• Journal of Korean Society on Water Environment
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• v.22 no.6
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• pp.1068-1074
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• 2006

For receiving water quality protection a control systems of urban drainage for CSOs reduction is needed. Examples in combined sewer systems include downstream storage facilities that detain runoff during periods of high flow and allow the detained water to be conveyed by an interceptor sewer to a centralized treatment plant during periods of low flow. The design of such facilities as storm-water detention storage is highly dependant on the temporal variability of storage capacity available as well as the infiltration capacity of soil and recovery of depression storage. For the continuous long-term analysis of urban drainage system this study used analytical probabilistic model based on derived probability distribution theory. As an alternative to the modeling of urban drainage system for planning or screening level analysis of runoff control alternatives, this model has evolved that offers much ease and flexibility in terms of computation while considering long-term meteorology. This study presented rainfall and runoff characteristics of the subject area using analytical probabilistic model. Runoff characteristics manifested the unique characteristics of the subject area with the infiltration capacity of soil and recovery of depression storage and was examined appropriately by sensitivity analysis. This study presented the average annual CSOs, number of CSOs and event mean CSOs for the decision of storage volume.

• Journal of Korean Society on Water Environment
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• v.36 no.1
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• pp.55-68
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• 2020

Because of the intensified environmental problems such as climate change and resource depletion, sewage treatment technology focused on energy management has recently attracted attention. The conversion of primary sludge from the primary sedimentation tank and excessive sludge from the secondary sedimentation tank into biogas is the key to energy-positive sewage treatment. In particular, the primary sedimentation tanks recover enriched biodegradable organic matter and anaerobic digestion process produces methane from the organic wastes for energy production. Such technologies for minimizing oxygen demand are leading the innovation regarding sewage treatment plants. However, sewage treatment facilities in Korea lack core technology and operational know-how. Actually, the energy potential of sewage is higher than sewage treatment energy consumption in the sewage treatment, but current processes are not adequately efficient in energy recovery. To improve this, it is possible to apply chemically enhanced primary treatment (CEPT), high-rate activated sludge (HRAS), and anaerobic membrane bioreactor (AnMBR) to the primary sedimentation tank. To maximize the methane production of sewage treatment plants, organic wastes such as food waste and livestock manure can be digested. Additionally, mechanical pretreatment, thermal hydrolysis, and chemical pretreatment would enhance the methane conversion of organic waste. Power generation systems based on internal combustion engines are susceptible to heat source losses, requiring breakthrough energy conversion systems such as fuel cells. To realize the energy positive sewage treatment plant, primary organic matter recovery from sewage, biogas pretreatment, and co-digestion should be optimized in the energy management system based on the knowledge-based operation.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.5
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• pp.571-577
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• 2016

Phosphorus is an essential and irreplaceable element for all living organisms and its resource is limited. Significant amount of used phosphorus is collected in sewage treatment plant as sludge. Sludge ash after incineration contains about 10% of phosphorus in dry mass basis, which is comparable to phosphate rocks, and it is an important source of phosphorus recovery. Acid and alkali were used to leach phosphorus from sludge ash and compared for their leaching kinetics and performance. Phosphorus leaching by NaOH was fast and 0.2 N and 2 N NaOH leached 49% and 56% of the total phosphorus in the sludge ash at the L/S ratio of 100. Phosphorus leaching by sulphuric acid and hydrochloric were very fast and most of the phosphorus was leached in 5 minutes. In case of sulphuric acid 95% of the total phosphorus in the sludge ash was leached by 0.2 N at the L/S ratio of 100 and 93% was leached by 1 N at the L/S ratio of 10. 1 N hydrochloric acid leached 99% of the total phosphorus at the L/S ratio of 10. The results showed acids were more effective than alkali for phosphorus leaching from sludge ash and hydrochloric acid leached more phosphorus than sulphuric acid.

• Journal of the Korean GEO-environmental Society
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• v.14 no.10
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• pp.5-9
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• 2013

Electrokinetics technology is proposed for improving the recovery metals ion and oil from clay-sandy soil. In order to restore or extract them from clay-sandy soil, the gas produced by anode chamber is re-injected to the clay-sandy soil(sample). Samples produced in this study were completed to verify the proposed performance for 7 days by gradually increasing the pressure to the final pressure of 30psi($2.11kgf/cm^2$) through the compression process. Before compression, the copper rings were inserted into the sample, allowing us to observe the changes in appearance of copper ring after the end of the experiment. In this study, pressurized module and non-pressurized module were tested, respectively. The condition of test is a continuous process and the voltage gradient is 2V/cm during 24 hours. As a result, the efficiency of pressurized module is better than non-pressurized module.

