Release Of Petroleum Hydrocarbons From Bioremediated Soils

This article presents a qualitative evaluation of the extent to which the bioavailability (release) of a chemical is related to the biodegradation of hydrocarbons in a field bioremediation unit. The objectives of this research were to (1) quantify the rate of release of petroleum hydrocarbons from two soils that were bioremediated, (2) explore hydrocarbon release as a process affecting bioremediation; and (3) investigate the impact of bioremediation on chemical release in the two soils. An experimental protocol was used to quantify the rate of release of these hydrocarbons from two soils that had been bioremediated in a field-scale prepared bed land treatment unit. One soil showed little change in hydrocarbon concentration during 55 weeks of prepared bed bioremediation. The field study results indicated that, prior to the bioremediation, this soil had reached an environmentally acceptable endpoint. The second soil showed considerable hydrocarbon loss as a result of the bioremediation. The rate of hydrocarbon release was determined for the first soil and for the second soil at time zero and after 1, 2, and 7 months of prepared bed bioremediation. The results indicated: (1) the fraction (F) of the specific hydrocarbons that were released rapidly from the soil and the rates of release (k₂) of the residual hydrocarbons that were released slowly, (2) that the mass of each chemical of concern that was released from the first soil was very low; and (3) that the hydrocarbon released rapidly from the second soil decreased as treatment progressed. The experiments also verified, qualitatively, that some portion of each chemical evaluated was not able to be released, and thus was unavailable for bioremediation in the prepared bed land treatment unit.     

Microbial Factors Rather Than Bioavailability Limit the Rate and Extent of PAH Biodegradation in Aged Crude Oil Contaminated Model Soils

The rate and extent of polynuclear aromatic hydrocarbons (PAH) biodegradation in a set of aged model soils that had been contaminated with crude oil at the high concentrations (i.e.,>20,000?mg/kg) normally found in the environment were measured in 90-week slurry bioremediation experiments. Soil properties such as organic matter content, mineral type, particle diameter, surface area, and porosity did not significantly influence the PAH biodegradation kinetics among the 10 different model soils. A comparison of aged and freshly spiked soils indicates that aging affects the biodegradation rate and extent only for higher-molecular-weight PAHs, while the effects of aging are insignificant for 4-ring PAHs and total PAHs. In all model soils with the exception of kaolinite clay, the rate of abiotic desorption was faster than the rate of biodegradation during the initial phase of bioremediation treatment, indicating that PAH biodegradation was limited by microbial factors. Similarly, any of the higher-molecular-weight PAHs that were still present after 90 weeks of treatment were released rapidly during abiotic desorption tests, which demonstrates that bioavailability limitations were not responsible for the recalcitrance of these hydrocarbons. Indeed, an analysis of microbial counts indicates that a severe reduction in hydrocarbon degrader populations may be responsible for the observed incomplete PAH biodegradation. Therefore, it can be concluded that the recalcitrance of PAHs during bioremediation is not necessarily due to bioavailability limitations and that these residual contaminants therefore might pose a greater risk to environmental receptors than previously thought.     

Inoculants and Biodegradation of Crude Oil Floating on Marsh Sediments

The efficacy of ten commercial bioremediation products in enhancing the biodegradation of crude oil was investigated in the laboratory at 10 or 30a°C for 90 d with and without supplemental nitrogen and phosphorus. Oil was added to a 1-cm layer of water covering sediments from a salt marsh. The products did not increase the numbers of hydrocarbon-degrading microorganisms in water and sediments but did increase heterotrophic populations at 21 d. Some bioremediation products more than doubled the quantity of hydrocarbons degraded in 45 d at 10°C. At 30°C, no product increased degradation compared to the fertilized control in which 70% of the added hydrocarbons were degraded. Two products increased the percentage of hydrocarbons degraded from 42% to approximately 65% in 45 d at 30°C when supplemental fertilizer was not provided. The hydrocarbon concentration was not significantly reduced between 45 and 90 d for most product treatments at either temperature. At 10°C, products seemed to have the greatest potential for enhancing oil bioremediation compared to the control.     

