• Microbiology and Biotechnology Letters
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• v.22 no.4
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• pp.436-442
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• 1994

The characteristics of activated sludge affecting the biodegradation of plastic materials under aerobic condition were studied using cellophane film as a model system. The activated sludges of site 3, which treat a mixture of domestic sewage and supernatant of septic tank, obtained from December 1993 to April 1994 showed similar biodegradation activities. Biodegradations for 28 days reached around 80%. Viable cell number of inoculums maintained at a level of 10$^{6}$~10$^{7}$ /ml. In this range, viable cell number showed no relationship with biodegradation activities. The activa- ted sludges of site 2, which treat a mixture of domestic sewage and anaerobic digest of nightsoil, obtained four times from April 1993 to April 1994 showed very different biodegradation activities ranged from 20% to 80% for 28 days. Inoculum size affects biodegradation significantly. One percent inoculum showed the best biodegradation among the inoculum sizes of 0.1, 1.0 and 10%. Ten percent inoculum revealed inhibitory effects on the biodegradation activity which can be greatly reduced by centrifugation and filtration. Filtration was better than centrifugation in reducing inhibitory effects.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.603-608
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• 2010

More than 8 millions of chemical have been used for human activities and lots of chemicals can not be degraded by microbial activities in this world. To show the biodegradability of a chemical, biodegradability index (B.I.) is suggested using aerobic biodegradability by $BOD_5$/COD, anaerobic biodegradability by methane potential (M.P.) and toxicity by the luminiscent bacteria. In this study, PVA (polyvinyl alcohol), HEC (hydroxy ethyl cellulose), 2,4,6-TCP (tri-chloro phenol) and 2,4-DCP (di-chloro phenol) are used for test chemicals. Though they show little toxicity, PAV and HEC have low B.I. because they are polymers having high molecular weight. That means that there are no bacteria that has enzyme to degrade polymer molecules. Also, anaerobic treatment is suggested better than aerobic treatment from B.I. 2,4,6-TCP and 2,4-DCP show high toxicity and have low B.I. Their low biodegradabilities seem to be originated from their toxicities. If B.I. is used in wastewater treatment, better treatment process can be suggested and finally it can lead our society to make more environment-friendly chemicals.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.467-470
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• 2003

Leaking underground storage tanks are a major source of groundwater contamination by petroleum hydrocarbons. Aerobic bioremediation has been highly effective in the remediation of many fuel releases. However, Bioremediation of aromatic hydrocarbons in groundwater and sediments is ofen limited by the inability to provide sufficient oxygen to the contaminated zones due to the low water solubility of oxygen. Nitrate can also serve as an electron acceptor and results in anaerobic biodegradation of organic compounds via the processes of nitrate reduction and denitrification. Because nitrate is less expensive and more soluble than oxygen. it may be more economical to restore fuel-contaminated aquifers using nitrate rather than oxygen. And denitrifying bacteria are commonly found in the subsurface and in association with contaminated aquifer materials. These studies have shown that BTEX and MTBE can be degraded by the nitrate-amended microcosms under aerobic and anaerobic conditons. Biodegradation of the toluene and ethylbenzne compounds occurred very quickly under denitrifying conditions. MTBE, benzene and p-xylene were recalcitrant under denitrifying conditions in this study, But finally Biodegradaton was observed for all of the test compounds.

• Microbiology and Biotechnology Letters
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• v.37 no.3
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• pp.243-247
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• 2009

The usage of ethanol (EtOH)-blended gasoline (gasohol), has been increasing in recent years. EtOH has influence on the distribution and biodegradation of aromatic compounds such as BTEX (benzene (B), toluene (T), ethylbenzene (B), and xylene (X)) that are gasoline compositions. In this study, the effect of EtOH on the aerobic biodegradation of B, T and E was investigated using a BTEX and EtOH-degrading bacterium, Rhodococcus sp. EH831. The degradation rates of B in the conditions of 1:1, 1:4, and 1:0.25 mixtures with EtOH (B:EtOH, mol:mol) were ranged from $3.82{\pm}0.20$ to $5.00{\pm}0.37{\mu}mol{\cdot}g-dry$ cell wight $(DCW)^{-1}{\cdot}h^{-1}$. The degradation rate of T was the fastest in the 1:0.25 mixture ($6.63{\pm}0.06{\mu}mol{\cdot}g-DCW^{-1}{\cdot}h^{-1}$), and it was the lowest in the 1:4 mixture ($4.41{\pm}0.04{\mu}mol{\cdot}DCW^{-1}{\cdot}h^{-1}$). The degradation rates of E were increased with increasing the addition amount of EtOH: The degradation rate of E was the highest in the 1:4 mixture ($1.60{\pm}0.03{\mu}mol{\cdot}g-DCW^{-1}{\cdot}h^{-1}$), and the rates were $1.42{\pm}0.06$, $1.30{\pm}0.01$, and $1.01{\pm}0.30{\mu}mol{\cdot}g-DCW^{-1}{\cdot}h^{-1}$ in the 1:1, 1:0.25, 1.0 mixtures, respectively. In conclusion, the biodegradation of B, T, E by Rhodococcus sp. EH831 was not significantly inhibited by the co-existence of EtOH.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.120-123
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• 2001

