• Journal of Korean Society for Atmospheric Environment
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• v.25 no.5
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• pp.402-409
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• 2009

Sodium bicarbonate ($NaHCO_3$) was used as a reactant for the removal of acid gases from a waste incinerator. The removal efficiencies of HCl and $SO_x$ were tested with a reactant mixing apparatus and a distributor installed at the bag filter inlet. It was shown that the stoichiometric ratio of $NaHCO_3$ to the acid gases which allows a removal of over 90% for both HCl and $SO_2$ was about 1.2. When a reactant mixing apparatus was installed on the duct, the removal efficiencies of HCl and $SO_2$ at the end of the duct were increased by approximately 1.5 and 3 times respectively, compared to when the apparatus was not installed. At the end of the bag filter, the removal efficiencies of the both were as high as 98% with a stoichiometric ratio of 1.35. Installing a reactant mixing apparatus on the duct and a distributor at the entrance of the bag filter and using $NaHCO_3$ as a reactant helped overcome the problem of low removal efficiencies of acid gases by dry scrubbing.

• Journal of environmental and Sanitary engineering
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• v.18 no.1
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• pp.15-22
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• 2003

Treatability tests were conducted using EMC process to study the feasibility of applying this process as recycling-water treatment system in high density seawater aquaculture farm. To study the effect of organic and ammonia nitrogen loading on system performance, hydraulic retention time of reactor was reduced gradually from 12hr to 10min. The conclusions are can be summarized as follows. When the system HRT was reduced from 12hr to 10 min gradually, there was little noticeable change(reduction) in ammonia nitrogen removal efficiencies until 2hr of HRT, however, removal efficiencies were decreased dramatically when the system was operated under the HRT of less than 2hr. In case of organics(COD), there was no dramatic deterioration in removal efficiencies depending on HRT reduction. More than 90% of removal efficiencies were maintained successfully when the system was operated at the HRT of 10 min. In case of system performance depending on media packing ratio in reactor, there was little difference in each reactor performance depending on media packing ratio in reactor when the reactors were operated under the HRT of longer than 1hr, however, differences in reactor performances were considerably evident when the reactors were operated under the HRT of shorter than 1hr. That is, the more reactor was packed, the better reactor performed. When comparing reactor performance among 25%, 50%, 75% packed reactor, it can be judged that media packing ratio more than 50% plays no significant role in increasing reactor performance. For this reason, packing the media less than 50% is more reasonable way in view of economic. Such a tendency well agreed with the variation of ammonia-nitrogen removal efficiencies according to the media packing ratio in reactors at each HRT. Difference in effluent ammonia-nitrogen concentration between 50% media packing reactor and 75% media packing reactor was negligible. When comparing with the results of 25% packing reactor, difference was not so great.

• Journal of the Korean GEO-environmental Society
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• v.12 no.4
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• pp.25-31
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• 2011

In this study, the experimental design methodology was applied to optimize 1,4-dioxane treatment in E-beam process. Main factor was mathematically described as a function of parameters 1,4-dioxane removal efficiencies(%), TOC removal efficiencies(%) modeled by the use of the central composite design(CCD) method among the response surface methodology(RSM). Concentration of 1,4-dioxane is designated as "$x_1$" and Irradiation intensity is designated as "$x_2$". The regression equation in coded unit between the 1,4-dioxane concentration and removal efficiencies(%) was $y=71.00-10.85x_1+20.67x_2+{1.53x_1}^2-{7.92x_2}^2-1.23x_1x_2$. The regression equation in coded unit between the 1,4-dioxane concentration and TOC removal efficiencies(%) was $y=44.48-13.25x_1+9.54x_2+{5.43x_1}^2-{1.35x_2}^2+4.45x_1x_2$. The model predictions agreed well with the experimentally observed results $R^2$(Adj) over 90%. Toxicity test using algae Pseudokirchneriella Subcapitata showed that the inhibition was reduced according to increasing an E-beam irradiation.

• Journal of Environmental Science International
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• v.21 no.9
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• pp.1043-1051
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• 2012

Coagulation, flocculation, and dissolved air flotation (DAF) experiments were performed with humic acid to evaluate the influence of operational conditions on removal efficiencies. We investigated coagulation, flocculation, and flotation conditions of humic acid removal using a laboratory-scale DAF system. This paper deals with coagulant type (aluminum sulfate and PSO-M) and the most relevant operational conditions (velocity gradients for coagulation and flocculation, retention time and recycle ratio and flotation time). Results showed that optimal conditions for removing humic acid, yielding CHA removal efficiencies of approximately 85 %, are a recycle ratio of 40 %, coagulant dosages of 0.15 - 0.20 gAl/gHA as aluminum sulfate and 0.03 - 0.12 gAl/gHA as PSO-M, coagulation($400s^{-1}$ and 60s), flocculation($60s^{-1}$ and 900s or more), and flotation(490 kPa or more and at least 10 min).

