• Journal of Environmental Science International
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• v.17 no.12
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• pp.1343-1351
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• 2008

The activated sludge obtained from wastewater coke oven plant was immobilized by entrapment with polyethylene glycol (PEG). The effects of several factors on the biodegradation of $CN^-$ from. synthetic wastewater were investigated using batch and continuous reactors. The degradation rate of $CN^-$ increased with increasing of the immobilized bead volume in the reactor. Approximately 7.65mg/L of $NH_4-N$ was produced upon the degradation of 35mg/L of $CN^-$. When high concentrations of the toxic cyanide complex were used in the testing of cyanide degradation, the free activated sludge could be inhibited more than that of the immobilized activated sludge. When the phenol concentration was higher than 400mg/L in the synthetic wastewater, approximately 98.4% of $CN^-$ was removed within 42 hours by the immobilized activated sludge. However, the cyanide was not completely degraded by the tree activated sludge. This indicates that high phenol concentrations can act as a toxic factor for the free activated sludge. A $CN^-$ concentration of less than 1mg/L was achieved by the immobilized sludge at the loading rate of 0.025kg $CN^-/m^3-d$. Moreover, it was found that the HRT should be kept for 48 hours in order to obtain stable treatment conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.10
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• pp.861-867
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• 2001

In this paper, in order to investigate the catalytic effect of the sludge exhausted from waterworks on NO$_{x}$ removal, we measure NO removal characteristics with and without sludge pellets in BaTiO$_3$-sludge packed-bed reactor of plate-plate geometry. NO initial concentration is 50 ppm balanced with air and a gas flow rate is 5ι/min. Gas temperature is changed from 25 to 10$0^{\circ}C$ to investigate the role of sludge pellet on removing active oxygen species and NO$_2$. BaTiO$_3$pellets is filled for coronal discharge at upstream of reactor and sludge pellets is filled for catalytic effect at downstream of reactor. The volume percent of sludge pellets to BaTiO$_3$pellets is changed from 0% to 100% and AC voltage is supplied to the reactor for discharging simulated gases. In the results, when sludge pellets is put at the downstream of plasma reactor, NO removal rate is slightly increased. However, NO$_2$and $O_3$ as by-products during NO removal is significantly decreased from 51ppm without sludge pellets to 5 ppm with sludge pellets and from 50 ppm without sludge pellets to 0.004ppm with sludge pellets, respectively. Therefore, NO$_{x}$(NO+NO$_2$) removal rate is increased up to 93%. It is thought that sludge pellet maybe react with active oxygen species and NO$_2$ generated by corona discharge in surface of BaTiO$_3$pellets, the then NO$_2$O$_3$as by-products are considerably decreased. When we increase gas temperature from room temperature to 10$0^{\circ}C$, NO removal rate is decreased, while NO$_2$ concentration is independent on gas temperature. These result suggest that the removal mechanism of active oxygen species and NO$_2$in sludge pellet is not absorption, but chemical reaction. Therefore we expect that sludge pellets exhausted for waterworks could be used as catalyst for NO$_{x}$ removal with high removal rate and low by-product.oduct.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3173-3177
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• 2007

Recently, we have many problems on the process of the sludge. In past, the sewage sludge was treated by reclaimed land or thrown away in the sea. But these methods caused environmental pollution. Today, many researchers are studying various methods for reducing its volume. One of these method, this study is to reduce the moisture of sewage sludge and to solidify it using a dryer and curing equipment. In this research, we investigated about design parameter and operation condition of the equipment. The curing equipment reduces the percentage of water content from 30% of dryer to 10%. So, we have to study the curing characteristics and performance of curing equipment. For example, there are internal flow characteristics and change of the percentage of water content. And we investigated the change of data at outlet along the initial condition, temperature, humidity and air flow. Using this data, we achieve the experimental results of curing efficiency by each geometry and operating condition. And we also investigated numerical analysis of internal flow using CFD code. This research is basic study for optimal design of the curing equipment.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.4
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• pp.449-454
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• 2008

Some pretreatment methods have been proposed to enhance the biodegradability and to shorten the hydrolysis reaction time. By means of efficient pretreatment the suspended solids (SS) can be made of better accessible for the anaerobic bacteria. There are several ways how this can be accomplished, which include biological, mechanical, thermal, and chemical methods. For the sludge solubilization using the cavitation phenomenon, we have tried to develop a pretreatment process consisted of a reactor and pumps. The objectives of this study were to develop a advanced wastewater treatment consisted of IABR and the cavitation with PGA. The most effective removal for organic matter and nutrients were occured when both cavitation pretreatment and ${\gamma}$-PGA were applied at the IABR process. Only small portion of ${\gamma}$-PGA at a rate of 1.38mg/L, was enough to improve sedimentation ability, SS removal efficiencies, and sludge volume reduction. After the sludge solubilization by the cavitation, SCOD increased to 193% and SS decreased to 36%. The removal ratio of BOD was 94.5%, T-N removal ratio was 85.5% and T-P removal ratio was 84.9%. The combination process of the IABR with the cavitation and PGA addition seems to be very effective alternative wastewater treatment process.

• Clean Technology
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• v.10 no.2
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• pp.89-100
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• 2004

The optimization for the water bath design and the skimmer installation are conducted to separate floated-sludge from the waste water in a water bath of a painting booth. VOF(volume of fluid) model is used to analyze the flow pattern of sludge-water-air mixture in a water bath. From the results of numerical analysis, the design criteria of the skimmer, the separation plate and the sludge inlet port of a water bath are obtained for effective sludge separation from water in bath. Furthermore, the installation condition of the skimmer immersed in water is optimized to minimize entrained air and pressure loss.

