• Korean Journal of Plant Resources
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• v.11 no.3
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• pp.307-314
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• 1998

The response of water stree under high and low temperatures, was shown differently according to the longer the suspension period of water supply. Leaf photosynthetic rate(LPS), leaf water potential(WP), relative leaf water content and relative soil water content were lower. At the higher temperatures, the percentate of reduction in LPS and WP was greater than at low temperatures. It is suggested that evaporation rate should be higher in the high temperature than the lower temperature. Also leaf water potential was lower at high temperature than at low temperature. After the 9 th day of treatment , LSP was remarkably reduced at high temperature, but the reduction of LPS was not significant at low temperature. Solidago virga-aurea var. asiatic that maintained LPS of 3rd day after treatment was more strong than other varieties at low temperatures. The silting and curling of leaves were observed symptoms of stress on the 9th day at the both temperatures. The leaves of aster scaber and Ligularia fischeri turned red on the 9th day after treatment at low temperature.

• Journal of Ecology and Environment
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• v.33 no.3
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• pp.195-204
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• 2010

In the study, the effects of elevated $CO_2$ and temperature on the photosynthetic characteristics, chlorophyll content, nitrogen content, carbon content, and C/N ratio of Phytolacca insularis and Phytolacca americana were examined under control (ambient $CO_2+$ ambient temperature) and treatment (elevated $CO_2+$ elevated temperature) for 2 years (2008 and 2009). The photosynthetic rate, transpiration rate and water use efficiency of two plant species were higher under the treatment than the under the control. The stomatal conductance of P. insularis was higher under the control, but that of P. americana was not significantly affected by $CO_2$ and temperature under the treatment. The chlorophyll contents of two species were decreased about 72.5% and 20%, respectively, by elevated $CO_2$ and temperature. The nitrogen contents of two species were not significantly altered by increase in $CO_2$ and temperature. The carbon contents of the two species were higher under the treatment than under the control. The C/N ratio of P. insularis was higher under the treatment but that of P. americana was not significantly affected by $CO_2$ and temperature. These results demonstrated that the physiological responses of P. insularis native plants might be more sensitively influenced by a $CO_2$-mediated global warming situation than those of the P. americana invasive plants.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.06a
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• pp.25-48
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• 1998

Current topics related to membrane technology under the recent water environment are as follows: - Cryptosporidum Outbreak - Integrity Control System - Water re-use - Recycle Society - Biotreatment and Membrane - Slurry or Sludge Treatment I would like to introduce the actual examples regarding water re-use. mainly on the above 5 topics.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2179-2183
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• 2009

As urbanization is progressed, the network for distributing water in a basin become complex due to the spatial expansion and parameter uncertainties of water supply systems. When a long range water supply plan is determined, the total construction and operation cost has to be evaluated with the system components and parameter uncertainties as many as possible. In this paper, the robust optimization approach of Bertsimas and Sim is applied in a hypothetical system to find a solution which remains feasible under the possible parameter uncertainties having the correlation effect between the uncertain coefficients. The system components to supply, treatment, and transport water are included in the developed water supply system and construction and expansion of the system is allowed for a long-range period. In this approach, the tradeoff between system robustness and total cost of the system is evaluated in terms of the degree of conservatism which can be converted to the probability of constraint violation. As a result, the degree of conservatism increases, the total cost is increased due to the installation of large capacity of treatment and transportation systems. The applied robust optimization technique can be used to determine a long-range water supply plan with the consideration of system failure.

• Journal of Korean Society on Water Environment
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• v.26 no.5
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• pp.768-774
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• 2010

This study was conducted to provide a technical solution to treat effectively perchlorate from inorganic wastewater of zinc smelting. Despite an inhibition dissolved inorganic substances in the wastewater discharged from zinc smelting has demonstrated with the activity of microbes, biological treatment technology could reduce perchlorate to a satisfactory level under such stressful conditions. It was found that either conductivity or $SO{_4}^{2-}$ concentration of the wastewater was able to be used as the adequate index and the values were $2,450{\mu}S/cm$ and 1,200 ppm respectively. When $SO{_4}^{2-}$ increased from 0 to 16,000 ppm (conductivity : $428{\rightarrow}24,800{\mu}S/cm$), perchlorate biodegradation rate was reduced due to 1/10 times from 0.0365 to 0.0033/h, however, most of perchlorate was removed under the condition of hydraulic retention time (HRT) at 0.5day and mixed liquor volatile suspended solid (MLVSS) at 2,000 ~ 3,000 ppm.

