• Korean Journal of Materials Research
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• v.9 no.12
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• pp.1170-1175
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• 1999

The microstructures and mechanical properties of $Si_3N_4$ ceramics produced by nitridation and post-sintering using semiconductor-waste-Si sludge were investigated. Lots of microcracks were observed in the waste-Si powders which contained some amounts of amorphous $SiO_2$. The nitridation rate of waste-Si compacts showed lower value than that of commercial Si powder compacts. The nitridation rate was increased with increasing nitridation temperature and then the percent of nitridation at 1470$^{\circ}C$ showed 98%. The phases of $Si_3N_4$ in the reaction-bonded bodies were mixed with ${\alpha}$ and ${\beta}$-type, and small amounts of $Si_2N_2O$ phase while those after post-sintering were ${\beta}$-$Si_3N_4$ and ${\alpha}$-Sialon. The sample post-sintered at 1950$^{\circ}C$ showed the fracture toughness of 5.6 $^MPa{\cdot}m^{1/2}$ and the fracture strength of 497 MPa which were lower than those of sintered body using commercial Si powder possibly due to the formation of ${\alpha}$-Sialon phase.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.82-88
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• 2007

The objective of this study is to examine the effect of the waste oyster shell powder as the addition agent in bulking sludge thickening of paper manufacturing plant using DAF(Dissolved Air Flotation) and gravitational sedimentation. The effect of parameters such as dosage and size distribution of oyster shell were examined. The results showed that the optimum dosage of mixed oyster shell(size range : $\sim250{\mu}m$) was 0.8 g/L. The oyster shell addition of 5.0 g/L in sedimentation process was increased thickening concentration of 3.25 times. When 5.0 g/L of oyster shell was added in DAF process, water content of sludge was decreased from 95.5% to 82.7% in dewatering process using Buchner funnel test device. When size of oyster shell was divided four ranges($\sim53{\mu}m$, $53\sim106{\mu}m$, $106\sim150{\mu}m$, $150\sim250{\mu}m$), optimum size range for the flotation and dewatering was $53\sim106{\mu}m$.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.302-309
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• 2020

This paper is a basic study for applying the dried recycled sludge of waste sludge generated in construction waste intermediate treatment facility and the crushed recycled glass aggregate of waste glass bottles that cannot be recycled to the recycled cold asphalt mixtures. This paper reviewed the characteristics of recycled cold asphalt mixtures using recycled sludge and recycled glass aggregate. As a result, as contents of recycled sludge and recycled glass aggregate increased, the Marshall stability, indirect tensile strength, and tensile strength ratio of the recycled cold asphalt mixtures decreased, but flow and void ratio of that increased.

• Journal of the Korean GEO-environmental Society
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• v.17 no.8
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• pp.5-15
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• 2016

As the increase of domestic sewage treatment plant and reinforcement of the standard of effluent water quality continues, the volumes of sewage sludge are consistently increasing. Existing treatment of sewage sludge, such as incineration and ocean dumping has been prohibited because of air pollution and prohibitions towards ocean dumping, and in turn, recycling and energy recovery from waste methods have being studied recently. However, the lack of technical level and systematic analyses of application technique are problems, that future analysis of such relative technique would be required. The present study has been investigated as follows, management technique of sludge, patent on refuse-derived fuel and increase biogas production and utilizable technology, trend of research paper. Furthermore, research development from five developed nations (Korea, Japan, China, United States, and United Kingdom), domestic and foreign have been investigated and analyzed by section. In this study, the future technical field which is required for effective management of sludge has been suggested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.16-23
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• 2018

Alternative technologies for sludge treatment and disposal need to be developed urgently because the amount of produced production has increased continuously. In this study, Pulsed Electric Fields (PEF) technique was applied for sludge solubilization and the performance was evaluated. The PEF equipped with electrodes coated by epoxy resin and teflon was inducted to the activated sludge suspension, and the effect of the coating materials on the solubilization was determined. In addition, the effect of the applied voltage on the solubilization yield was investigated as the applied voltage was increased from 6 to 12 and 15 kV. Sludge solubilization was not observed when the epoxy-coated electrode was used for PEF induction regardless of the applied voltage. However, sludge solubilization occurred when 12 and 15 kV were applied to the teflon-coated electrodes. The MLSS decreased to 9%, and the soluble-COD increased to 496% when the applied voltage was 15 kV. But sludge solubilization did not happen under 6 kV condition. The corona discharge was observed at applied voltages of 12 and 15 kV, (Ed- sorry but I cannot understand the following highlight) but if 6 kV, strongly indicating that the corona discharge make the sludge solubilized, which suggests that the critical voltage for sludge solubilization lies between 6 and 12 kV. Consequently, proper selection of electrode-coating materials and the applied voltage of PEF could lead to sludge solubilization by corona discharge.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.4
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• pp.325-332
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• 2010

