• Journal of Korean Society of Environmental Engineers
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• v.34 no.10
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• pp.651-655
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• 2012

This study aimed to investigate the effect of an inorganic conditioner composed of natural inorganic materials on the dewaterbility of sewage sludge and compare the performance with those of conventional organic polymeric conditioners. A dosage of 2.0 mg inorganic conditioner/g sludge TS decreased time to filter test (TTF), specific resistance to filtration (SRF), water content of dewatered sludge cake, turbidity from 146 to 41 sec, from $8.3{\times}10^{14}$ to $2.4{\times}10^{14}$ m/kg, from 82.1 to 77.1%, from 112 to 61.1 NTU, respectively, which was compatible to the conventional cation organic polymer. An inorganic conditioner would be used in sewage sludge treatment as a suitable alternative conditioner. Regression analysis showed a strong relationship among TTF, SRF, and water content.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.1
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• pp.35-45
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• 2017

In order to improve the anaerobic digestion efficiency of the sewage sludge, the methane potential of the hydrolysate generated from the hydro-thermal reaction at 170, 180, 190, 200, 210, $220^{\circ}C$ was analyzed and the constitutional characteristics of the organic materials were estimated by dividing organic materials of hydro-thermal hydrolysate into easily biodegradable, decomposition resistant, and non-biodegradable organic materials applying the parallel first order kinetics model. The ultimate methane potential of sewage sludge hydro-thermal hydrolysate increased to 0.39, 0.39, 0.40, 0.44, 0.45, and $0.46Nm^3/kg-VS_{added}$ as hydro-thermal reaction temperature increased from 170, 180, 190, 200, 210, $220^{\circ}C$. It has been shown that the organic matter of sewage sludge is solubilized to increase the content of biodegradable organic material($VS_B$). The easily degradable organic matter($VS_e$) content was highest at hydro-thermal reaction temperature of 200 and $210^{\circ}C$, and optimum hydro-thermal reaction temperature for organic matter solubilization of sewage sludge was in the range of $200{\sim}210^{\circ}C$. In addition, the amount of biodegradable organic material($VS_B$) and easily biodegradable organic matter ($VS_e$) in the hydrolysate of sewage sludge was the highest at hydro-thermal reaction temperature of $200^{\circ}C$.

• Current Research on Agriculture and Life Sciences
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• v.17
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• pp.45-52
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• 1999

This study was conducted to evaluate the effects of microbial inoculation on sewage sludge composting. The number and species of microorganisms in sewage sludge sampled on February were higher than those sampled on August. The composting of sewage sludge is inhibited by the polyacrylamide cation, which was used as a coagulant and known to repress the growth of microorganisms. The growth of all microorganisms was inhibited by the addition of the polyacrylamide cation at a concentration of more than 0.8%. The species and viable counts of microorganisms were observed to increase during composting sewage sludge by inoculation of the effective microorganisms and addition of the pine tree sawdust as a bulking agent, compared with those without inoculation. A variety of organisms in compost(sewage sludge plus sawdust) were observed after composting for 30 days, such as Fragilaria sp., Proales sp., Vorticella sp., Schizothrix sp., Anabaena sp., Zoothaminium sp., Epstylis sp., Arcella sp., Balantidium sp., Actinophrys sp., Synedra sp., Euglypha sp., Ulothrix sp., Anacystis sp., and Clostium sp.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.11
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• pp.781-784
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• 2013

Ocean dumping of sewage sludge is banned. Therefore, it is needed to develop alternative treatment method. Sewage sludge and waste glass are used to prepare lightweight brick. Large amount of energy is consumed to prepare building material, because of its high preparation temperature, or above $1,200^{\circ}C$. We study to prepare lightweight brick, using sewage sludge and waste glass as raw materials in this research. Lightweight brick was made at low temperature of below $800^{\circ}C$ to reduce $CO_2$ emission by geopolymer technique. Calcination temperature, mixing ratio of sewage sludge/waste glass and water glass/water were discussed to evaluate their effect on the brick prepared. In this study, the optimal conditions for preparing bricks was $750^{\circ}C$ of firing temperature, 1.5 of mixing ratio for water glass/water and 10 : 90 wt% of sewage sludge/waste glass. At this condition, compressive strength and specific gravity of brick prepared were 5.1 MPa and 0.46, respectively. These values satisfy the criteria on a lightweight brick.

• Clean Technology
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• v.25 no.1
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• pp.74-80
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• 2019

Thermochemical treatment of sewage sludge is an energy-intensive process due to its high moisture content. To save the energy consumed during the process, the hydrothermal carbonization process for sewage sludge can be used to convert sewage sludge into clean solid fuel without pre-drying. This study is aimed to investigate co-firing characteristics of the hydrothermally carbonated sewage sludge (HCS) to a pulverized coal combustion system. The purpose of the measurement is to measure the pollutants produced during co-firing and combustion efficiency. The combustion system used in this study is a furnace with a down-firing swirl burner of a $80kW_{th}$ thermal input. Two sub-bituminous coals were used as a main fuel, and co-firing ratio of the sewage sludge was varied from 0% to 10% in a thermal basis. Experimental results show that $NO_x$ is 400 ~ 600 ppm, $SO_x$ is 600 ~ 700 ppm, and CO is less than 100 ppm. Experimental results show that stable combustion was achieved for high co-firing ratio of the HCS. Emission of $NO_x$ and $SO_x$ was decreased for higher co-firing ratio in spite of the higher nitrogen contents in the HCS. In addition, it was found that the pollutant emission is affected significantly by composition of the main fuel, regardless of the co-firing ratios.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.3
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• pp.27-39
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• 2019

