• KSBB Journal
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• v.8 no.3
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• pp.193-199
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• 1993

To find out the optimum conditions for indigo cell culture in air-lift bioreactor, effects of media composition including nutrients and precursors of the indigo colorants on the cell growth and characteristics of the cell growth under various cultural conditions were analyzed. Optimum cultural conditions were tested and the growth characteristics were analyzed in external and internal loop type air-lift bioreactors during 14-day culture. Better cell growth was obtained when the inoculum size was higher in the range of 0.5∼2.5% packed cell volume tested. In the sucrose concentration of 2 to 4%, the cell growth was better when the sucrose concentration was 4% (w/w) in both types of reactors. Sucrose was used up in the early stage of exponential phase of growth At the optimum concentration of a Precursor tryptophan at 1 U UW was 3.8 g/l in internal loop bioreactor, and 3.5 g/l in external one after 14 days of cultivation. Addition of indole showed negative effect on cell growth of suspension culture in air-lift biorector culture and cell mass of 2.5 g/l and 2.2 g/l were obtained in external and internal loop bioreactor, respectively. Selected inorganic nitrogen source potassium nitrate showed about 110% increase in cell growth than that of control. DCW was 16.34 g/l under optimum conditions during 14-day cultivation in internal loop bioreactor.

• KSBB Journal
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• v.17 no.3
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• pp.241-246
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• 2002

Today, many problems of dye-processing wastewaters were raised due to industry of dyeing and textiles. It is difficult to treat them perfectly because they contain many poorly degradable matters, such as surfactants, ethylene glycol, polyvinyl alcohol, and so on. To improve the performances of conventional physicochemical treatment and activated sludge process, new systems of combining jet-loop reactor (JLR) with physicochemical treatment were developed. Volumetric oxygen transfer coefficient ($k_{L}a$) of JLR was significantly larger than that of air-lift reactor. Also, for the effective treatment of dye-processing wastewater, JLR with active carbon supports (JLRAS) were investigated. Removal efficiency of BOD, $COD_{Mn}$, $COD_{Cr} and color were found as 99, 86, 84, 83%, respectively, when HRT was 8 hrs. And performance of JLRAS was rapidly restored after step change of $COD_{Mn}$ loading late. The optimal coagulant and dosage of second physicochemical treatment after JLRAS were polyferric sulfate and 130 mg/L, respectively, when removal efficiencies of $COD_{Mn} and color were 85 and 73%, respectively. In conclusion, this system enables the reduction of operation cost, and the effective removal of many organics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.33-44
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• 1987

To improve the ability of oxygen transfer in Biological Fluidised Bed(BFB) processes, air lift aeration system was introduced, experimental investigations were performed for the oxygen transfer in reactor, the fluidisation as to Biomass Volatile Solids variation and the relationship between substrate removal rate and oxygen utilization. The experiments for this purpose were executed for the synthetic wastewater by continuous type reactor at $20^{\circ}C$ using reticulated polypropylene sheets as media. The obtained results showed that the oxygen transfer by air lift aeration would be more effective than any other aeration systems used in BFB reactor. Also, it has observed that the critical biomass concentration in reactor took a range of 20 to 23g/l. Applying cages to BFB reactor, biomass would be maintained uniformly in the bed and the fluidisation characteristics of media could be improved. Varying F/M ratio from 0.36 to 0.73, BOD removals were 91% or more. Therefore, this process was suited to the treatment of which F/M ratios are variable and specific oxygen uptake rates ($K_r$) were 0.23 to 0.26g $O_2/g\;VSS{\cdot}day$ at range of 15 to 20g BVS/l.

• KSBB Journal
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• v.14 no.1
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• pp.119-123
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• 1999

A jet-loop reactor was used for the biological treatment of ethylene glycol(EG) which is a main component of polyester weight-loss wastewater, and is difficult to be removed by physicochemical treatments. Volumetric oxygen coefficient(kLa) of jet-loop reactor was significantly larfgeer that of air-lift reactor. When organic loading rates of synthetic polyester weight-loss wastewater were 2.64 $kgOD_{Mn}/m^3$.day and 3.07 $kgCOD_{Cr}/m^3$.day, the effluent concentrations were measured as 154 $mgCOD_{Mn}/L$ and 156$mgCOD_{Cr}/L$, and removal efficiencies were found as 93%and 93.6%, respectively. The specific removal rate was proportionally increased from 0.25 to 1.60 $kgCOD_{Mn}$-removed/kgMLVSS.day as specific loading rate was increased from 0.25 to 1.72 $kgCOD_{Mn}$/kgMLVSS.day. Also, kinetics constants such as $K_s$, k, $K_d$, and Y were estimated as 89 mg/L, $0.05 hr^{-1}$, 0.1$day^{-1}$ and 0.78 respectively. When the organic loading rates of real polyester weight-loss wastewater were 2.64 $kgOD_{Mn}/m^3$. and 5.24 $kgCOD_{Cr}/m^3$. day, the effluent concentrations were measured as 150 $mgCOD_{Mn}$/L, and 306 $mgCOD_{Cr}$/L, and removal efficiencies were found as 93.2% and 93%, respectively. This study demonstrated that EG in the wastewater could be efficiently removed biologically using a jet-loop reactor.

