• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.330-334
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• 2016

Because several wood barks are massively produced in the forest area of Chungbuk province, it is required to develop technologies for their effective utilization. In this study, three kinds of barks from Robina pseudoacacie, Pinus densiflora, and Castanea crenata were used to remove water-soluble cadmium ions having 10, 20, 50, and 100 mg/L concentrations in each batch experiments, and R. pseudoacacie bark was selected as the most excellent biosorbent. Also, treatments with various acids and bases were performed to increase the removal efficiency of 100 mg/L cadmium ions using R. pseudoacacie bark as a biosorbent. When R. pseudoacacie bark was modified with 0.5 M KOH, the relatively high removal efficiency and adsorption amount of cadmium ions were obtained. In addition, when 9 M KOH-treated R. pseudoacacie bark was used for 30 min, the highest removal efficiency of 100 mg/L cadmium ions was 84.3%. Therefore, this experimental result can be effectively used as an environmental-friendly bioremediation technology to remove cadmium ions existed with various concentrations in water bodies and soils.

• Journal of Microbiology and Biotechnology
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• v.15 no.1
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• pp.14-21
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• 2005

By using PCR with nirS gene primers, three nirSharboring denitrifying bacteria (strain N6, strain N23, and strain R13) were newly isolated from activated sludge of a weak municipal wastewater treatment plant. Small-subunit rRNA gene-based analysis indicated that strain N6, strain N23, and strain R13 were closely related to Arthrobacter sp.,Staphylococcus sp., and Bacillus sp., respectively. In an attempt to identify their roles in biological nitrate and nitrite removal from sewage, we investigated their specific denitrification rates (SDNRs) for $NO_-^3$ - and $NO_-^2$ - in various cultures. All purecultures of each isolated nirS-harboring bacterial strain could remove $NO_-^3$ - and $NO_-^2$ - simultaneously in high efficiency, and the carbon requirements for $NO_-^3$ - removal of strain N6 and strain R13 were effectively low at 3.1 and 4.1 g COD/g $NO_3N$, respectively. In the case of mix-cultures of the strains (N6+N23, N6+R13, N23+R13, and N6+N23+R13), their SDNRs for $NO_-^3$ - were also effective, and their carbon requirements for $NO_-^3$ - removal were also effective at 3.0- 3.8 g COD/g NO3N. However, all tested mix-cultures accumulated $NO_-^2$ - in their culture media. On the other hand, the continuous culture of activated sludge mixed with strain N6 showed no significant increase of $NO_-^3$ - removal in comparison with strain N6's pure culture. These results suggest that nitrate and nitrite removal in biological wastewater treatment might be dependent on complicated bacterial interactions, including several effective denitrifying bacteria isolated in this study, rather than the specific bacterial types present and the number of bacterial types in activated sludge.

• KSBB Journal
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• v.19 no.3
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• pp.236-240
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• 2004

Korean wastewaters have higher nitrogen concentrations than typical wastewaters of other countries. Most treatment processes such as activated sludge processes will need to supplement extra carbon sources for a complete removal of remaining nitrogen after the initial wastewater treatment, Because of these difficult matters, we have searched wastewater treatment methods that require no additional carbon sources. Wastewater treatment by microalgae in photobioreactors, using a green eukaryotic microalgae, Chlorella kessleri, showed a promising results and thus was selected to study further. This system is not intended to replace the conventional system but is to assist the existing biological treatment systems as a supplemental nitrogen removal process. Thus the secondary treated livestock wastewater was tested. Column type photobioreactors developed in our laboratory were used. When aerated with 5% CO$_2$ balanced with air at 1 vvm and illuminated at 100 ${\mu}$mol/㎡/s under 25$^{\circ}C$ and PH 7-8 by CO$_2$ buffering effect, the maximum nitrogen removal rate was 2.6 mg/L/hr. The results confirmed a possibility of microalgal wastewater treatment system as a secondary system to remove extra nitrogen sources. Based on these experimental results, the size of the optimal microalgal wastewater system was calculated. For the wastewater whose initial nitrogen concentration of 150 mg/L, the optimal batch system was found to be a 2 stage system with a combined retention time of 4.6 day. From the continuous experiments, nitrogen removal rates were examined under different dilution rates and 2 stage system was also found to be the optimal system. The combined retention time for the continuous system was 3.5 days. It is expected that conventional biological wastewater treatment systems followed by microalgal systems would reliably decrease the nitrogen concentration below the government criteria even for the livestock wastewater with low C/N ratio.

• Analytical Science and Technology
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• v.13 no.2
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• pp.234-240
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• 2000

The efficiency of Photocatalytic Oxidation Process were investigated for the treatment of Aquatic Humic Substances (AHS). In UV-only system, pH 7-9 was the optimum pH range for TOC removal, and alkali range was the optimum pH for absorbance decrease. In UV/$TiO_2$ system, the optimum $TiO_2$ dosage was 50ppm and over 50ppm of $TiO_2$ dosage was not effective for removal of AHS. In UV/$H_2O_2$ system, optimum $H_2O_2$ dosage was 20mM, when over 20mM dosage, removal of TOC (Total Organic Carbon) and absorbance was decreased. Radical scavenger affected on the photo-oxidation of AHS. Removal rate of TOC and absorbance was decreased by addition of carbonate ions and TOC removal was more effected than that of absorbance.

• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.571-576
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• 2004

Since anaerobic/anoxic/oxic process, which is a typical mainstream biological nitrogen and phosphorus removal process, utilizes influent organic matter as an external carbon source for phosphorus release in anaerobic or anoxic stage, influent COD/T-P ratio gives a strong influence on performance of phosphorus removal process. In this study, a bench scale experiment was carried out for SBR process to investigate nitrogen and phosphorus removal at various influent COD/T-P ratio and nitrate loadings of 23~73 and 1.6~14.3g $NO_3{^-}-N/kg$ MLSS, respectively. The phosphorus release and excess uptake in anoxic condition were very active at influent COD/T-P ratios of 44 and 73. However, its release and uptake was not obviously observed at COD/T-P ratio of 23. Consequently, phosphorus removal efficiency was decreased. In addition, the phosphorus release and uptake rate in anoxic condition increased as the nitrate loading decreased. Specific denitrification rate had significantly high correlation with organic materials and nitrate loadings of the anoxic phase too. The rate of phosphorus release and uptake in the anoxic condition were $0.08{\sim}0.94kg\;S-P/kg\;MLSS{\cdot}d$ and $0.012{\sim}0.1kg\;S-P/kg\;MLSS{\cdot}d$, respectively.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.971-976
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• 2008

Water pollution by ammonium ion and nitrate is a common and growing problem in the ecosystem. Process of biological removal consists of nitrification and denitrification by bacteria. Ammonium is oxidized generally to nitrate by nitrification and nitrate is reduced to dinitrogen gas in the subsequent denitrification process. Although natural zeolite is well known for its ability to preferentially remove ammonium, it is not sufficiently removing ammonium ion and nitrate by adsorption. In order to overcome this problem, a method of biological removal with zeolite is used for simultaneous removal of ammonium and nitrate. As a result, in case of shaking culture with 1% seed and passing through zeolite column, the process revealed that ammonium ion could be removed completely after 14 hours. The removal of nitrate using columns with naturally adsorbed bacteria onto zeolite reached approximately 100% after 4 hours.

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.649-659
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• 2023

This study was initiated to evaluate the phosphorus (P) removal and diesel oil degradation by bacteria isolated from industrial wastewater. The bacteria isolated were identified as Bacillus sp. The P removal efficiencies by Bacillus sp. were 99% at the initial 20 mg/L P concentration. The diesel degradation efficiencies by Bacillus sp. were 86.4% at an initial 1% diesel concentration. Lipophilicity by bacteria was the highest in the log phase, whereas it was the lowest in the death phase. As the diesel was used as a carbon source, P removal efficiencies by Bacillus sp. were 68%. When glucose, acetate, and a mixture of glucose and acetate as second carbon sources were added, the diesel degradation efficiencies were 69.22%, 65.46%, and 51.46%, respectively. The diesel degradation efficiency was higher in the individual additions of glucose or acetate than in the mixture of glucose and acetate. When P concentration increased from 20 mg/L to 30 mg/L, the diesel degradation efficiency was increased by 7% from 65% to 72%, whereas when P concentration was increased from 30 mg/L to 40 mg/L, there was no increase in diesel degradation. One of the five proteins identified by proteome analysis in the 0.5% diesel-treated samples may be involved in alkane degradation and is known as the cytochrome P450 system. Also, two of the sixteen proteins identified in the 1.5% diesel-treated samples may be implicated in the fatty acid transport system and alcohol dehydrogenation.

• Journal of Applied Biological Chemistry
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• v.50 no.1
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• pp.6-12
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• 2007

Feasibility of laboratory-synthesized zerovalent iron was investigated to remove arsenic from leachates of tailings taken from an Au-Ag abandoned mine. The tailings were seriously contaminated with arsenic, and its potential adverse effect on the ecosystems around the mine seems to be significantly high. Long-term column experiments were conducted for about 3.5 months to evaluate the effectiveness of the synthesized zerovalent iron for removal of arsenic. Over than 95% removal efficiency of As was observed in the zerovalent iron mediated tests. In addition, the XRD data suggest that the corrosion products of ZVI were identified magnetite, maghemite, goethite, and lepidocrocite, all of which support Fe(II) oxidation as an intermediate step in the zerovalent iron corrosion process. The results indicate that arsenic can be removed from the tailing-leachate by the mechanism of coprecipitation and/or adsorption onto those iron oxides formed from ZVI corrosion.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.5
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• pp.537-546
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• 2005

This study was carried out to evaluate EPS and SMP variation of sludge and effluent in nitrification and denitrification process with zeolite addition, a possible reduction of effluent DOC by URC(Ultra Rapid Coagulation) process. As a biological wastewater treatment result, EPS formation of both aeration and anoxic sludges are not affect by SRT variation. However, EPS concentration of sludges is higher in aeration tank than in anoxic tank by 6~8 mg EPS/ g VSS. Linear relationship between SMP to DOC indicates that SMP of bulk solution contributes to most of the biological treatment effluent DOC. DOC and turbidity removal efficiency was more improved with URC process than in a conventional coagulation. For pretreatment of UF filtration DOC removal was advanced by URC process than only UF filtration.

• Journal of Microbiology and Biotechnology
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• v.13 no.3
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• pp.385-393
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• 2003

Microbial communities were analyzed in an anaerobic/aerobic sequencing batch reactor (SBR) fed with glucose as a sole carbon source. Scanning electron microscopy (SEM) showed that tetrad or cuboidal packet bacteria dominated the microbial sludge. Quinone, slot hybridization, and 165 rRNA gene sequencing analyses showed that the Proteobacteria beta subclass and the Actinobacteria group were the main microbial species in the SBR sludge. However, according to transmission electron microscopy (TEM), the packet bacteria did not contain polyphosphate granules or glycogen inclusions, but only separate coccus-shaped bacteria contained these, suggesting that coccus-shaped bacteria accumulated polyphosphate directly and the packet bacteria played other role in the enhanced biological phosphorus removal (EBPR). Based on previous reports, the Actinobacteria group and the Proteobacteria beta subclass were very likely responsible for acid formation and polyphosphate accumulation, respectively, and their cooperation achieved the EBPR in the SBR operation which was supplied with glucose.