摘要:

The standard biological oxygen demand (BOD) test was modified for application to petroleum hydrocarbon-contaminated groundwater. The goal was to assess the potential oxygen demand of plume constituents as part of a field trial investigating oxygen-enhanced in situ bioremediation. Modifications to standard BOD protocol included the use of an adapted microbial population developed from site groundwater and methods to minimize both the loss of volatile compounds and the exposure of samples to air. Results from this study indicated that the measured oxygen demand was significantly greater than the oxygen demand estimated solely by stoichiometric calculations from the concentrations of the analytes of typical regulatory concern, that is, benzene, toluene, ethylbenzene, and xylenes (BTEX). This is not surprising, because the petroleum hydrocarbon sources typically contain many organic contaminants other than BTEX, as well as potentially oxidizable natural dissolved organic matter and inorganic species typically present in hydrocarbon plumes. However, in practice, estimation of the total oxygen demand of a contaminated groundwater by exhaustive analyses of all oxidizable or aerobically degradable species typically will be infeasible. The modified BOD test may be a simple, low-cost, useful tool when assessing the potential for natural attenuation by aerobic biodegradation or designing methods to supply oxygen for enhanced aerobic bioremediation.

ISSN:1088-9868    

DOI:10.1080/10889869809351332

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Soil contaminated with oil is bioremediated by optimizing conditions for microbial activity. Often the question arises about the benefits of bulking with organic materials to improve soil conditions to enhance degradation of the less biodegradable or less bioavailable components. An investigation was undertaken in the laboratory with the objective of measuring the influence of bulking with dried plant material, bermudagrass, and alfalfa on the degradation of oily sludge added to soil. The oily sludge was diluted 50:50 on a weight basis with soil to achieve a final concentration of 100 g oil and grease kg−1of final soil mixture. Bulking agents were added 40 d after dilution of the sludge and optimization of environmental conditions to allow time for the readily decomposable fraction to be degraded before amendment with bulking agents. Populations of heterotrophic microorganisms increased approximately ten times by 40 and 80 d after addition of bulking agents, but the numbers of hydrocarbon-degrading microorganisms did not significantly increase above the number in the nonbulked control. Bulking agents increased the quantity of total petroleum hydrocarbons degraded by approximately 20% during the first 40 d after being added. Disappearance of hydrocarbons for bulked treatments was much slower during the next 40 d, such that the total petroleum hydrocarbon content for both bulked and nonbulked treatments generally was not significantly different at the end. It appears that adding bulking agents may enhance the rate of decomposition of total petroleum hydrocarbons by stimulating the general heterotrophic population of microorganisms, but the influence may not be sustained to influence the extent of decomposition.

ISSN:1088-9868    

DOI:10.1080/10889869809351333

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Results of a 7-month field test of in situ bioremediation of carbon tetrachloride (CT) under denitrifying conditions are reported. The demonstration was conducted in a portion of a several-square-mile CT and nitrate plume. Pretest CT and nitrate levels were 12.5 ± 0.14 μM and 3.87 ± 0.26 mM, respectively. During the test, the CT concentration dropped by 3.71 ± μM, representing an estimated total of 1.42 kg of CT destroyed. The total quantities of acetate and nitrate injected during the demonstration were 221 and 300 kg, respectively. Nitra injection was composed of short-duration, high-concentration pulses added with acetate pulses, and continuously injected nitrate that was present in the surrounding groundwater. Biomass was distributed successfully within the flow field without fouling the injection well. Levels of planktonic denitrifiers increased 10- and 5-fold in monitoring wells 3 and 6 m downstream from the injection well, respectively. A distributed growth pattern was indicated through reductions in the concentrations of acetate, nitrate, and nitrite between these wells. Chloroform (CF) production was controlled by adjusting acetate and nitrate pulsing to keep low levels of nitrate in most of the flow field. Under this regime only 1 mol% of transformed CT appeared as CF. In contrast, approximately 33 mol% of CT transformed to appear as CF when nutrient-feeding conditions were adjusted so that nitrate was consistently absent.

