• Journal of Korea Water Resources Association
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• v.55 no.spc1
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• pp.1251-1260
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• 2022

Recently, due to the deterioration of watermains and the detachment of scale which is accumulated on the watermain surface, water quality accidents in a water supply network occur frequently. As scale accumulated on watermains is stabilized, it may not cause water quality accidents under the normal operating condition. However, due to water hammer or transient flow caused by the abrupt velocity and/or direction of flow change, it can be detached from the watermain surface resulting in water quality accidents. To prevent these kinds of water quality accidents, it is required to remove scale by watermain cleaning regularly. Many researches about flushing which is the most popular water cleaning method are focused on the desirable velocity criteria and the cleaning condition to accomplish the effect of flushing whereas less amount of research effort is given to develop a method to consider whether the desirable velocity for flushing can be obtained before flushing is performed. During flushing, the major and minor headloss is occurred when flushing water flows through a hydrant or drain valve. These headloss may slow down the velocity of flushing water so that it can reduce the flushing effect. Thus, in this study, we suggest a method to simulate the flow velocity of flushing water using "MinorLoss Coefficient" and "Emitter Coefficient" in EPANET. The suggested method is applied to a sample network and the water supply network of "A" city in Korea to compare the flushing effect between "flushing through a hydrant" and "flushing through a drain valve". In case of "flushing through a hydrant", if the hydraulic condition ocurring from a watermain pipe connecting to the inlet pipe of a hydrant to the outlet of a hydrant is not considered, the actual flowrate and velocity of a flow is less than the simulated flowrate and velocity of a flow. In case of "flushing through a drain valve", the flushing velocity and flowrate can be easily simulated and the difference between the simulated and the actual velocity and flowrate is not significant. Also, "flushing through a drain valve" is very effective to flushing a long-length pipe section because of its efficiency to obtain the flushing velocity. However, the number and location of a drain valve is limited compared to a hydrant so that "flushing through a drain valve" has a limited application in the field. For this reason, the engineer should consider various field conditions to come up with a proper flushing plan.

• Membrane Journal
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• v.24 no.1
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• pp.39-49
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• 2014

The effects of pH and oxygen back-flushing were investigated in hybrid process of ceramic microfiltration and PES (polyethersulfone) beads loaded with titanium dioxide ($TiO_2$) photocatalyst for advanced drinking water treatment in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). As increasing pH, $R_f$ decreased and J increased. Finally the maximum $V_T$ could be acquired at pH 9. Treatment efficiencies of turbidity was almost same independent of pH. Treatment efficiency of dissolved organic matters (DOM) decreased as increasing pH. As results of comparing the oxygen and nitrogen back-flushing, $R_{f,180}$ at oxygen back-flushing was the lower than that at nitrogen back-flushing, and the dimensionless final permeate flux ($J_{180}/J_0$) by initial permeate flux ($J_0$) at oxygen back-flushing was maintained the higher than that at nitrogen back-flushing except 10 and 12 min of back-flushing period (FT). Treatment efficiency of turbidity at oxygen back-flushing was a little higher than that at nitrogen back-flushing. Treatment efficiency of the DOM at nitrogen back-flushing was the higher than that at oxygen back-flushing. Also, treatment efficiency of turbidity at saturated oxygen was similar with those of oxygen and nitrogen back-flushing, but the treatment efficiency of DOM was increased significantly because OH radical could be generated by reaction between saturated oxygen and photocatalyst.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.93-103
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• 2008

This study was conducted to optimize a unidirectional flushing program in distribution pipes by analysis of water pressure, velocity, quality, and other parameters during flushing. As a result, correlation coefficient between flushed pipe length and the flushing duration was obtained $R^2=0.83$ and the equation $Y_{Time}=0.0571{\cdot}X_{Pipe\;length}+4.7648$ for 10 pipes. The averaged flushing velocity in the pipes, 1.1 m/s, was enough to remove loose deposits on the inner wall of the pipes. 3 of 92 water samples taken during flushing met the National Drinking Water Quality Standard for Fe and Mn, but not for Al. Turbidity less than 1 NTU is suggested for the appropriate criteria to finish flushing in pipes. The coefficient of determination ($R^2$) between turbidity and TSS was 0.95 and the equation was induced as $Y_{TSS}=1.2068{\cdot}X_{Turbidity}$. The amount of removed deposits could be estimated from the turbidity data of discharged water in field because turbidity and TSS in the discharged water is highly correlated.

