• Journal of Korean Society of Water and Wastewater
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• v.12 no.4
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• pp.59-69
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• 1998

Biological treatment systems generally can be divided into two main classes of a suspended sludge process and attached one like a fluidized bed reactor. These process are considered to bring remarkable change in species composition of microorganisms, due to difference of a state of biofilm, a concentration and diffusion velocity of dissolved oxygen, a concentration and diffusion velocity of substance or poisonous matter. The change of species composition bring different treatment result for influence factors like F/M ratio, DO concentration, pH or poisonous matter. This study is to investigate the reaction characteristics of both microorganisms, namely, a suspended sludge and attached sludge, through the changes of pH, temperature and substance concentration.

• Journal of Environmental Health Sciences
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• v.28 no.5
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• pp.77-85
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• 2002

The objective of this study was to evaluate the performances of the ASBR under critical conditions of solid-liquid separation, caused by extremely high solids concentration, for wider application of the ASBR to various wastes. The ASBRs and completely-mixed daily-fed control runs were operated using a municipal mixed sludge at 35$^{\circ}C$ and 55$^{\circ}C$. Conversion of completely-mixed daily-fed reactor to sequencing batch mode and changes in HRT of all ASBRs were easily achieved without adverse effect, regardless of digestion temperature. Solids accumulation was remarkable in the ASBRs, and directly affected by settleable solids concentration of the feed sludge. Noticeable difference in solids-liquid separation was that flotation thickening occurred in the mesophilic ASBRs, while gravity thickening was a predominant solid-liquid separation process in the thermophilic ASBRS. Solids profiles at the end of thickening step dramatically changed at solid-liquid interface, and slight difference in solids concentrations was observed within thickened sludge bed. Organics removals based on subnatant or supernatant after thickening always exceeded 80% in all reactors. Thickened sludge volume and gas production of the ASBRs affected mutually. Gas production increased as thickened sludge accumulated, and continuous gas evolution during thickening could cause thickened sludge to expand or resuspend. Thickened sludge volume exceeding a predetermined withdrawal level resulted in loss of organic solids as well as biomass during withdrawal step, leading to decrease in gas production ind SRT. Such an adverse mutual effect was significant in gravity thickening, while it was not sensitive in flotation thickening. Changes in organic loading had no significant effect on organic removals and gas production after build-up of solids in the ASBRs.

• Journal of Environmental Science International
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• v.2 no.4
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• pp.317-324
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• 1993

Effluent recycling effect on UASB reactor performances is known as an important operational factor. In the present study, the possibility of intermittent recycle in UASB process for saving the power consumption was examined at different organic loading and various operational modes in recycle time period. The organic removal efficiencies of the reactors operated with the intermittent effluent recycle were considerably higher compared to those without the effluent recycle. In the intermittent recycle mode, the organic removal efficiencies slightly decreased as the non-recycle time period in the operational mode increased. Proper ratio of recycle and non-recycle time period in the mode seemed to be required to prevent the produced biogas from accumulation in the sludge bed, which caused dead zone in the reactor and sludge loss when the gas was escaped from the bed at the certain pressure.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.3
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• pp.79-89
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• 2017

Changes in pH, EC and water soluble cation and anion of the bed material in the rearing box of earthworms were investigated while sewage sludges or night soil sludge were cumulatively supplied to the 15 grams of initial earthworm population in the rearing box. Initial biochemical properties of sludges such as pH, EC, V.S. and water content were at the edible levels for earthworm. However, as the cumulative amount of sludges supplied to the earthworms were increased, pH of bed material in the rearing box was lowered and EC was increased, which meant that salt contents of bed material in the rearing box had been accumulated. Water soluble cations and anions were also accumulated in the bed material of the rearing box. Accumulation rates of ${NO_3}^-$ were especially prominent. Consequently, feeding rates of earthworm populations were reduced to nearly zero and earthworm populations finally died.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.3
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• pp.29-34
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• 2003

This paper describes the effects of sewage amount, temperature, and years in operation on the infiltration rate of a sewage disposal system. The self-purifying sewage disposal system, which is typically used in rural areas, consists of reeds and fine gravel. Water plants are planted on the gravel bed which provides the habitat for microbes. The basic process is that the gravel bed filters incoming sewage. Thus this system requires the smooth flow of sewage through the gravel. However, the efficiency of the disposal system will be lowered if the gravel bed is clogged with sewage sludge. A three year study shows that infiltration rate slows down significantly until the 7th day, depending on the sewage amount and the temperature. After the 7th day, the infiltration rate remains almost constant. In addition, the infiltration rate decreases as the temperature falls. It also decreases as the number of years in operation increase. But there is no significant change in the infiltration rate after the 7th day, independent of the temperature, the sewage amount, and years in operation. In order to take advantage of high infiltration rate, which improves the efficiency of the disposal system in its early stages, having two gravel beds and using them alternatively will be efficient. This operation method is called intermittent load and makes the disposal system last longer. The water plant roots above the gravel bed make the effective filtration possible because they delay accumulation of the sewage sludge and stabilize the filtration ability.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.222-229
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• 2006

