• Korean Journal of Environmental Agriculture
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• v.29 no.3
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• pp.232-238
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• 2010

The objective of this study was to investigate a small sewage treatment system. This system was developed to improve a nitrogen and phosphorus removal efficiency and generate less solid using upflow septic tank(UST) - aerobic filter(AF) system. The UST equipped with an aerobic filter, the filter was fed with both raw sewage and recycled effluent from the UST to induce the denitrification and solid reduction simultaneously. Overall removal efficiencies of COD and total nitrogen(TN) were above 96% and 73% at recycle ratio of 200%, respectively. Critical coagulant dose without the biochemical activity was found to be 40 mg/L. Removal efficiency of total phosphorus(TP) in influent was above 90% by chemical and biological reactions. Although the phosphorus concentration was low under the high alkalinity in raw sewage, the pH value was unchanged by the coagulant dose.

• Journal of the Korea Organic Resources Recycling Association
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• v.21 no.2
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• pp.71-78
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• 2013

This study examined the feasibility of phosphorus removal from dewatering centrate/filtrate in wastewater treatment by struvite formation. Since dewatering centrate/filtrate obtained after anaerobic digestion contains a high content of ammonia, magesium addition and pH adjustment could remove phosphorous. The optimum magnesium dose, reaction time, settling time, and pH value was found at 2 mol Mg/mol $PO_4^{3-}$, 10 min, 120 min, and 8.5, respectively. A bench-scale continuous operation at the optimum condition showed 80% of total phosphorus removal and 82% of phosphate removal in dewatering centrate. The elemental composition and crystal structure of the chemical precipitate was similar to the reported values of struvite.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.283-290
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• 2002

Generally polymer mortar and concrete using unsaturated polyester resin has high strengths and good chemical resistance. However it also has high brittleness and because of this reason, it is not used for the purpose that demands high resistance to impact. The purpose of this study is to improve the brittleness of unsaturated polyester mortar(UPE mortar) which could be used for the flooring material with recycled aggregates and UPE. Polyurethane liquid rubber(PU) and recycled aggregates were used to complement the brittleness and to recycle the resources respectively. The characteristics of mortar were investigated according to the molecular weight and substitution rate of PU. As the molecular weight and PU substitution rate were increased, the viscosity was increased, working life became fast and curing shrinkage was reduced. Compressive and flexural strengths were also reduced but tile brittleness was improved. Therefore, it is seemed that the improved WE mortar could be obtained by using polyurethane liquid rubber with the polyol of molecular weight 2000, 3000.

• Journal of the Korean Ceramic Society
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• v.50 no.4
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• pp.251-256
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• 2013

Multiwalled carbon nanotubes (MWCNTs) modified with Pd and $TiO_2$ composite catalysts were synthesized by the sol-gel method followed by solvothermal treatment at low temperature. The chemical composition and surface structure were characterized by X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Photocatalytic recycle degradation experiments were carried out under both UV and visible light irradiation in the presence of MWCNT/$TiO_2$ and Pd-MWCNT/$TiO_2$ composites. As expected, the nanosized Pd-MWCNT/$TiO_2$ photocatalysts had enhanced activity over the non Pd treated MWCNT/$TiO_2$ material in the degradation of a rhodamine B (Rh.B) solution. An increase in photocatalytic activity was observed and attributed to an increase in the photo-absorption effect by MWCNTs and the cooperative effect of Pd and $TiO_2$ nanoparticles. According to the recycled results, the as-prepared Pd-MWCNT/$TiO_2$ sample had a good effect on it.

• Journal of Microbiology and Biotechnology
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• v.27 no.9
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• pp.1670-1680
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• 2017

Lignocellulose, composed mostly of cellulose, hemicellulose, and lignin generated through secondary growth of woody plant, is considered as promising resources for biofuel. In order to use lignocellulose as a biofuel, biodegradation besides high-cost chemical treatments were applied, but knowledge on the decomposition of lignocellulose occurring in a natural environment is insufficient. We analyzed the 16S rRNA gene and metagenome to understand how the lignocellulose is decomposed naturally in decayed Torreya nucifera (L) of Bija forest (Bijarim) in Gotjawal, an ecologically distinct environment. A total of 464,360 reads were obtained from 16S rRNA gene sequencing, representing diverse phyla; Proteobacteria (51%), Bacteroidetes (11%) and Actinobacteria (10%). The metagenome analysis using single molecules real-time sequencing revealed that the assembled contigs determined originated from Proteobacteria (58%) and Actinobacteria (10.3%). Carbohydrate Active enZYmes (CAZy)- and Protein families (Pfam)-based analysis showed that Proteobacteria was involved in degrading whole lignocellulose, and Actinobacteria played a role only in a part of hemicellulose degradation. Combining these results, it suggested that Proteobacteria and Actinobacteria had selective biodegradation potential for different lignocellulose substrates. Thus, it is considered that understanding of the systemic microbial degradation pathways may be a useful strategy for recycle of lignocellulosic biomass, and the microbial enzymes in Bija forest can be useful natural resources in industrial processes.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.2
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• pp.104-116
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• 1996

Anaerobic digestion is generally used for the treatment of volatile organic solids such as manure and sludge from waste water treatment plants. However, the reaction rate of anaerobic process is slow, and thus it requires a large reactor volume. To minimize such a disadvantage, physical and chemical pre-treatment is generally considered. Another method to reduce the reactor size is to adopt different reactor system other than CSTR. In this paper, the effects of heat pre-treatment and reactor configurations on the anaerobic treatability of volatile solids was studied. Carrot, kale, primary sludge, and waste activated sludge was chosen as the test materials, and the BMP method was used to evaluate the maximum methane production and first order rate constants from each sample. After the heat treatment at $130^{\circ}C$ for 30min., the measured increase in SCOD per gram VS was up to 394 mg/L for the waste activated sludge. However, the methane production potential per gram VS was increased for only primary and waste activated sludge by 17-23%, remaining the same for carrot and kale. The overall methane production process for the tested solids can be described by first order reactions. The increased in reaction constant after heat pre-treatment was also more significant for the primary and waste activated sludge than that for carrot and kale. therefore, the heat pre-treatment appeared to be effective for the solids with high protein contents rather than for the solids with high carbohydrate contents. Among the four reactor systems studied, CSTR, PFR, CSTR followed by PFR, and PFR with recycle, CSTR followed by PFR appeared to be the best choice considering methane conversion rate and the operational stability.