• Journal of Embryo Transfer
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• v.26 no.3
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• pp.159-164
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• 2011

This study was performed in order to determine optimum flushing solution using the direct embryo collection (DEC). Donors, at random stages of the estrous cycle, received a CIDR. 7 days later, 200 mg FSH was treated with 40, 30, 20, 10 mg FSH levels in declining doses twice daily by intramuscular injection for 4 days. On the 3$^{rd}$ day administration of FSH, 25 mg $PGF_2{\alpha}$ was administered and CIDR was withdrawn. After FSH injections were complete, donors were artificially inseminated twice at 12 hr intervals. The donor cattle received 250 ${\mu}g$ GnRH at time of 1$^{st}$ insemination and embryos were recovered 8 days after the 1$^{st}$ insemination. Embryo collection from superovulated donors were performed to flushing by DEC and conventional method. As a results, the average number of recovered embryos were significantly higher as 19.1${\pm}$1.40 with DEC method than 12.0${\pm}$0.44 with conventional embryo collection method, respectively (p<0.05). Also, The average number of transferable embryos were significantly higher (p<0.05) as 15.8${\pm}$1.72 with DEC method than 6.9${\pm}$0.35 from conventional embryo recovery procedures. Meanwhile, number of recovered embryos and number of recovered transferable embryos following the number of flushing times until 6${dr}$ flushing were significantly higher as 8.6${\pm}$0.53 and 8.6${\pm}$0.53 from 2$^{nd}$ flushing time than other groups (p<0.05). No. of Ear. B stage embryos were significantly higher as 3.9${\pm}$0.90 and 3.9${\pm}$0.90 with 2$^{nd}$ flushing time in total collected embryos and transferable embryos (p<0.05). Com M stage embryos were significantly higher as 3.7${\pm}$1.00 in 2$^{nd}$ flushing time and as 2.2${\pm}$0.76 in 3$^{rd}$ flushing time for recovered embryos (p<0.05). In transferable embryos, Com. M stage embryos were significantly higher (p<0.05) as 3.7${\pm}$1.00 in 2$^{nd}$ flushing time and as 2.2${\pm}$0.76 in 34$^{dr}$ flushing time, also. No. of degradation embryos was significantly higher as 2.2${\pm}$0.72 in 5${rd}$ flushing time, On the other hand, degradation embryos was not observed in transferable embryos (p<0.05). In conclusion, these results suggest that DEC method should effective methods for production of in vivo embryos using less flushing solution following perform until 4$^{rd}$ flushing time than conventional embryo collecting method. Also, it might be effectively collection of transferable embryos following more less procedure times compared to conventional embryo recovery methods.

• Korean Membrane Journal
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• v.11 no.1
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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.

• International Journal of Ocean System Engineering
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• v.2 no.2
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• pp.71-81
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• 2012

Several methods have been proposed to control the sedimentation process. These include catchment management, flushing, sluicing, density current venting, and dredging. Flushing is used to erode previously deposited sediments. In pressurized flushing, the sediment in the vicinity of the outlet openings is scoured and a funnel shaped crater is created. In this study, the effect of localized vibrations in the sediment layers on the dimensions of the flushing cone was investigated experimentally. For this purpose, experiments were carried out with two bottom outlet diameters, five discharge releases for each desired water depth, and one water depth above the center of the bottom outlets. The results indicate that the volume and dimensions of the flushing cone are strongly affected by localized vibrations.