• Resources Recycling
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• v.14 no.5 s.67
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• pp.54-61
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• 2005

In 2006, the coal usage that is used as energy source of power plant will meet 16,000 MW which is 30% of the whole energy usage. A Coal deposits among the fossil fuels is very plentiful in natural resources and has high economical efficiency but application technique is very inconvenient. Also when burned for utilization, it generate various toxic and untoxic air pollution materials; fly ash, bottom ash, sulfurous acid gas etc. In this study, we could establish a preparation of clean coal by triboelectrostatic separation. In this study, we made a bench-scale's triboelectrostatic separation equipment using electrostatic technology, and got an optimum conditions of various factors for increasing recovery rate and purification in separation. A test result, we got a clean coal that recovery rate is 68.10%, rejection rate of ash and sulfur content is 31.23% and 28.33%.

• Resources Recycling
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• v.14 no.2
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• pp.43-55
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• 2005

As world population increases and the world economy expalds, so does the demand for natural resources especially strategic metals such as cobalt. An accurate assesment of the nation's minerals must include not only the resources available in the ground but also those that become available through recycling. In this paper, data on domestic and international supply of cobalt and its applications by end-user were analyzed for stable security of cobalt resources and effective recycling of cobalt scraps. Also, an initial evaluation of the flow of cobalt-containing materials in the United States was prepared. In 2003, 8,000 metric tons of cobalt were consumed in the United States and an estimated 28% of U.S. cobalt supply was derived from scrap. The superalloy industry and catalyst industries have well-established recycling or cobalt recovery practices. Recycling rates of cobalt scraps from magnet alloy and cemented carbide were relatively low.

• Resources Recycling
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• v.22 no.4
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• pp.33-37
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• 2013

A study on the removal of arsenic from gold concentrate was conducted using thermal decomposition method at $700^{\circ}C$ as a function of reaction time. In addition, the arsenic removed from the concentrate was also collected in the bag-filter as a form of AsS. The content of arsenic in the concentrate was dramatically decreased from 12.62 wt/% to 1.40 wt.% for 1 hour and even lower than 1 wt.% after two hours. The removal efficiency of arsenic was finally achieved to be about 95% after 2 hours at a given temperature.

• Resources Recycling
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• v.31 no.6
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• pp.18-24
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• 2022

Dry reduction using natural gas was proposed to recover tin from waste tin oxide generated in a tin bath that was used for controlling the smoothness of architectural glass during production, and the reduction behavior was investigated. The utilized vertical natural gas dry reduction system is capable to process 4 L or 20 kg depending on input raw materials. The system was established by applying the upper intake and lower discharge method. The recovery rate was 97.2% at 800 ℃ and 4 sccm flow rate and increased with the amount of input gas. Hydrogen accounted for 23% of the discharge gas, showing a 16.6% hydrogen conversion rate. The reaction behavior of tin recovered via natural gas reduction provides basic data on the new waste resource reduction/recovery technology.

• Journal of Digital Convergence
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• v.20 no.3
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• pp.377-388
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• 2022

Various researches are actively studied to satisfy exponentially increasing the usage of the Internet as well as the diverse service demands. Especially the Optical Internet that delivers several Tbps through a single optical fiber requires the intelligence to satisfy the various types of survivability requirements. In the paper, a novel recovery scheme that satisfies the various restoration demands in IP over WDM networks is proposed. The scheme classifies the restoration services into three classes and applies dedicated protection and shared restoration scheme with different priorities for each class. Also, a configuration scheme for information database to support the scheme is proposed. This scheme satisfies the different degree of restoration demands in terms of restoration time, blocking rate and resource usage. With the scheme, medical data can be transmitted without loss.

• Journal of People, Plants, and Environment
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• v.22 no.6
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• pp.575-582
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• 2019

Moss is used as an important material in indoor landscaping as well as outdoor landscaping. Moss is vivid green during growth and excellent in ornamental value. But when temperature drops, moss stops growth, turns brown or loses its ornamental value. In the present experiment, for the purpose of classifying native mosses according to the growth response to low temperature, the temperature of the plant growth chamber was set to 15℃/5℃ (16h/8h, day/night) and 5℃ (24h) for 8 weeks using nine native moss species. Thereafter, the temperature of the plant growth chamber was set to 20℃, and then the changes of moss block area and moss color were measured. The changes of moss block area and moss color were measured using a Photoshop program, after each moss block was photographed. As a result, Atrichum undulatum (Hedw.). Beauv., Etodon luridus (Griff.) A. Jaeger, Bachythecium plumosum (Hedw.) Schimp, Plagiomnium cuspidatum (Hedw.) T.J. Kop, and Hypnum plumaeforme Wilson showed a small decrease in moss block area at low temperature, and their recovery were the fastest at 20℃. These three species had higher green values at low temperature compared to other species, and the greenness increased rapidly at 20℃. On the other hand, Atrichum undulatum (Hedw.). Beauv., Marchantia polymorpha L., and Thuidium cymbifolium (Mitt.) A. Jaeger showed the smallest block area at low temperature and the lowest recovery even at 20℃. Their green values also decreased significantly at low temperature, and maintained low green value even at 20℃. These results showed that these three moss species are sensitive to low temperature. The remaining Myuroclada maximowiczii, Plagiomnium cuspidatum, and H. erectiusculum showed moderate responses to low temperature compared to other six species of mosses.