• Journal of Powder Materials
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• v.30 no.2
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• pp.130-139
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• 2023

Thermoelectric materials and devices are energy-harvesting devices that can effectively recycle waste heat into electricity. Thermoelectric power generation is widely used in factories, engines, and even in human bodies as they continuously generate heat. However, thermoelectric elements exhibit poor performance and low energy efficiency; research is being conducted to find new materials or improve the thermoelectric performance of existing materials, that is, by ensuring a high figure-of-merit (zT) value. For increasing zT, higher σ (electrical conductivity) and S (Seebeck coefficient) and a lower κ (thermal conductivity) are required. Here, interface engineering by atomic layer deposition (ALD) is used to increase zT of n-type BiTeSe (BTS) thermoelectric powders. ALD of the BTS powders is performed in a rotary-type ALD reactor, and 40 to 100 ALD cycles of ZnO thin films are conducted at 100℃. The physical and chemical properties and thermoelectric performance of the ALD-coated BTS powders and pellets are characterized. It is revealed that electrical conductivity and thermal conductivity are decoupled, and thus, zT of ALD-coated BTS pellets is increased by more than 60% compared to that of the uncoated BTS pellets. This result can be utilized in a novel method for improving the thermoelectric efficiency in materials processing.

• Korean Journal of Environmental Agriculture
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• v.42 no.3
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• pp.177-183
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• 2023

Rendering, is attracting attention as a technology that can stably and quickly process livestock carcasses. However, large amounts of livestock carcass solid residues are discharged in this process and limited methods are available for recycling them. In this study, rendered animal carcass solid residues were pyrolyzed to produce carbonized materials (350℃; RACR-C) and their chemical properties were investigated. Further, RACR-C were applied to cabbage cultivation for investigating their crop growth characteristics and soil improvement effects. RACR-C contained large amounts of fertilizer components such as nitrogen and phosphorus, and showed no toxic effects on the seedling growth of crops. The content of water-soluble nutrients released from RACR-C under the reaction time increased rapidly within 30 min, but was insignificant compared to the total content. Thus, most fertilizer components in RACR-C were not readily soluble in water. The optimal application amount for applying RACR-C to cabbage cultivation based on the changes in cabbage growth, inorganic content, and soil chemistry was 200 kg/10a. Overall, pyrolysis of solid residues after rendering livestock carcass to produce carbonized material as a soil improver is an effective method to recycle the waste discharged from the rendering process.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.31-38
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• 2015

At present, carbon dioxide ($CO_2$) emission, which causes global warming, is a major issue all over the world. To reduce $CO_2$ emission directly, commercial deployment of $CO_2$ separation processes has been attempted in industrial plants, such as power plant, oil refinery and steelmaking plant. Besides, several studies have been done on indirect reduction of $CO_2$ emission from recycle of reducing gas (carbon monoxide or hydrogen containing gas) in the plants. Unlike many competing gas separation technologies, pressure swing adsorption (PSA) and membrane filtration are commercially used together or individually to separate a single component from the gas mixture. However, there are few studies on operation of sequential separation process of multi-component gas which has more than two target gas products. In this paper, process simulation model is first developed for two available configurations: $CO_2$ PSA-CO PSA-$H_2$ PSA and $CO_2$ PSA-CO PSA-$H_2$ membrane. Operation optimization and economic evaluation of the processes are also performed. As a result, feed gas contains about 14% of $H_2$ should be used as fuel than separating $H_2$, and $CO_2$ separation should be separated earlier than CO separation when feed gas contains about 30% of $CO_2$ and CO. The simulation results can help us to find an optimal process configuration and operation condition for separation of multicomponent gas with $CO_2$, CO, $H_2$ and other gases.

• Clean Technology
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• v.26 no.3
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• pp.177-185
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• 2020

All coal ash, generated from coal-fired power plants, is entirely dumped onto a landfill site. As coal ash contains 80% fly ash, a clean floating process was developed in this study to recover useful components from coal ash and to use them as high value-added industrial materials. When the unburned carbon (UC) was recovered from the fly ash, soybean oil, an eco-friendly vegetable oil, was used as collector instead of a non-ionic kerosene collector to prevent the occurrence of odor from the kerosene. After the UC was separated by flotation, particulate ceramic microsphere (CM) was recovered, without generating acidic wastewater, through hydro-cyclone instead of sulfuric acid solution in order to separate ceramic microsphere (CM) and cleaned ash (CA) from the residue. By utilizing soybean oil as a collector, the recovery rate of UC turned high at 85.8% due to the increased adsorption of UC, the high viscosity of soybean oil, and the increase in floating properties caused by the linoleic acid contained in soybean oil. All of the combustible components contained in the recovered UC were carbon components, with the carbon content registering high when soybean oil was used. The recovered UC had many pores with a rough surface; thus, it could be easily ground and then used as an industrial material for its fine particles. The CM and CA recovered by the clean separation process using hydro-cyclone had a spherical shape, and the particles were clearly separated without clumping together. The average diameter (D₅₀) of the particles was 5 ㎛, so it was possible to realize the atomization of CM through a process change.