• Preventive Nutrition and Food Science
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• 제21권1호
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• pp.73-77
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• 2016

Flow and dynamic rheological properties of thickened waters prepared with commercial food thickeners were investigated at different pH levels (3, 4, 5, 6, and 7). The commercial xanthan gum (XG)-based thickener (thickener A) and starch-based thickener (thickener B), which have been commonly used in a domestic hospital and nursing home for patients with swallowing difficulty (dysphagia) in Korea, were selected in this study. Thickened samples with both thickeners at different pH levels showed high shear-thinning flow behaviors (n=0.08~0.22). Thickened samples at pH 3 showed higher n values and lower consistency index (K) values when compared to those at other pH levels. The K values of thickener A increased with an increase in pH level, while the n values decreased, showing that the flow properties greatly depended on pH. There were no noticeable changes in the K values of thickener B between pH 4 and 7. At pH 3, the thickened water with thickener A showed a higher storage modulus (G') value, while that with thickener B showed a lower G'. These rheological parameters exhibited differences in rheological behaviors between XG-based and starch-based thickeners, indicating that the rheological properties of thickened waters appear to be greatly influenced by the acidic condition and the type of food thickener. Appropriately selecting a commercial food thickener seems to be greatly important for the preparation of thickened acidic fluids with desirable rheological properties for safe swallowing.

• Clinical Nutrition Research
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• 제13권2호
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• pp.89-95
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• 2024

Thickened beverages or swallowing aid jelly (SAJ), commonly used as tablet-swallowing aids for dysphagic patients, may influence the disintegration of orally administered tablets. With this in mind, we evaluated the disintegration times of therapeutic tablets immersed in thickened beverages or SAJ compared to immersion in ones without them. Thickened beverages and SAJs were prepared with various beverages (water, orange juice, and milk) using food thickeners and SAJ powders marketed in Korea. The tablet disintegration times were the same in thickened beverages and SAJs, and there was no statistically significant difference associated with the thickness levels of the thickened beverages. The disintegration times of Tylenol immersed in orange juice or milk were slightly higher compared to those immersed in water. Moreover, there was no difference in disintegration time when using the thickened beverages and SAJs. The disintegration times of Aspirin were similar in all of the thickened beverages or SAJs, and there were no differences between non-immersed and immersed tablets. These results demonstrate that the disintegration of Tylenol and Aspirin is not greatly affected by immersion in any of the thickened beverages and SAJs.

• 상하수도학회지
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• 제20권5호
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• pp.677-684
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• 2006

Electro-flotation(EF), a novel sludge thickening method, could improve the dewaterability of activated sludge. The gas(microbubbles) generated during EF decreased the solid-liquid separation time below 1/5 of the time required for gravity sedimentation. In addition, over 90% of the sludge volume reduction could be achieved by EF although the settling characteristics of the sludge was very poor. The SRF(specific resistance to filtration) of the thickened sludge by EF was much lower than that of the sludge thickened by gravity sedimentation. The SRF of the thickened sludge decreased exponentially with increase of gas generation rate of the EF system. Gas generation rate could be controlled by varying the current density of the electrode. Degasing of the microbubbles by vigorous mixing of the thickened sludge layer deteriorated the dewaterability of the sludge. Therefore, it is obvious that the gas bubbles entrapped in the thickened sludge play a key role in the observed dewaterability improvement.

• 상하수도학회지
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• 제7권1호
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• pp.13-19
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• 1993

Anaerobic Digestion of thickened septage was investigated in this study. Thickening could reduce the volume of septage to be treated to about 40% with 12hr HRT. The VS and BOD removal efficiencies were respectively 28 to 45%, and 75% when digested the thickened septage with 30 day HRT Or $1.4kgVS/m^3/d$. The BOD removal efficiency could be increased to about 90% with subsequent settling tank with about 6 hours HRT. The gas production rate was 0.22 to $0.35m^3gas/kgVSadd$($0.75m^3gas/kgVSrm$), or $1.32m^3gas/kgBOD_{rm}$. In addition, the supernatant of thickener could be returned to the aeration tank treating domestic sewage. In this case, a BOD loading rate of 0.5 to $0.7kgBOD/m^3/d$ or 0.5kgBOD/kgMLVSS/d was proposed for 80% BOD reduction.

