• Journal of environmental and Sanitary engineering
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• v.7 no.2
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• pp.1-10
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• 1992

Since 1960's along with industrialization and urbanization, economic growth has been . achieved, however, at the same time, environmental condition has been seriously deteriorated. . Currently, volume of wastewater has been increasing at annual rate of 7% in sewage and 20% in industrial wastewater. However, the nation's sewage treatment serves only 33% of the municipal wastewater as of 1991. Major portion of air pollutants comes from combustion of oil and coal which comprise 81% of total energy use and emission gases from motor vehicles increasing at an accelerated rate. It is known that Korea generates the highest amount of waste per capta. Nevertheless, it is not sufficient to reduce the volume of waste by means of resources recovery and recycling. Recognizing the importance of global environmental problems such as ozone layer depletion, global warming and acid rain, international society has been making various efforts since the 1972 Stockholm conference. In particular, it is expected that the Rio conference which has adopted the Rio declaration and Agenda 21 will form a crucial turning point of the emerging new world order after the Cold War confrontation. To cope with such issues as domestic pollution and global environmental problems, the fundamental national policy aims at harmonizing "environmental protection and sustainable development". The Ministry of Environment has recently set up a mid-term comprehensive plan which includes annual targets for environmental protection. According to the government plan, gradual improvement of various environmental conditions and specific measures to achieve them is planned in time frame. Additional sewage treatment plants will be constructed in urban areas with the target to treat 65% of the nation's municipal sewage by 1996. Supply of clean fuels such as LNG will also be expanded starting from large cities as a cleaner substitute energy for coal and oil. In parallel with expansion of LNG, emphasis will be placed on installation of stack monitoring system. Due to the relatively limited land, government's basic policy for solid waste treatment is to develop large scale landfill facilities rather than small sized ones. Thirty three regional areas have been designated for the purpose of waste management. For each of these regions, big scale landfill site is going to be developed. To increase the rate of waste recycling the government is planning to reinforce separate collection system and to provide industries with economic incentives. As a part of meeting the changing situation on global environmental problems after UNCED, and accommodation regulatory measures stipulated in the global environmental conventions and protocols, national policy will try to alter industrial and economic structure so as to mitigate the increasing trends of energy consumption, by encouraging energy conservation and efficiency. In this regard, more attention will be given to the policy on the development of the cleaner technology. Ultimately, these policies and programs will contribute greatly to improving the current state of national public health.

• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.235-242
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• 2010

Froth flotation using the residual water in the end of flotation process has been performed through controlling of pH. IEP (isoelectric point) of molybdenite and quartz in distilled water was below pH 3 and pH 2.7, respectively and the stabilized range was pH 5~10. In case of a suspension in reusing water, zeta potential of molybdenite decreased to below -10 mV or less at over pH 4 due to residual flocculants. As result of pH control, flotation efficiency in the alkaline conditions was deteriorated by flocculation, resulting from expanded polymer chain, ion bridge of the divalent metal cations ($Ca^{2+}$), and hydrophobic interactions between the nonpolar site of polymer/the hydrophobic areas of the particle surfaces. However, the weak acid conditions (pH 5.5~6) improved the efficiency of flotation as hydrogen ions neutralize polymer chains and then weakened its function. In cleans after rougher flotation, the Mo grade of 52.7% and recovery of 90.1% could be successfully obtained under the conditions of 20 g/t kerosene, 50 g/t AF65, 300 g/t $Na_2SiO_3$, pH 5.5 and 2 cleaning times. Hence, we developed a technique which can continuously supply waste water filtered from tailings into the grinding-rougher-cleaning processes.

• Resources Recycling
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• v.22 no.5
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• pp.20-28
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• 2013

This study was carried out to evaluate the possibility of resource recovery for municipal solid waste(MSW) that sorted by a MBT system. First, physical property of MSW was similar to wastes carried into Sudokown landfill site. However, moisture of MSW was little higher than that. As a result of BMP test using organic fraction of MSW(OFMSWs), approximately 60 ~ 80 mL $CH_4/g$-VS of methane was occurred. Compared to the other studies, the value of methane is lower. It seems to be caused that high ratio of vinyl/plastic in OFMSWs. The other BMP test using sample of MBT system located in Sudokwon landfill was conducted each physical properties. According to the result of experiment, food waste makes 193 mL $CH_4/g$-VS, and paper is 102 mL $CH_4/g$-VS. However, there was not methane production in vinyl and rubber. Additionally, others that can't sort no more show 30 m $CH_4L/g$-VS of methane production. From the result of experimental data OFMSWs has high fraction of vinyl, rubber and other substance that difficult for biodegradation. Therefore it is need to sort of them.

