• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.109-114
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• 2012

In this study, both sedimentation and thickening experiments were conducted for residuals produced from an advanced water treatment plant for more accurate and practical design of residual treatment train. In order to design a backwashed residual sedimentation basin (SRSB) in the filter backwash water recycle system, two kinds of backwash waters, one from sand filter (SFBW) and the other from GAC adsorption bed (GACBW), were separately collected and their surface loading rate measured. In addition, in order to design a gravity thickener, batch thickening tests were conducted for concentrated residuals taken from sedimentation basin and their limiting solid flux ($SF_{L}$) measured. From the experimental results and consideration of the seasonal characteristics of the residual, surface loading rate of $70m^{3}/m^{2}{\cdot}d$ was proposed as a design parameter for SRSB and solid loading rate of 20 kg $TS/m^{2}{\cdot}d$ was proposed as a design parameter for gravity thickeners. Finally, the material mass-balance was made for the design of each unit process in the residual treatment train.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2905-2918
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• 2023

The valve assembly used in nuclear power plants is important safety-related equipment. In the new standard, the physical attributes are measured using a valve diagnosis test, which is used in the expansion to other non-tested valves using a quantitative test-basis methodology. With a motor-operated actuator, the state of stem's lubrication is related to physical attributes such as the stem factor and the friction coefficient. This study analyzed the numerical transient of fluid and solid lubrication with a squeeze film effect due to the loading rate on the stem and the stem nut using the experimental data. The differential equation that governs the motion mechanism of the stem and stem nut is established and analyzed. The flow rate, the fluid and the solid contact forces are calculated with the friction coefficient. Finally, we found that a change in the friction coefficient results from a change of the shear force in the solid contact mode during the interchange process between the solid contact mode and the fluid contact mode. The qualitative understanding of the squeeze film effect is expanded quantitatively for forces, thread surface distance, velocity, and acceleration, with consideration of the metal solid contact and fluid contact.

• Journal of environmental and Sanitary engineering
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• v.14 no.2
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• pp.25-31
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• 1999

Energy recovery technology from municipal solid waste has been increasingly established in many countries. Anaerobic treatment of municipal sewage sludge has low digestion efficiency because of low organic loading rate of sewage sludge. The purpose of this study was to evaluate anaerobic biodegradability of food waste which was based on organic loading rate and seeding rate. From the results of anaerbic biodegration, the optimum condition for seeding rate was turn out over 40%, which did not inhibition of methane production.

• Journal of Environmental Science International
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• v.15 no.10
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• pp.975-982
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• 2006

This study has been conducted to optimum operating conditions for effective acid fermentation according to OLR(organic loading rate) in the mesophilic and thermophilic acid fermentation process. The results are summarized as follows. In order to obtain reasonable acid fermentation efficiency in performing acid fermentation of food wastes in thermophilic condition, organic loading rate was required below 20 gVS/L.d. As $SCOD_{Cr}/TKN,\;SCOD_{Cr}/T-P$ of thermophilic acid fermented food wastes In organic loading rate 20 gVS/L.d were 18.9, 73.4 respectively, it was possible to utilize as external carbon source for denitrification in sewage treatment plant after solid-liquid separation as well as co-digestion of fermented food wastes and sewage sludge.

• Membrane Journal
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• v.14 no.4
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• pp.289-297
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• 2004

In this study, membranes were coupled to a sequencing batch reactor for simultaneous removal of organic matter and nitrogen, and the influences of MLSS (mixed liquor suspended solid) concentration and the sludge loading rate on membrane fouling and bioactivity were investigated. The amount of membrane fouling slightly increased with MLSS concentration at both non-aeration and aeration conditions, but effect of MLSS concentration was more significant at aeration condition. Although the effect of MLSS concentration on membrane fouling was found to be insignificant at low concentration level, extremely low sludge loading, which were generated by the maintenance of large amount of biomass in the reactor, caused severe membrane fouling, and air scouring effect decreased significantly in this condition. Specific bioactivity was constantly reduced as sludge loading rate decreased. In spite of high MLSS concentration over 17,000 mg/L, the activity of the reactor decreased at extremely low sludge loading rate presumably due to the lower oxygen transfer and the competition of biomass to deficient substrate.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.5
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• pp.747-753
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• 2006

