• Korean Membrane Journal
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• 제11권1호
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• pp.15-20
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• 2009

The periodic water-back-flushing using permeate water was performed to minimize membrane fouling and to enhance permeate flux in tubular ceramic ultrafiltration (UF) system for Gongji stream water treatment in Chuncheon city. The filtration time (FT), which was the water-back-flushing period, 2 min with periodic 15 sec water-back-flushing showed the highest value of dimensionless permeate flux ($J/J_o$), and the lowest value of resistance of membrane fouling ($R_f$), and we acquired the highest total permeate volume ($V_T$) of 6.35 L. Consequently FT 2 min at back-flushing time (BT) 15 sec could be the optimal condition in advanced UF water treatment of Gongji stream. Then the average rejection rates of pollutants by our tubular ceramic UF system were 99.4% for Turbidity, 31.8% for $COD_{Mn}$, 22.6% for $NH_3$-N and 65.9% for T-P.

• 아시안잔디학회지
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• 제4권2호
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• pp.85-100
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• 1990

Turfgrass management had not been recognized as the subject to research until the social demand for turfgrass increased. This study was carried out to compare the effects of several complete fertilizers and ureaform(UF) with those of traditional fertilizers used for general agriculture. Complete fertilizers used in this study include Jandibiryo, Chojikwanri, Wonyebokbi and 18 - 18 - 18. Three exteriments were conducted in the established zoysiagrass field (over 5 years), in the recently established zoysiagrass field(1 years), and in the pots using artificially mixed media. In the established zoysiagrass, UF, Wonyebokbi, Chojikwanri and 18 - 18 - 18 resulted in higher growth rate, while Chojikkwanri and Jandibiryo showed better performance in the recently established zoysiagrass. Jandibiryo resulted in higher growth rate of zoysiagrass with the artificially mixed soil which is relatively infertile. Righer growth rates were maintained longer with UF, Jandidiryo, Chojikwanri than urea 18-18-18 and Wonyebokbi. Wonyebokbi had the characteristics of producing more stolons and rhyzomes than the other fertilizers.

• 한국발생생물학회지:발생과생식
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• 제13권4호
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• pp.239-247
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• 2009

속성장 육종 넙치(selected line of olive flounder cultured, SF)의 수정란의 부화율 및 기형률, 자치어의 성장을 일반 넙치(unselected line of olive flounder cultured, UF)와 비교하였다. 동일한 날에 획득한 SF구 및 UF구 수정란의 부화율은 SF구가 96.2${\pm}$1.7%, UF구는 90.4${\pm}$2.1%로 SF구가 높았으며, 기형률은 UF가 유의하게 높았다. 이들 수정란으로부터 부화한 자어를 8주 동안 사육한 결과, 부화후 1주째에 SF 및 UF구의 전장은 각각 4.36${\pm}$0.24, 4.25${\pm}$0.20 mm였던 것이 실험 종료시에 각각 50.49${\pm}$2.67, 40.55${\pm}$3.13 mm로 SF구가 UF구에 비해 24.5% 빨랐다. 체고는 부화후 1주째에 각각 1.13${\pm}$0.08, 1.18${\pm}$0.07 mm였으며, 종료시에 각각 16.30${\pm}$0.085, 13.50${\pm}$0.96 mm로 SF가 UF구에 비해 20.7% 크게 나타났다. 실험 종료시에 체중은 각각 1.036${\pm}$0.118, 0.557${\pm}$0.073 g으로 SF구가 UF에 비해 43.0% 빨랐다. 또한 실험 종료시에 SF구와 UF구의 체형지수는 각각 0.85${\pm}$0.02, 0.82${\pm}$0.03으로 SF구가 유의하게 높았으며, 비만도는 각각 7.99${\pm}$0.33, 8.22${\pm}$0.52로 SF구가 UF구에 비해 낮았다. 이상의 결과는 속성장을 위해 선발 육종된 넙치가 일반 넙치에 비해 성장이 월등이 우수하며, 체형이 자연산 넙치에 가깝게 개선되었음을 나타내었다.