• Resources Recycling
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• v.22 no.6
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• pp.3-11
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• 2013

This study was carried out to estimate greenhouse gas reduction potentials under treatment methods of combustible wastes excavated from closed landfill. The treatment methods of solid wastes were landfilling, incineration, and production of solid recovery fuel. The greenhouse gas reduction potentials were calculated using the default emission factor presented by IPCC G/L method of IPCC (Intergovernmental Panel on Climate Change). The composition of excavated waste represented that screened soil was the highest (65.96%), followed by vinyl/plastic (19.18%). This means its own component is similar to the other excavated waste from unsanitary landfill sites. Additionally, its bulk density was 0.74 $t/m^3$. In case of landfilling of excavated waste, greenhouse gas emission quantity was 60,542 $tCO_2$. In case of incineration of excavated waste, greenhouse gas emission quantity was 9,933 $tCO_2$. However, solid recovery fuel from excavated waste reduced 33,738 $tCO_2$ of the greenhouse gas emission quantity. Therefore, solid recovery fuel production is helpful to reduce of greenhouse gas emission.

• Resources Recycling
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• v.29 no.1
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• pp.43-52
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• 2020

The objectives of this study were to identify the optimal mix of foam concrete with the low-strength and high-flow for the repairing ground subsidence situation emergently by utilizing a large amount of industrial by-products and evaluate the possibility by applying it to the site. The factors of the experiment were the mixing ratio of mixing water and a foaming agent and the mixing ratio of foam over paste volume. The optimal mix identified by the experiment was applied to the field and basic properties were evaluated. The results of the experiment showed that the optimal mixing ratio of mixing water and the foaming agent was 10%. Moreover, when the mixing ratio of pre-foam over paste volume was 170%, it satisfied the target. However, to ensure stable quality when applying to the field, the foam mixing ratio was set 140% for the field application. The field application test of foam concrete with the low-strength and high-flow using an eco-friendly binder satisfied all target performances. Therefore, the possibility of using it as a mixture and construction method for a ground repair system is confirmed. However, there was a quality deviation between the upper part and the lower part due to the separation between foam and paste. Consequently, further studies are needed to improve it.

• Resources Recycling
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• v.29 no.1
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• pp.53-61
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• 2020

This study aimed to develop a foam concrete material for a ground repair system that has low strength and low fluidity by using an eco-friendly binder, which substitutes industrial by-products for more than 90% of cement. Basic properties were evaluated after substituting a small amount of calcium sulfo aluminate (CSA) for the binder to improve the sinking depth rate and volume change, commonly found when it had a large amount of industrial by-products. The substitution rates of CSA for the eco-friendly binder used for the foam concrete were 2.5, 5, and 10%. Fresh properties, hardened properties, pore structure, and hydrates were analyzed. Experimental results showed that using only 2.5% of CSA could improve the deep sinking depth which occurred when using an eco-friendly binder. As a result, the weight difference between the upper, middle, and lower parts of cast specimens was improved even after being hardened. The addition of CSA also contributed to the formation of small, uniformly sized closed pores and improved initial strength. However, when the proportion of CSA increased, the long-term strength decreased. However, it satisfied the target strength when 5% or less of CSA was used. The results of this study revealed that it was possible to manufacture foam concrete with low strength and high fluidity for repairing ground satisfying target qualities by adding 2.5% of CSA to the eco-friendly binder containing a large amount of industrial by-products.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.1
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• pp.77-85
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• 2019

