Browsing by Author "Lee, DJ"

Now showing 1 - 10 of 10

Bound water content and water binding strength on sludge flocs
(1998-03-01)
Wu, CC
;
Huang, CP
;
Lee, DJ
;
環境工程研究所
;
Institute of Environmental Engineering
On the basis of the thermodynamic hypothesis and using the thermodynamic approach, a binding strength was calculated to define the physical meaning of bound water content of sludge as measured by dilatometer. The sludge samples considered in this study included kaolin, alum and biological sludge. The binding strength of bound water at -20 degrees C was calculated as 24.5 kJ/kg, which is close to that of the normal physico-adsorption process. Most of the frozen moisture in st dilatometric measurement should be interstitial water or vicinal water. Results also indicated that moisture with a lower binding strength easily became free water. The release of interstitial water from sludge flocs would cause less bound water. When solid concentration is higher, the expelling strength induced by the compacting action of sludge flocs is increased over the binding strength, thereby forcing out the interstitial water. Lower bound water contents are attained. Accurate measurement of bubble volumes with the calculated stem on the top of the dilatometer could improve the precision of expansion coefficient and bound water content measurement. (C) 1998 Elsevier Science Ltd. All rights reserved.
Determination of the optimal dose of polyelectrolyte sludge conditioner considering particle sedimentation effects
(2000-08-01)
Wu, CC
;
Lee, DJ
;
Huang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
The specific resistance to filtration (SRF) of sludge was determined using both a leaf filter and a Buncher funnel. The filterability of a kaolin suspension and an alum sludge were characterized using SRF data and capillary suction time (CST) measurements. Filter orientation during the leaf filter test and stirring during the Buncher funnel test affected the SRF values, and the optimal dosage of polyelectrolyte conditioner (defined as the dosage that yields the minimum resistance to filtration) varied depending on the type of test used. Therefore, the optimal dose of polyelectrolyte was an operationally defined value that depended on the geometry of the filter chamber and fluid/particle interactions, such as sedimentation. (C) 2000 Elsevier Science Ltd. All rights reserved.
Development of a modal LQG active noise canceler
(1995)
Bai, MR
;
Shieh, CF
;
Lee, DJ
;
機械工程學系
;
Department of Mechanical Engineering
Effects of polymer dosage on alum sludge dewatering characteristics and physical properties
(1997-04-14)
Wu, CC
;
Huang, CP
;
Lee, DJ
;
環境工程研究所
;
Institute of Environmental Engineering
The proper use of polymers as conditioners is a critical aspect of dewatering processes. In this study, we investigate their physical properties, i.e. size, density and fractal dimension and correlate them with their dewatering characteristics (bound water content, CST and SRF) on alum sludge with cationic polymer conditioning. Using CST measurement to determine the optimum polymer dose may lead to an over-dosing for polymer conditioned sludge. Bound water depletion and interstitial water formation significantly affect the moisture content during polymer conditioning. Moreover, the magnitude of bound water content reflects net change in moisture content, which is decreased by bound water depletion and increased by water formation. Flee size and density measurement suggest poor dewatering performance and increased bound water content are attributable to enlargements in flee size and decreases in flee density. Experimental results indicate that increases in bound water and decreases in flee density are caused by variations of both flee size and aggregation configuration type, not degree of flee compactness.
Expression dewatering of alum-coagulated clay slurries
(1997-05-01)
Chang, IL
;
Chu, CP
;
Lee, DJ
;
Huang, CP
;
環境工程研究所
Filtration followed by expression characteristics of the alum-coagulated clay slurries are first reported in this paper. A strong correlation between alum chemistry and the dewatering efficiency exists. At pH 3, where the positively charged ions are the dominating species, the alum addition has only a minor improvement on dewatering efficiency. At pH 7 and pH 10, where sweep flocs enmeshment play the major role, dewatering performance improves continuously as alum dose increases. At pH 5.2, where a charge reversal regime exists, the dewatering efficiency exhibits a reversal phenomenon as well. The overall dewaterability follows: pH 5.2 > pH 3 > pH 7 > pH 10. A complete test consists of the filtration and expression stages, which are discussed separately. The filtration stage is discussed based on the average specific resistance and the residual moisture in the filtration cake. The expression stage is discussed based on the combined Terzaghi-Voigt rheological model, from which the fraction contributed by the secondary consolidation (B) and the particle creeping factor (eta) are evaluated. For the dewatering sake, a lower B and a higher eta are desired. Both parameters B and eta increase at elevated alum dose and/or lower pH value, while exhibiting a local minimum in charge reversal regime at pH 5.2. The optimal alum dose considering sludge dewaterability is discussed.