• Journal of Radiation Protection and Research
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• v.48 no.2
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• pp.77-83
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• 2023

Background: The purpose of this study is to purify uranium (U[VI])-contaminated soil-flushing effluent using the precipitation-distillation process for clearance. Precipitation and distillation are commonly used techniques for water treatment. We propose using a combination of these methods for the simple and effective removal of U(VI) ions from soil-flushing effluents. In addition, the U concentration (Bq/g) of solid waste generated in the proposed treatment process was analyzed to confirm whether it satisfies the clearance level. Materials and Methods: Uranium-contaminated soil was decontaminated by soil-flushing using 0.5 M sulfuric acid. The soil-flushing effluent was treated with sodium hydroxide powder to precipitate U(VI) ions, and the remaining U(VI) ions were removed by phosphate addition. The effluent from which U(VI) ions were removed was distilled for reuse as a soil-flushing eluent. Results and Discussion: The purification method using the precipitation-distillation process proposed in this study effectively removes U(VI) ions from U-contaminated soil-flushing effluent. In addition, most of the solid waste generated in the purification process satisfied the clearance level. Conclusion: The proposed purification process is considered to have potential as a soil-flushing effluent treatment method to reduce the amount of radioactive waste generated.

• Membrane Journal
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• v.23 no.4
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• pp.267-277
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• 2013

The effect of water back-flushing period (FT) and water back-flushing time (BT) was compared with the previous study of nitrogen back-flushing in viewpoints of resistance of membrane fouling ($R_f$), permeate flux (J), and total permeate volume ($V_T$) in hybrid process of tubular ceramic microfiltration and PES (polyethersulfone) beads loaded $TiO_2$ photocatalyst for advanced drinking water treatment. As FT decreasing, Rf decreased, but J and $V_T$ increased. Turdity treatment efficiency was the maximum at NBF (no back-flushing) and increased a little as FT decreasing in both water and nitrogen back-flushing. Organic matter treatment efficiency was the maximum at FT 4 min in water back-flushing, but increased as FT decreasing in nitrogen back-flushing. As BT increasing, Rf and resistance of reversible membrane fouling ($R_{rf}$) decreased, but J and $V_T$ increased. The turdity treatment efficiency was almost constant beyond 98% in water back-flushing, but increased as BT increasing except NBF in nitrogen. The organic matter treatment efficiency was the maximum at BT 6 sec in water back-flushing, but increased as BT increasing except NBF in nitrogen. The $V_T$ was the maximum at BT 30 and FT 2 min, and optimal condition was BT 30 sec per FT 2 min in this experimental range.

• Membrane Journal
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• v.24 no.2
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• pp.123-135
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• 2014

The effects of pH, saturated oxygen, and back-flushing media were investigated in hybrid process of tubular ceramic microfiltration and $TiO_2$ photocatalyst-loaded PES (polyethersulfone) beads for advanced drinking water treatment, and compared results of water, nitrogen, or oxygen back-flushing in the viewpoints of membrane fouling resistance ($R_f$), permeate flux (J) and total treated water ($V_T$). $R_f$ decreased, and J and $V_T$ increased as decreasing pH. Turbidity treatment efficiencies were similar at water or nitrogen back-flushing independent of pH, but DOM (dissolved organic matter) treatment efficiency did not have a trend at water back-flushing. $R_f$ at NBF (no back-flushing) with SO (saturated oxygen) was the lower than that at NBF without SO. Also, the DOM treatment efficiency at NBF with SO was the lower than that at NBF without SO. It happened because OH radicals produced by reaction of SO and photocatalyst could dilute with water inside the module. The DOM treatment efficiency of gas back-flushing showed the larger than that of water back-flushing at back-flushig period 10 min. It proved that the adsorption or photo-oxidation of PES beads could be activated by the more effective bead-cleaning of gas back-flushing than water back-flushing.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.1
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• pp.30-36
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• 1998

For successful soil flushing process selection of appropriate flushing reagents is essential. Futhermore, obtaining operating parameters for site remediation application through various bench-scale tests is also important. In this research a series of organic acids (acetic, citric, oxalic, and succinic acids) were tested for flushing capability. Copper-contaminated natural soil was used as a test medium, and flushing experiments were performed with batch system. All the organic acids used did not provide effective flushing conditions at concentration of 1 mM. At the acid concentration of 50 and 100 mM copper was removed efficiently although 50 and 100 mM did not show any significant differences in removal efficiencies. Citric acid and oxalic acid removed copper more efficiently than the others, and especially, citric acid showed over 87% of removal efficiency of copper at near neutral pH of 5 to 7. Speciation of extracted copper using GEOCHEM simulation showed majority of extracted copper existed as complexed with organic acids and only small portion of organic acids were complexed with copper indicating promising application of soil flushing with organic acid to heavy metal-contaminated site remediation.