The treatment performance and operational parameters of a tertiary wastewater treatment process a biological filtration system were investigated. The biological filtration system consisted of a nitrification filter (Fiter 1) and a polishing filter with anoxic and aerobic parts (Filter 2). SS, T-C-BOD, and T-N in effluent were kept stable at less than 3, 5 mg/L, and 5 mgN/L, respectively, under a HRT in Filter (filter-bed) of 0.37~2.3 h. T-N at the outlet of Filter 2 were about 1~5 mgN/L under the condition of LV of 50~202 m/d. In Filter 2, denitrification was accomplished under LV of 50~168 m/d in a 1 m filter-bed. However, the denitrification capacity reached the maximum when the linear velocity was increased to 202 m/d. Relationship between increase in microorganism and headloss was clearer in Filter 2. As a result, the denitrification rate increased from 1.0~2.3 kgN/($m^3-filter-bed{\cdot}d$) as the headloss increased. The COD removal rate was 6.0~9.6 kgCOD/($m^3-filter-bed{\cdot}d$) when operated with Filters 1 and 2. These results mean that captured bacteria contributed a part of COD consumption and denitrification. The maximum nitrification and denitrification rate was 0.5 and 4 kgN/($m^3-filter-bed{\cdot}d$) in Filter 1 and 2.The ratio of backwashing water to the treated water was about 5~10 %. In Filter 1, wasted sludge in backwashing was only 0.7~5.3 gSS/($m^3$-treated water). In Filter 2, added methanol was converted into sludge and its value was 8.0~24 gSS/($m^3$-treated water). These results proved that this process is both convenient to install as tertiary treatment and cost effective to build and operate.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.5
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• pp.437-442
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• 2010

This work was initiated both to maximize purity of calcium fluoride sludge and to minimize water content in the settled sludge. The sludge was produced in the process of fluoride removal of semiconductor wastewater by the addition of $Ca^{2+}$ ion. Fludized bed reactor(FBR) using calcium fluoride as a seed was adapted. Optimum pH and molar ratio of $Ca^{2+}/F^-$ were determined in lab-scale study. The experimental results showed that fluoride removal was increased as pH and molar ratio of $Ca^{2+}/F^-$ increased, with the best removal of 79.8% in an optimum condition. In the optimum point of fluoride removal, very low ${PO_4}^{3-}$-P removal of 9.3% was observed. It indicates forming $CaF_2$ crystal of high purity, when side reaction of calcium with phosphate was minimized. In addition, water content of settled sludge was 19.3%, which is relatively low compared to other fluoride removal processes. Consequently, the FBR process proposed in this study was very effective in fluoride removal, producing good sludge of high purity and less water content.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.718-722
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• 2012

$H_2S$ adsorption characteristics of adsorbent made by sewage sludge were investigated. For analyses of the manufactured adsorbent, various methods such as Iodine adsorptivity, scanning electron microscope (SEM), and measurements of BET surface area and pore volume were adopted. As the major adsorption characteristic, breakthrough curve was measured by using a continuous fixed bed adsorption column for operating variables such as adsorption temperature ($25{\sim}45^{\circ}C$), aspect ratio (L/D)(3~9), gas flow rate (0.1~2.0 liter/min) and $H_2S$ gas concentration (50~200 ppm). The experimental result showed that the carbonization and activation of sewage sludge are very important for the improvement in $H_2S$ adsorption capacity.

• 한국연소학회:학술대회논문집
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• 2000.12a
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• pp.236-245
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• 2000

A laboratory scale fluidized bed reactor was developed to treat the combustion characteristics of some fuels (wood, paper sludge, refuse derived fuel). The aims were to introduce the means of experiment and interpretation of the results and finally determine the particle characteristics on the pyrolysis and combustion process of the fuel. A single particle combustion process in the fluidized bed was closely observed. Understanding experimental facility characteristics and determining parameters were also carried out. The fuel combustion processes were observed by carbon conversion rate, recovery and mean carbon conversion time. They were estimated with the CO, $CO_2$ gas concentration monitored at the exit of the combustor. Fuel drying and pyrolysis process were governed by temperature distribution in the fuel particle. There was a significant overlap of the drying and devolatilization. However, transition process from devolatilization to char combustion seemed to be determined by mechanical solidity of the fuel particle after devolatilization process.

• Microbiology and Biotechnology Letters
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• v.24 no.6
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• pp.738-742
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• 1996

An efficient packed-bed type biofilm reactor charged with immobilized phototrophs was developed to treat organic wastewater at an extremely high volumetric loading rate. The packed bed reactor (PBR) charged with porous ceramic beads was superior to a fluidized-bed reactor suspended with activated carbon powders in terms of many aspects such as BOD removal efficiency, operational stability, and overall economics. For wastewater with BOD concentration as high as 20, 000mg/l, the BOD removal efficiency was maintained above 90% when the hydraulic retention time (HRT) was longer than 1 day. The allowable volumetric BOD loading rate of this reactor (20gBOD/l day) is more than ten-folds higher than that of an ordinary activated sludge method. The behaviour of the reactor was represented well by a Monod type kinetic equation with a maximum specific BOD loading rate(P) of 22.2gBOD/l day and a half saturation constant(K$_{s}$) of 1, 750 mgBOD/l.