be reduced more as the amount of treated sewage increase, while the concentration of T-P would stay 0.49 mg/$\ell$. The results obtained from simulation of the impacts of future Tan stream water quality improvement on the main stream of the Han river showed that with implementation of advanced treatment in both Sungnam and Tanchun sewage treatment plants, the concentration of T-N, T-P and chlorophyll-a at Hangang bridge and Heangju bridge would be reduced by 11.6%, 7.7% and 20.9%, respectively in 2..6 and by 13.6%, 9.4% and 22.2%, respectively in 2011, which indicates that the effect on the reduction of T-N and T-P would be relatively significant while the effect on the decrease of algae would be slight.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.487-497
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• 2001

Investigated data on Lake Okjeong were used for the simulation of water quality. According to the simulation results, the effective scheme of water quality management on reservoir has been proposed. It has been recognized that the water quality of Lake Okjeong is under eutrophic and mesotrophic condition even though there are seasonal variation. The water quality of lake is mainly affected by the inflow of pollutant load from watershed. Therefore, to estimate and quantify the accurate amounts of pollutants flowing into reservoir is absolutely necessary for the effective management of water quality on Lake Okjeong. When the pollutant load measured during 7 different rainy periods in 1999 was compared with total pollutant load in 1999. TN and TP measured during 7 different rainy periods showed almost 50% of total pollutant load. In case of SS, it was 72.8%. On the other hand, the rainfall amount measured during the 7 different rainy periods was about 17.5% of total rainfall amount in 1999. Release rate of TP shows 11.92 mg/L at fish farm site and 0.2∼1.9 mg/L at monitoring station of water quality on Lake Okjeong, and which is considered to be less than that of other foreign reservoirs under the circumstances of anoxic condition. For the effective management of water quality on Lake Okjeong. WASP5 water quality simulation model has been applied and verified, and the verified model was used to propose the effective scheme of water quality management. In this case, 6 different scenarios were applied, by changing the amount of inflow of pollutant load in each subbasin. The most effective scheme has turned out that pollutant load generated from Imsil and Gwanchon subbasin should be reduced, and the best way to improve the water a quality is to reduce the pollutant load at every subbasin. According to the simulation result, wastewater treatment facility should be located at every subbasin.

• Transactions of the Korean hydrogen and new energy society
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• v.12 no.3
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• pp.219-229
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• 2001

Hydrogen production by a 2-step water-splitting thermochemical cycle using metal oxides (ferrites) redox pairs and $CH_4$ have been studied in this experiment. The ferrites were reacted with $CH_4$ at $700{\sim}800^{\circ}C$ to produce CO, $H_2$ and various reduced phases (reduction step); these were then reoxidized with water vapor to generate $H_2$ in water-splitting step (oxidation step) at $600{\sim}700^{\circ}C$. The reduced ferrites, Ni-FeO and Ni-Fe alloy showed respectively different reactivity for $H_2$ formation from $H_2O$. In reduction reaction at $800^{\circ}C$, carbon was deposited on surface of Ni-ferrite due to $CH_4$ decomposition. This reduced phase containing carbon, which was taken quite different feature from other phase, produced $H_2$, CO, $CO_2$ by reacting with $H_2O$ at $600^{\circ}C$. The amount of $H_2$ evolved using reduced phase containing carbon was much higher than that of other phase.

• The Journal of Engineering Geology
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• v.25 no.3
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• pp.339-347
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• 2015

Riverbank filtration has been suggested as a cost-effective method for improving water quality. However, high concentrations of Fe²⁺ and Mn²⁺ cause problems for the use of water and the maintenance of facilities. We evaluated the effectiveness and efficiency of an Fe²⁺ and Mn²⁺ removal technique based on the in situ injection of highly oxygenated water at a site on the Anseong River, between Anseong City and Pyeongtaek City, Gyeonggi Province. The removal process consists of three steps: injection, resting, and extraction. Results show that the removal efficiency increases with repeated application of the process. The amount of Fe-reduced drinking water satisfying water regulations (limit, 0.3 mg/L Fe) obtained using oxygenated water injection was five times higher than the amount of injected oxygenated water. Levels of Mn²⁺ were also reduced following the injection of oxygenated water.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.333-341
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• 2021

Irrigation scheduling is a water management strategy of applying the proper amount of water in a plant's root zone at the right time to maximize profit. We conducted an experimental evaluation of the response of soybean, sorghum, and sesame to an irrigation scheduling scheme. The soil water contents were adjusted in the root zone between 20% and 28% to reflect changes in crop water consumption. The other ones fixed at 25% during the whole growing season were compared to evaluate the effectiveness of irrigation scheduling. Surface drip irrigation (SDI) were employed as an irrigation method. For all three crops, the evapotranspiration (ET) was the greatest at flowering stage (6.93 mm), followed by vegetative growth stage (5.00 mm) and maturity stage (2.53 mm). The irrigation amount was significantly reduced by 21.8% (soybean), 22.2% (sorghum), and 16.1% (sesame), respectively, compared with the ones at constant soil water content treatment. Their water use efficiency (WUE) were also much higher than the controls: 2.65-fold increase at soybean, 1.82-fold increase at sorghum, and 1.47-fold increase at sesame. These results showed that an effective irrigation scheduling on upland crops (soybean, sorghum, sesame) could increase crop yield while minimizing water use.