• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.29-32
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• 2004

Gaseous partitioning tracer test has been used for determining the volume and spatial distribution of residual non-aqueous phase liquid (NAPL) in the unsaturated soils. In this study, an experimental method for measuring the content of gas-exposed NAPL as well as that of total NAPL in a sand during air sparging was developed. Two different gaseous phase NAPL-partitioning tracers were used; n-pentane, with very low water solubility, was used as the tracer that partitions into NAPL that is only in contact with the mobile gas, and chloroform, with fairly good water solubility, was selected for detecting total NAPL content in the sand. Helium and difluromethanewere used as the non- reactive tracer and water-partitioning tracers, respectively. Using n-decane as a model NAPL (NAPL saturation of 0.018), 25.6% of total NAPL was detected by n-pentane at the water saturation of 0.68. Oniy 9.1% of total NAPL was detected by n-pentane at the water saturation of 0.84. This result implies that the quantity of gas-exposed NAPL increased about three times when the water saturation decreased from 0.84 to 0.68. At the water saturation of 0.68, more than 90% of total NAPL was detected by chloroform while 65.8% of total NAPL was detected by chloroform at the water saturation of 0.84. Considering that the removal rate of NAPL during air sparging for NAPL-contaminated aquifer is expected to be greatly dependent upon the spatial arrangement of NAPL phase with respect to the mobile gas, this new approach may provide useful information for investigating the mass transfer process during air-driven remedial processes fer NAPL-contaminated subsurface environment.

• KSBB Journal
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• v.9 no.2
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• pp.180-185
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• 1994

The productivity of alkaloid in the airlift fermentor operation was less than that of suspension coltures of Eschscholtzia californica cells in the shake flask. To overcome the productivity reduction, a gas recycle airlift fermentor was developed because the gas-stripping in normal airlift fermentor was believed to play a significant role for productivity reduction. The alkaloid content in the gas recycle system with Eschscholtzia californica suspension cells was 2.7 times higher than that of normal airlift fermentor. The productivity of alkaloids and $CO_2$ concentration were affected by the volume of gas reservoir in the gas recycle airlift fermentor.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.269-270
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• 2002

Oxygen is a key substrate in animal cell metabolism and its consumption is thus a parameter of great interest for monitoring and control in animal cell culture bioreactor. The use of a gas-permeable membrane offered the possibility to provide the required quantity of oxygen into the culture. while avoiding problems of foaming or shear damage generally linked to sparging. For determining the optimum DO control strategy of this gas-permeable membrane aeration bioreactor, the oxygen transfer rate coefficient was measured with varying $N_2$ ratio in inlet air. The results showed that an increasing mass flow rate of nitrogen reduced the $K_La$ value. and 5% nitrogen in air did not result in any oxygen limitation.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.505-510
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• 2012

The gas hold-up has a strong relationship with the size distribution and rising velocities of bubbles in a bubble column. Therefore, many previous researchers have studied on the hydrodynamics focusing on the bubble size variation in bubble column. In this study, the bubble behavior was influenced by partitioning porous plates installed at a certain height in a trayed bubble column. The gas hold-up was increased in non-sparging region (H/D > 5) as well as sparging region. We identified the effect of the partitioning porous plate using three trayed bubble columns with different reactor geometries. Furthermore, the bubble break-up frequency and size distribution were observed before and after individual bubbles penetrated through the plate. The arrangement of the plates was also investigated using a 0.15-m-in-diameter bubble column. Based on the result, we applied this design concept to a 0.36-m-in-diameter, 22 m tall trayed bubble column and identified the effect of the partitioning porous plate on the gas hold-up increase.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.705-712
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• 2000

The fluid generally flows through fractures in crystalline rocks where most of underground storage facilities are constructed because of their low hydraulic conductivities. The fractured rock is better to be conceptualized with a discrete fracture concept, rather continuum approach. In the aspect of fluid flow in underground, the simultaneous flow of groundwater and gas should be considered in the cases of generation and leakage of gas in nuclear waste disposal facilities, air sparging process and soil vapor extraction for eliminating contaminants in soil or rock pore, and pneumatic fracturing for the improvement of permeability of rock mass. For the purpose of appropriate analysis of groundwater-gas flow, this study presents an unsteady-state multi-phase FEM fracture network simulator. Numerical simulation has been also conducted to investigate the hydraulic head distribution and air tightness around Ulsan LPG storage cavern. The recorded hydraulic head at the observation well Y was -5 to -10 m. From the results obtained by the developed model, it shows that the discrete fracture model yielded hydraulic head of -10 m, whereas great discrepancy with the field data was observed in the case of equivalent continuum modeling. The air tightness of individual fractures around cavern was examined according to two different operating pressures and as a result, only several numbers of fractures neighboring the cavern did not satisfy the criteria of air tightness at 882 kPa of cavern pressure. In the meantime, when operating pressure is 710.5 kPa, the most areas did not satisfy air tightness criteria. Finally, in the case of gas leaking from cavern to the surrounding rocks, the resulted hydraulic head and flowing pattern was changed and, therefore, gas was leaked out from the cavern ceiling and groundwater was flowed into the cavern through the walls.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.362-367
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• 2006

Waste activated sludge(WAS) collected from domestic wastewater treatment plant is biomass that contains large quantities of organic matter. However, relevant literature show that the bio-hydrogen yield using WAS was too low. In this study, the effect of pretreatment of WAS on hydrogen yield was investigated. Pretreatment includes acid and alkali treatments, grinding, heating, ozone and ultrasound methods. After pretreatment organic matters of WAS were solubilized and soluble chemical oxygen demand(SCOD) was increased by 14.6 times. Batch experiments were conducted to investigate the effects of pre-treatment methods and buffer solution, hydrogen partial pressure, and sodium ion on hydrogen production from WAS by using heated anaerobic mixed cultures. Experimental results showed that addition of buffer solution, efficient pre-treatment method with alkali solution, and gas sparging condition markedly increased the hydrogen yield to 0.52 mmol $H_2/g$-DS.

