• Journal of the Korean Ceramic Society
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• v.42 no.10 s.281
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• pp.691-697
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• 2005

Porous ceramics which have closes pore were fabricated by heat treatment at 100$\∼$ 600$^{\circ}C$ for 30 min using dried water glasses with 25, 35, and 45 wt$\%$ water contents. Size and distribution of the closed pore were varied depending on the water contents and heat treatment temperature. The expansion procedure could be distinguished by two stages. The frist stage occurred around loo$\%$ due to the evaporation of water and the second stage occurred at 200$\∼$400$^{\circ}C$ due to the decomposition of Si-OH compounds. The specimen was not expanded successfully because of the softening of the dried water glass at 500$\∼$600$^{\circ}C$.

• Korean Membrane Journal
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• v.10 no.1
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• pp.33-38
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• 2008

In this study periodic water-back-flushing using permeate water was performed to minimize membrane fouling and to enhance permeate flux in tubular ceramic micro filtration system for Gongji stream water treatment in Chuncheon city. The filtration time (FT) 2 min with periodic 6 sec water-back-flushing showed the highest value of dimensionless permeate flux ($J/J_0$), and the lowest value of resistance of membrane fouling ($R_f$), and we acquired the highest total permeate volume ($V_T$) of 7.44L. Also in the results of BT effect at fixed FT 10 min, BT (back-flushing time) 20 sec showed the lowest value of $R_f$ and the highest value of $J/J_0$, and we could be obtained the highest $V_T$ of 8.04 L. Consequently FT 10 min and BT 20 sec could be the optimal condition in Gongji stream water treatment. Then the average rejection rates of pollutants by our tubular ceramic MF system were 93.8% for Turbidity, 20.7% for $COD_{Mn}$, 39.2% for $NH_3$-N and 31.5% for T-P.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.4
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• pp.321-329
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• 1999

The effect of water deficits on soybean [Glycine max (L.) Merr.] could appear on seed quality through changes of morphological plant characteristics. Two Korean genotypes, Hwangkeum (determinate growth habit) and Muhan (indeterminate growth habit), were used to examine the influences of treatment stage and method of water deficit during reproductive growth period on yield and seed quality of soybean. Water deficit at R5 or R6 stages was as damaging to seed quality as double water-deficit treatments at R2+R5 or R2+R6. However, seed from double water-deficit treatment tended to have lower oxidation-reduction potential compare to the corresponding single water-deficit treatment. In comparison with Muhan, Hwangkeum had significantly greater oxidation-reduction potential value. Seed yield per plant in both genotypes depended greatly on seed yield of branches. However, the proportion of number of branch seed to total seed umber in Hwangkeum was increased as the water deficit was applied during later reproductive stage, whereas, in Muhan the proportion was lower. Water-deficit treatments including the single and double water-deficit treatments and non-stressed treatment were able to be classified into five groups for Hwangkeum and four groups for Muhan based on the influences on yield components, number of pod, number of seed, and single seed weight, using principal component analysis. In both genotypes, R2+R5 water-deficit treatment decreased number of pod and seed, but increased single seed weight. On the contrary, R6 or R2+R6 stress increased the pod and seed number, but decreased single seed weight.

• Journal of the Korean GEO-environmental Society
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• v.14 no.4
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• pp.15-27
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• 2013

In order to plan out the Daegu G membrane filtration water treatment plant, water quantity, water quality and process stability were evaluated using the field pilot-scale tests, during the six months of continuous operation, including low water temperature period. The field model experiments, which were carried out according to the Installation Criteria of Ministry of Environment, consisted of two series : series 1 - water quality verification, and series 2 - membrane process evaluation. The process water quality met all drinking water standards with less than 0.03 NTU. Moreover, process operation showed a stable membrane pressure with 99% of recovery ratio. This shows that the tests were properly designed in terms of the influence of water loading and temperature. In conclusion, the purpose of this study is to establish core technology for advanced drinking water treatment, through on-going accumulation of engineering and construction know-how.

• Development and Reproduction
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• v.17 no.3
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• pp.289-297
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• 2013

Bisphenol A (BPA) is an estrogenic endocrine disrupter. However, depending on a way of treatment, the harmful effects of BPA have not been confirmed. Also, trans-generational effects of BPA on male reproduction are still controversial. Because the reabsorption of testicular fluid in the efferent ductules (ED) and initial segment (IS) is important for sperm maturation, the present study was designed to determine trans-generational effect of BPA administrated orally on expression of water transport-related molecules in the mouse ED and IS. Ethanol-dissolved BPA was diluted in water to be 100 ng (low), $10{\mu}g$ (medium), and $1mg/m{\ell}$ water (high). BPA-containing water was provided for two generations. Expression of ion transporters and water channels in the ED and IS were measured by relative real-time PCR analysis. In the ED, BPA treatment caused expressional increases of carbonic anhydrase II, cystic fibrosis transmembrane regulator, $Na^+/K^+$ ATPase ${\alpha}1$ subunit, and aquaporin (AQP) 1. No change of $Na^+/H^+$ exchange (NHE) 3 expression was detected. BPA treatment at medium dose resulted in an increase of AQP9 expression. In the IS, the highest expressional levels of all molecules tested were observed in medium-dose BPA treatment. Generally, high-dose BPA treatment resulted in a decrease or no change of gene expression. Fluctuation of NHE3 gene expression by BPA treatment at different concentrations was detected. These findings suggest that trans-generational exposure to BPA, even at low dose, could affect gene expression of water-transport related molecules. However, such effects of BPA would be differentially occurred in the ED and IS.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.1-8
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• 2011

