• Journal of Korean Society of Water and Wastewater
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• v.20 no.3
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• pp.443-450
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• 2006

For understanding sludge concentration profile as a function of time, sludge was sampled at each sampling port. When sludge concentration was 3g/L, the vertical sludge concentration distribution was similar to that of 2g/L of sludge concentration. During the early stage of sludge settling, sludge concentration increased remarkably as the sludge interface height in batch column became lower. The higher sludge concentration became, the worse sludge setteability became. Also, the type of sludge settling was influenced with sludge concentration gradient in batch column. In the same concentration, the greater sludge concentration gradient was, the faster sludge interface settled down. And the changing sludge concentrations in a batch settling or a continuous settling were simulated by using the equation of sludge interface height change model.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.3
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• pp.451-460
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• 2006

While sludge settles down in a batch column, sludge concentration becomes high. Sludge concentration change is one of the most critical causes of the sludge settling velocity variation. Therefore, sludge concentration change causes sludge index to change. SVI is more sensitive than other sludge indexes to the change of sludge concentration. And if sludge-water interface has reached final height within 30minutes, SVI is not suitable for prediction of sludge settling characteristic, Therefore, SVIs of each sludge are, in some cases, different although each sludge has the same settling velocity. But SVI has been widely used to interpret sludge settling characteristic by a simple testing method. This work has two purposes. The first purpose is to predict sludge settling velocity by using sludge-water interface settling velocity. And the second purpose is to develop new sludge settling characteristic index to exactly interpret sludge settling characteristic by overcoming the limit of SVI.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.1
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• pp.147-155
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• 2006

For the further study of the solids flux theory, several researchers have proposed models to predict sludge settling velocity for each different concentration by using sludge indexes, SVI, SSVI and $SSVI_{3.5}$. It is difficult to apply the above models to predict sludge-water interface height in a batch column because sludge settling velocity changes while sludge settle down. While sludge settle down in a batch column, sludge concentration becomes high. The sludge concentration change is one of the most critical causes of the change of sludge settling velocity. Also, sludge concentration change causes of sludge index to change. SVI is more sensitive than SSVI or $SSVI_{3.5}$ to the change of sludge concentration. Each sludge has physical characteristics of its own which makes the settling velocity for each sludge different. The purpose of this study is to establish the correction factors that are able to compensate the errors derived from each different sludge settling characteristic by using sludge indexes, therefore the correction factors are applicable to the model for the change of sludge-water interface height.

• KSBB Journal
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• v.13 no.3
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• pp.279-283
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• 1998

To investigate the feasibility of the microbial process for removal of heavy metals from the high solid content sludge, the effect of sludge concentration on the solubilization of heavy metals by an iron oxidizing bacterium Thiolbacillus ferrooxidans was examined. With increasing the sludge concentration, the removal efficiency of heavy metals and the oxidation rate of iron were inhibited. Especially, when the sludge concentration is over 5% (w/v), the activity of T. ferrooxidans was remarkably inhibited. This inhibition is considered to occur due to the dissolved inhibitory materials such as organic compounds, heavy metals, and others which were extracted from the sludge during incubation period. In conclusion, the microbial process by T. ferrooxidans is only effectively used in ranges of 1.3 to 4.0% (w/v) sludge concentration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.922-926
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• 2002

In this paper, in order to investigate the catalytic effect of the sludge exhausted from waterworks as heating temperature for NOx removal, we measure NO, $NO_2$ concentration as increasing temperature of sludge pellets and applying high voltage to sludge pellets in a quartz-glass reactor at the same time. NO initial concentration is 100ppm balanced with air gas in a mixing chamber. The gas flow is 5[l/min] and the heating temperature of sludge pellets in a quartz-glass reactor is adjusted from $200[^{\circ}C]$ $400[^{\circ}C]$ to investigate the effect of sludge pellets for removal NOx$(NO+NO_2)$ as increasing temperature. $BaTiO_3$ pellets is filled in a packed-bed reactor for corona discharge to measure how much NOx$(NO+NO_2)$ is removed after generating $NO_2$ from the packed-bed reactor. AC[60Hz] voltage is supplied to the reactor for discharge. In the result, $NO_2$ concentration is decreased by sludge pellets without heating temperature for sludge pellets in case of sludge pellets done heat treatment, however NO concentration is almost the same to be compared NO initial concentration. As increasing heating temperature for sludge pellets, $NO_2$ adsorbed on the sludge surface done heat treatment is converted to NO by the thermal energy, so NO concentration is extremely increased by reduction decomposition of $NO_2$. Finally, We think the sludge is possible to use for reduction catalysts, however we need to study more about the possibility and endurance of sludge as catalysts for NOx removal.