Biogasification is a technology that uses organic wastes to reproduce as environmental fuels containing methane gas. Biogasification has attracted worldwide attention because it can produce renewable-energy and stable land treatment with prohibit from landfilling and ocean dumping of organic waste. Biomethane is produced by refining biogas. It is injected into natural gas pipeline or used transportation fuel such as cars and buses. 90 bio-gasification facilities are operating in 2016, and methane gas production is very low due to it is limited to organic wastes such as food waste, animal manure, and sewage sludge. There are seven domestic biomethane manufacturing facilities, and the use of high value-added such as transport fuels and city-gas through upgrading biogas should be expanded. On the other hand, the rapid biogasification of organic wastes in domestic resulted in frequent breakdowns of facilities and low efficiency problems. Therefore, the problem is improving as technical guidance, design and operational technical guidance is developed and field experience is accumulated. However, while improvements in biogas production are being made, there is a problem with low utilization. In this study, the problems of biomethane manufacturing facilities were identified in order to optimize the production and utilization of biogas from organic waste resources. Also, in order to present the design and operation guideline of the gas pretreatment and the upgrading process, we will investigate precision monitoring, energy balance and economic analysis and solutions for on-site problems by facility.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.2
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• pp.57-66
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• 2019

This study carried out on-site investigation and precision monitoring to prepare proper design and operation technical guidelines for the use of bio gas in organic waste resources (fertilizing urine, food waste, food waste, food waste, etc.). According to the government's mid- and long-term policy on bio gasification, the expansion of waste resources is actively being pushed forward. However, facilities that use the biogas produced for urban gas and transportation are still under-efficient. Precision monitoring was carried out for biogasification facilities of organic waste resources in seven locations nationwide. When the results of precision monitoring were summarized with the four-season average, the efficiency analysis of each organic waste resource showed that the organic breakdown rate was 66.3% on average on VS basis. Analysis of biogas characteristics before and after pretreatment revealed that the $H_2S$ average of the entire facility was measured at 949.7 ppm using iron salts and desulfurization (dry, wet) and that the quality refining facility shearing and rear end was 29.0 ppm and 0.3 ppm. The methane content was found to be reduced by 65.6% at the rear of the fire tank, 63.5% at the back and 97.5% at the rear.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.2
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• pp.67-73
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• 2019

In this study, to optimize the production and utilization of biogas for organic waste resources, the precision monitoring of on-site facilities and the energy balance by facility were analyzed, and the solutions for field problems were investigated, and the design and operation guidelines for pretreatment facilities and generators were presented. Gas pre-treatment is required to solve frequent failures and efficiency degradation in operation of high quality refining facilities, and processing processes such as desulfurization, dehumidification, deoxidization, dust treatment, volatile organic compounds, etc. Since these processes are substances that are also eliminated from the high-quality process, quantitative guidelines are not presented in the gas pretreatment process, but are suggested to operate during the processing process as a qualitative guideline. In particular, dust, siloxane, and volatile organic compounds are the main cause of frequent failure of high-quality processes if they are not removed from the gas pretreatment process. Design of the biogas high-quality process. The operation guidelines provide quality standards [Methane content (including propane) of 95% or more] with 90% or more utilization of the total gas generation, two systems, and a margin of 10% or more. It also proposed installing gas equalization tank, installing thermal automatic control system for controlling equalization of auxiliary fuel, installing dehumidification device at the back of high quality for removing moisture generated in the process of gas compression, installing heat-resisting facilities to prevent freezing of facilities in winter and reducing efficiency, and installing membrane facilities in particular.

• Resources Recycling
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• v.28 no.4
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• pp.59-64
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• 2019

This study suggests a conceptual strategy and methodology for the risk assessment of the domestic abandoned mine fillers with fly ash. The fillers are composed of coal fly ash and solidification materials, and contain little toxic substances such as carbonates but also some heavy metals; therefore, those requires a risk assessment. The risk assessment should primarily focus on estimation of the effects to human health both on carcinogen and non-carcinogen aspects. The significant data such as toxicity and partition coefficients can be obtained from the national soil or mine environmental risk assessment guidelines. Accurate risk assessment of heavy metal contamination in the fillers may consume lots of time and efforts through site survey and instrumental analyses, etc. Moreover, it is inefficient to explore all of the factors as concentrations and categories in every heavy metal in the fillers, due to a high variety and complexity. Therefore, implementation of a preliminary risk assessment is suggested by using the literature data and the basic characteristics of the filler samples prior to the detailed risk assessment. Certainly, this presumes a thorough understanding of reliable sample analysis methods, exposure pathways, and relevant physicochemical and biological mechanisms.