ISSN:1088-9868    

DOI:10.1080/10889869809351334

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A remote site in the Tallgrass Prairie Preserve of Oklahoma (The Nature Conservancy) was contaminated with crude oil from a pipeline break and is being bioremediated using landfarming techniques. Landfarming is designed to stimulate microbial-based catabolism of petroleum through combined dilution/mixing and fertilization-based effects. To evaluate nitrogen-based effects during remediation, the site was sectioned and treated with urea, ammonium sulfate, or ammonium nitrate. Samples were obtained from prairie soil without chemical nitrogen addition and with or without hydrocarbon contamination. Nitrogen cycling dynamics were followed by measuring ammonium, nitrite, nitrate, and volatile nitric oxide (NOx) levels. Nitrifying and denitrifying bacterial numbers were estimated and compared to soil oxygen, carbon dioxide, and methane levels as well as to overall total petroleum hydrocarbon (TPH) reduction. For a prairie ecosystem of this type, a high level of fertilization, particularly with nitrogen, can have ecological effects almost as profound as the petroleum contamination itself. Fertilization of the oil-contaminated soil with the reduced and/or oxidized forms of nitrogen quickly resulted in elevated steady-state levels of both ammonium and nitrate, and exceptionally high levels of NOxreleased from soil. Although nitrogen fertilization increased microbial nitrogen metabolism and nitrogen cycling, it had minimal effects on the overall remediation efficiency.

ISSN:1088-9868    

DOI:10.1080/10889869809351335

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Methanotrophic bacteria were enriched from marine sediments and screened for their ability to biotransform polycyclic aromatic hydrocarbons (PAHs). Characterization of the methanotrophic enrichment showed that it was dominated by a Type I methanotroph, although significant amounts of 18:1 fatty acids were detected, suggesting the presence of Type II methanotrophs in marine systems. The methanotrophic enrichment degraded phenanthrene, anthracene, and fluorene to below detectable levels in 15 days. Partial transformation of fluoranthene occurred over 15 days, but pyrene was not transformed. Radiolabeled phenanthrene was oxidized to carbon dioxide with significant production of polar intermediates. The oxidation was inhibited by acetylene, an inhibitor of methane monooxygenase. The addition of the methanotrophic enrichment to a marine culture grown on PAHs as the sole carbon sources increased the transformation rate of phenanthrene, anthracene, and fluorene. The highest removal rates were obtained with a mixture containing 90% methanotroph enrichment and 10% PAH-degrading enrichment (by biomass). Fluoranthene and pyrene degradation rates by the PAH-degrading enrichment were not significantly increased by the addition of the methanotrophic enrichment. A possible mechanism for the increased transformation rate was the rapid oxidation of PAHs by methane monooxygenase, forming an intermediate that is more bioavailable for utilization by the PAH-degraders.

ISSN:1088-9868    

DOI:10.1080/10889869809351336

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Two samples of oily waste organics (OWO) from petroleum wells were added to heath soils from Tierra del Fuego, Argentina, and the effects on hydrocarbon leaching, microbial population, and plant growth were studied. These mixtures and a control soil were subjected to four deionized water leachates. For each leachate, total petroleum hydrocarbons (TPH), aliphatic hydrocarbons (ALH), aromatic hydrocarbons (ARH) with three or fewer rings, ARH with more than three rings, and oil and grease (O&G) were measured. After leaching, six Dactylis glomerata L. plants were grown in each soil column. Plant growth and the total number of aerobic and nitrifier microorganisms were measured in soil. The 10% OWO sample increased the TPH in the leachate, but the 1% sample did not. The ALH, ARH, and O&G of each leachate followed patterns similar to that for TPH. Plant growth diminished and the total number of aerobic and nitrifier microorganisms decreased with increasing OWO, especially when the OWO was from a fresh residue rather than an aged residue. The greater inhibitive effect of fresh residue on plant growth was attributed to a higher concentration of light hydrocarbons, which are more toxic than heavy hydrocarbons. For soil with 1% OWO added, the TPH and other organics did not differ from the control soil. This result, combined with the 10-year average annual rainfall and the water table elevation at the site, suggests that the risk of contaminating the water table is relatively low. Thus, a 1% addition of OWO in soil would be appropriate to use in landfarming of OWO.

ISSN:1088-9868    

DOI:10.1080/10889869809351337

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1088-9868    

DOI:10.1080/10889869809351338

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor