• Journal of Microbiology
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• v.43 no.4
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• pp.319-324
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• 2005

Estuarine sediments are frequently polluted with hydrocarbons from fuel spills and industrial wastes. Polycyclic aromatic hydrocarbons (PAHs) are components of these contaminants that tend to accumulate in the sediment due to their low aqueous solubility, low volatility, and high affinity for particulate matter. The toxic, recalcitrant, mutagenic, and carcinogenic nature of these compounds may require aggressive treatment to remediate polluted sites effectively. In petroleum-contaminated sediments near a petrochemical industry in Gwangyang Bay, Korea, in situ PAH concentrations ranged from 10 to 2,900 ${\mu}g/kg$ dry sediment. To enhance the biodegradation rate of PAHs under anaerobic conditions, sediment samples were amended with biostimulating agents alone or in combination: nitrogen and phosphorus in the form of slow-release fertilizer (SRF), lactate, yeast extract (YE), and Tween 80. When added to the sediment individually, all tested agents enhanced the degradation of PAHs, including naphthalene, acenaphthene, anthracene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, and benzo [a] pyrene. Moreover, the combination of SRF, Tween 80, and lactate increased the PAH degradation rate 1.2-8.2 times above that of untreated sediment (0.01-10 ${\mu}g$ PAH/ kg dry sediment/day). Our results indicated that in situ contaminant PAHs in anoxic sediment, including high molecular weight PAHs, were degraded biologically and that the addition of stimulators increased the biodegradation potential of the intrinsic microbial populations. Our results will contribute to the development of new strategies for in situ treatment of PAH-contaminated anoxic sediments.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.94-103
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• 2016

Landfarming that supplies aerobic biodegradation condition to indigenous microbes in soils is a biological remediation technology. In this research, volatilization and biodegradation rate by indigenous microbes in the soil contaminated with total petroleum hydrocarbons (TPH) were measured. Soils were contaminated with diesel artificially and divided into two parts. One was sterilized by autoclave to remove indigenous microorganism and the other was used as it was. Various moisture contents and number of tillings were applied to the soil to find out proper condition to minimize volatilization and enhance bioremediation. Volatilization of TPH was inhibited and biodegradation was enhanced by increase on moisture content. Tilling was usually used to supply air for microbes, but tillings did not affect the growth of microbes in our study. Enough moisture content and proper aeration are important to control volatilization in landfarming. Also, TPH degradation was a function of the microbe counts (x₁), numbers of tilling (x₂), and moisture content (x₃) from the application of the response surface methodology. Statistical results showed the order of significance of the independent variables to be microbe counts > numbers of tilling > moisture content.

• Journal of Microbiology and Biotechnology
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• v.11 no.4
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• pp.607-613
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• 2001

The biodegradation rates of diesel oil by a selected diesel-degrading bacterium, Pseudomonas stutzeri strain Y2G1, and microbial consortia composed of combinations of 5 selected diesel-degrading bacterial were determined in liquid and soil systems. The diesel degradation rate by strain Y2G1 linearly increased $(R^2=0.98)$ as the diesel concentration increased up to 12%, and a degradation rate as high as 5.64 g/l/day was obtained. The diesel degradation by strain Y2G1 was significantly affected by several environmental factors, and the optimal conditions for pH, temperature, and moisture content were at pH8, $25^{\circ}C$, and 10%, respectively. In the batch soil microcosm tests, inoculation, especially in the form of a consortium, and the addition of nutrients both significantly enhanced the diesel degradation by a factor of 1.5 and 4, respectively. Aeration of the soil columns effectively accelerated the diesel degradation, and the initial degradation rate was obviously stimulated with the addition of inorganic nutrients. Based on these results, it was concluded that the major rate-limiting factors in the tested diesel-contaminated soil were the presence of inorganic nutrients, oxygen, and diesel-degrading microorganisms. To resolve these limiting parameters, bioremediation strategies were specifically designed for the tested soil, and the successful mitigation of the limiting parameters resulted in an enhancement of the bioremediation efficiency by a factor of 11.