• Journal of the Korean Wood Science and Technology
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• v.43 no.6
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• pp.792-797
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• 2015

In this study, three softwood species were treated with water-soluble melamine resin by different concentration and treatment time under vacuum pressure for improving mechanical property, abrasion resistance, and incombustibility. After the treatment, a compreg was manufactured and then evaluated on physical properties. Additionally, incombustibility of compreg was determined by comparing with a wood that was treated by spraying a water-soluble fire retardant on surface. As concentration of resin increased, bending strength and Brinell hardness increased as well as abrasion resistance, but there was no correlation on treatment and mechanical properties by treatment time. The wood impregnated by water-soluble melamine resin under vacuum pressure showed better incombustibility than that of a water-soluble fire retardant sprayed wood. Therefore, this treatment could be used for improving incombustibility of wood.

• Parasites, Hosts and Diseases
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• v.49 no.1
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• pp.9-15
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• 2011

To understand the distribution of Giardia cysts in drinking water supplies in Seoul, Korea, we collected water samples quarterly at 6 intakes in the Han River, its largest stream and 6 conventional water treatment plants (WTPs) serving drinking water, from 2000 to 2009. Giardia cysts in each of 10 L water were confirmed in 35.0% of intake water samples and the arithmetic mean was 1.65 cysts/10 L (range 0-35 cysts/10 L). The lowest cyst density was observed at Paldang and Kangbuk intakes, and the pollution level was higher at 4 intakes downstream. It seemed that these 4 intakes were under influence of Wangsuk stream at the end of which cysts were found in all samples with the mean of 140 cysts/10 L. The annual mean number of cysts was 0.21-4.21 cysts/10 L, and the cyst level at the second half of the 10 years was about 1/5 of that at first half on average. The cysts were more frequently found in winter, and their mean density was 3.74 cysts/10 L in winter and 0.80-1.08 cysts/10 L in other seasons. All finished water samples collected at 6 WTPs were negative for Giardia in each of 100 L sample for 10 years and cyst removal by physical process was average 2.9-log. It was concluded that conventional water treatment at 6 WTPs of Seoul appears to remove the cysts effectively under the present level of their source water. Domestic wastewater from the urban region could be an important source of Giardia pollution in the river.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.06a
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• pp.155-170
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• 1998

1. The flux for hydrophilic CA membrane is higher than that for hydrophobic PES membrane at any operating conditions. The difference in bpth fluxes becomes greater as the water recovery is lower. 2. Backwash pressure should be more than twice as high as filtration pressure in order to maintain the higher flux. Backwash frequency is independent of the flux when the UF is operated under the same water recovery. 3. The relatively lower crossflow velocity of around 0.1 m/s would be appropriate because of the lower energy consumption per treated water. 4. The membrane fouling occurring at high turbidity and high concentration of organic compounds in raw water can reduce the flux and increase the removal of the organic compounds. 5. It is confirmed by the pilot plant testing that the UF by using the CA membrane module was well applicable to the drinking water treatment.

• Membrane and Water Treatment
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• v.2 no.2
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• pp.121-136
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• 2011

A bench-scale test has recently been proposed as a predictive tool to minimize the scope of pilot-scale testing or to optimize the operation of full-scale membrane filtration systems. Consequently, a bench-scale testing unit was developed for this purpose and systematically evaluated in this study. This unit was capable of accommodating commercially available, low pressure, hollow fiber (LPHF) membranes with various configurations for testing under conditions comparable to real-world applications. Reproducibility of this unit in assessing membrane fouling and microbial removal efficiency of LPHF membranes was tested and statistically comparable results were obtained. This unit serves as a useful apparatus for academic researchers and utilities to evaluate the performance of LPHF membranes used for water treatment.

• Membrane and Water Treatment
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• v.8 no.2
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• pp.149-160
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• 2017

This study investigated effects of NaOH cleaning on the intrinsic permeability of polyvinylidene fluoride (PVDF) membranes and flux recoveries and membrane resistances under various conditions encountered during ultrafiltration in water treatment plants. The NaOH cleaning using 10,000 mg/L NaOH led to discoloration of PVDF membranes and had little effect on water flux. The NaOH cleaning was efficient in removing the fouling layer caused by humic water. However, long filtration induced a fouling layer that was not removed easily by NaOH cleaning. The lower temperature during filtration yielded rapid increases in transmembrane pressure and decreases in NaOH cleaning efficiency. The alkaline cleaning of PVDF changed the membrane properties such as the hydrophobicity and morphology. Foulant properties, operational conditions such as temperature, and chemical agents should be considered for cleaning strategies for PVDF applied in water treatment.