Browsing by Author "Pan, JRS"

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Adsorption behavior of iron-cyanide onto gamma-Al2O3 interface: A coagulation approach
(1999-05-01)
Cheng, WP
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Huang, CP
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Pan, JRS
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環境工程研究所
;
Institute of Environmental Engineering
Ferrocyanide and ferricyanide ions have strong coagulation ability in a natural water system due to their high valences. Studies with aluminum oxide turbid waters showed significant differences in coagulation between simple ions (Cl-, SO42-, Fe(CN)(6)Fe3-(CN)(6)(4-)) and other species (H2PO4-) that interact chemically with the oxide surface. The evidence suggested that the adsorption of ferrocyanide and ferricyanide on aluminum oxide surface is an outer-sphere reaction. The linear relationship between the logarithm of the significant coagulation concentration and Schultz-Hardy ratios indicated that the coagulation obeyed the DLVO rule. Therefore, it is concluded that the coagulation of aluminum oxide by ferrocyanide and ferricyanide is essentially caused by compression of the electric double layer rather than by charge neutralization. (C) 1999 Academic Press.
Collision efficiencies of algae and kaolin in depth filter: The effect of surface properties of particles
(1999-04-01)
Huang, CP
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Pan, JRS
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Huang, SH
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環境工程研究所
;
Institute of Environmental Engineering
Column filtration experiments with 2 mm-Phi glass beads were conducted to investigate the behavior of colloids during filtration. Algae and kaolin were used as model particles, while the chemical system was altered by changing the electrolyte concentration and pH. The collision efficiencies from the interaction between colloids and the filter medium were calculated with a semi-empirical approach of the single sphere model and clean-bed filtration theory. The experimental results indicate that ionic strength enhance the removal efficiencies for both algae and kaolin particles significantly. The removal efficiency of the filter for algae decreased with the increase in pH for up to pH 6. No significant change was observed beyond pH 6. Removal efficiencies for kaolin decreased with an increase in pH. It is concluded that collision efficiencies are sensitive to ion strength and pH. (C) 1999 Elsevier Science Ltd. All rights reserved.
Correlation between dewatering index and dewatering performance of three mechanical dewatering devices
(2003-05-01)
Pan, JRS
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Huang, CP
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Cherng, MY
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Li, KC
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Lin, CF
Efficient sludge conditioning can improve sludge dewatering characteristics and promote the separation of flocs from the liquid phase to achieve a high solid content. To optimize this process, a reliable dewatering index must be established. Although numerous researches investigated sludge conditioning, few are devoted to the correlation between the conditioning index and the dewatering efficiency. In this study, sludges were conditioned with both synthetic and natural polymers, and their dewatering characteristics after three different mechanical dewatering devices, the filter press, belt press, and the centrifuge, were compared. The result shows that the traditionally used dewatering index may not reflect sludge conditioning properly. Correlation between sludge conditioning indices and dewaterability depends upon both the type of sludge and the means of sludge conditioning and dewatering. It is therefore concluded that dewatering index must be properly chosen for optimum sludge conditioning. (C) 2002 Elsevier Science Ltd. All rights reserved.
Effect of surfactant on alum sludge conditioning and dewaterability
(2000)
Pan, JRS
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Huang, C
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Fu, CG
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環境工程研究所
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Institute of Environmental Engineering
Sludge disposal has become a new challenge for the Taiwan government due to the increasing demand for better quality and greater quantity of water. in some water treatment plants, surfactant has been applied in the flotation process to improve ifs performance, which suggests the use of surfactant in sludge conditioning. In this study. effects of surfactants on the conditioning of the alum sludge collected from Feng-Yuan Water Treatment Plant were investigated. Surfactants of various charges, namely CTAB and SDS, were added to sludge samples in various amounts, and their effects on sludge dewaterability were evaluated. Surfactants were also added with either cationic or anionic polymers to better understand their effects on the mechanism of sludge conditioning and the feasibility as coagulant aid. Experimental results indicate that applying surfactants alone in sludge system decrease the filterability of sludge, but increase the sludge dewatering rate at optimum dosage. Cationic surfactant was proven possible as conditioning aid for the cationic polymer. The order of surfactant and polymer addition is the key to additive function. On the other hand, when the polymer of opposite charge was added with the surfactant, co-precipitation occurred which resulted in decreased filterability and dewaterability.