• Preventive Nutrition and Food Science
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• 제20권2호
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• pp.137-142
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• 2015

Rheological properties of thickened fluids used for consumption by people with dysphagia (swallowing difficulty) are very sensitive to several factors, such as thickener type, temperature, pH, sugar, protein, and NaCl. In this study, steady and dynamic rheological properties of thickened water samples mixed with five commercial xanthan gum-based food thickeners (A~E) were studied in the presence of NaCl at different concentrations (0.3%, 0.6%, 0.9%, and 1.2%). The magnitudes of apparent viscosity (${\eta}_{a,50}$), consistency index (K), yield stress (${\sigma}_{oc}$), and dynamic moduli (G' and G") showed significant differences in rheological behaviors between thickened samples with various NaCl concentrations. Dynamic moduli values of all thickened samples, except for samples with thickener C, were much higher than those of the control (0% NaCl). All rheological parameter values (K, G', and G") in a thickener A were much higher than those in other thickeners. These results suggest that rheological properties of thickened samples containing NaCl are strongly affected by xanthan gum-NaCl interaction and depended on the type of thickener.

• 한국환경보건학회지
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• 제37권6호
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• pp.467-473
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• 2011

Objectives: Wastewater treatment plants typically produce a large volume of waste sludge. In this study, the conditioning and dewatering properties of a digested and thickened sludge from an industrial wastewater treatment plant were investigated in order to improve the dewaterbility of the sludge. Methods: Jar-tests and Buchner funnel tests were carried out to assess the conditioning and dewatering properties of a waste sludge. TTF (Time to Filter Test) and SRF (Specific Resistance to Filtration) were adopted as the indices of sludge dewaterbility. Results: The valuation indices influencing the dewaterbility of the waste sludge, including TTF, SRF, water contents, VS/TS ratio and turbidity, were measured. The TTF and SRF of the digested and thickened sludge were decreased to 40 sec, $3.43{\times}10^{12}$ m/kg, and 39 sec, $1.09{\times}10^{12}$ m/kg, respectively. Conclusions: The conditioner composed of natural inorganic materials turned out to be effective in the reduction of sludge water contents.

• 대한화학회지
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• 제21권5호
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• pp.384-388
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• 1977

벤톤-폴리에틸렌 및 벤톤-폴리프로필렌을 적당한 온도에서 광유에 분산시키므로써 점토-고분자를 농조제로 사용한 그리이스를 만들었으며, 내마모성, 내수성, 산화안정성, 혼화안정성 및 직점등의 그리이스의 물성을 측정하였다. 그리이스의 성질중 내수성과 같이, 좋지 못한 성질이 간혹 나왔으나 이들 그리이스의 성상을, 이 실험에서 만든 점토-금속비누 그리이스의 성상과 비교 검토할 때 특수목적에 쓸 수 있음을 알았다.

• 한국물환경학회지
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• 제25권5호
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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.

• 상하수도학회지
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• 제20권5호
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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.

• 대한토목학회논문집
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• 제26권6B호
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• pp.661-667
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• 2006

본 연구에서는 동전기를 이용한 하수 슬러지 탈수 실험을 실시하였다. 소화 과정을 거치고 탈수과정에 투입되기 전 응집제가 첨가되지 않은 슬러지에 중력 및 가압, 전기삼투 및 전기삼투펄스 기법을 적용하여 탈수 효율을 분석하였으며, 소화 과정을 거치지 않고 농축조에서 배출된 슬러지에 대하여도 동일한 방법으로 탈수 실험을 실시하여 농축 슬러지의 탈수율을 평가하였다. 압력을 가하지 않은 중력 탈수 방식에 직류전기장을 적용한 경우 적용 전압에 비례하여 탈수율이 증가하여 전기삼투에 의한 슬러지 탈수의 가능성이 입증되었다. 그러나, 짧은 시간에 높은 탈수율을 얻기 위해서는 고전압이 필요한 문제점이 대두되었다. 이를 보완하기 위하여 슬러지 내에서 높이에 따른 함수비 변화폭을 줄여줄 것으로 기대되는 펄스 기법을 도입한 결과 실험 중반부터 배출량 및 부피감소량이 정전압에 비해 증가하는 특성을 보여 슬러지 내 함수비가 감소하면서 그 효과가 나타나는 것으로 해석된다. 농축 슬러지에 대한 중력식 및 압력식 전기삼투 탈수 기법도 소화 슬러지와 마찬가지로 높은 탈수율을 나타내어 동전기에 의한 탈수 가능성이 입증되었으며, 소화조 운영 목적 중 화학적인 부분들이 전기 삼투에 의한 탈수에 의해 어느 정도 보완될 수 있는지가 평가된다면 슬러지 처리 공정 및 비용을 단축시킬 수 있을 것으로 기대된다.