• 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.

• Journal of environmental and Sanitary engineering
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• v.15 no.3
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• pp.50-56
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• 2000

In this study, sewage were treated with operating Two-step Aeration System and conventional activated sludge process together in a condition. At the same HRT 8hr of Two-step Aeration System and Activated Sludge Process, BOD treatment efficiency of 1st sedimentation basin effluent 36.9% by Two-step Aeration system was 12.3% higher than 24.65 by Activated Sludge Process and the COD treatment efficiency 39.8% by two-step Aeration System was 11.6.3% higher than 28.2% by Activated Sludge Process. BOD and COD treatment efficiencies of 2nd sedimentation basin effluent were 88.1% and 85.6% Two-step Aeration System and were 83.8% and 82.3% Activated Sludge Process. In the first treatment, as BOD was relatively removed a lot, F/M ratio 0.17, $0.21{\cdot}BOD/kg{\cdot}MLSS.d$ was maintained by Activated Sludge Process. Therefore it was proved that organic matter treatment efficiency by Two-step Aeration System os Higher than by Activated Sludge Process in a aeration time 8hr. $NH_4^{+}-N$ treatment efficiencies were 55.5% by Two-step Aeration System and 39.75 by Activated sludge Process. $NO_3^{-}-N$ concentration in 2nd. sedimentation basin effluent were 3.33% by Two-step Aeration System and 2.36% by Activated Sludge Process. From this result, Two-step Aeration System was proved more advantageous treatment process for nitrification than Activated Sludge Process. The fluctuation range of BOD, COD and SS concentration in 2nd sedimentation basin effluent $16~33mg/{\ell}$, $15~23mg/{\ell}$ and $14~22mg/{\ell}$ by Two-step Aeration System was smaller than $16~57mg/{\ell}$, $15~25mg/{\ell}$ by Activated sludge Process. Overall the fluctuation range in 2nd sediment basin effluent by was smaller than by Activated Sludge Process. As a result, it is possible for this Two-step Aeration with no facility investment and a little of operation condition change in a conventional sewage treatment plant to get stability and nitrification of treatment water quality.

• Journal of the Korean Wood Science and Technology
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• v.29 no.2
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• pp.109-117
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• 2001

This research was carried out to develop the Hanji(Korean paper) sludge wood particle composite utilizing the waste sludges occurring from the making process of Hanji(Korean paper). In the research, four mixing ratios of white or black sludge to wood particle(10:90, 20:80, 30:70, and 40:60), three types of the resin adhesives(PMDI, urea and phenol resin) and three levels of the densities(0.60, 0.75 and 0.90) were designed to investigate the physical properties of Hanji(Korean paper) sludge wood particle composite. The linear expansion of Hanji(Korean paper) sludge wood particle composite was not always increased, compared to control boards. For thickness swelling, PMDI-bonded composites had the lowest value, and thickness swelling of composite was generally decreased with the increase of Hanji sludge. The water absorption of white sludge wood particle composite had no tendency, hut that of black sludge wood particle composite was decreased with an increase of mixing ratio of Hanji sludge.

• Journal of Soil and Groundwater Environment
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• v.15 no.6
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• pp.72-80
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• 2010

Possibility of the usage of sludge generated in coal mine drainage treatments as a briquette additive was investigated by the combination of industrial, elemental, and combustion experiments. A series of briquettes having 2% and 6% of sludge were used for the experiments. Compared to the control sample, our results show that all experimental values for the briquettes are very similar. In particular, it is worthy to note that there is no obvious difference in calorific values for the briquettes containing 2% or 6% of sludge. The calorific values are 4,250~4,360 kcal/kg, 4,240~4,250 kcal/kg, 4,180~4,210 kcal/kg, and 4,270~4,360 kcal/kg for the control sample, briquette containing 6% of Hambaek sludge, briquette containing 6% of Hamtae sludge, and briquette containing 2% of Hambaek sludge, respectively. Results of ash fusion temperature show that the temperature is greater than $1,550^{\circ}C$ for the control sample. However, the temperature for the briquettes with 6% of Hambaek sludge and 2% of Hambaek or Hamtae sludge is $1,510^{\circ}C$. For a briquette containing 6% of Hamtae sludge, the temperature of ash fusion is $1,530^{\circ}C$. After combustion, environmental impacts of the briquettes with sludge were tested. Little environmental influence was observed for the combusted briquettes with sludge.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.609-615
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• 2010

This study examined the change of water content in sludge using direct current electric equipment for decreasing the amount of sludge. The experiment showed that the average density of solids in the sludge treated by direct current before the centrifugal dewatering process was increased by 47.8%, when compared to those not treated by direct current. From the result of measuring the granularity of the sludge by the direct current treatment, that the average particle size of the sludge that was not exposed to the electric current was 52.36 ${\mu}m$, and more than 90% of the sludge was <94.29 ${\mu}m$ in size. On the other hand, the average particle size of the sludge passed through the direct current was 28.67 ${\mu}m$, and more than 90% of the sludge was 52.46 ${\mu}m$. This means that the average particle size of the sludge treated by the direct current was 45.2% smaller, and the standard deviation of granularity was improved. Because of water that separated from sludge moves to the (+) pole, larger particles become smaller and fine particles combine together, resulting in the equalization of the particle size. On the sludge after the centrifugal dehydrator, the change of the water content by the direct current was measured. The results showed that the average density of the solids was increased by 44.2% compared.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.3
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• pp.53-59
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• 2014