• 멤브레인
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• 제9권4호
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• pp.193-201
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• 1999

기존의 정수처리 공정인 응집 침전 과정을 대체하여 분리막을 이용한 상수처리 시스템의 개발을 목적으로한다. 따라서 4가지 형태의 정수처리 공정과 분리막의 분획 분자량을 변화시켰을 때 막 투과수의 변화와 안정적이며 높은 투과수를 얻기 위해 필요한 운전 조건의 최적화를 실험하였다 실험결과 한외여과막이 정밀여과막보다 막 투과수 감소경향이 완만했으며 초기 투과수 회복율은 더 높았다. 수질 분석의 결과 한회여과막이 정밀 여과막보다 우수하였지만 전처리에 의한 차이는 나지 않았다. 운전 조건에 따른 flux 는 온도, 선속도가 높을수록 압력이 낮을수록 flux 감소율이 적은 경향을 나타내었다.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1931-1938
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• 2021

Uranium ingot is produced by metallothermic reduction of uranium tetrafluoride using magnesium or calcium as reductant. Presence of oxygen containing compounds viz. uranyl fluoride and uranium oxide in the starting uranium fluoride has a significant effect on the firing time, final temperature of the charge, slag-metal separation and hence the metal recovery. As reported in the literature, the maximum tolerable limit for uranyl fluoride in the UF₄ is 2.5 wt% and limit for uranium oxide content is in the range 2-3 wt%. No theoretical or experimental basis is available till date for these limits. Analyses have been carried out in this study to understand the effect of UO₂F₂ concentration in the starting fluoride on the final temperature of the products and thus the reduction characteristics. UF₄ having uranyl fluoride concentration, less than as well as more than 2.5 wt%, have been investigated. Thermodynamic calculations have been carried out to arrive at a general expression for the final temperature attained by the products during calciothermic reduction of UF₄. Finally, an upper limit for the oxygen containing impurities has been estimated using the CaO-CaF₂ phase diagram.

• Membrane and Water Treatment
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• 제2권3호
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• pp.175-185
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• 2011

Ultrafiltration is an emerging technology for drinking water treatment because it produces better water quality as compared with conventional treatment systems. More recently, the combination of UF technology with other processes in order to improve its performance has been observed. These associations aim to maximize the contaminants removal and reduce membrane fouling. The operational performance of contaminants removal and water production of two UF pilot plants was compared. The first plant (Guarapiranga) was fed with raw water and the second plant (ABV) with pre-treated water by the coagulation, flocculation and sedimentation processes at Alto da Boa Vista WTP (Sao Paulo, Brazil). Both units operated continuously for approximately 2,500 hours, from September/2009 to January/2010. The results showed that the ABV UF pilot plant was able to operate at higher specific fluxes (6.2 $L.d^{-1}.m^{-2}.kPa^{-1}$ @ $25^{\circ}C$) than Guarapiranga (3.1 $L.d^{-1}.m^{-2}.kPa^{-1}$ @ $25^{\circ}C$). However, the number of chemical cleanings conducted in both pilot units during the considered operation period was the same (4 chemical cleanings for each plant), which shows that the pre-treatment reduced the membrane fouling. The water quality at ABV for all the variables analyzed was better, but the feed water quality was also better due to pretreatment. The rejection values for the different contaminants were higher at Guarapiranga mainly because of a pollution load reduction after pre-treatment at ABV. Even with the better performance of the ABV UF pilot plant, it is necessary to take into consideration the complexity of the complete treatment system, and also the costs involved in the construction and operation of a full-scale treatment unit.

• Membrane and Water Treatment
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• 제11권5호
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• pp.323-331
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• 2020

With the increasing demand on reverse osmosis (RO) membranes for water purification worldwide, the number of disposed membrane elements is expected to increase accordingly. Thus, recycling and reuse of end-of-life RO membranes should be a global environmental action. In this work, we aim to reuse the spent RO membrane for nanofiltration (NF) and ultrafiltration (UF) process by subjecting the spent membrane to solvent and oxidizing solution treatment, respectively. Our results showed that solvent-treated RO membrane could perform as good as commercial NF membrane by achieving similar separation efficiencies, but with reduced water permeability due to membrane surface fouling. By degrading the polyamide layer of RO membrane, the transformed membrane could achieve high water permeability (85.6 L/㎡.h.bar) and excellent rejection against macromolecules (at least 87.4%), suggesting its reuse potential as UF membrane. More importantly, our findings showed that in-situ transformation on the spent RO membrane using solvent and oxidizing solution could be safely conducted as the properties of the entire spiral wound element did not show significant changes upon prolonged exposure of these two solutions. Our findings are important to open up new possibilities for the discarded RO membranes for reuse in NF and UF process, prolonging the lifespan of spent membranes and promoting the sustainability of the membrane process.