• KSBB Journal
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• v.14 no.6
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• pp.672-676
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• 1999

Encapsulated Aspergillus niger was prepared in order to inspect the effect of oxygen supply on the production of citric acid. A. niger cells which had been immobilized in the calcium alginate capsule grew and mycellia penetrated through the capsule membrane after two days of cultivation and covered over all of the capsule after eight days. The mycellia became loose when the nitrogen source was sufficient of oxygen was deficient. The larger amount of encapsulated cells were put into a given growth medium, the smaller quantity of citric acid was produced. The increase of volumetric oxygen transfer coefficient from 1.8 $hr^-$ to 2.55 $hr^-$ in the flask culture accelerated cell growth rate but did not influence the production of citric acid. The high oxygen supply rate($k_La:\;150\;hr^-$) in the concentric air lift reactor hastened the growth of cells and hindered the production of the citric acid. The reduction of nitrogen source level in the growth medium in the concentric air lift reactor increased citric acid production by 40 percent of that of flask cultivation and the culture period was shortened by 3 days. The variation of the geometry of the concentric air lift reactor did not influence the growth rate of encapsulated cells and production rate of citric acid.

• KSBB Journal
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• v.11 no.4
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• pp.398-404
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• 1996

Escherichia coli was inoculated in calcium alginate capsules and cultivated to prepare encapsulated whole cell ${\beta}$-galactosidase. The dry cell weight in the capsule reached 100 g/L based on the inner space of the capsule. The activity of the encapsulated whole cell ${\beta}$-galactosidase increased with the dry cell weight increase during cultivation in the production medium. The activity of the encapsulated whole cell ${\beta}$-galactosidase was increased 25% by adding $2{\times}10^{-4}M Zn^{+2}$ ion in the production medium and 10% by coencapsulating with 2% (v/v) sunflower seed oil. The activity of encapsulated whole cell ${\beta}$-galactosidase produced in the concentric air lift reactor in which kLa was 82/hr was 86% higher than that in the shaking flask incubator where kLa was 2.55/hr.

• KSBB Journal
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• v.7 no.1
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• pp.59-65
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• 1992

Hydrodynamics and mixing characteristics such as circulation time, mixing time, circulation velocity and axial dispersion coefficient were investigated using highly viscous pseudoplastic solutions of carboxymethyl cellulose(CMC) in an external circulation loop air-lift reactor with 13$\ell$ working volume. The superficial gas velocity was changed from 1.9 to 6.2cm/s and CMC concentration from 0 to 1.0wt%. The theoretical model based on the pressure balance is developed mathematically to predict liquid circulation velocity. Gas hold-up, circulation velocity and axial dispersion coefficient of liquid phase increased with increasing gas velocity and decreased slightly with increasing liquid viscosity. Mixing time and circulation time decreased with increasing gas velocity and increased with increasing liquid viscosity. Experimental data on liquid circulation velocity were in good agreement with the predicted values.

• Clean Technology
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• v.18 no.4
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• pp.398-403
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• 2012

Selective nitrification and granulation have been carried out in a pilot scale air-lift sequencing batch reactor (SBR) for stable and economical nitrogen removal from wastewater. The SBR showed about 100% nitrification efficiency up to 1.0 kg ${NH_4}^+-N/m^3{\cdot}d$, about 90% efficiency at 1.0-2.0 kg ${NH_4}^+-N/m^3{\cdot}d$, and it was less than 90% when the load was higher than 2.0 kg ${NH_4}^+-N/m^3{\cdot}d$. Nitrite accumulation was induced by selective inhibition of nitrite oxidizing bacteria by free ammonia inhibition and dissolved oxygen limitation. For the purpose, high nitrite ratio (> 0.95) was obtained by keeping the pH higher than 8.0 and dissolved oxygen lower than 1.5 mg/L. In addition, sludge granulation was achieved by keeping reactor settling time to 5 minutes to wash out poor settling sludge and to promote the growth of granulation sludge. The operation accelerated sludge granulation and the sludge volume index (SVI) decreased and stably maintained to less than 75 in 60 days.

• KSBB Journal
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• v.10 no.3
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• pp.241-248
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• 1995

For the treatment of poorly biodegradable polyvinyl alcohol(PVA) in dye-processing wastewater, immobilized microbial beads were prepared by uslng agar-acrylamide method. PVA removal efficiency for the synthetic wastewater was 85% at the PVA volume loading rate of $3.1g/\ell$.day. In case of real desizing wastewater, PVA removal efficiency was 81.3% at the PVA volume loading rate of $3.25g/\ell$.day. In observation of cross section of immobilized bead passed 5 months with diameter of 2.4mm, the growth of cell was limited by the resistance of substrate and oxygen transfer for the inners region of more than 48% of bead radius from the surface. It was estimated that 70% of total removed PVA was degraded by the immobilized cells in the continuous immobilized reactor. Substrate utilization rate in the suspended reactor was decreased with increasing dilution rates above 0.083 hr-1, but that in the immobilized reactor was increased with increasing dilution rates up to 0.125hr-1. The substrate removal efficiency of immobilized reactor was much superior to that of suspended reactor with increasing dilution rates. Saturation constant of substrate utilization rate equation, Ks was $6.6 g PVA/\ell$, and maximum specific substrate utilization. k was 0.175g PVA/g cell.hr

• KSBB Journal
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• v.25 no.5
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• pp.421-428
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• 2010

This paper reports on the experimental investigation carried out to evaluate the physical optimal conditions in the absorption column to remove odorous hydrogen sulfide gas. Hydrogen sulfide gas, as a highly undesirable contaminant, is most widely emitted from environmental treatment facilities. The absorbent mixed with natural second metabolites extracted from conifer trees and chemical absorbent of 2-aminoethanol was applied to remove it via chemical neutralization. The absorbent of natural second metabolites was achieved by a removal efficiency of 20-40% by itself depending on the treatment conditions, but the complex absorbent mixed with 0.1% amine chemical provides the removal efficiency of 98%. The optimal removal efficiencies have been examined against the two major parameters of temperature and pH. This study shows that the aqueous solution by natural second metabolites can be used as an appropriate absorbent in the column absorbed for the removal of hydrogen sulfide gas.