Air flotation is a solid-liquid separation process that utilizes up-flow microbubbles to thicken activated sludge and enhance clarification efficiency. Continuous air flotation experiments were performed to investigate the effect of operation parameters such as initial MLSS (mixed liquor suspended solid) concentration, air pressure, surface loading rate, air to solid (A/S) ratio, and flotation time on thickening efficiency. An initial activated sludge concentration ranged from 3,000 to 12,000mgSS/L and thickened sludge concentration varied from 6,400 to 28,100mgSS/L. The result showed that the thickening efficiency was mainly dependent on surface loading rate, A/S ratio, and flotation time. The pressure did not affect the thickening efficiency when it kept in the range of 1.6 to 1.8 bar. Experimental results showed that the thickening efficiency of activated sludge was increased only when the feed sludge concentration exceeded 5,000mgSS/L and the thickened concentration was over 20,000mgSS/L. At this time, SS concentration in the clarified liquid was ranged from 5 to 10mg/L.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.71.1-71.1
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• 2007

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.764-767
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• 2009

For a more effectively designed gravity thickener, thickening experiments were conducted for residuals produced by a ceramic membrane water treatment plant (WTP). Two kinds of residuals, one from backwashing (BW) and the other from chemically enhanced backwashing (CEB) procedure, were separately collected during a pilot plant experiment and their limiting solid flux ($SF_L$) measured. Batch thickening experiments showed that the BW and CEB residual had $SF_L$ of 10 and $25kg/m^2{\cdot}d$, respectively. Continuous operation of a pilot-scale gravity thickener proved that a mixed BW and CEB residual could be successfully thickened at the solid loading rate (SLR) of $12kg/m^2{\cdot}d$, allowing the concentration of the thickened residual to be about $15kg/m^2{\cdot}d$. From the experimental results and consideration of the seasonal thickening characteristics of the residual, SLR of $15kg/m^2{\cdot}d$ was proposed as a design parameter for full-scale gravity thickeners.

• Environmental Engineering Research
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• v.19 no.4
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• pp.395-399
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• 2014

Operation characteristics of the sequencing batch reactor (SBR) process with electro-flotation (EF) as a solid liquid separation method (EF-SBR) were investigated. EF-SBR process showed excellent solid-liquid separation performance which enabled to separate biosolids from liquid phase within 30 min and to extend cyclic reaction time. Although influent organic loading rate was increased stepwise from 5 to 15 g COD/day, food to microorganisms (F/M) ratio could be maintained about 0.3 g COD/g VSS/day in EF-SBR because biomass concentration could be easily controlled at desired level by EF. However, it was impossible to increase biomass concentration at the same level in control SBR (C-SBR) process because solid-liquid separation by gravity settling showed a limitation at higher mixed liquor suspended solids (MLSS) concentration with 60 min of settling time. Total chemical oxygen demand (TCOD) removal efficiency of EF-SBR process was not decreased although influent organic loading rate became 3 times higher than initial value. However, it was seriously deteriorated in C-SBR process after increasing the rate over 10 g COD/day, which was accounted for insufficient organic removal by relatively higher food to microorganisms (F/M) ratio as well as biosolids wash-out by a limitation of gravity sedimentation.

• Journal of Powder Materials
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• v.29 no.6
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• pp.499-504
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• 2022

The objective of this study is to assess the impact of spray drying conditions on medium-chain triglyceride (MCT) loading, solubility, and release of an MCT-loaded solid self-emulsifying system in a water-insoluble oily substance. MCT-loaded solid self-emulsifying systems are prepared by spray drying with SDS and calcium silicate. The effects of inlet temperature (60, 80, or 100℃) and feed solution composition (0, 10, 50, 90, or 100% ethanol) on physicochemical properties of MCT-loaded solid self-emulsifying systems are studied. The inlet temperature significantly affects the water solubility of MCT. Moreover, the feed solution composition significantly affects water solubility, release rate, and MCT loading. The MCT-loaded solid self-emulsifying system obtained at 60℃ using 90% ethanol feed solution shows the best physicochemical properties among the synthesized products and exhibits better water solubility (4.43 ± 0.44 vs. 0 ㎍/mL) and release (94.4 ± 1.6 vs. 32.8 ± 7.4%, 60 min) than a commercial product. Furthermore, the MCT-loaded solid self-emulsifying system shows an excellent emulsion droplet size (approximately 230 nm).