• 한국막학회:학술대회논문집
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• 한국막학회 1991년도 추계 총회 및 학술발표회
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• pp.4-8
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• 1991

The characterization of pore properties (mean pore size and pore size distribution) of the active layer in a UF membrane is important not only in order to obtain information about the factors affecting pore formation during membrane manufacturing but also to understand deeply the mechanism of solute and solvent transport through pores. Many methods of characterizing quantitatively the pore properties of UF membranes have been suggested in the literature: solvent and gas flow measurement, bubble point determination, electron microscopy, gas adsorption/desorption measurement, rejection measurement etc. But most of these methods involve time-consuming procedures and involve some wellknown problems and uncertainties.

• 한국식품영양과학회지
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• 제40권5호
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• pp.753-758
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• 2011

고로쇠수액의 채취적기인 3월에 채취한 수액과 후기인 4월에 채취한 수액의 이화학적 특성을 비교분석하고, 고로쇠 수액의 품질을 향상시키고자 한외여과 전후의 품질특성을 살펴보았다. 4월에 채취된 고로쇠수액이 3월에 채취된 수액보다 총균수 및 탁도가 높았지만, 한외여과 후 탁도는 비슷한 수준으로 감소하였고 미생물을 검출되지 않았다. 유기산, 총산, 유리당 및 총당 함량은 4월의 고로쇠수액이 3월 수액보다 약간 낮았지만, 조회분과 무기성분은 높은 함량을 나타내었다. 특히 칼슘은 3월과 4월에서 각각 129.40 및 166.38 mg/L로 4월이 높았다. 고로쇠나무 수액의 영양성분은 한외여과 후 약간의 감소를 나타내었지만 채취적기 이후(4월)에 채취되는 수액을 한외여과 할 경우 미생물제거 및 탁도 향상 등 품질을 향상시킬 수 있으며, 무기성분이 더 많이 함유되어 있기 때문에 영양적으로 우수할 것으로 판단되었다.

• Toxicological Research
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• 제17권
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• pp.25-35
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• 2001

In 1990, Tolerable Daily Intake (TDI) of 10 pg TCDD/kg/day for dioxins based on carcinogenicity and reproductive toxicity was determined by WHO/EURO, that resulted in the establishment of TDIs in other countries. In Japan, Ministry of Health and Welfare and Environment Agency, respectively established the TDI of 10 pg TCDD/kg/day and Health Risk Assessment Index of 5 pg TCDD/kg/day in 1996. Accumulation of new scientific data, especially by molecular toxicology since 1990, resulted in the reevaluation of TDI by WHO-ECEH and IPCS in May, 1998. At this meeting, it was stressed that \circled1 toxic effects of dioxin is mediated through Ah-receptor in both animals and humans, \circled2 use of ebody burdeni concept is better than the use of traditional NOAEL/UF approach, \circled3 inclusion of coplanar PCBs in the TDI by the use of new WHO-TEF. LOAELs (0.16~200 ng TCDD/kg/day) obtained from reproductive toxicity and immunotoxicity in rats, and neurobehavioral toxicity and induction of endometriosis in rhesus monkeys are calculated to be the body burden of 10~50 ng TCDD/kg that is 14~37 pg TEQ/kg/day as human daily intake. Finally TDI of 1~4 pg TEQ/kg/day was established by applying the UF of 10. In Japan, reproductive toxicity and immunotoxicity in rats were used to obtain LOAELs (100~200 ng TCDD/kg/day). Finally TDI of 4 pg TEQ/kg/day was established in June 1999 by applying the UF of 10 to human daily intake of 43.6 pg TEQ/kg/day which corresponds to the body burden of 86 ng TCDD/kg.