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11b
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• pp.319-321
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• 2003

This research was carried out to evaluate the removal efficiencies of CODcr and colour for the dyeing wastewater by ferrous solution in Fenton process. The results showed that COD was mainly removed by Fenton coagulation, where the ferric ions are formed in the initial step of Fenton reaction. On the other hand colour was removed by Fenton oxidation rather than Fenton coagulation. The removal mechanism of CODcr and colour was mainly coagulation by ferrous ion, ferric ion and Fenton oxidation. The removal efficiencies were dependent on the ferric ion amount at the beginning of the reaction. However the final removal efficiency of COD and colour was in the order of Fenton oxidation, ferric ion coagulation and ferrous ion coagulation. The reason of the highest removal efficiency by Fenton oxidation can be explained by the chain reactions with ferrous solution, ferric ion and hydrogen peroxide.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2008.10a
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• pp.446-448
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• 2008

• Environmental Engineering Research
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• v.17 no.4
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• pp.179-184
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• 2012

The light absorbance of photocatalysts and reaction kinetics of environmental pollutants at the liquid-solid and gas-solid interfaces differ from each other. Nevertheless, many previous photocatalytic studies have applied the science to aqueopus applications without due consideration of the environment. As such, this work reports the surface and morphological characteristics and photocatalytic activities of carbon-embedded (C-$TiO_2$) photocatalysts for control of gas-phase methyl tertiary-butyl ether (MTBE) under a range of different operational conditions. The C-$TiO_2$ photocatalysts were prepared by oxidizing titanium carbide powders at $350^{\circ}C$. The characteristics of the C-$TiO_2$ photocatalysts, along with pure TiC and the reference pure $TiO_2$, were then determined by X-ray diffraction, scanning emission microscope, diffuse reflectance ultraviolet-visible-near infrared (UV-VIS-NIR), and Fourier transform infrared spectroscopy. The C-$TiO_2$ powders showed a clear shift in the absorbance spectrum towards the visible region, which indicated that the C-$TiO_2$ photocatalyst could be activated effectively by visible-light irradiation. The MTBE decomposition efficiency depended on operational parameters, including the air flow rate (AFR), input concentration (IC), and relative humidity (RH). As the AFRs decreased from 1.5 to 0.1 L/min, the average efficiencies for MTBE increased from 11% to 77%. The average decomposition efficiencies for the ICs of 0.1, 0.5, 1.0, and 2.0 ppm were 77%, 77%, 54%, and 38%, respectively. In addition, the decomposition efficiencies for RHs of 20%, 45%, 70%, and 95% were 92%, 76%, 50%, and 32%, respectively. These findings indicate that the prepared photocatalysts could be effectively applied to control airborne MTBE if their operational conditions were optimized.

• Journal of Environmental Science International
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• v.27 no.11
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• pp.1059-1072
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• 2018

Bioremediation has been recognized as a suitable alternative to conventional methods of removing contaminants, and it uses fungi, bacteria and microalgae. In contrast to other organisms, microalgae are unique in that they have the ability to perform photosynthesis like plants and to utilize organic/inorganic carbon substrates, in a process called phytoremediation. Microalgae can populate a reaction site rapidly and enhance the bioremediation efficiency. In this study, Chlorella vulgaris was used to evaluate the removal potentials of the nutrients (N and P) and heavy metals (Cu and Zn) from swine wastewater. The optimum growth conditions for Chlorella vulgaris and the removal potentials of N, P, Cu, and Zn from synthetic wastewater using Chlorella vulgaris were investigated. Based on the results, the applicability of this microalga to on-site wastewater treatment was examined. Optimal growth conditions for Chlorella vulgaris were established to be $28^{\circ}C$, a pH of 7, and light and dark cycles of 14:10 h. As the concentrations of the nutrients were increased, the efficiencies of N and P removal efficiencies by Chlorella vulgaris were decreased in the single and binary mixed treatments of the nutrients, respectively. Further, the efficiencies of Cu and Zn removal also decreased as the heavy metals concentrations added were increased, both in the single and binary mixed treatments. In addition, the efficiency of Cu removal was higher than that of Zn removal. Our results indicate that Chlorella vulgaris could be used in treatment plants for the removal of nutrients and heavy metals from swine wastewater.

