• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.1
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• pp.98-103
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• 2010

This study was carried out on the composting of the most part of the plant waste materials inflowed-drifting into the dam during the localized heavy rain and the rainy season, due to the abnormal climate change, and for the sewage sludge banned to dispose legally into the ocean from the year of 2012. It was analysed the distinctive physicochemical qualities of the compost with treatment S-1(dam suspended particle sawdust : oak tree bark : sewage sludge : chicken manure = 30 : 20 : 40 : 10) and treatment S-2(dam suspended particle sawdust : oak tree bark : sewage sludge : chicken manure = 30 : 30 : 30 : 10). Both S-1 and S-2 maintained for 10 days at above $65^{\circ}C$ of the compost pile temperature, and the most of its pathogen were destroyed. In case of pH, until the 90th day into composting, S-1 with the pH value of 7.78 was slightly higher than S-2. The C/N value of S-1 was 15.3 and that of S-2 was 16.9. The quality of its final product was satisfied to the manufacture-standards. The GI value of S-1 was 91 higher than that of S-2, which was 84. In conclusion, it is highly recommendable to manufacture S-1 for its frequent usage of dam suspended particle sawdust and sewage sludge, and for its excellent quality and safety.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.457-465
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• 2013

This study discussed the influence of mixtures and curing conditions on the development of strength and microstructure of RPC using ternary pozzolanic materials. Through pilot experiment, various RPC was manufactured by adding single or mixed ternary pozzolanic materials such as silica fume, blast furnace slag and fly ash by mass of cement, up to 0~65%, and cured by using 4 types of method which are water and air-dried curing at $20^{\circ}C$, steam and hot-water curing at $90^{\circ}C$. The results show that the use of ternary pozzolanic materials and a suitable curing method are an effective method for improving development of strength and microstructure of RPC. The unit volume of cement was greatly reduced in RPC with ternary pozzolanic materials and unlike hydration reaction in cement, the pozzolanic reaction noticeably contributes to a reduction in hydration heat and dry shrinkage. A considerable improvement was found in the flexural strength of RPC using ternary pozzolanic materials, and then the utilization of a structural member subjected to bending was expected. The X-ray diffractometer (XRD) analysis and Scanning Electronic Microscope (SEM) revealed that the microstructure of RPC was denser by using the ternary pozzolanic materials than the original RPC containing silica fume only.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.105-115
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• 2010

In this study, as one of solutions associated with the shortage of treatment area of industrial waste and the containment of its harmful components, the bottom ash which is known to be by-products of thermoelectric power plant was selected and its applicability for aggregate of concrete mixture was measured. Hardness test, sieve analysis, water-absorption test and SEM analysis were carried out to investigate the possibility of using bottom ash as a replacement of coarse and fine aggregate. Chemical analyses such as ignition loss test and X-ray incidence were carried out also. In addition, values for slump, strength, permeability, freeze and thaw, and carbonation were evaluated in terms of effects of replacement ratio of bottom ash. As the results, it was found that, though bottom ash is in short supply of fine particles and is in lack of cohesion, these problems can be solved by partially mixing with natural aggregates or improving in a process of production. In addition, bottom ash has not only advantage of durability but also acquirement of general compressive strengths in case that a certain proportion of natural aggregate is applied to mixture, in spite that unit water or chemical admixture should be increased to acquire good workability due to plenty of porosity.

• Environmental Analysis Health and Toxicology
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• v.23 no.1
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• pp.53-62
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• 2008