Oil desorption from mineral and organic materials using biosurfactant complexes produced by Rhodococcus species

Rhodococcus strains from the culture collection at the Institute of Ecology and Genetics of Microorganisms, Perm, Russia were examined for biosurfactant production during growth on n-alkanes and the ability to remove oil associated with contaminated sands and oil shale cuttings. Members of the genus, particularly R. ruber, were shown to produce low toxicity surfactants effective in removing oil from surfaces. The extent of desorption was inversely related to the concentration of high molecular weight hydrocarbons, namely asphaltenes and resins. In addition, crude surfactant complexes enhanced the degradation of crude oil, in the short term, when added to contaminated agricultural soil during bioremediation studies utilizing biopiling technology.     

Bioremediation of Crude Oil-Contaminated Soil Using Slurry-Phase Biological Treatment and Land Farming Techniques

Field-scale experiments on bioremediation of soil heavily contaminated with crude oil were undertaken on the territory of the Kokuyskoye oil field (Perm region, West Urals, Russia) owned by the LUKOIL Company. The pollution consisted of the contents of a oil waste storage pit, which mostly received soils contaminated after accidental oil spills and also the solid n-alkane (paraffin) wastes removed from the surface of drilling equipment. Laboratory analyses of soil samples indicated contamination levels up to 200?g/kg of total recoverable petroleum hydrocarbons (TRPH). Average oil composition consisted of 64% aliphatics, 25% aromatics, 8% heterocyclics, and 3% of tars/asphaltenes. Ex situ bioremediation techniques involved the successive treatment of contaminated soil using a bioslurry reactor and land farming cells. An oleophilic biofertilizer based on Rhodococcus surfactant complexes was used in both treatment systems. An aerobic slurry bioreactor was designed, and the biofertilizer applied weekly. Slurry-phase biotreatment of the contaminated soil resulted in an 88% reduction in oil concentration after 2 months. The resulting reactor product, containing approximately 25?g/kg of TRPH, was then loaded into land farming cells for further decontamination. To enhance bioremediation, different treatments (e.g., soil tilling, bulking with woodchips, watering, and biofertilizer addition) were used. The rates of oil biodegradation were 300 to 600?ppm/day. As a result, contamination levels dropped to 1.0 to 1.5?g/kg of TRPH after 5 to 7 weeks. Tertiary soil management involved phytoremediation where land farming cells were seeded with a mixture of three species of perennial grass. The effect of phytoremediation on the residual decontamination and rehabilitation of soil fertility is being evaluated.     

Isolation and Characterization of Novel Hydrocarbon-Degrading Euryhaline Consortia from Crude Oil and Mangrove Sediments

Two novel and versatile bacterial consortia were developed for the biodegradation of hydrocarbons. They were isolated from crude oil from the Cormorant Field in the North Sea (MPD-7) and from sediment associated with mangrove roots (MPD-M). The bacterial consortia were able to degrade both aliphatic and aromatic hydrocarbons in crude oils very effectively in seawater (35 g/L NaCl) and synthetic media containing 0 to 100 g/L NaCl (1.7 M). Salinities over twice that of normal seawater decreased the biodegradation rates. However, even at the highest salinity biodegradation was significant. Ratios of nC17 to pristane and nC18 to phytane were significantly lowered across the range of salinity. The lowest values were at 0 and 20 g/L (0.34 M). Phytane was degraded in preference to pristane. The degradation of these compounds was constant over the salinity range, with evidence of a slight increase for consortium MPD-M with increasing salinity. In general, the consortium isolated from mangrove root sediments was more efficient in metabolizing North Sea crude oil than the consortium isolated from Cormorant crude oil. The 5 strains that comprise MPD-M have been tentatively identified as species of the genera Marinobacter, Bacillus, and Erwinia. This is the first report of hydrocarbon-degrading consortia isolated from crude oil and mangrove sediments that are capable of treating oily wastes over such a wide range of salinity. Received June 30, 1999; accepted May 29, 2000.     