• Environmental Engineering Research
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• v.13 no.1
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• pp.8-13
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• 2008

The extent of solubility enhancement by biosurfactant was examined at various pHs prior to the biodegradation experiments. The molar solubilization ratio (MSR) was calculated from the batch solubilization experiments and the highest MSR was detected at pH 5. The effect of the biosurfactant, rhamnolipids, on the phenanthrene mineralization in soil-water system was investigated. The strain 3Y was selected for the mineralization assay and large amounts of phenanthrene were degraded at neutral pH in soil-water system without the biosurfactant. The addition of 150 mg/L rhamnolipids showed no effect on mineralization of phenanthrene in soil-water system, and total mineralization rates after 6 weeks incubation at each pH showed no differences in presence and absence of rhamnolipids. Our result indicated that the toxic effect of rhamnolipids can disappear when soil particles exist, and also the enhanced solubility of phenanthrene does not work for mineralization enhancement in this soil-water system.

• Journal of Environmental Science International
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• v.4 no.5
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• pp.115-115
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• 1995

Reuse of industrial effluents through the cooling systems in a petrochemical complex was described. The partial oxidation of the effluents from the biological treatment plant was examined, using Fenton''s reagent as a pretreatment step prior to a next treatment of the effluents. Next tertiary treatment using fixed-film reactor resulted in marked reductions in COD and suspended solids. The continuous fixed-film process with Fenton oxidation pretreatment showed a 23% increase in the COD removal efficiency when compared to that without pretreatment of Fenton oxidation under the volumetric organic loading rate of 0.1 kg COD/m3/day. The Fenton oxidation treatment seemed to be a possible method for tertiary biological treatment to reduce the residual toxicity with the enhanced biodegradation of the effluents.

• Journal of Environmental Science International
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• v.4 no.5
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• pp.501-508
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• 1995

Reuse of industrial effluents through the cooling systems in a petrochemical complex was described. The partial oxidation of the effluents from the biological treatment plant was examined, using Fenton's reagent as a pretreatment step prior to a next treatment of the effluents. Next tertiary treatment using fixed-film reactor resulted in marked reductions in COD and suspended solids. The continuous fixed-film process with Fenton oxidation pretreatment showed a 23% increase in the COD removal efficiency when compared to that without pretreatment of Fenton oxidation under the volumetric organic loading rate of 0.1 kg COD/m3/day. The Fenton oxidation treatment seemed to be a possible method for tertiary biological treatment to reduce the residual toxicity with the enhanced biodegradation of the effluents.

• Journal of Soil and Groundwater Environment
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• v.19 no.3
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• pp.56-65
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• 2014

Contamination of explosive compounds in the soils of military shooting range may pose risks to human and ecosystems. As shooting ranges are located at remote places, active remediation processes with hardwares and equipments are less practical to implement than natural solutions such as bioremediaton. In this study, a series of experiments was conducted to select a suitable carbon source and to optimize dosing rate for the enhanced bioremediation of explosive compounds in surface soils and sediments of shooting ranges with indigenous microorganisms activated by external carbon source. Treatability study using slurry phase reactors showed that the presence of indigenous microbial community capable of explosive compounds degradation in the shooting range soils, and starch was a more effective carbon source than glucose and acetic acid in the removal of TNT. However, at higher starch/soil ratio, i.e., 2.0, the acute toxicity of the liquid phase increased possibly due to transformation products of TNT. RDX degradation by indigenous microorganisms was also stimulated by the addition of starch but the acute toxicity of the liquid phase decreased with the increase of starch/soil ratio. Taken together, the optimum range of starch/soil ratio for the degradation of explosive compounds without significant increase in acute toxicity was found to be 0.2 of starch/soil.