To evaluate the biodegradability of contaminants in an aquifer, computer modeling with RT3D model (Clement, 1997) was used. The RT3D model simulates the biodegradation of organic contaminants using a number of aerobic and anaerobic electron acceptors. The RT3D model was applied to a well-studied petroleum hydrocarbon plume in a shallow unconfined aquifer in Uiwang, Korea. The results of this study demonstrate tile importance of biodegradation processes in the monitored natural attenuation and in reducing contaminant concentrations in a shallow aquifer. The modeling results tell that the amount of electron acceptors is the key factor affecting biodegradation of TEX, the petroleum hydrocarbon contaminant in shallow groundwater

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.89-91
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• 2000

Polynuclear aromatic hydrocarbon (PAH) compounds are highly carcinogenic chemicals and common groundwater contaminants that are observed to persist in soils. The adherence and slow release of PAHs in soil is an obstacle to remediation and complicates the assessment of cleanup standards and risks. Biological degradation of PAHs in soil has been an area of active research because biological treatment may be less costly than conventional pumping technologies or excavation and thermal treatment. Biological degradation also offers the advantage to transform PAHs into non-toxic products such as biomass and carbon dioxide. Ample evidence exists for aerobic biodegradation of PAHs and many bacteria capable of degrading PAHs have been isolated and characterized. However, the microbial degradation of PAHs in sediments is impaired due to the anaerobic conditions that result from the typically high oxygen demand of the organic material present in the soil, the low solubility of oxygen in water, and the slow mass transfer of oxygen from overlying water to the soil environment. For these reasons, anaerobic microbial degradation technologies could help alleviate sediment PAH contamination and offer significant advantages for cost-efficient in-situ treatment. But very little is known about the potential for anaerobic degradation of PAHs in field soils. The objectives of this research were to assess: (1) the potential for biodegradation of PAH in field aged soils under denitrification conditions, (2) to assess the potential for biodegradation of naphthalene in soil microcosms under denitrifying conditions, and (3) to assess for the existence of microorganisms in field sediments capable of degrading naphthalene via denitrification. Two kinds of soils were used in this research: Harbor Point sediment (HPS-2) and Milwaukee Harbor sediment (MHS). Results presented in this seminar indicate possible degradation of PAHs in soil under denitrifying conditions. During the two months of anaerobic degradation, total PAH removal was modest probably due to both the low availability of the PAHs and competition with other more easily degradable sources of carbon in the sediments. For both Harbor Point sediment (HPS-2) and Milwaukee Harbor sediment (MHS), PAH reduction was confined to 3- and 4-ring PAHs. Comparing PAH reductions during two months of aerobic and anaerobic biotreatment of MHS, it was found that extent of PAHreduction for anaerobic treatment was compatible with that for aerobic treatment. Interestingly, removal of PAHs from sediment particle classes (by size and density) followed similar trends for aerobic and anaerobic treatment of MHS. The majority of the PAHs removed during biotreatment came from the clay/silt fraction. In an earlier study it was shown that PAHs associated with the clay/silt fraction in MHS were more available than PAHs associated with coal-derived fraction. Therefore, although total PAH reductions were small, the removal of PAHs from the more easily available sediment fraction (clay/silt) may result in a significant environmental benefit owing to a reduction in total PAH bioavailability. By using naphthalene as a model PAH compound, biodegradation of naphthalene under denitrifying condition was assessed in microcosms containing MHS. Naphthalene spiked into MHS was degraded below detection limit within 20 days with the accompanying reduction of nitrate. With repeated addition of naphthalene and nitrate, naphthalene degradation under nitrate reducing conditions was stable over one month. Nitrite, one of the intermediates of denitrification was detected during the incubation. Also the denitrification activity of the enrichment culture from MHS slurries was verified by monitoring the production of nitrogen gas in solid fluorescence denitrification medium. Microorganisms capable of degrading naphthalene via denitrification were isolated from this enrichment culture.

