• Journal of Environmental Science International
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• v.24 no.9
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• pp.1221-1231
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• 2015

The present study was conducted to find a way to recycle the coir substrate by investigating changes in its physical and chemical properties based on the number of use year. Specific gravity of unused coir substrate was $0.212g/cm^3$, while it was higher for the substrate used for 2 years. Porosity was different depending on the number of use year. The porosity of unused substrate was 51.9%, but it increased to 68.6% after used for 2 years. In general, physical and chemical properties were better in the coir substrate used for 2 years than in unused one. The number of leaves, leaf area, flesh weight and dry weight of oriental cabbage and lettuce were higher in coir substrate used for 2 years than those in unused one. Whereas, no significant difference was observed between the substrates used for one year and 2 years, indicating that the one time-used wast substrate could be recycled for cultivating vegetables. Growth of the vegetables was improved when organic fertilizer composed of complex organics with different mixing ratios was provided to the coir substrate, compared to untreated plot. The optimum mixing ratio of the wast substrate and complex organics was 2:8(v/v) for fertilization using wast coir substrate. Therefore, coir substrate generally wasted after being used for one time was reuseable by supplying organic fertilizer.

• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.669-678
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• 2014

The amount of waste water generated from the domestic sources is consistently increasing in proportion to economic growth, and the conventional activated sludge process is widely being used for general waste water treatment. But the ministry of environment becomes stringthent treatment standards of N and P (less than 20mg/L of N, 2mg/L of P) to prevent the eutrophication of lake water, and therefore highly advanced treatment technology is required not only in the existing treatment plants where the activated sludge process is being used, but also in newly constructed treatment plants for the treatment of N and P. This study is aimed at highly operating the engineering technology method was developed by domestic to eliminate N and P at the same time. Experiments were conducted in the treatment plant located in Yong In city. The bioreactor was started from the principal equipment for the elimination of N and P and the elimination of organic compounds. It consists of an internal recycle piping from the end of the aerobic tank to the anoxic tank and external recycle piping from the final settling basin to the denitrification tank. By experiment of 4 types separate inflow of waste water to the denitrification tank and the anaerobic tank, and changes in staying time at the anoxic tank and the aerobic tank, the elimination of organic compounds in each type and the relationship in the efficiency between the elimination of N and P were researched.

• Microbiology and Biotechnology Letters
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• v.13 no.3
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• pp.245-250
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• 1985

In order to increase citric acid productivity. several attempts were made; isolation and characterization of the mutant strain produced citric acid in a high yield, citric acid fermentation in a medium containing relatively higher amount of glucose and citric acid production by the use of semicontinuous ceil recycle system. By the treatment of Candide lipolytica S-109 with NTG, a mutant J-24 was selected as the highest producer of citric acid among the strains formed larger CaCO$_3$ lytic zone. it produced 72g/1 citric acid in 10％ glucose medium. Because mutant J-24 produced 85g/l citric acid and showed 53％ yield in 16％ glucose medium, several factors were adjusted to increase the yield in 16％ glucose medium. 0.8-1.0$\times$10$^{-3}$ P/C ratio, 0.15％ urea, 0.25％ yeast extract were suitable at citric acid production in 16％ glucose medium. Under this condition, J-24 strain produced 93g/l citric acid and showed 58％ yield. Semicontinuous cell recycle system was used to protons the effective production phase, to minimize the product inhibition and to shorten the lag phase. The productivity of semicontinuous cell recycle system was 0.79g/l h while that of batch system was 0.53g/l.h

• Journal of Korean Society of Water and Wastewater
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• v.21 no.3
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• pp.273-278
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• 2007

Modern society has moved from a phosphorus recycling loop, where animal manure and human wastes were spread on farming land to recycle nutrients, to a once-through system, where phosphates are extracted from mined, non-renewable phosphate rock and end up either in landfill(sewage sludge, incinerator ash) or in surface waters. In this research, crystallization of nitrogen and phosphate with natural sources of $Mg^{2+}$ in synthetic water was tested. The operational parameters of pH, mixing time, and the magnesium molar ratio were investigated to find optimal conditions of the MAP precipitation using synthetic wastewater. The removal efficiency of phosphate increased with pH up to 11. By MAP precipitaiton of the synthetic waste water, 94% of the phosphate were eliminated at pH 11. It was found that at least 10 minutes mixing time was required and 20 minutes mixing time was recommended for efficient phosphate removal. High efficiency removal of phosphate was possible when the magnesium molar ratio was 1.0~2.0. The comparative study of different magnesium sources showed that coagulants (PAC) was the more efficient sources than only magnesium. The result showed that 97% of phosphate removal. In conclusion, coagulants (PAC) induced crystallization of struvite and hydroxyapatite was shown to be a technically viable process that could prove cost effective for removing phosphate in wastewater.