Expression dewatering of alum-coagulated clay slurries
(1997-05-01)
Chang, IL
;
Chu, CP
;
Lee, DJ
;
Huang, CP
;
環境工程研究所
Filtration followed by expression characteristics of the alum-coagulated clay slurries are first reported in this paper. A strong correlation between alum chemistry and the dewatering efficiency exists. At pH 3, where the positively charged ions are the dominating species, the alum addition has only a minor improvement on dewatering efficiency. At pH 7 and pH 10, where sweep flocs enmeshment play the major role, dewatering performance improves continuously as alum dose increases. At pH 5.2, where a charge reversal regime exists, the dewatering efficiency exhibits a reversal phenomenon as well. The overall dewaterability follows: pH 5.2 > pH 3 > pH 7 > pH 10. A complete test consists of the filtration and expression stages, which are discussed separately. The filtration stage is discussed based on the average specific resistance and the residual moisture in the filtration cake. The expression stage is discussed based on the combined Terzaghi-Voigt rheological model, from which the fraction contributed by the secondary consolidation (B) and the particle creeping factor (eta) are evaluated. For the dewatering sake, a lower B and a higher eta are desired. Both parameters B and eta increase at elevated alum dose and/or lower pH value, while exhibiting a local minimum in charge reversal regime at pH 5.2. The optimal alum dose considering sludge dewaterability is discussed.
Polymer dose effects on filtration followed by expression of clay slurries
(1997-01-15)
Chang, IL
;
Chu, CP
;
Lee, DJ
;
Huang, C
;
環境工程研究所
Filtration followed by expression characteristics of cationic polymer conditioned clay slurries are reported for the first time in this work. As the polymer dosage increases, the resistance to filtration greatly decreases until a specific dose has been reached, where the zeta potential is close to zero. And further increase in polymer dose conversely raises the resistance. The expression data are interpreted by the Terzaghi-Voigt combined model, from which the model parameters are evaluated. The polymer conditioning has only a mild effect on the primary consolidation process but has, however, a considerable influence on secondary consolidation characteristics. When zeta potential changes from negative to positive, both the easiness of creeping of constituent particles within the sludge cake and the fraction of moisture removal by the secondary consolidation attain a maximum., The optimal polymer dose criterion considering the filtration and expression stages separately, or in combination, is (sic). (C) 1997 Academic Press
Steady-state humic-acid-containing blanket in upflow suspended bed
(2005-03-01)
Sung, SS
;
Lee, DJ
;
Huang, C
;
環境工程研究所
;
Institute of Environmental Engineering
We investigated the effects of turbidity and concentration of humic acid on the steady-state behavior of the blanket, which was coagulated using polyaluminum chloride (PACl) as coagulant. The three-dimensional solid-flux plot was constructed. Based on fixed PACl dosage, the iso-humic-acid solid-flux surfaces stacked that enveloped the feasible regime for the blanket bed. The steady-state point moved toward low solid flux and low solid fraction regime with decreasing initial raw water turbidity and/or increasing humic-acid concentration. Low water turbidity and high humic-acid concentration yielded a bulky blanket, with the former producing clean, and the latter turbid effluent. The presence of humic acid was thereby harmful to blanket strength, except for the case of low raw water turbidity. An optimal range of humic acid for blanket strength and clarification efficiency existed at 1 mg l(-1). Low level of humic acid is beneficial to blanket development with low-turbidity raw water. (c) 2005 Elsevier Ltd. All rights reserved.
The role of ionic surfactants in compression dewatering of alum sludge
(1998-10-01)
Chu, CP
;
Lee, DJ
;
Huang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
This work has experimentally investigated the characteristics of filtration followed by consolidation dewatering of an alum sludge, with especial attention to the effects of adding ionic surfactants (SDS or CTAB), The filtration and consolidation stages at a pressure of 3000 psi were discussed separately, The efficiency of filtration is enhanced in the presence of surfactant molecules; however, the cationic surfactant (CTAB) raises the consolidation rate while the anionic surfactant (SDS) retards it, A newly proposed rheological model has been employed for interpreting the consolidation data. CTAB would not alter markedly the moisture distribution in the sludge, but SDS does increase markedly the amount of the tightly bound moisture by diminishing the portion occupied by pore water. The possible role of surfactants in the sludge flocs is considered. Both surfactants can be used as conditioning aids during the filtration stage. However, the applications of SDS to the consolidation stage are not encouraged. (C) 1998 Academic Press.
Treating high-turbidity water using full-scale floc blanket clarifiers
(2004-12-01)
Lin, WW
;
Sung, SS
;
Chen, LC
;
Chung, HY
;
Wang, CC
Dynamic responses of the blanket in full-scale flat-bottom type floe blanket clarifiers at the PingTsan Water Works, Taiwan Water Supply Corporation, were monitored given a step-change in coagulant (polyaluminum chloride, PACl) dosage. The blankets in the clarifiers were easily washed out using the conventional coagulation-clarification process (the "single-stage process"), seriously threatening drinking water quality. Consequently, the PingTsan Water Works included a pretreatment stage before the single-stage process to enhance treatment efficiency. The performance of this full-scale "two-stage process" for treating high-turbidity storm water was monitored on November 9 to 10, 2000. The two-stage process achieved a stable blanket and good quality clarified water that was insensitive to variation in raw water turbidity or PACl dose. Pilot tests were also conducted on October 6 to 7, 2001 to reveal performance differences between the single-stage and two-stage processes in dealing with high-turbidity water. The single-stage process yielded a blanket that was sensitive to PACl change. Not only was the produced blanket easily washed out when the PACl dose was step-decreased, it was also slow to recover when the chemical dosage was returned to its original value. The blanket yielded by the two-stage process was more robust to low coagulant dose, and recovered more easily when coagulant supply was increased. Applying the two-stage process to achieve the same effluent quality from single-stage process could significantly reduce total PACl dosage.