• Environmental Engineering Research
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• v.22 no.3
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• pp.329-338
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• 2017

Nanofiltration (NF) technology is a membrane-based separation process, which has been pervasively used as the high-effective technology for drinking water treatment. In this study, a kind of composite polyamide NF thin film is selected to investigate the removal efficiencies and mechanisms of 14 trace drugs, which are commonly and frequently detected in the drinking water. The results show that the removal efficiencies of most drugs are quite high, indicating the NF is an effective technology to improve the quality of drinking water. The removal efficiencies of carbamazepine, acetaminophen, estradiol, antipyrine and isopropyl-antipyrine in ultrapure water are $78.8{\pm}0.8%$, $16.4{\pm}0.5%$, $65.4{\pm}1.8%$, $71.1{\pm}1.5%$ and $89.8{\pm}0.38%$, respectively. Their rejection rates increase with the increasing of their three-dimensional sizes, which indicates that the steric exclusion plays a significant role in removal of these five drugs. The adsorption of estradiol with the strongest hydrophobicity has been studied, which indicates that adsorption is not negligible in terms of removing this kind of hydrophobic neutral drugs by NF technology. The removal efficiencies of indomethacin, diclofenac, naproxen, ketoprofen, ibuprofen, clofibric acid, sulfamethoxazole, amoxicillin and bezafibrate in ultrapure water are $81{\pm}0.3%$, $86.3{\pm}0.5%$, $85.7{\pm}0.4%$, $93.3{\pm}0.3%$, $86.6{\pm}2.5%$, $90.6{\pm}0.4%$, $59.7{\pm}1.7%$, $80.3{\pm}1.4%$ and $80{\pm}0.5%$, respectively. For these nine drugs, their rejection rates are better than the above five drugs because they are negatively charged in ultrapure water. Meanwhile, the membrane surface presents the negative charge. Therefore, both electrostatic repulsion and steric exclusion are indispensable in removing these negatively charged drugs. This study provides helpful and scientific support of a highly effective water treatment method for removing drugs pollutants from drinking water.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.4
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• pp.403-411
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• 2009

This study was performed to propose appropriate conditions suited to the analysis of naphthalene by comparing desorption efficiencies under various conditions. 1. As to influence by adsorbing media and desorbing solvent on desorption efficiency of naphthalene, when adsorbed by CCT, o-xylene gave the highest desorption efficiency of $73.96{\pm}0.53%$ while the lowest of $1.14{\pm}0.03%$ desorbed by ether. Both XAD-2 and Chromosorb 106 showed around 90% of desorption efficiencies for each solvent, especially desorption efficiencies more than 95% were achieved when adsorbed by Chromosorb 106 and desorbed by $CS_2$ or o-xylene. 2. Desorption efficiencies descended over the storage period in any condition(p<0.05). For all three adsorbing media, while desorption efficiencies showed no significant difference(p>0.05) between room temperature and refrigeration a day of loading, samples kept in room temperature had higher desorption efficiencies than refrigerated ones in 7 and 14 days with significant difference(p<0.05).Also, desorption efficiencies dropped drastically in 7 days, from that point the decreasing tendency went mild. 3. When respective 1 TLV and 0.1 TLV of naphthalene were spiked on CCT and desorbed by CS2($46.45{\pm}0.59%$ vs. $30.15{\pm}0.81%$), o-xylene($73.96{\pm}0.53%$ vs. $67.51{\pm}1.34%$), and ether($1.14{\pm}0.03%$ vs. N.D.) desorption efficiencies increased as the amount of loading increased(p<0.05).On the other hand, naphthalene spiked on XAD-2 and Chromosorb 106 indicated no significant difference(p>0.05) in desorption efficiencies between 1 TLV and 0.1 TLV. In conclusion, in order for favorable desorption efficiencies of naphthalene it is important to select appropriate adsorbing media and desorbing solvent accordingly. The result revealed that adsorbing media of XAD-2 and Chromosorb 106 outperformed CCT and desorbing solvents of $CS_2$ and o-xylene achieved over 90% of desorption efficiencies when adsorbed on XAD-2 and Chromosorb 106. Also, considering the tendency that desorption efficiencies of naphthalene decrease with time, the samples should be analyzed as soon as possible.