In this study, the sewage sludge dryer is installed before and after dehydration of the sludge and aqueous phase composition, the heavy metal content, and measurement and analysis were investigated. The removal efficiency of water content of sewage sludge was about 95.7% in the sewage sludge dryer. The removal efficiency of water content for primary dryer was designed for 35% of primary drying, secondary drying to remove the water content to 10%, but as the measurement revealed that 20.8% of primary drying, the second dryer 3.3% a better effect to the actual operation respectively. Before the installation of the sewage sludge dryer, the content of heavy metal was as follows, Cu:352~614 ppm, Hg: 1.3~1.44ppm, Cd : 1.1~1.86ppm, Pb : 17.25~ 28.93 ppm, As : 1ppm. And after the installation of the sewage sludge dryer, the content of heavy metal changed to as follows, Cu : 340~350 ppm, Hg : 0 ppm, Cd : 0~0.021 ppm, Pb : 0 ppm, As : 0~0.043 ppm which is Also below the legal limits. Also, the sewage sludge dryer produce 1/4 of the sewage sludge into dried sludge.

• Journal of the Korean Wood Science and Technology
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• v.30 no.2
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• pp.121-127
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• 2002

This research was carried out to develop the Hanji(Korean paper) sludge·wood particle composite utilizing the waste sludges occurring from the making process of Hanji(Korean paper). At the research, four mixing ratios of white or black sludge to wood particle(10:90, 20:80, 30:70 and 40:60), three types of the resin adhesives(PMDI, urea and phenol resin) and three levels of the densities(0.60, 0.75 and 0.90) were designed to investigate the mechanical properties of Hanji(Korean paper) sludge·wood particle composite. In the white and black sludge·wood particle composites, bending properties(MOR, MOE) showed the decreasing tendency according to the increase of sludge additive, but it was clearly increased with the increase of specific gravity. Also tensile strength had the same tendency as in these bending properties. The internal bond strength of white sludge·wood particle composite had no tendency, but that of black sludge·wood particle composite was decreased as an increase of Hanji sludge additive.

• Microbiology and Biotechnology Letters
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• v.36 no.3
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• pp.233-239
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• 2008

A new approach to the solubilization of excess activated sludge by the inoculation of lactic acid bacteria was studied to reduce the amount of sludge produced in the activated sludge treatment process. Aerobic microorganism in sludge was lysed in anaerobic condition and the cytoplasmic substance eluted was utilized as a carbon source by lactic acid bacteria. On the basis of sludge solubilization efficiency, Lactobacillus brevis and Leuconostoc mesenteroides subsp mesenteroides were selected the best candidates among five kinds of Lactobacillus sp. and seven kinds of Leuconostoc sp. The sludge solubilization efficiency by heterofermentative lactic acid bacteria was more efficient than that of homofermentative bacteria. Initial value of soluble COD (sCOD) was 1050 mg/L at the initial inoculation time increased to 3070 mg/L (192% solubilization) at 96 h of the incubation time. The inoculation of lactobacillus brevis to the sludge resulted in 2824% increase in sCOD value after 96 h of incubation than the control experiment. Leuconostoc mesenteroides subsp mesenteroides showed 152% increase of solubilization and 30% increase of S-COD/T-COD on 96 h of incubation time. Considering the increase of S-COD by the inoculation of Leuconostoc sp. on 24 h, 10% inoculation of lactic acid bacteria to the sludge was most effective.

• Journal of Environmental Health Sciences
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• v.37 no.6
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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.

• Environmental Engineering Research
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• v.19 no.1
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• pp.59-66
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• 2014

The aim of this study was to assess the effect of pre-aeration on sludge solubilization and the behaviors of nitrogen, dissolved sulfide, sulfate, and siloxane. The results of this study showed that soluble chemical oxygen demand in sewage sludge could be increased through pre-aeration. The pre-aeration process resulted in a higher methane yield compared to the anaerobic condition (blank). The pre-aeration of sewage sludge, therefore, was shown to be an effective method for enhancing the digestibility of the sewage sludge. In addition, this result confirms that the pre-aeration of sewage sludge prior to its anaerobic digestion accelerates the growth of methanogenic bacteria. Removal rates for $NH_3$-N and T-N increased simultaneously during pre-aeration, indicating simultaneous nitrification and denitrification. The siloxane concentration in sewage sludge decreased by 40% after 96 hr of pre-aeration; in contrast, the sulfide concentration in sewage sludge did not change. Therefore, pre-aeration can be employed as an efficient treatment option to achieve higher methane yield and lower siloxane concentration in sewage sludge. In addition, reduction of nitrogen loading by pre-aeration can reduce operating costs to achieve better effluent water quality in wastewater treatment plant and benefit the anaerobic process by minimizing the toxic effect of ammonia.