• Title/Summary/Keyword: Flushing time

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Advanced Water Treatment of High Turbidity Source by Hybrid Process of Ceramic Ultrafiltration and Photocatalyst: 1. Effects of Photocatalyst and Water-back-flushing Condition (세라믹 한외여과 및 광촉매 혼성공정에 의한 고탁도 원수의 고도정수처리: 1. 광촉매 및 물역세척 조건의 영향)

  • Cong, Gao-Si;Park, Jin-Yong
    • Membrane Journal
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    • v.21 no.2
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    • pp.127-140
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    • 2011
  • The effects of $TiO_2$ photocatalyst coating bead concentration, water-back-flushing period (FT), and back-flushing time (BT) were investigated in hybrid process of ceramic ultrafiltration and photocatalyst for advanced drinking water treatment in this study. Photocatalyst coating bead concentration was changed in the range of 10~40 g/L, FT in 2~10 min and BT in 6~30 sec. Then, we observed the effects on resistance of membrane fouling $(R_f)$, permeate flux (J) and total permeate volume $(V_{\Upsilon})$ during total filtration time of 180 min. As decreasing photocatalyst coating bead concentration, $R_f$ increased and J decreased. $V_{\Upsilon}$ was the highest value of 8.85 L at 40 g/L of photocatalyst coating bead concentration. At FT change experiment, $R_f$ decreased and J increased as decreasing FT. Then $R_f$ decreased and J increased according to increasing BT at BT change experiment. Because at NBF (no back-flushing) dramatic membrane fouling reduced membrane pore size, turbid and dissolved organic matters ($UV_{254}$ absorbance) could be removed efficiently. Therefore, treatment efficiencies of turbidity and dissolved organic matters were the highest at NBF. Then by cleaning effect of photocatalyst coating bead, the treatment efficiencies of turbidity and dissolved organic matters increased as decreasing FT and increasing BT.

Effect of Water-back-flushing Time and Period in Advanced Water Treatment System by Ceramic Microfiltration (세라믹 정밀여과에 의한 고도정수처리 시스템에서 물 역세척 시간 및 주기의 영향)

  • Park, Jin-Yong;Lee, Hyuk-Chan;Cho, Jae-Hyeong
    • Membrane Journal
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    • v.18 no.1
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    • pp.26-34
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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 advanced water treatment system by ceramic microfiltration. We investigated effect of water-back-flushing period (FT) and time (BT), and tried to find the optimal operating conditions. BT was fixed at 3 sec and FT was changed in $30{\sim}120$ sec to inspect effect of FT. Also, FT was fixed at 120 sec and BT was changed as $3{\sim}12$ sec at experiment of BT effect. At both two experiments, TMP was fixed at 1.52 bar, water-back-flushing pressure at 0.98 bar, feed flow rate at 0.5 L/min, and feed water temperature at $20^{\circ}C$. As the result, optimal FT was 30 sec at fixed BT 3 sec in our experimental range. It means that the more frequent back-flushing was the more effective to reduce membrane fouling. However, there were not large effects of FT due to a short BT. Then, increasing BT at fixed FT 120 sec could decrease resistance of membrane fouling ($R_f$) and increase permeate flux (J) and dimensionless permeate flux ($J/J_o$), and the most total permeate volume ($V_T$) could be produced at the maximum BT 12 sec.

Pilot Study of a Brief WeChat Intervention in China to Increase Students' Willingness to Assist a Flushing Student to Reduce Alcohol Use

  • Zhang, Fan;Yuen, Lok-Wa;Ding, Lanyan;Newman, Ian M.;Shell, Duane F.
    • Journal of Preventive Medicine and Public Health
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    • v.51 no.6
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    • pp.320-325
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    • 2018
  • Objectives: This pilot study tested the effectiveness of a brief alcohol-related intervention delivered by the social media app WeChat to teach about ethanol-induced facial flushing and increase the willingness of students who see another student flushing to suggest that he or she should reduce or stop drinking. In the context of Chinese drinking culture, it is sometimes socially difficult to refuse a drink, even when experiencing physical discomfort, such as flushing. Methods: Classrooms of students in a medical university in China were randomly assigned to the intervention or control group. Students in the intervention group were invited to view 3 alcohol education lessons on WeChat during a 2-week period. A pretest and posttest before and after the 2-week period assessed changes in students' willingness to intervene if they saw someone flush while drinking. Data were collected about students' alcohol use and their ratings of the lessons. Results: Mixed-design analysis of variance yielded a significant time-by-treatment interaction effect on the variable of willingness to suggest that a flushing person stop or slow down their drinking, and the change was significant between the intervention and control groups. One-way analysis of covariance yielded a significant treatment effect at the posttest, after controlling for the pretest score. Students rated the lessons above the midpoint of the scale for being informative, interesting, and useful. Conclusions: The pilot study showed that a brief alcohol-related intervention delivered by WeChat could produce a measurable positive change in the willingness of university students to suggest that a student who flushes should stop drinking. This pilot study also suggested improvements for future lessons and evaluation design.