• Journal of Environmental Science International
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• v.9 no.5
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• pp.437-441
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• 2000

A study on the removal of Pb ion from Pb-contaminated soil was carried out using ex-site extraction process. Tartaric acid (TA) and iminodiacetic acid sodium salt(IDA) as a washing agent were evaluated as a function of concentration reaction time mixing ratio of washing agent and recycling of washing agent. TA showed a better extraction performance than IDA. The optimum washing condition of TA and IDA were in the ratio of 1:15 and 1:20 between soil and acid solution during 1 hr reaction. The total concentrations of Pb ion by TA and IDA at three repeated extraction were 368.8 ppm and 267.5 ppm respectively. The recovery of Pb ion from washing solution was achieved by adding calcium hydroxide and sodium sulfide form the precipitation of lead hydroxide and lead sulfide and optimum amounts of sodium sulfide and calcium hydroxide were 7 g/$\ell$ for the TA washing solution and 4 g/$\ell$, 5g/$\ell$ for the IDA washing solution respectively. The efficiency of recycle for TA and IDA washing solution were 78.8% , 95.1%, and 89.2%, 96.6% at third extractions under $Na_2S$ and $Ca(OH)_2$, respectively.

• Environmental Engineering Research
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• v.17 no.2
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• pp.59-63
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• 2012

This paper proposes a modified Ludzack-Ettinger (MLE) type membrane bioreactor (MBR) as a method of treatment for wastewater from food waste disposer. Micro-membrane filtration allows for an extremely low concentration of suspended solids in the effluent. The effluent of the reactor in question is characterized by a relatively high level of non-biodegradable organics, containing a substantial amount of soluble microbial products and biomass. Results obtained in this paper by measurement of membrane fouling are consistent with biomass concentration in the reactor, as opposed to chemical oxygen demand (COD). The MLE process is shown to be effective for the treatment of wastewater with a high COD/N ratio of 20, resulting in are markedly high total nitrogen removal efficiency. Denitrification could be improved at a higher internal recycle ratio. Despite the low concentration of influent phosphorus, the phosphorus concentration of the outflow is seen to be relatively high. This is because outflow phosphorous concentration is related to COD consumption, and the process operates at along solids retention time.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.5
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• pp.678-685
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• 2011

An Ejector enhances system efficiency, are easily operated, have a mechanically simple structure, and do not require a power supply. Because of these advantages, the ejector has been applied to a variety of industrial fields such as refrigerators, power plants and oil plants. In this work, an ejector was used to safely recycle anode tail gas in a 75-kW Molten Carbonate Fuel Cell (MCFC) system at KEPCO Research Institute. In this system, the ejector is placed at mixing point between the anode tail gas and the cathode tail gas or the fresh air. Commercial ejectors are not designed for the actual operating conditions for our fuel cell system. A new ejector was therefore designed for use beyond conventional operating limits. In the first place, a few sample ejectors were manufacured and the entrainment ratio was measured at a dummy stack. Through this experiment, the optimum ejector was chosen. The 75-kW MCFC system equipped with this optimum ejector was operated successfully.

• Journal of the Korean Geotechnical Society
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• v.22 no.11
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• pp.5-11
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• 2006

The purpose of this study was to examine the proper mixing ratio of ordinary portland cement and Bottom Ash to recycle the Bottom Ash, which is an industrial waste. After the evaluation, the compressive strength and durability were assessed using the mixture of completely weathered soil (Hwangto), weathered granite soil, and Bentonite. Then environmental friendliness of this mixed material was examined through heavy metal leaching method. It was found out that proper mixing ratio is 6:4, and that the 6% mixture quantity of completely weathered soil (Hwangto), weathered granite soil, and Bentonite is the most effective for compressive strength and durability It was also found out through heavy metal leaching method that the Bottom Ash could be below the standard of the Clean Water Law.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.3
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• pp.459-465
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• 1994

Performance of a continuous cocurrent supercritical fluid extraction column for processing of anhydrous milk fat (AMF) was determined. The extract loading increased and the extraction yield decreased as the superficial velocity of AMF increased. The maximum solubility of AMF in $CO_2$ at 4$0^{\circ}C$/3,500 psig was 0.0195g/g. The increase of the carbon dioxide density enhanced the solubility of milk fat and decreased the cholesterol concentration in the extract. Three operation conditions, such as recycle , reflux, and temperature gradient of extraction column, were tested. More short-chain fatty acvids were extracted by the reflux operation . Longchain fatty acids and thehighest ratio fo long-chain unsaturated to saturated fatty acids were also obtained in the raffinate phase with refluex.

• Journal of Environmental Science International
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• v.13 no.2
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• pp.143-148
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• 2004

In this paper, the properties of inter - locking block using fly ash are discussed in order to provide economical advantages and improve quality, and protect environment and recycle resources. Fly ash is the by-product of coal in thermal power plant. The experimental parameters are fly ash content, the amount of AE water - reducing agent and mixing proportion of cement mortar. According to the experimental results, the improvement of quality in the side of strength, absorption ratio and freeze - thaw resistance for manufacturing inter -locking block and the curtailment of cost can be achieved in case of 15% of fly ash and 0.3% of AE water- reducing agent are mixed into mortar mixture of 1 :6(C:S).