Treatment of Used Diesel Invert Drilling Mud to Remove Hydrocarbons,Fix Lead,and Leach Brine

A sample of used, highly saline diesel invert drilling mud (DIDM), artificially contaminated with lead, was tested for remediation using ICPET/ NRC's Solvent Extraction Soil Remediation (SESR) process. The work comprised investigation of the concurrent solvent extraction of diesel oil and fixation of lead by co-agglomeration of metal binding agents. Peat, soluble and insoluble phosphates, coal combustion fly ashes, and flue gas desulfurization scrubber sludge were tested as lead fixation agents. Virtually complete extraction of diesel oil was achieved in a five-step extraction process using toluene, trichloroethylene, or hexane as solvents. The effect of the metal fixation agents on solvent extraction efficiency was also investigated. After remediation to remove hydrocarbons and fix heavy metals, the DIDM sample remained saline. Successful leaching of brine from the dried agglomerates was accomplished by water percolation through a fixed bed of the dried, agglomerated soil. The cleaned DIDM was evaluated for resistance to acid leaching of lead using the U.S.-EPA's toxicity test method 1310A and Toxicity Characteristics Leaching Procedure method 1311. Long-term stability of the treated solids to acid leaching was tested using the U.S.EPA's multiple extraction procedure method 1320. Bioavailability of fixed lead to barley plants grown on synthetic soils prepared from remediated DIDM was determined by analyzing the roots and shoots for lead content. Acid phosphatase, peroxidase, and protein levels were determined in plant roots and soil leachates by biochemical analysis methods. These results were used to assess the effect of enzymes produced by plant root systems, or soil associated microorganisms, on the stability of fixed lead. The presence of fixation agents reduced the bioavailability of lead to the plants.     

Physical and Biological Treatment of Oil-Contaminated Soil in a Baffled Roller Bioreactor

Physical and biological removal of diesel oil from contaminated soil was studied in a baffled roller bioreactor. Initially, the effects of four factors (soil loading, temperature, pH, and surfactant) on physical removal of diesel oil were investigated. Only the presence of a surfactant (sodium dodecyl sulfate [SDS]) demonstrated a significant effect on diesel oil removal. Diesel oil removal efficiency was increased from 32.0% to 63.9% in the presence of 100 mg/L SDS. Using a microbial culture enriched from contaminated soil, biological treatment of diesel oil polluted soil under different soil loadings (15% to 50%), different diesel oil concentrations (1 to 50 g/L), and different types of soil (sand, silt, and clay) was then investigated in the baffled roller bioreactor. Biodegradation consisted of both fast and slow stages for degradation of light and heavy compounds, respectively. All biodegradation experiments demonstrated significant decreases in diesel oil concentrations (88.3% in 14 days for initial diesel oil concentrations of 1000 mg/L and a wide range of soil loadings). The presence of silty or sandy soils enhanced the biodegradation rate compared to the control bioreactor (without soil). The sandy soil loading had no effect on the biodegradation results. Using the enriched culture, the baffled roller bioreactor was able to biodegrade high diesel concentrations (up to 50 g/L) with biodegradation rates of 112.2 and 39.3 mg/L· h during fast and slow stages, respectively.     

Biodegradation of Crude Oil by Constructed Bacterial Consortia and the Constituent Single Bacteria Isolated From Malaysia

Three bacterial isolates identified as Pseudomonas aeruginosa (UKMP-8T), Rhodococcus sp. M15-2 (UKMP-5T), and Rhodococcus sp. ZH8 (UKMP-7T) based on biochemical, physiological, and morphological characteristics and on 16S rDNA sequences were isolated from groundwater of a crude oil refinery plant. From these three isolates, four bacterial consortia were designed by mixing the single bacterial cultures in the following ratios: (P. aeruginosa:Rhodococcus sp. M15-2, 1:1), (P. aeruginosa:Rhodococcus sp. ZH8, 1:1), (Rhodococcus sp. M15-2: Rhodococcus sp. ZH8, 1:1), and (P. aeruginosa: Rhodococcus sp. ZH8:Rhodococcus sp. M15-2, 1:1:1), respectively. Bacterial isolates and consortia showed differing preferences for nitrogen source (0.01% ammonium chloride, 0.10% yeast extract, or 0.50% peptone) to reach optimum growth. When fortified with the preferred nitrogen sources and grown in minimal salt medium, within 7 days all three single isolates and the four bacterial consortia biodegraded 97.6-99.9% of Tapis Massa oil without any significant differences.     