In this study, thermal-alkali pre-treatment (THAP) optimal condition and co-digestion efficiency with THAP of the mixture food waste and sewage sludge were evaluated for improving the performances of co-digestion for mixed food waste and sewage sludge. The optimal condition of THAP was evaluated for solubilization COD, CST(Capillary Suction Time), TTF(Time to Filter), and volatile fatty acids (VFAs) with THAP temperature and NaOH concentration. In addition, the co-digestion of mixed food waste and sewage sludge were evaluated using biochemical methane potential (BMP) test. The optimal THAP reaction temperature and NaOH concentration of food waste and sewage sludge were $140^{\circ}C$ and 60 meq/L to solubilization COD over 20%, CST and TTF under 60sec and VFAs concentration over 12,000 mg-COD/L, respectively. The optimal condition of co-digestion of mixed food waste and sewage sludge equal to THAP condition. Therefore, it was determined that the optimal condition of THAP reaction temperature and NaOH concentration for co-digestion of mixed food waste and sewage sludge were $140^{\circ}C$ and 60 meq/L, respectively.

• Journal of Korean Society on Water Environment
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• v.38 no.2
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• pp.95-102
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• 2022

Studies for improving the efficiency of the traditional anaerobic digestion process are being actively conducted. To improve anaerobic digestion efficiency, this study tried to derive the optimal pretreatment conditions and mixing conditions by integrating the heat solubilization pretreatment of sewage sludge, livestock manure, and food waste. The soluble chemical oxygen demand (SCOD) increase rate of sewage sludge before and after heat solubilization pretreatment showed an increased rate of 224.7% compared to the control group at 170℃ and 25 min and showed the most stable increase rate. As a result of the biomethane potential test of sewage sludge before and after heat solubilization pretreatment, the total chemical oxygen demand (TCOD) and SCOD removal rates increased as the heat solubilization temperature increased, but did not increase further at temperatures above 170℃. In the case of methane generation, there was no significant change in the cumulative methane generation from 0.134 to 0.203 Sm³-CH₄/kg-COD at 170℃ for 15 min. As a result of the integrated digestion of organic waste, the experimental condition in which 25% of the sewage sludge, 50% of the food waste, and 25% of the livestock manure were mixed showed the highest methane production of 0.3015 m³-CH₄/kg-COD, confirming that it was the optimal mixing ratio condition. In addition, under experimental conditions mixed with all three substrates, M4 conditions mixed with 25% sewage sludge, 50% food waste, and 25% livestock manure showed the highest methane generation at 0.2692 Sm³-CH₄/kg-COD.

• Journal of Soil and Groundwater Environment
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• v.18 no.3
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• pp.58-64
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• 2013

This study proposed a low temperature hydrothermal carbonization to treat and recycle sewage sludge and determined the optimal conditions for the biochar production. The physical and chemical properties of biochar were analyzed and its sorption capacity for heavy metals was evaluated. To produce biochar, 50 g of sewage sludge was heated at 220, 230, and $240^{\circ}C$ for 1, 2, 3, 5, 8, and 10 hours in a reactor. The optimal conditions to produce biochar was $230^{\circ}C$ and 8 hours. Sorption capacity tests were conducted for arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn) and nickel (Ni). Among them, lead was shown the highest heavy metal adsorption efficiency of biochar, followed by copper, cadmium, zinc, and nickel, but arsenic was hardly adsorbed overall.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.6
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• pp.743-750
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• 2013

In this study, the carbonized aggregate of light weight and high mechanical strength using sewage sludge was evaluated with changing carbonation variables of temperature, detention time and feed condition. Porosity and mechanical strength was simultaneously increased according to increase of carbonization temperature unexpectedly. Carbonization detention time above 1 hour nearly affect on the porosity, but mainly on mechanical strength of the carbonized aggregate in case of clay addition. On $900^{\circ}C$, porosity and mechanical strength was increased rapidly, but above $1000^{\circ}C$, porosity began to decrease. Clay addition was very effective on increase of mechanical strength following much loss in porosity. The carbonized aggregate manufactured at $900^{\circ}C$ adding 30 % clay in sewage sludge was higher a little in porosity and 3 times in mechanical strength than those at $700^{\circ}C$ not adding clay. Consequently, in manufacturing the carbonized aggregate having simultaneously high porosity and mechanical strength, it is desirable to have operational condition of $900{\sim}1000^{\circ}C$ temperature and 1 hour time, and clay addition within 30 % for further higher mechanical strength.

• Journal of Environmental Science International
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• v.11 no.4
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• pp.367-373
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• 2002

The polycyclic aromatic hydrocarbons(PAHs) content in sewage sludge was determined by gas chromatography linked to ion trap mass spectrometry(GC/ITMS) with five deuterated PAHs as internal standards. The minimum detection limit was from 1.66 to 7.14 pg for individual PAH by GC/ITMS. For determining total PAHs(∑PAH) in sewage sludge 84 samples from 74 waste water treatment plants in whole country were analyzed. The average content of ∑PAH far whole samples was 3,289$\pm$3,098 $\mu\textrm{g}$/kg, and ranged from 142 to maximum 20,102 $\mu\textrm{g}$/kg. According to the number of population of the city, the areas were classified as five regions, ie. big, large, middle, small, and rural area in which the waste water treated plants were grown. The contents of PAHs were 4,689$\pm$5,503, 5,839$\pm$6,401, 3,725$\pm$2,053, 2,237$\pm$2,069, and 2,475$\pm$1,489 $\mu\textrm{g}$/kg, in big, large, middle, small, and rural area, respectively.