• Journal of Korean Society on Water Environment
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• v.20 no.4
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• pp.370-375
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• 2004

Synthetic organic polyelectrolytes can be used to condition sludges to enhance their dewaterability. When conditioning biological sludges, the charge on the polymer has a significant impact on the effectiveness of the polymer as a conditioner. The objectives of this investigation were to determine the most effective type and dosage of polymer for conditioning digested sludge prior to dewatering, and to investigate the relationship between dewaterability and particle size. 3 types of digested sludge were used under the different digestion processes like anaerobic digestion, aerobic digestion and intermittent aerobic digestion. CST(capillary suction time), TTF(time-to-filter) and SRF(specific resistance to filtration) were tested as a dewaterability index and the number of particle distribution was analyzed using particle size analyzer. The results indicate that cationic polymer appears to be required for effective conditioning of these 3 types digested sludge and the optimal polymer dosage is about 0.6% of SS. CST and TTF are well correlated with mean particle diameter of which the dimension order is 1.7.

• Journal of Environmental Health Sciences
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• v.30 no.3
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• pp.239-244
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• 2004

The purposes of this study were to examine applicability of limestone as a conditioning agent and to determine the optimum conditions for improving dewaterability of digested sludge. The optimum conditions for temp., pH, dosage, particle size, time, and pressure was $30^{\circ}C$, 7, 45 g/l, 100 mesh, 30 min., and $2.66 {\times} 10^4 N/m^2$, respectively. On the basis of induced optimum conditions, if adding limestone in digested sludge, it estimated that its specific resistance was $1.43 {\times} 1012 m/kg$. Therefore, it seemed that we could utilize limestone as conditioning agent for improving dewaterability of digested sludge.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.1
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• pp.41-46
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• 2008

In this study, dewaterability, one of the important properties of wastewater sludge, was investigated using a simple capillary suction time (CST) measurement method. It turned out that one could use the results of CST to find optimum flocculants ratio to improve drainage in wastewater treatment for the printing paper, tissue paper, and newsprint paper mill. Since the optimum ratio of flocculants could be determined with the value of CST, COD removal efficiency could be improved and optimum floc strength could be achieved with precise ratio of flocculants. It was thus that using CST for determining the optimum ratio of flocculants could be economical by reducing the amount of flocculants. Dewaterability could be measured within several seconds using the values of CST in a precise way. The dewaterability could also be useful in investigating the optimum ratio of flocculants.

• Journal of Korean Society of Water and Wastewater
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• v.8 no.1
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• pp.1-8
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• 1994

Laboratory experiments were conducted to investigate the effect of digestion temperature on the settleability and dewaterability of anaerobically digested sludge. The digesters were operated at a hydraulic retention time of 20 days with a loading rate of 0.63~0.66kg volatile solids per cubic meter per day at the temperature of $35^{\circ}C$ and $55^{\circ}C$. A mixed primary and secondary municipal sludge was used as a feed. The interface height of the sludge during settling test was recorded to identify settleability. As a measure of dewaterability of the sludge, specific resistance and capillary suction time were also measured with and without chemical conditioning. Higher digestion efficiency was obtained at $55^{\circ}C$ than $35^{\circ}C$. However, the settleability and dewaterability of the sludge at $35^{\circ}C$ were quite higher than those of the sludge digested at $55^{\circ}C$. The optimum dosages of ferric chloride for sludge conditioning were 0.4% and 0.6% at $35^{\circ}C$ and $55^{\circ}C$, respectively. The filtrate COD of the sludge digested at $55^{\circ}C$ was higher than at $35^{\circ}C$, which means that poor dewaterability of the sludge result in high filtrate COD.

• Journal of Forest and Environmental Science
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• v.30 no.1
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• pp.85-90
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• 2014

Dewaterability, one of the important properties of wastewater sludge, was investigated using a simple capillary suction time (CST) measurement method. CST and SRF have a very close co-relation. It was convinced that CST method was quite effective, and compensating the time-consuming SRF of conventional drainage measuring method. It turned out that one could use the results of CST to find optimum flocculants ratio to improve drainage in wastewater treatment for the tissue paper production at a mill. Since the optimum ratio of flocculants could be determined with the value of CST and COD removal efficiency could be improved with precise ratio of flocculants. Thus, using CST for determining the optimum ratio of flocculants could be economical by reducing the amount of flocculants. Dewaterability might be measured within several seconds using the values of CST in a precise way. The dewaterability could also be useful in investigating the optimum ratio of flocculants.