Inhibition of Acetoclastic Methanogenesis in Crude Oil- and Creosote-Contaminated Groundwater

Results from a series of studies of methanogenic processes in crude oil- and creosote-contaminated aquifers indicate that acetoclastic methanogenesis is inhibited near non-aqueous sources. At a crude oil-contaminated site, numbers of acetoclastic methanogens found close to crude oil were one hundred times fewer than those of hydrogen- and formate-utilizing methanogens. In laboratory toxicity assays, crude oil collected from the site inhibited methane production from acetate but not from formate or hydrogen. Toxicity assays with aqueous creosote extract completely inhibited acetate utilization over the range of tested dilutions but only mildly affected formate and hydrogen utilization. The combined results from the laboratory and field studies suggest that in methanogenic contaminated aquifers, inhibition of acetoclastic methanogenesis may lead to a buildup of acetate relative to dissolved organic carbon.     

Inhibition of Acetoclastic Methanogenesis in Crude Oil- and Creosote-Contaminated Groundwater

Results from a series of studies of methanogenic processes in crude oil- and creosote-contaminated aquifers indicate that acetoclastic methanogenesis is inhibited near non-aqueous sources. At a crude oil-contaminated site, numbers of acetoclastic methanogens found close to crude oil were one hundred times fewer than those of hydrogen- and formate-utilizing methanogens. In laboratory toxicity assays, crude oil collected from the site inhibited methane production from acetate but not from formate or hydrogen. Toxicity assays with aqueous creosote extract completely inhibited acetate utilization over the range of tested dilutions but only mildly affected formate and hydrogen utilization. The combined results from the laboratory and field studies suggest that in methanogenic contaminated aquifers, inhibition of acetoclastic methanogenesis may lead to a buildup of acetate relative to dissolved organic carbon.     

Leaching of BTEX from Aged Crude Oil Contaminated Model Soils: Experimental and Modeling Results

It is generally assumed that soil properties such as organic matter content, porosity, and mineral surface area have a significant effect on the bioavailability and leachability of aged petroleum hydrocarbons. In order to test this hypothesis, nine model soils or sorbents (i.e., fine and coarse quartz sand, montmorillonite and kaolinite clay, peat, 60Å and 150Å silica gel, a loam soil, and non-porous glass beads) were spiked with a crude oil, aged for 27 months in the laboratory, and transferred to glass columns for the performance of continuous flow leaching experiments. The column effluents were periodically sampled for 43 days and analyzed for BTEX. A one-dimensional flow model for predicting the dissolution and dispersion of individual hydrocarbons from a multi-component NAPL such as crude oil was used to fit the leaching data (i.e., the BTEX concentration versus time curves) by adjusting the equilibrium oil-leachate partitioning coefficient (K ^ol ) for each respective hydrocarbon. The Peclet number, which is a measure of dispersion and a required modeling parameter, was measured in separate chloride tracer experiments for each soil column.

Results demonstrate that soil properties did not significantly affect the leaching kinetics of BTEX from the columns. Instead, BTEX leaching curves could be successfully fitted with the one-dimensional NAPL dissolution flow model for all sorbents with the exception of montmorillonite clay. The fitting parameter K ^ol for each hydrocarbon was found to be similar to the K ^ol values that were independently measured for the same crude oil by Rixey et al. (Journal of Hazardous Materials B, 65: 137–156, 1999 Rixey, W. G., Garg, S. and Nie, Y. 1999. Comparison of the fixed-bed and batch leaching characteristics of aromatic compounds in residually trapped crude oils and oily wastes. J. Hazard. Mat. B, 64: 137–156. [CSA][CROSSREF] [Google Scholar]). In addition, the fitted K ^ol values were very similar for BTEX leaching from aged compared to freshly spiked loam soil. These findings indicate that leaching of BTEX in the aged soils that are contaminated with crude oil at the high concentrations commonly found in the environment (i.e., > 20,000 mg/kg) was not affected by soil properties or aging but rather was governed by the equilibrium dissolution of these hydrocarbons from the crude oil NAPL that is coating the soil particles.     