In the present study, the concentration levels of polychlorinated biphenyls (or PCBs) in the environments in Korea are estimated based on some measured data in Korea, in comparison with the data from the other countries. Even though PCBs were banned as electrical fluids in 1970s in Korea, PCBs are still detected in the environment. PCBs levels in Korea are greatly lower than those in other countries, which are gradually decreased as well. However, the measured data are not sufficient in both numbers and quality, to estimate the average PCBs levels in Korea. The regulation limit on polychlorinated biphenyls (or PCBs) is 2mg/kg (ppm), which is too low compared to 50 ppm of many other countries including U.S. With this strict regulation, there are many problems expected, for example, in the analysis of PCBs in the transformers using in the field as well as the safe treatment of PCBs. The risk assessment on the PCBs in the environment is surely necessary prior to the change in the limit. Also the PCBs concentration monitoring in the environmental media (i.e. air, water, soil and sediment) and exposure assessment will be essential for the accurate risk assessment. If the PCB-waste guideline maintain as 2 ppm after 10 years, the excess cancer risk of PCBs exposure by ambient air, drinking water and soil was $10^{-8}$. But if the guideline mitigate as 50 ppm after 10 years, the cancer risk was increased by $10^{-7}$. The ecological risk quotient by regulation change was not exceed '1'.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.385-388
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• 2008

Recycled fine aggregate has low quality because it contains large amount of old mortar. So, its usage is limited to a lower value-add, such as the roadbed material etc. Also, alkaline water occurred from treatment process of the waste concrete is becoming the cause of environmental problem. Accordingly, this study is to develop on the high quality recycled fine aggregate produced by low speed wet abraser using sulphuric. We investigated the properties of compressive strength of the mortar which was manufactured using recycled fine aggregate containing calcined gypsum produced by earlier mentioned process. Test results indicate that concrete using recycled fine aggregate containing calcined gypsum is higher compressive strength than concrete using other sands.

• Korean Journal of Environmental Agriculture
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• v.33 no.2
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• pp.78-85
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• 2014

BACKGROUND: Recent studies using various industrial wastes for heavy metal stabilization in soil were conducted in order to find out new alternative amendments. The acid mine drainage sludge(AMDS) contains lots of metal oxides(hydroxides) that may be useful for heavy metal stabilization not only waste water treatment but also soil remediation. The aim of this study was to investigate the applicability of acid mine drainage sludge for heavy metals stabilization in soils METHODS AND RESULTS: Alkali soil contaminated with heavy metals was collected from the agricultural soils affected by the abandoned mine sites nearby. Three different amounts(1%, 3%, 5%) of AMDS were applied into control soil and contaminated soil. For determining the changes in the extractable heavy metals, $CaCl_2$ and Mehlich-3 were applied as chemical assessments for metal stabilization. For biological assessments, lettuce(Lactuca sativa L.) and chinese cabbage(Brassica rapa var. glabra) were cultivated and accumulation of heavy metals on each plant were determined. It was revealed that AMDS reduced heavy metal mobility and bioavailability in soil, which resulted in the decreases in the accumulation of As, Cd, Cu, Pb, and Zn in each plant. CONCLUSION: Though the high level of heavy metal concentrations in AMDS, any considerable increase in the heavy metal availability was not observed with control and contaminated soil. In conclusion, these results indicated that AMDS could be applied to heavy metal contaminated soil as an alternative amendments for reducing heavy metal mobility and bioavailability.

• Journal of the Korea Organic Resources Recycling Association
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• v.7 no.2
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• pp.57-64
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• 1999

The purpose of this study is to establish effective conditions for controlling $CH_4$, $N_2O$ emission from organic Waste / wastewater treatment processes. Continuous and batch experiments were conducted to treat the micro algae from polluted and eutrophicated lakes through the thermophilic oxic process. The microalgae used were mainly Microcystis sp.(collected from eutrophic lake) and Chlorella sp. (cultured in laboratory) Wasted cooking oil was added by aid-heating source. Physico-chemical components of sludges and microalgae were analyzed. In batch experiments, air supply was changed from 50ml/min to 150ml/min. The temperature. water content and drained water were affected by the air flow rate at initial stage. However, there was almost no influence of air flow rate on them in middle and last stages. At air flow rate of 100ml/min, the degradation rate of organic material was higher than that at other air flow rates. $CO_2$ concentration in exhaust was proportional to the strength of aeration, especially at initial stage when degradation was active. $CH_4$ with low concentration was detected only at starting stage when air diffusion was not enough. $N_2O$ production was not affected by variation of air supply. In continuous experiments no matter what the dewatering methods (with PAC and without PAC) and media (wood chip and reed chip) were changed, $N_2O$ was almost not affected by variation of injected air. Result showed that the reed chips using for lake purification could be used as media for thermophilic oxic process in lake and marshes area. $CO_2$ concentration was not so much affected by the change of dewatering methods and media types. $CH_4$ was not detected in the experimental period. So it can be shown that the thermophilic oxic process had been well operated in wide handling conditions regardless of media and dewatering methods.

• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.237-245
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• 2005

The batch tests were performed to evaluate the applicability of the permeable reactive barrier (PRB) to in-situ treatment of groundwater with high concentration of heavy metals. The lead\chates used in this study were collected from waste rock dump of the Imgy mine, and have a low pH and high metal concentration. The acidity loading was 65kg as $CaCO_3/day$, metal loading of Fe+Al+Mn was 11.6kg/day. This type of water could be treated with biological-mediated sulfate reduction using the organic carbon mixture as a reactive media. The batch tests were carried out with five mixtures that were composed with different mixing ratios of mushroom compost, pine-tree bark, and limestone cheep. Results indicated that the PRB could reduce the acidity loading $CaCO_3/day$ to 12.3kg and reduce the metal loading to 3.3kg/day. Considering about the low pH and high metal loading, the contaminated water may be ameliorated by passing it through the buffering PRB composed with inorganic carbonate materials and then through the PRB composed with the organic carbon mixture which can induce sulfate reduction.

• Journal of environmental and Sanitary engineering
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• v.13 no.3
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• pp.148-157
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• 1998

Leachate is a result of the percolation of precipitation, uncontrolled runoff, and irrigation water into the landfill and can also include water initially contained in the waste as well as infiltrating groundwater. Behaviour of leachate by rainfall was studied to evaluate the variation of leachate generation and contaminants by rainfall in Sudokwon Landfill from January 1998 to October 1998. The quantity of leachate generated was measured with a flow meter, and the concentrations $BOD_5$, CODcr, T-N, $NE_3-N$, SS of leachate were also measured. Principal outcome obtained in this study are as follows : the quantity of leachate generated was the highest on August, the highest leachate generation volume in this period was 11,913㎥ and the lowest was $6,261m^3$. Although the similar amount of precipitation of 80mm applied to the two samples, there were difference in leachate generation due to precipitation duration, precipitation frequency, wet condition of solid wastes. As the result of regression analysis, the correlation coefficients(r) between the quantity of leachate generated and precipitation were 0.823, 0.976 between $BOD_5$ and CODcr, 0.992 between T-N and $NE_3-N$. As the quantity of leachate generated increased 48%, the concentration of $BOD_5$ and CODcr decreased 51% and 50% respectively. Therefore it was showed that the pollutant concentrations in leachate were diluted by precipitation. The concentrations of $BOD_5$ and COBcr in the rainy season were 2000~4000mg/1, 4000~6000mg/1 respectively, and 1000~3000 mg/1, 3000~5000 mg/l in the dry season. The loading of SS, $BOD_5$, CODcr(kg/month) on July was increased by 2.9 times, 2.8 times, 2.2 times with a basis on March. Therefore countermeasure of treatment facilities according to increase of loading by rainfall in summer is necessary.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.485-488
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• 2008

Recycled fine aggregate has low quality because it contains large amount of old mortar. So, its usage is limited to a lower value-add, such as the roadbed material etc. Also, alkaline water occurred from treatment process of the waste concrete is becoming the cause of environmental problem. Accordingly, this study is to develop on the high quality recycled fine aggregate produced by low speed wet abraser using sulphuric. We investigated the properties of compressive strength of the mortar which was manufactured using recycled fine aggregate containing calcined gypsum produced by earlier mentioned process. Test results indicate that mortar using recycled fine aggregate containing calcined gypsum has lowest compressive strength. It seems that low compressive strength is closely associated with the expansion of the specimen by excessive formation of ettringite.