This study was conducted with the experiment of solubilisation of excess sludge by microbubble ozone process. To improve ozone contact efficiency, microbubble ozones which its diameter were the avearge 30 ${\mu}m$, microbubble size less than 40 ${\mu}m$ occupied about over 90% of all. In treating sludge using microbubble ozones, in case microbubble ozones are injected at microbubble ozone dosage of 0.34 g $O_3/g$ SS or less regardless of sludge concentration, microbubble ozone consumption rate was found to be 100% with no emission of waste ozones. In treating sludges by each concentration, in case the initial SS concentration of sludge is set to 6,447 mg/L, 5,557 mg/L, 3,180 mg/L, 1,092 mg/L and 515 mg/L, the amount of removed SS tended to increase with increase in initial SS concentration for the same microbubble ozone dosage, and treatment of sludge with high initial SS concentration was effective in raising the oxidation efficiency of microbubble ozones. On the other hand, as a result of reviewing acid, alkali and microbubble ozone treatment as composite treatment of sludge, use of acid treatment for the pre-treatment of microbubble ozone was more effective than alkali treatment, and in case of treatment at microbubble ozone dosage 0.05g $O_3/g$ SS with the concentration of sulfuric acid infused in the sludge, the amount of removed SS, 153.9 g, was 1.9 times more than 81.2 g the amount of single treatment of microbubble ozone.

• Resources Recycling
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• v.13 no.3
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• pp.12-18
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• 2004

A study on the enhancement of the dewaterability of sewage sludge was carried out by using the sea waste materials as a dewatering aid. It was made from a starfish and a shell by heating at $105∼700 ^{\circ}C$ and centrifuge and belt press were used as a mechanical dewatering process. The moisture content of sludge cake was reduced by 15∼22% (w/w) after addition of the dewatering aid at the dose of 1∼8 g/100mL of digested sludge. CST (capillary suction time) was measured to evaluate the effect of dewatering aid on sludge dewatering properties. CST was reduced after addition of a shell while increased after addition of a starfish. Enhancement of dewaterability after addition of a shell was better than that of a starfish. The heating temperature effect of the dewatering aid on dewaterability was not clear.

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1138-1142
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• 2002

Slag cement and supersulfated slag cement were fabricated by mixing blast furnace slag and ordinary portland cement and adapted to solidify/stabilize heavy metal contained hazardous waste sludge. In case of slag cement, it showed continuous increase of their compressive strengths, which is attributed to the formation of the C-S-H, ettringite and monosulfate with STS sludge. However, BF and COREX sludge has a different shape and composition. therefore, adequate compressive strength could not be achieved with this slag cement. In case of the mixture of the each sludge like the STS-BF or the STS-COREX, the compressive strength over the standard level for disposing the wastes could be obtained with slag cement. The supersulfated slag cement that contain accelerators was very effective in solidifying the COREX sludge, which was difficult to solidify using different cement and obtained high compressive strength only for 3 days.

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.195-203
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• 2012

Recycling method of waste LCD glass is the essential process for developing the total recycling process of LCD pannel. Pulverizing of LCD glass, determination of proper carbonacious foaming agent, the properties of residue from the recovery of valuable materials through an acid leaching process and the feasibility for the foaming of the residue obtained from leaching for indium and tin recovery were investigated for the developing of recycling method of waste LCD glass as industrial feed materials, such as heat insulation materials, sound absorbing materials, carrier of water treatment. Waste LCD glass could be pulverized finely for foaming process. Natural graphite was proper agent for foaming of the residue and the foaming technology of LCD glass would be effective recycling alternatives.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.7
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• pp.694-699
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• 2008

Considering the severe regulation associated with sludge treatment such as direct landfill and ocean dumping, there is no doubt in that an advanced study for the proper treatment of sludge is urgently needed in near feature. As one of viable method for sludge treatment, fry-drying of sludge by waste oil has been investigated in this study. The fundamental mechanism of this drying method lies in the phenomenon of rapid moisture escape in the sludge pore toward oil media. This is caused by the severe pressure gradient formed by the rapid oil heating between sludge and oil. As part of research effort of fry-drying using waste oil, a series of basic study has been made experimentally to obtain typical drying curves as function of important parameters such as drying temperature, drying time, oil type and geometrical shape of sludge formed. Based on this study, a number of useful conclusion can be drawn as following. The fry-drying method by oil immersion was found quite effective in the removal efficiency of sludge moisture, in general, the moisture content decreases significantly after 10 minutes and the whole moisture content was less than 5% after 14 minutes regardless of the drying temperature. The increase of oil temperature up to 140$^{\circ}C$ favors significantly for the removal of moisture but there was no visible difference above 140$^{\circ}C$. As expected, the decrease of diameter in sludge was efficient in drying due to the increased surface area per unit volume. Further, the effect of oil property by the change of oil type was noted. To be specific, for the case of engine oil the efficiency was found to be remarkably delayed in moisture evaporation compared with that of vegetable oil due to the increased viscosity of engine oil. It produced a result of increasing the evaporation of moisture largely relatively high in the drying temperature over 140$^{\circ}C$ compared with the drying temperature 120$^{\circ}C$ drying temperature as the drying time passed. Accordingly, the drying temperature is considered desirable as keeping over 140$^{\circ}C$ regardless of a sort of used oil.