Effect of $N_2$-back-flushing Time and TMP in Lake Water Treatment Using Multichannel Ceramic Microfiltration Membranes (다채널 세라믹 정밀여과막으로 호소수 처리시 질소 역세척 시간 및 막간 압력차의 영향)

  • Park, Jin-Yong;Park, Bo-Reum
    • Membrane Journal
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    • v.17 no.2
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    • pp.124-133
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    • 2007
  • In this study, we treated lake water by 2 kinds of multichannel ceramic micro filtration membranes. We could investigate effects of $N_2-back-flushing$ time (BT) and transmembrane pressure (TMP), and find optimal operating conditions. The BT were changed in $10{\sim}60$ sec, TMP in $0.6{\sim}2.0$ bar at fixed filtration time (FT) 8 min, flow rate 2.0 L/min and back-flushing pressure 2.0 bar. Also, the optimal conditions were discussed in the viewpoints of resistance of membrane fouling $(R_f)$, dimensionless permeate flux $(J/J_o)$, permeate flux (J) and total permeate volume $(V_T)$. As result, optimal back-flushing conditions for HC04 ($0.4{\mu}m$ pore size) and HC10 membrane $(1.0{\mu}m)$ were BT=10 sec and BT=20 sec, respectively. Then, higher TMP should increase the driving force, and could produce more VT. Average rejection rates of pollutants were higher than 95.4% for turbidity, $12.7{\sim}20.1%\;for\;COD_{Mn},\;0.0{\sim}6.4%\;for\;NH_3-N,\;1.9{\sim}4.6%$ for T-N and $34.9{\sim}88.4%$ for T-P.

A Study on the Treatment of Soil Flushing Effluent Using Electrofloatation : Effects of Electrolyte and pH (전기부상을 이용한 토양세정 유출수 처리에 관한 연구 : 전해질 및 pH의 영향)

  • 소정현;최상일;조장환
    • Journal of Soil and Groundwater Environment
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    • v.8 no.3
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    • pp.56-60
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    • 2003
  • The optimal operation conditions of electrofloatation for oil-water separation of soil flushing effluent including electrolyte and pH were investigated. The reactor (200 ${\times}$ 10 ${\times}$ 15 cm) for the experiment was constructed by using acrylic plate. Diesel concentration was 1,000 mg/L in the 1 % mixed surfactant solution ($POE_5$: $POE_{14}$ 1: 1). Titanium coated electrode was used as cathode and stainless steel electrode as anode. Reaction time was 62 minutes (reaction time: 60 min., flotation time: 2 min.) and voltage was 6 V. The separation efficiency of electrofloatation was improved to 40% by electrolyte addition. Furthermore, NaCl (1N) added as electrolyte was showed enhanced efficiency compared to NaOH (1N). While, the effect of both NaCl and NaOH was sequentially increased in the range of 0.2∼1.0% (0.02∼0.1 M). The equilibrium time was found as 20 min. in the range of 0.4∼1.0% (0.04∼0.1M) for both of them.

Improvement of sampling method for bacteriological test in tap water (수도꼭지에서 미생물 검사 목적의 샘플링 방법 개선 연구)

  • Lee, Eun-Sook;Lee, Dong-Sik;Lee, Mok-Young;Lee, Man-Ho;Han, Sun-Hee
    • Journal of Korean Society of Water and Wastewater
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    • v.25 no.4
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    • pp.519-525
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    • 2011
  • We studied on the effect of faucet cleanliness, faucet conditions (screen, mixing faucet), and flushing time for bacterial detection in tap water. As results, tap water should be left to run to waste for 2 to 3 minutes and if a questionable cleanliness is questionable, disinfect the faucet by using flaming or other methods before sampling. We proposed sampling method to decrease effect of factors associated with bacterial detection in tap water and contributed to be evaluated more accurate water quality.