• Advances in environmental research
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• v.1 no.3
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• pp.201-210
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• 2012

The bioavailability of sorbed organic contaminants is one of the most important factors used to determine their fate in the environment. This study was conducted to evaluate the bioavailability of slow-desorbable naphthalene in soils. An air sparging system was utilized to remove dissolved (or desorbed) naphthalene continuously and to limit the bacterial utilization of dissolved naphthalene. A biological air sparging system (air sparging system with bacteria) was developed to evaluate the bioavailability of the slow-desorption fraction in soils. Three different strains (Pseudomonas putida G7, Pseudomonas sp. CZ6 and Burkholderia sp. KM1) and two soils were used. Slow-desorbable naphthalene continuously decreased under air sparging; however, a greater decrease was observed in response to the biological air sparging system. Enhanced bioavailability was not observed in the Jangseong soil. Overall, the results of this study suggests that the removal rate of slow-desorbable contaminants may be enhanced by inoculation of degrading bacteria into an air sparging system during the remediation of contaminated soils. However, the enhanced bioavailability was found to depend more on the soil properties than the bacterial characteristics.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.9
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• pp.893-899
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• 2008

Changes in spectroscopic characteristics and pyrene binding coefficients of terrestrial dissolved organic matters(DOM) were investigated during microbial incubation. The incubation studies were conducted for 21 days using a leaf litter DOM and a soilderived DOM with an inoculum from a river. The dissolved organic carbon(DOC), the specific UV absorbance(SUVA), the synchronous fluorescence spectra, and the pyrene organic carbon-normalized binding coefficient(K$_{oc}$) of the DOM were measured at the incubation days of 0, 3, 7, 14 and 21. After the 21-day incubation, DOC were reduced to 61% and 51% of the original concentrations of the litter DOM and the soil-derived DOM, respectively. Comparison of the spectroscopic characteristics before and after the incubation revealed that the SUVA, the fulvic-like fluorescence(FLF), the humic-like fluorescence(HLF) of the different DOM were enhanced by the incubation whereas the protein-like fluorescence(PLF) was reduced. This indicates that more aromatic and humic-like compounds were enriched during the biodegradation process while biodegradable and weak carbon structures were depleted. Irrespective of the DOM sources, SUVA values showed a positive relationship with pyrene K$_{oc}$ with a correlation coefficient of 0.97. The FLF and HLF also exhibited good correlations with K$_{oc}$ values although different regression equations were obtained from the different DOM. Our results suggest that the selected spectroscopic characteristics could be good estimation indices for the changes of the binding reactivity of DOM for hydrophobic organic contaminants during biodegradation process.

• Journal of Korea Soil Environment Society
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• v.1 no.2
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• pp.35-42
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• 1996

Seawater samples were collected from P'ohang coastal area during April 1995 - January 1996. The distribution of total heterotrophic bacteria and crude oil-degrading bacteria (CDB) were studied. In addition, biodegradation of crude oil was investigated through mono and mixed culture. The heterotrophic bacterial distribution was in the range of 4.1 $\times$ $10^4$- 1.2 $\times$ $10^5$ CFU/$m\ell$, respectively. The percent of crude oil-degrading bacteria against total heterotrophic bacteria was 0.05-0.54% which was lower than other marine samples reported. Therefore it could be suggested that the distribution of crude oil-degrading bacteria in the seawater of P'ohang coastal area was highly affected by presence of petroleum hydrocarbon. Taxonomical characteristics of 26 isolates were investigated. The results of identification were showed 7 genera which were Acinetobacter spp., Bacillus spp., Citrobacter spp., Micrococcus spp., Moraxella spp., Rhodococcus spp., and Serratia spp. Appearance of Enterobacteriaceae indicated that the seawater was polluted with wastewater. Also genus of Bacillus had predominant in CDB on P'ohang coastal area. In flask culture, biodegradation of crude oil was enhanced by addition of mixed culture of CDB.