• Environmental Engineering Research
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• 제24권2호
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• pp.347-353
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• 2019

Although membrane distillation (MD) has great promise for desalination of saline water sources, it is crucial to improve its thermal efficiency to reduce the operating cost. Accordingly, this study intended to examine the thermal energy efficiency of MD modules in a pilot scale system. Two different modules of hollow fiber membranes were compared in direct contact MD mode. One of them was made of polypropylene with the effective membrane area of $2.6m^2$ and the other was made of polyvinylidene fluoride with the effective membrane area of $7.6m^2$. The influence of operation parameters, including the temperatures of feed and distillate, feed flow rate, and distillate flow rate on the flux, recovery, and performance ratio (PR), was investigated. Results showed that the two MD membranes showed different flux and PR values even under similar conditions. Moreover, both flow rate and temperature difference between feed and distillate significantly affect the PR values. These results suggest that the operating conditions for MD should be determined by considering the module properties.

• 한국환경보건학회지
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• 제37권1호
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• pp.57-63
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• 2011

Crocidolite quality control (QC) sampling created by the wet generation method has been validated by validation tests such as the accuracy, precision, and storage tests. For this study we designed and developed a manufacturing apparatus and standard operating procedure for making these QC samples. The most important step in the procedure of making QC samples was the stage eliminating static electricity in asbestos fibers. This static electricity hampers the fibers clog functioning. In accuracy and precision tests by phase contrast microscopy analysis, the difference between the reference values and the studied values was at maximum 17.8%. This satisfies the AIHA proficiency analytical test criteria for asbestos. We could confirm the nearly even distribution of crocidolite fibers on the membrane filter. Also, there was no loss of fibers in the storage test after the one month.

• Environmental Engineering Research
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• 제9권5호
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• pp.238-247
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• 2004

The objective of this study was to develop kinetic model for the MBR and investigate kinetic characteristics of the gravitational flow transverse direction MBR system. Kinetic model was derived by mass balance of substratc and biomass combined with empirical membranc filtration rerm for the MBR. To find kinctic values, permeale flux and COD removal were analyzed through the laboratory, MBR operation as different solids retention times. Permeate flux was ranged 2.5-5.0 LMH (L/m$^2$/hr) as sludge characteristics in each run. Although the soluble COD in the bioreactor was changed, the effluent COD was stable as average 99% removal rate during the experimental periods. Y$_g$ of this MBR system was higher than those of cross-flow MBR processes. The kinetics of this MBR showed that smaller k, larger b, and larger K$_s$ values than the conventional activated sludge process. These results indicated that substrate was used for cell maintenance rather than growth in this MBR system.

• Environmental Analysis Health and Toxicology
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• 제20권4호통권51호
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• pp.279-286
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• 2005

Earthworm (Eisenia fetida) acute toxicity test was carried out and ecological risk assessment in soil was performed with national monitoring data. 14 day - $LC_{50}$ of nonylphenol and bisphenol A were 288.1 mg/kg and 90.1 mg/kg, respectively. And NOECs of nonylphenol and bisphenol A were 250 mg/kg and 50 mg/kg, respectively. Significant weight decrement was appeared at 70 mg/kg of bisphenol A, however, nonylphenol at concentrations tested did not severe adverse effect on the weight decrement. The environmental monitoring has been carrying out by NIER since 1999. Exposure levels of nonylphenol in soil were ND$\sim$10.55 $\mu$g/kg and those of bisphenol A were ND$\sim$15.50$\mu$g/kg in National Monitoring data which had been performed from 2000 to 2004. The measured soil exposure level was applied to evaluate the environmental risk assessment. The values of PNEC for bisphenol A and nonylphenol were determined as 0.5 mg/kg and 2.5 mg/kg, respectively using the safety factors which were suggested in EU and OECD. The values of HQ (PEC/PNEC) were determined to be below I for bisphenol A and nonylphenol when the maximum exposure levels for bispheol A (15.50$\mu$g/kg) and nonylphenol (10.55$\mu$g/kg) were applied. Conclusively, the environmental risk assessment of bisphenol A and nonylphenol was not critical in soil.

• 한국환경교육학회지:환경교육
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• 제18권1호
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• pp.82-96
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• 2005

The purpose of this study was to evaluate Korean and foreign environmental education programs: 3 Korean programs including 'Environmental Education Program' for primary school level, 'Environment' for middle school level, 'Ecology and Environment' for high school level and 2 foreign programs including 'TLSF(Teaching and Loaming for a Sustainable Future) Program and IEEIA(Investigating and Evaluating Environmental Issues and Actions) Program using IAEEC (The Inventory for Assessing Environmental Education Curricula) by Kim (2003). The IAEEC include four goal levels of the foundations level, the conceptual awareness level, the investigation level, environmental action skills level and an optical level: teaching methods and practice. The IAEEC use a 5-point Likert scale to identify the extent to which an environmental education curriculum or a program reflects the goals of environmental education. It was found that our school environmental education programs need to be more involved, especially in the areas of social foundations (political & legal); personal beliefs and values in environmental issue and the critical analysis of the issue by identifying important players' positions, beliefs, and values; and the environmental action to solve the issue and evaluate the consequences and effectiveness of the action plan. This study can provide a meaningful direction for program development in environmental education and especially provide school-teachers with reliable sources in analyzing environmental education programs for their school classes.