• Microbiology and Biotechnology Letters
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• v.29 no.4
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• pp.240-247
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• 2001

The effect of microsparged aeration in mammalian cell bioreactor on the oxygen transfer rate and cell viability was studied. The microspargers with differ- ent micron-sized pores were used to supply oxygen to the medium. The oxygen transfer coefficients (k$_{L}$a) measured in the bioreactor were markedly increased, which is due to the increase of the contacting area between air bubbles and liquid medium when the pore size of microsparger decreases. When the impellers of two different types (square-pitch marine impeller and $45^{\circ}$ pitched flat blade impeller) were used for agitation, the k$_{L}$a values were slightly higher with the marine impeller than with the blade impeller. The detrimental effect of direct gas sparging with microsparger on mammalian cells was investigated in bubble columns with various air flow rates and different pore sized microspargers. The first-order cell death rate constant ($k_{d}$ /7) was shown to be directly proportional to the air flow rate and inversely proportional to the pore size. During the cultivation of hybridoma cells using microsparger with the pore size of $0.57\mu$m in the mammalian cell culture bioreactor, the continuous sparging caused the cell death and suppressed the cell growth. However, cells grew normally and cell viability was maintained above 90% in the logarithmic phase when the air was intermittently sparked in order to maintain the dissolved oxygen level above 20%.

• Microbiology and Biotechnology Letters
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• v.20 no.6
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• pp.681-686
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• 1992

In the conversion of D.L-2-amino-$\Delta^2$-thiazoline-4-carboxylic acid(D,L-ATC) to L-cysteine using Pseudomonas sp. CU6. the effects of surfactants on whole cells and the stabilities of cellfree enzyme solution and continuous reactor packed with immobilized whole cells were investigated. The enzymatic reaction was little accomplished by whole cells without adding surfactants, whereas it was well carried out with SDS or Triton X-loo comparable to the case using cell-free enzyme solution. Enzyme activity of the cell-free solution was lost by 50% after 7 hours of storage at $30^{\circ}C$, but not at all under an anaerobic condition by sparging nitrogen gas. On the other hand. effect of nitrogen gas did not appear in a continuous reactor using immobilized whole cells, and hydroxylamine, an inhibitor of L-cysteine desulfhydrase, lowered the enzyme stability.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.6
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• pp.522-527
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• 2004

Barley growing in paddy fields often suffers from wet-injury due to oxygen deficiency in rhizospere caused by excessive water in the soil. This study was conducted to investigate responsiveness of growth, development and anaerobic glycolysis enzymes to acute hypoxia in barley seedlings. Barley seedlings at the third leaf stage were subjected to hypoxia (1 ppm dissolved oxygen) by sparging the culture solution with nitrogen gas for up to seven days. Length and fresh weights of the shoot and root were affected little by hypoxia for up to 5 days. But root dry weight was slightly decreased by hypoxia for 7 days. In the root, alcohol dehydrogenase and lactate dehydrogenase activities increased drastically under hypoxia, reaching at their maximum levels in 3 to 5 days of hypoxia and decreasing slightly thereafter. However, the activities of both enzymes changed little in the shoot. Increases of their activities in the root were contributed by all the isozymes found in barley. These results suggest that barley seedlings first adapt to hypoxia by rapidly activating fermentative glycolysis to stabilize cellular pH and to increase energy production for the following morphological adaptative changes.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.441-451
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• 2000

Sludge produced from water treatment plants contains plenty of aluminum due to addition of coagulants, polyaluminum chloride(PACI) which has been widely used in most of water treatment plants. however. the whole of PACI is imported from other countries. In this research. the effective methods for recycling PACI from sludge of water treatment plants were developed and evaluated. Aluminum chloride hexahydrate($AlCl_3{\cdot}6H_2O$) was obtained by sparging HCl gas aluminum extracted from sludge using hydrochloric acid (HCI). This aluminum chloride hexahydrate was solidified by decomposition at $180^{\circ}C$. and dissolved in water to produce PACI. The optimum extraction rate was obtained at the condition of 10 minutes of reaction time. $105^{\circ}C$ of reaction temperature. 27.65%(W/W) of HCI concentration. The KS experiment proved that manufactured aluminum chloride hexahydrate was 98.7% degree and the recycled PACI coagulants agreed with the KS standard. The optimum temperature of decomposition was $180^{\circ}C$ and the basicity of the PACI was decided upon the extent of decomposition The compared experiments between purchased coagulant and manufactured coagulant presented that both coagulants had same performance for turbidity, DOC, $UV_{254}$ absorbance. and chlorophyll-a.