Evaluation of a modified chitosan biopolymer for coagulation of colloidal particles
(1999-02-15)
Pan, JRS
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Huang, CP
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Chen, SC
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Chung, YC
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環境工程研究所
Chitosan, a deacetylated derivative of chitin, is a biodegradable cationic polymer. Chitosan can be a potential substitute for aluminum salts and synthetic polyelectrolytes in water treatment because it can: (1) avoid the health effects from residual aluminum (III) and synthetic polymers; (2) produce biodegradable sludge; and (3) reuse the crab shell. Chitosan can be modified with various pretreatments including dissolution in acid solution and various deacetylation conditions to improve its coagulation efficiency. In this study, coagulations of synthetic and real water with the modified chitosan, mixed coagulant of chitosan and PACl at various ratios, and PACl were compared. The efficiency was evaluated by the factors of settling rate, hoc diameter, and residual turbidity. Coagulation with chitosan alone required least dosage. Chitosan coagulants also produced larger flee with higher settling velocity. Satisfactory results were obtained from the mixed coagulant of chitosan/PACl = 4:1. Although low pH decreased the optimal dosage, the flocs produced were smaller with slower settling rate. Increasing the rapid mixing strength improved the coagulation only when the applied dosage was less than the optimum dosage. Studies using other particles such as kaolinite and clay indicate that the properties of particles have a significant effect on the chitosan coagulation efficiency. (C) 1999 Elsevier Science B.V. All rights reserved.
Mixing water treatment residual with excavation waste soil in brick and artificial aggregate making
(2005-02-01)
Huang, CP
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Pan, JRS
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Liu, YR
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環境工程研究所
;
Institute of Environmental Engineering
A large quantity of water treatment residual is generated each year from fresh water treatment plants in Taiwan. Landfill disposal of the nonhazardous sludge is impractical because of the high cost of transportation and an increasing scarcity of landfill sites in Taiwan. The water treatment residual was characterized; the ceramic bodies were prepared and sintered to formulate into building bricks and artificial aggregates. The sintering temperature requirement by the water treatment residual was higher than normally practiced in brick works due to the higher Al2O3 and lower SiO2 content. The excavation waste soil, practically clay, was blended with water treatment residual to improve the brick quality. Under the commonly practiced brick-making condition, up to 15% of water treatment residual could be added to produce first grade brick specified by the National Science Council (NSC). Test results of specific gravity, water absorption, and compressive strength of the artificial aggregates confirmed its applicability in constructions as various degrees of light-weight aggregates.
Time requirement for rapid-mixing in coagulation
(2002-04-25)
Kan, CC
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Huang, CP
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Pan, JRS
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環境工程研究所
;
Institute of Environmental Engineering
Mechanisms of coagulation have been widely investigated by many researchers. Little is understood about the critical role of rapid-mixing in water treatment. In this study, a photometric dispersion analyzer (PDA) was employed to monitor clay coagulation by alum and polymeric aluminum chloride (PACl). The effect of rapid-mixing time on particle removal was studied. A standard jar test was performed to determine the degree of destabilization of particles. Maximum ratio outputs of PDA measurements were inversely related to residual turbidities. Adequate rapid-mixing times evaluated from both PDA and mixing tests were close to each other. Studies of coagulation mechanisms at various rapid-mixing times indicated that mixing time had significant impact on charge neutralization and sweep coagulation. The difference in residual turbidity can be attributed to the characteristics of microflocs. The rise in residual turbidity in sweep coagulation suggested the breakage of microflocs. (C) 2002 Elsevier Science B.V. All rights reserved.