• 한국환경보건학회지
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• 제44권6호
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• pp.548-555
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• 2018

Objectives: We conducted ecological risk assessment for cadmium, a heavy metal and carcinogen, to identify safety standards by environmental media and to determine its impact on ecosystems by estimating and evaluating exposure levels. Methods: Species sensitivity distributions (SSDs) were generated using ECOTOX DB. A hazardous concentration of 5% (HC5) protective of most species (95%) in the environment was estimated. Using this estimate, predicted no effect concentrations (PNECs) were calculated for aquatic organisms. Based on the calculated PNECs for aquatic organisms, PNEC values for soil and sediment were calculated using the partition coefficient. Predicted exposure concentrations (PECs) were also calculated from environmental monitoring data with hazard quotients (HQs) calculated using PNECs for environmental media. Results: Chronic toxicity data were categorized into four groups and 11 species. In species sensitivity distribution (SSD) analysis, HC5 was $0.340{\mu}g/L$. Based on this value, the PNEC value for aquatic organisms was calculated as $0.113{\mu}g/L$. PNEC values for soil and sediments using a partition coefficient were calculated as 15.02 mg/kg and 90.61 mg/kg, respectively. In an analysis of environmental monitoring data, PEC values were calculated as $0.017{\mu}g/L$ for water, 1.01 mg/kg for soil, and 0.521 mg/kg for sediment. Conclusions: HQs were 0.150, 0.067 and 0.006 for water, soil and sediment, respectively. HQs of secondary toxicity were 0.365 for birds and 0.024 for mammals. In principle, it is judged that an HQ above 1 indicates a high level of risk concern while an HQ less than 1 indicates an extremely low level of risk concern. Therefore, with HQs of cadmium in the environment being <1, its risk levels can be considered low for each media.

• 한국식물생명공학회:학술대회논문집
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• 한국식물생명공학회 2005년도 추계학술대회 및 한일 식물생명공학 심포지엄
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• pp.437-437
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• 2005

• Environmental Analysis Health and Toxicology
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• 제6권1_2호
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• pp.1-6
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• 1991

The quality of water in Kyungan stream was analyzed in three different areas between season of irrigation on May and of nonirrigation on august in 1990. The results of Water quality from this study were summarized as follows: 1. The quality of water is season of irrigation containing metal ions, such as Cu and Zn as well as TN was exceeded standard levels of quality of agricultural water However, in season of nonirrigation, the quality of water in Kyungan stream was not suitable for using agricultural water due to over standard levels of containing ions of Cu and Zn or DO, COD and TN. 2. The correlation of water quality exception of pH was shown a reliance when p values were greater than 0.01 for containing ions such as Cu and Zn with the DO, COD and TN. 3. The comparison of water qualities for pH between season of irrigation and season of nonirrigation in Kyungan stream was a considerable significance property when p values were less than 0.05. The water quality containing ions of Cu and Zn with DO, COD, TN and SS also indicated a significant property when p values were less than 0.01. 4. The average water qualities of a year in three different areas for pH have shown a significant property when p values are less than 0.01. The average water qualities of a year containing DO have also shown a significant property having p values of less than 0.05. But other constituents have shown no significant property in the above three different areas.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권2호
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• pp.76-84
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• 2002

On-line conversion estimation of enzymatic esterification reactions in solvent-free media was investigated. In principle, conversion to ester can be determined from the amount of water produced by the reaction, because water is formed as a by-product in a stoichiometric manner. In this study, we estimated the water production rate only from some measurements of relative humidity and water balances without using any analytical methods. In order to test the performance of the on-line conversion estimation, the lipase-catalyzed esterification of n-capric acid and n-decal alcohol in solvent-free media was performed whilst controlling water activity at various values. The reaction conversions estimated on-line were similar to those determined by offline gas chromatographic analysis. However, when the water activity was controlled at higher values, discrepancies between the estimated conversion values and the measured values became significant. The deviation was found to be due to the inaccurate measurement of the water content in the reaction medium during the initial stages of the reaction. Using a digital filter, we were able to improve the accuracy of the on-line conversion estimation method considerably. Despite the simplicity of this method, the on-line estimated conversions were in good agreement with the off-line measured values.

• 자원ㆍ환경경제연구
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• 제10권1호
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• pp.95-126
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• 2001

Functional values for wastewater treatment and atmospheric regulation in coastal wetland and rice paddy ecosystems are quantified, and an illustration is given on how to integrate biophysical parameters into a valuation framework. This is one of most controversial issues in economic analysis for wetland preservation versus wetland conversion to agricultural use. This paper includes theoretical considerations for estimating functional values of environmental ecosystems, and the integration of biophysical data and replacement cost method employed. Specific physical and geographical characteristics and data on ecosystem functions and services in coastal wetlands and rice paddies are addressed for evaluating their values in economic terms. In particular this paper indicates double counting problems and overestimation in the previous studies, and demonstrates how to avoid them and to maintain the consistency of valuation process involving a least-cost method, thus enables an accurate integration of the coastal wetland ecology and wetland economics. As a result which is far away from the previous studies, the total economic present value of wastewater assimilation by coastal wetland is estimated at 7,484,640 won/ha, and the net present value of positive effect for atmospheric regulation, negative effects for air pollution and water pollution by rice paddy is estimated at -37,934 won/ha, assuming that resources are infinitely long-lived and the annual value and the rate of discount (10%) is constant every year. In conclusion, for further reliability and validity of functional values for natural resources it is very noteworthy that a general equilibrium framework that could directly incorporate the interdependence between ecosystem functions and services would be preferred to the partial equilibrium framework.