• Journal of Korean Society of Water and Wastewater
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• v.17 no.4
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• pp.567-573
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• 2003

The pretreatment process was carried out to solubilize the sewage sludge for enhancing its biodegradability using alkaline treatment, ultrasonic treatment(15kHz), ozone treatment and different combination of these three methods: alkaline followed by ultrasonic as well as ozone, and ultrasonic followed by alkaline. The solubilization efficiency was evaluated based on the SCOD/TCOD ratio and VSS/TS ratio. In results, the proper condition of alkaline treatment was shown as 30meq/l of NaOH, pH 12 and 3hours of reaction time. Solubilization efficiency increased to 17% from initial 2% based on SCOD/TCOD ratio under this condition. In ultrasonic treatment, the higher ultrasonic power, the longer treatment time and the lower sludge volume resulted in higher solubilization respectively. There was a rapid increase in solubilization efficiency after 20 minute, then it was measured as 32% of SCOD/TCOD ratio in 1 hour at a ultrasonic power of 1,300W with 1/sludge. Solubilization efficiencies in combined treatment using alkaline and ultrasonic were 47-53% higher than single treatment at a sonicated time of 1 hour. Ozone treatment followed by alkaline treatment also represented the enhanced solubilization compared to ozone treatment. Therefore, ultrasonic or ozone treatment assisted by alkaline could achieve the short treatment time as well as high solubilizetion efficiency.

• Journal of Environmental Science International
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• v.28 no.7
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• pp.629-637
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• 2019

The purpose of this study was to evaluate the effect of high-salinity wastewater on the microbial activity of Aerobic Granule Sludge (AGS). Laboratory-scale experiments were performed using a sequencing batch reactor, and the Chemical Oxygen Demand (COD), nitrogen removal efficiency, sludge precipitability, and microbial activity were evaluated under various salinity injection. The COD removal efficiency was found to decrease gradually to 3.0% salinity injection, and it tended to recover slightly from 4.0%. The specific nitrification rate was 0.043 - 0.139 mg $NH_4{^+}-N/mg$ $MLVSS{\cdot}day$. The specific denitrification rate was 0.069 - 0.108 mg $NO_3{^-}-N/mg$ $MLVSS{\cdot}day$. The sludge volume index ($SVI_{30}$) ultimately decreased to 46 mL/g. The specific oxygen uptake rate decreased from an initial value 120.3 to a final value 70.7 mg $O_2/g$ $MLVSS{\cdot}hr$. Therefore, salinity injection affects the activity of AGS, causing degradation of the COD and nitrogen removal efficiency. It can be used as an indicator to objectively determine the effect of salinity on microbial activity.

• Journal of Environmental Science International
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• v.30 no.12
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• pp.1081-1092
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• 2021

In this study, the effect on the stability of Aerobic Granular Sludge (AGS) caused by an AGS separator was investigated. The AGS separator was a hydrocyclone. The main factors of the AGS separator were filter pore size (0.125~0.600 mm), conical-to-cylindrical ratio (1.5~3.0), and operating time (1~20 min). The AGS/mixed liquor suspended solid (MLSS) ratio gradually increased to 0.500 mm (AGS/MLSS: 84.3±3.0%). AGS was best separated at the conical-to-cylindrical ratio of 2.5 (AGS/MLSS: 84.7±3.3%). As the operating time increased, the AGS separation performance also tended to increase. The shortest AGS separator run time, but the highest AGS separation performance was 10 min (87.0±2.5%). AGS stability was evaluated by operating the selected AGS separator and sequencing batch reactor. The average removal efficiencies of TOC, TCOD_Cr, SS, TN, and TP were 95.7%, 96.9%, 93.0%, 89.0%, and 96.2%, respectively, which met the effluent standards in Korea. In addition, the AGS/MLSS ratio tended to remain constant, and the sludge volume index demonstrated a tendency to decrease from 140 mL/g to 70 mL/g. During the operation, the particles of AGS in optical microscope observations gradually increased.

• Applied Biological Chemistry
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• v.45 no.1
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• pp.25-29
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• 2002

The kernel of wastewater treatment by activated sludge is elimination of organic substances and maintenance of well-flocculated sludge sedimentation. By the conventional activated sludge treatment, the optimum F/M ratio of soybean wastewater treatment was 0.24 (kg-BOD/kg-MLVSS day) and sludge bulking was generated at 0.48 (kg-BOD/kg-MLVSS day). To improve the treatment capacity and operation quality in higher loading of soybean wastewater, influent pH was constantly controlled by 9.0 using NaOH as a coagulant agent. In this process, higher loading up to 2.88 (kg-BOD/kg-MLVSS day) was possible and SVI was maintained under 150 without bulking. This was equivalent to 7.2 times higher than maximum permissible load of the conventional activated sludge process.

• Journal of the Korean Chemical Society
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• v.61 no.5
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• pp.238-243
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• 2017

In this study, water treatment sludge carbonized with $400^{\circ}C$ was tested as an adsorbent for the removal of Pb and Cd in water. The carbonized sludge was characterized by thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray fluorescence spectrometry (XRF), and surface area analysis. Carbonized sludge exhibited much higher specific surface area and total pore volume than water treatment sludge itself. In batch-type adsorption process, carbonized sludge represented better adsorption performance for Pb than Cd, achieving 90~98% at the concentrations conducted in the experiments. Equilibrium data of adsorption were analyzed using the Freundlich and Langmuir isotherm models. It was seen that both Freundlich and Langmuir isotherms have correlation coefficient $R^2$ value larger than 0.95. The results of studies indicated that carbonized water treatment sludge by heat treatment could be used as an efficient adsorbent for the removal of Pb and Cd from water.