• Journal of Environmental Science International
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• v.6 no.2
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• pp.113-124
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• 1997

The basic mechanism of the granular sludge formation which is the most important factor in the start-up and stable operators is not confirmed yet. In this study, the effect of granular sludge formation was investigated with the different substrate concentrations and the various ratios of substrate supply/deficiency. The granular sludge formation in the UASB reactor was closely related to the substrate concentrations and the ratio of substrate supply/deficlency The granular sludge formation was not accelerated at low substrate concentration. It was convinced that granular sludge formation was accelerated when the substrate supply with high concentration was stopped at UASB reactor. From this experiment, it was estimated that granular sludge was formed by the combination of hydrogen utilizing bacteria that form hydrogen condition and acid forming bacteria at substrate deficit condition by mutual symbiosis. Though the removal efficiency of organic matter was decreased as the influent substrate concentration was Increased, the higher the influent substrate the better the granular sludge formation.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.2
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• pp.265-272
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• 2006

While sludge settles down in a column, sludge settling characteristic is influenced by effect parameters, interparticle force, wall effect etc. As the height of a column changes, the settling velocity of sludge-water interface changes, too. At lower sludge concentration, particular effect was not observed by the difference of column height, however it was observed that settleability of sludge was greatly influenced by column height when sludge settling was poor or sludge concentration was high. It is therefore required to consider the effect of column height when the power model for sludge interface settling is established. In the tests, there was hardly any $SVI_{ts}$(SVI after "t" minutes) difference in each column after 10min at $1.5kg/m^3$ of sludge concentration. When sludge concentration was at $2.5kg/m^3$, $SVI_{ts}$ tended to be constant after 20min. At $3.5kg/m^3$, $SVI_{ts}$ increased to 30minuets. The purpose of this work is to establish the correction factor that is able to compensate the errors derived from each different height of column.

• Journal of Environmental Science International
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• v.7 no.4
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• pp.559-564
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• 1998

The effects of temperature, initial $Pb^{2+}$concentration and initial sludge concentration on the initial $Pb^{2+}$ removal rate and maximal $Pb^{2+}$removal amounts in activated sludge, respectively, were investigated. The removal of $Pb^{2+}$ in activated sludge was proved to be temperature-dependent process. The initial $Pb^{2+}$ removal rate increased from 187.5 to 261.4 mg $Pb^{2+}$/g sludge dry weight min, in response to the promoted temperature from 1$0^{\circ}C$ to 6$0^{\circ}C$, while the maximal $Pb^{2+}$removal amount (78.5 mg $Pb^{2+}$/g sludge dry weight) occurred at 30t . As the initial $Pb^{2+}$concentration increased from 36 to 228 mg $Pb^{2+}$/L at the constant temperature of 30C and initial sludge concentration of 1.5 g sludge dry weight/L, the time to reach an equilibrium state was almost independent of the initial $Pb^{2+}$concentration and the equilibrium $Pb^{2+}$/removal amount was increased Irom 41.9 to 73.6 mg $Pb^{2+}$/g sludge dry weight. On the contrary, the equilbrium $Pb^{2+}$ emoval amount was decreased from 87.7 to 65.3 mg $Pb^{2+}$/g sludge dry weight as the in- crease of initial sludge concentration from 0.22 to 1.76 g sludge dry weight/L.

• 수도
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• v.24 no.5 s.86
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• pp.29-44
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• 1997

Sewage sludge produced in Korea was 1,275,800 tons (dewatered sludge cake) per year in 1996, which is 3,495 tons per day, 0.303% of 11,526,100 tons per day of sewage treated in 79 sewage treatment plants. Sludge production has been and will be increasing in accordance with construction of new facilities for sewage treatment. Most of the sludge is currently disposed by landfill and ocean dumping, but it is becoming difficult to find suitable sites for landfill, particularly in big cities such as Seoul. In addition, rapid increase of landfill cost is anticipated in a near future. Current trend for sludge disposal in advanced countries is land application. Over the past 10 to 20 years in the United States, sludge management practices have changed significantly, moving from disposal to beneficial use. They use biosolid for utilization instead of sludge for disposal. Under the Clean Water Act of 1972, amended in 1987 by Congress, the U.S. EPA was required to develop regulations for the use and disposal of sewage sludge. The EPA assessed the potential for pollutants in sewage sludge to affect public health and the environment through a number of different routes of exposure. The Agency also assessed the potential risk to human health through contamination of drinking water sources or surface water when sludge is disposed on land. The Final Rules were signed by the EPA Administrator and were published (Federal Register, 1993). These rules state that sewage sludge shall not be applied to land if the concentration of any pollutant in the sludge exceeds the ceiling concentration. In addition, the cumulative loading rate for each pollutant shall not exceed the cumulative pollutant loading rate nor should the concentration of each pollutant in the sludge exceed the monthly average concentration for the pollutant. The annual pollutant loading rate generally applies to applications of sewage sludge on agricultural lands. The most popular beneficial use of sewage sludge is land application. The sludge has to be stabilized for appling to land. One of the stabilization process for sewage sludge is lime stabilization process. The stabilization process is consisted of the stabilizing process and the drying process. Stabilization reactor can be a drum type reactor in which a crossed mixer is equipped. The additive agents are a very reactive mixture of calcium oxide and others. The stabilized sludge is dried in sun drier or rotary kiln.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.279-290
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• 2004

Sludge quantity has increased at "A"water treatment plant due to deterioration of raw water quality and GAC installation. Increased sludge resulted in overloading on sludge handling facilities. The object of this study is to survey sludge quantity and capacity of sludge handling facilities at "A"water treatment plant. Measured quantity of sedimentation sludge considerably exceeded the design capacity of sludge holding basin. Sludge holding basin was properly designed, but low concentration of sludge discharged from sedimentation basin caused production of large volume of the sludge. Timer operated control system for sludge withdrawal unit and leakage through a control valve were suspected to cause the low concentration. Augmentation of the control system by a turbidity meter and addition of a new control valve successfully reduced the sludge volume enough to satisfy the design capacity of sludge holding basin. Unlike sedimentation sludge, measured quantity of washwater was considerably less than the design capacity of washwater basin because it was over-designed.