Effects of Flushing in Dental Unit Waterlines on the Bacterial Contamination Level (치과용 유니트 수관 물 빼기(Flushing)가 세균 오염도 감소에 미치는 영향)

  • Yoon, Hye Young;Lee, Si Young
    • Journal of dental hygiene science
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    • v.15 no.5
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    • pp.659-665
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    • 2015
  • A wide variety of methods have been used to control Dental Unit Waterline (DUWL) contamination. Among the methods, flushing is mainly used because it is simple and easy to use. Generally, flushing of DUWL for 20 or 30 sec before using high speed handpieces or scalers is recommended. However, the appropriateness of flushing time was not investigated thoroughly. The purpose of this study was to check the effective time of flushing for decreasing bacterial contamination. Seven dental unit chairs were randomly selected in student clinical simulation laboratory for this experiment. DUWLs were continuously flushed and water samples were collected at an interval of 30 seconds for 15 minutes. From five dental unit chairs, water samples were collected every 10 seconds for 1 minute. Bacterial levels in water samples were examined by the culture method on R2A plates. After 10 second flushing of DUWLs, the number of bacteria significantly reduced and decreased continuously up to 40 seconds. However, even after the water was flushed for 15 minutes, the bacterial contamination level was not reduced below recommended bacteria level, 200 CFU/ml. In addition to flushing, the periodic chemical disinfection is required to control the DUWL water to the recommended level.

Advanced Water Treatment of High Turbidity Source by Hybrid Process of Photocatalyst and Ceramic Microfiltration: Effect of Water Back-flushing Period (광촉매 및 세라믹 정밀여과 혼성공정에 의한 고탁도 원수의 고도정수처리: 물역세척 주기의 영향)

  • Park, Jin Yong;Park, Sung Woo
    • Membrane Journal
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    • v.22 no.4
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    • pp.243-250
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    • 2012
  • The effect of water back-flushing period (filtration time, FT) was investigated in hybrid process of alumina microfiltration and photocatalyst for advanced drinking water treatment in this study, and compared with the previous studies with carbon microfiltration or alumina ultrafiltration membranes. The FT was changed in the range of 2~10 min with fixed 10 sec of BT. Then, the FT effects on resistance of membrane fouling ($R_f$), permeate flux (J) and total permeate volume ($V_T$) were observed during total filtration time of 180 min. As decreasing FT, $R_f$ decreased and J increased as decreasing FT, which was same with the previous results with carbon microfiltration or alumina ultrafiltration membranes. The treatment efficiency of turbidity was high beyond 98.1%, and the effect of FT was not shown on treatment efficiency of turbidity, which was same with the previous result of carbon microfiltration. The treatment efficiency of organic matters was the highest value of 89.6 % at FT 8 min, which was a little higher than those of the previous results, and the effect of FT was not shown on treatment efficiency of organic matters.

A Study on the Electrical Discharge Blind Hole Tap Machining of STD11 with Copper Electrode (구리전극봉을 이용한 합금공구강재(STD11)의 비관통 방전 탭 가공에 관한 연구)

  • Park, In-Soo;Wang, Duck-Hyun;Kim, Gi-Tae
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.16 no.3
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    • pp.38-44
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    • 2017
  • The technology of electrical discharge tap machining may be appropriate for making thread out of highly brittle material. Especially, it is very difficult to machine tap with the traditional method if the brittle material has been hardened by quenching. In this study, the shape of electrical discharge blind hole tap machining was analyzed by discharge time, discharge current, and the flushing hole condition after quenched the tool steel of STD11 has discharged the tap shape with a screw-shaped copper(Cu) electrode. An experimental design was planned and analyzed by Taguchi robust experimental design. The result showed that the shape of the blind hole discharge tap was influenced by the flushing hole, discharge time, and discharge current. The most important factor of the processing conditions was found to be the discharge current. When blind hole EDM with a copper electrode with a flushing hole was conducted, the discharged shape was found to be smooth and the angle of the discharged tapped thread was also found to be close to the thread angle of $60^{\circ}$. As the values of discharge time and discharge current increased, the EDMed surface coarsened due to the increase of the single discharge energy and the shape of the thread collapsing.

A Study on the Seasonal Variations of Fresh Water Distribution and Flushing Time in Suyoung Bay (수영만에 유입된 담수의 체류시간과 그 계절적 변동 특성)

  • Lee, Byeong-Geol;Jo, Gyu-Dae;Kim, Dong-Seon
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.27 no.3
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    • pp.170-177
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    • 1991
  • This paper presents the seasonal variation of distribution and flushing time of the fresh water in Suyoung Bay based on the monthly observation from May 1989 through April 1990 and Pusan City Report of Suyoung Bay. Most of Suyoung river water was trapped inside of the bay west of the Dong-Baek Island located. Low salinity water lies dominantly on the right hand side of the Suyong river. Salinity structure of the bay is the well mixed type in summer and the partially mixed type in other season. The fresh water fraction varied in an exponetial manner from unity at the head of bay toward a value of zero at the its mouth. The calculated average flushing time during a year was about 10-15days. About 1.5 days was in summer because the strong fresh water discharge from the river was dominated in the bay.

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