Fenton's Reagent-Based In Situ Chemical Oxidation Treatment of Saturated and Unsaturated Soils at a Historic Railroad Site

A targeted treatment program utilizing in situ chemical oxidation was used to remediate diesel fuel-derived petroleum compounds in unsaturated and saturated soils at a historic railroad facility. This program consisted of multiple injections at varying depths within temporary Geoprobe® injection points. The actual treatment time was less than 3 months. Overall concentrations of volatile and semivolatile organic petroleum compounds were reduced by approximately 70%, while the total petroleum hydrocarbon concentration was reduced by nearly 50%. Treatment efficiency in unsaturated soil was similar to that in saturated soil. The results of the remedial program indicate that the effect of grain size of the subsurface materials on treatment efficacy is significant. The project has shown that the use of this technology can be as effective as other in situ treatment technologies used for treating subsurface diesel fuel contamination.     

Biodegradation of Aliphatic and Aromatic Hydrocarbons by Nocardia sp. H17-1

We investigated the biodegradation of hydrocarbon components by Nocardia sp. H17-1 and the catabolic genes involved in the degradation pathways of both aliphatic and aromatic hydrocarbons. After 6 days of incubation, the aliphatic and aromatic fractions separated from Arabian light oil were degraded 99.0 ± 0.1% and 23.8 ± 0.8%, respectively. Detection of the catabolic genes involved in the hydrocarbon degradation indicated that H17-1 possessed the alkB genes for n-alkane biodegradation and catA gene for catechol 1,2-dioxygenase. However, H17-1 had neither the C23O gene for the degradation of aromatic hydrocarbons nor the catechol 2,3-dioxygenase activity. The investigation of the genes involved in the biodegradation of hydrocarbons supported the low degradation activity of H17-1 on the aromatic fractions.     

Analysis of Diesel Fuel Contamination in Soils by Near-Infrared Reflectance Spectrometry and Solid Phase Microextraction-Gas Chromatography

A feasibility study was undertaken to determine whether the rapid, nondestructive analytical technology, near-infrared reflectance spectrometry (NIRS) could be used to predict total petroleum hydrocarbon (TPH) in contaminated soil. Hydrocarbon concentrations were determined on samples of diesel-contaminated soils by the solid phase microextraction-gas chromatography (SPME-GC) method. The same samples were then scanned for near-infrared reflectance spectrometry over the wavelength range 1100 to 2498 nm. Calibrations were developed between the NIR spectral data and the reference SPME-GC chemical data using stepwise multiple linear regression. Linear regression relationships between NIR-predicted TPH concentrations and reference data had r² of 0.68 and 0.72. These results indicate that the combination of NIRS and SPME-GC shows promise as a method for rapid estimation of TPH in soil. A major hurdle in the evaluation of methodology for hydrocarbons residues in soil is the challenge posed by the weathering of such residues.     

Correlations between PID and FID Field Analytical Instruments in the Analysis of Soil Contaminated with Diesel Fuel

Research was conducted to determine if there is a correlation between the data gathered by field analytical instruments in analyzing soil contaminated with diesel fuel. One instrument was equipped with a flame ionization detector (FID) and the other a photoionization detector (PID). The results showed that the concentration readings of the PID and FID displayed a linear relationship for soil recently contaminated with diesel fuel. However, for soil containing weathered diesel fuel in the field, a logarithmic relationship between the PID and FID readings was displayed. It was also determined by laboratory experimentation that the PID and FID readings both exhibited log-linear decreases over time for uncovered diesel fuel-contaminated soil. It was concluded that the PID and FID can both individually be used to evaluate soil contaminated by diesel fuel and might be interchangeable depending on the needs of the researcher.     

燃料油植物乌桕的栽培与管理及桕籽加工

介绍燃料油植物乌桕的实生苗、嫁接苗、雾插苗的培育及组织培养,以及造林与抚育管理。