• Journal of Korean Society on Water Environment
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• v.30 no.3
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• pp.311-318
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• 2014

The purpose of this study is to investigate the effect of various types of coagulant on dewaterability and settleability of sewage sludge for the application of dewatering process. Cationic organic coagulants and inorganic coagulants of the aluminium base were used; PAC (Poly Aluminium chloride, $Al_2O_3$ 17%) and C-210P (0.2%). After Jar test, PAC 26 mg/L and 0.2% C-210P 55 mg/L was decided as the optimum concentration of the coagulant according to zeta potential measurement. pH, alkalinity and viscosity were measured in all experiments and the data on sedimentation characteristics is analyzed by SDI, SVI sedimentation rate and solid flux. The SRF(Specific Resistance of Filtration) experiment was conducted with the result of single and dual injection system as the dewaterability experiment. As a result, the organic coagulant making large floc has good characteristics of sedimentation and agglutination. Also, it is observed that the organic coagulants injection has a better dewaterability efficiency of coagulants under the condition of the lowest SRF value, followed by dual and inorganic coagulants injection.

• Advances in environmental research
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• v.3 no.3
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• pp.199-206
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• 2014

Dewatering is an extremely important step in wastewater treatment process to reduce the final sludge volume in order to minimize the cost of sludge transportation and disposal. In the present study, the effect of different sludge solids content (1, 2 and 3.8%) on the dewaterability of anaerobically digested sludge using Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans was studied. The pH reduction rate was higher during initial process in the sludge having low solids content, but after 48 h of bioleaching, similar pH of below 3 was observed with all the different solids content. Bio-oxidation rate of $Fe^{2+}$ was initially higher in sludge with low solids content, but 100% $Fe^{2+}$ was oxidized within 60 h in all the three treatment levels. Compared to the control, specific resistance to filtration was reduced by 75, 78 and 80% in the sludge with a solids content of 1, 2 and 3.8% respectively, showing improvement in dewaterability with an increase in sludge solids content. Sludge effluent quality and sludge settling rate were also improved in treatments with higher solids content after the bioleaching process.

• Journal of environmental and Sanitary engineering
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• v.8 no.1
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• pp.117-127
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• 1993

When incineration method is utilized as a disposal process of sludge, the treatment generally consists of thickening, dewatering and incineration, implying that sludge dewaterability has a colose relationship with operating condition of a thickener. Dewatering factors should be, therefore investigated for achieving effective sludge treatment. No research on this has been performed in Korea. This study has focused on the evaluation on the effects of thickener operating variables on sludge dewatering, including sludge feed types and retention time. Mixing ratio of the first and the second sludge and operation time were varied in order to observe the change of dewaterability and optimum input of chemical conditioner.

• Journal of environmental and Sanitary engineering
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• v.16 no.4
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• pp.38-46
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• 2001

The purposes of this study were to examine applicability of waste egg shells as conditioning agent, to determine the optimum conditions for improving digested sludge dewaterability and to compare with before and after adding them. It estimated that the optimum conditions were dosage 30 g/L, particle size 10mesh, temp. $30^{\circ}C$, pH 7 and dewatering pressure $2.66{\pm}10^4{\;}N/m^2$. On the basis of induced optimum conditions, if adding waste egg shells in digested sludge, its specific resistance was $1.13{\pm}10^{12}{\;}m/kg$ and was low about 3 times than raw digested sludge $3.5{\pm}10^{12}{\;}m/kg $. Therefore, in view of waste recycling, it seemed that we could utilize waste egg shells as conditioning assent for improving dewaterability of digested sludge.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.1
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• pp.85-95
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• 1996

Although the specific resistance to filtration is the most frequently employed means for characterizing dewaterability of a sludge, it presently is not possible to design nor to prediet performance of dewatering facilities using traditional linearized parabolic filtration equation, that is, the specific resistance model because of theoretical and practical inadequacies of the concept. Limitations of the specific resistance model reflect the need to examine fundamental sludge properties and filtration behaviors affecting dewaterability. From this study, two major limitations of the specific resistance model were noted. First, specific resistance values are very dependent on the sludge concentration because of the variations of particle size distribution and cake clogging to occur when surface area mean diameter is less than $25{\mu}m$ for activated sludge, $18{\mu}m$ for water treatment plant sludge. Second, nonparabolic filtration behavior can result from cake clogging, caused by the migration of fine particles into the cake pores, accelated by skin effect with highly compressible sludges.