Although Nepal is naturally bestowed with ample water resources, not all of the population has access to safe and clean drinking water. Waste water treatment is almost nonexistent. In the recent days the flow of population in the urban areas has increased the existing challenges of providing safe water and promoting sanitation. The prevalence of water borne diseases is high. This paper presents overview of issues like water pollution, arsenic contamination of drinking water, waste water treatment and effects of water contamination on public health. Comparison between waste water treatment regulations in South Korea and Nepal has also been made. Implementation strategies to tackle the existing water related problem for promoting public health is also recommended.

• Journal of Bio-Environment Control
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• v.19 no.4
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• pp.266-274
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• 2010

This study aim to investigate fundamentally the growth and physiological responses of tomato plants in responses to two different levels of water deficit, a weak drought stress (-25 kPa) and a severe drought stress (-100 kPa) in soil. The two levels of water deficit were maintained using a micro-irrigation system consisted of soil sensors for the real-time monitoring of soil water content and irrigation modules in a greenhouse experiment. Soil water contents were fluctuated throughout the 30 days treatment period but differed between the two treatments with the average -47 kPa in -25 kPa set treatment and the -119 kPa in -100 kPa set treatment. There were significant differences in plant height between the two different soil water statuses in plant height without differences of the number of nodes. The plants grown in the severe water-deficit treatment had greater accumulation of biomass than the plants in the weak water-deficit treatment. The severe water-deficit treatment (-119 kPa) also induced greater leaf area and leaf dry weight of the plants than the weak water-deficit treatment did, even though there was no difference in leaf area per unit dry weight. These results of growth parameters tested in this study indicate that the severe drought could cause an adaptation of tomato plants to the drought stress with the enhancement of biomass and leaf expansion without changes of leaf thickness. Greater relative water content of leaves and lower osmotic potential of sap expressed from turgid leaves were recorded in the severe water deficit treatment than in the weak water deficit treatment. This finding also postulated physiological adaptation to be better water status under drought stress. The drought imposition affected significantly on photosynthesis, water use efficiency and stomatal conductance of tomato plants. The severe water-deficit treatment increased PSII activities and water use efficiency, but decreased stomatal conductance than the weak water-deficit treatment. However, there were no differences between the two treatments in total photosynthetic capacity. Finally, there were no differences in the number and biomass of fruits. These results suggested that tomato plants have an ability to make adaptation to water deficit conditions through changes in leaf morphology, osmotic potentials, and water use efficiency as well as PSII activity. These adaptation responses should be considered in the screening of drought tolerance of tomato plants.

• Journal of Environmental Science International
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• v.24 no.12
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• pp.1551-1558
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• 2015

In Korea, many drinking water treatment plants (DWTPs) have introduced and are going to introduce biological activated carbon (BAC) process to treated dissolved organic matter (DOM) in water which are difficult to control by conventional water treatment processes. Even though more decade have passed since introduced BAC in Korea, most of BAC operating method was followed to the modified sand filter operating manuals. In case of BAC backwashing, many DWTPs set the periods of backwashing about 3~5 days. In this study, we have collected data to set the proper BAC backwashing periods from both pilot-plant and real DWTPs. We had measured heterotrophic plate count (HPC), turbidity, water temperature, dissolved organic carbon (DOC) and headloss from just after backwashing to the next backwashing time for two years. Considering water quality factors, the BAC run time from backwashing to the next backwashing could extend more 30 days without water quality deterioration if the head loss do not reach the limited level which depends on each BAC facilities' condition. It means the BAC treated water could be saved in the proportion of extended the backwashing period to the existing backwashing period.

• 수도
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• s.28
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• pp.27-36
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• 1983

Oxidation process constitute an important and often indispensable measure in the reliable production of safe drinking water. Optimal introduction of oxidation processes into the treatment of drinking water requires an exact knowledge of the reactions taking place and of their interrelationships. It is the aim of this paper to review the necessary knowledge in summarized form.

• Journal of environmental and Sanitary engineering
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• v.17 no.4
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• pp.1-9
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• 2002

In order to define about concern with discharge and water-quality, it is calculated drought flow, low flow, normal flow and wet flow in Chungju watershed from flow duration analysis. Water quality modeling study is performed for forecasting at upstream of Chungju lake. It is devided method of modeling into before and after the equipment of environmental treatment institution. And it is estimated the change of water quality. Before the equipment of environmental treatment, BOD concentration is increased from 23000 to 2006 years at all site and decrease on 2012 years. The rate of increasing BOD concentration is showed height between 2000 years and 2003 years most of all site. And after the equipment of environmental treatment, it is showed first grade of BOD water quality in most of sample site beside Jucheon river. The result of water quality modeling using drought flow showed that a lot of pollution occurred. And water quality using wet flow is good, so much discharge make more improve water quality than little discharge.