• Geotechnical Engineering
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• v.14 no.4
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• pp.151-162
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• 1998

The compressibility and the permeability of organic soil are so high that they cause many engineering problems when constructing a structure on the soil. If the organic content of the soil could be reduced by any applicable engineering technique, the engineering properties of the soils can be improved to some extent. The purpose of this study would thus be focused on how to decrease the amount of organic matters by applying aerobic biodegradation for eliminating post-construction settlement problems. To enhance the aerobic decomposition, oxygen was supplied to the soil samples prepared by the mixture of kaolinite and sawdust as organic matter. The dissolved oxygen and the organic content of the soil samples were measured, in accordance with the passage of time through the bests. As oxygen suppliers, HaOa liquid and pure oxygen gas were compared to meet the requirement of the test purposes. Newly manufactured oedometer with the diameter of 130 mm and the height of 300 mm was used for 100 days to perform the compressibility tests for the soils. Based on the results of this experiment, the oxygen gas-treated samples with nutrient settled 30% more than the samples untreated. This confirmed the efficiency of the aerobic biodegradation. $NaNO_3$ added into the soils as nutrients was proved more effective than $K_2HP0_4$. To confirm the activity of micro-organisms, sodium azide was also added to the soils.

• Environmental Analysis Health and Toxicology
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• v.6 no.3_4
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• pp.149-154
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• 1991

Biodegradation of carbon tetrachloride (CTC) in denitrifying and aerobic columns was investigated under various conditions of electron-acceptor and electron-donor availability. CTC removal increased when the electron-acceptor (nitrate) injection was stopped in the denitrifying column; however, CTC remova1 decreased when electron donor (acetate) was deleted in the denitrifying and the aerobic column. Small fractions of the CTC removed appeared as chloroform, indicating that reductive dechlorination of CTC was occurring. The results from the denitrifying column support the hypothesis that CTC behaves as an electron acceptor that competes for the pool of available electrons inside the bacterial cells.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.368-371
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• 2003

Accidental release of petroleum products from underground storage tank(USTs) is one of the most common causes of groundwater contamination. BTEX is the major components of fuel oils, which are hazardous substances regulated by many nations. In addition to BTEX, other gasoline consituents such as MTBE(methyl-t-buthyl ether), anphthalene are also toxic to humans. Natual attenuation processes include physic, chemical, and biological trasformation. Aerobic and anaerobic biodegradation are believed to be the major processes that account for both containment of the petroleum-hydrocarbon plum and reduction of the contaminant concentrations. Aerobic bioremediation has been highly effective in the remediation of many fuel releases. However, Bioremediation of aromatic hydrocarbons in groundwater and sediments is ofen limited by the inability to provide sufficient oxygen to the contaminated zones due to the low water solubility of oxygen. Anaerobic processes refer to a variety of biodegradation mechanisms that use nitrate, ferric iron, sulfate, and carbon dioxide as terminal electron accepters. The objectives of this study was to conduct laboratory-scale microcosm studies in assessing enhanced bioremediation potential of BTEX and MTBE under various electron accepters(aerobic, nitrate, ferric iron, sulfate) in contaminated Soil. these results suggest that, presents evidence and a variety pattern of the biological removal of aromatic compounds under enhanced nitrate-, Fe(III)-, sulfate-reducing conditions.

• The Microorganisms and Industry
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• v.18 no.1
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• pp.2-8
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• 1992

The present study was undertaken to characterize the biodegradation of phenoxy herbicides, 2,4-D and MCPP, under aerobic conditions. Specifically, the work had the following objectives; i) to develop and characterize bacterial mixed cultures for the 2,4-D and MCPP degradation, ii) to evaluate the degradation of 2,4-D and MCPP in shake-flasks and stirred tank reactors; and iii) to evaluate the treatment of industrial fertilizer solid wste material containing 2,4-D and MCPP.