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PETROLEUM MICROBIOLOGY EBOOK

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Annotation Petroleum Microbiology is a stateoftheart presentation of the specific microbes that inhabit oil reservoirs, with an emphasis on the ecological. Petroleum microbiology: an introduction to microbiological petroleum engineering. Front Cover. Ernest Beerstecher. Elsevier Press, - Science - pages. Petroleum microbiology. An annotated selection of World Wide Web sites relevant to the topics in Microbial Biotechnology. Lawrence P. Wackett. Additional .


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Get this from a library! Petroleum microbiology. [Ronald M Atlas;]. Ebook: Choose a downloadable PDF or ePub file. Petroleum Microbiology is a state-of-the-art presentation of the specific microbes that inhabit oil reservoirs. Petroleum microbiology. Front Cover. Ronald M. Atlas. Macmillan, - Technology & Engineering - pages. 0 Reviews.

Petroleum Microbiology. Bernard Ollivier , Michel Magot. Annotation Petroleum Microbiology is a stateoftheart presentation of the specific microbes that inhabit oil reservoirs, with an emphasis on the ecological significance of anaerobic microorganisms. An intriguing introduction to extremophilic microbes, the book considers the various beneficial and detrimental effects of bacteria and archaea indigenous to the oil field environment. Presenting fundamental and applied biological approaches, the book serves as an invaluable reference source for petroleum engineers, remediation professionals, and field researchers.

Petroleum microbiology Author: Ronald M Atlas Publisher: New York: Macmillan ; London: English View all editions and formats Rating: Subjects Petroleum -- Microbiology.

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Document, Internet resource Document Type: Ronald M Atlas Find more information about: Ronald M Atlas. Reviews User-contributed reviews Add a review and share your thoughts with other readers. Be the first. Add a review and share your thoughts with other readers. Similar Items Related Subjects: Petroleum -- Processing -- Role of microorganisms.

Linked Data More info about Linked Data. Primary Entity http: MediaObject , schema: Book , schema: Bartha and I. Iverson and G. Singer and W. This type of report should be examined with care. In an attempt to overcome the problem with trace carbon in agar preparations, some researchers turned to the use of silica gel as a solidifying agent.

However, this tedious procedure has not enjoyed widespread use. If isolates are not required, a rapid MPN test sheen-screen with tissue culture plates can be employed for nonvolatile hydrocarbons based on the formation of emulsions, avoiding the problem of trace carbon contamination altogether A similar assay to screen for hydrocarbon degraders based on a redox indicator has been described and combined with the sheen-screen to produce an MPN assay based on both emulsification and respiration Numerous studies have attempted to describe microbe-microbe and microbe-hydrocarbon interactions by extrapolating from detailed laboratory studies with isolates from hydrocarbon-contaminated environments.

For example, evaluations of functional and physiological isolate groupings have been carried out in an effort to quantify the oil emulsification abilities and type of hydrocabon accession mode used by environmental isolates Researchers have also constructed simplified consortia containing several well-defined strains in an effort to identify specific processes that may be important in environmental settings.

In a recent study evaluating 10 strains enriched with phenanthrene as the sole carbon and energy source 7 , isolates were examined without confounding interactions associated with complex media, substrates, and microbial mixtures. Strains from eight sites were able to metabolize PAHs with two to five rings following growth on phenanthrene.

In terms of metabolism oxidation, mineralization, or removal , each strain was unique with respect to substrate specificity, and all could oxidize at least one intermediate of the two known PAH degradation pathways salicylate or phthalate.

Despite widespread ability to metabolize benz[ a ]anthracene, chrysene, and benz[ a ]pyrene, none of the strains could mineralize pyrene alone. This led the authors to conclude that unique cometabolic processes are required for pyrene removal in natural environments. This is a common conclusion that, while probably correct, is typically unsubstantiated by any direct evidence or description of the specific processes involved. Komukai-Nakamura et al. The degradation of Arabian light crude oil was monitored, and a combination of the Acinetobacer sp.

Respirometry showed that P. Many bioremediation companies offer such mixed cultures for sale to cope with environmental pollution , but third-party testing of such products has not proven them to be more effective than autochthonous microbial communities once additional nutrients and sorbents are removed , Standard assay procedures with simple consortia are being developed for Environment Canada , and the U.

Evironmental Protection Agency in order to test such products. These types of study are essential for understanding general mechanisms but do not reveal environmental importance. To achieve a greater understanding, the molecular biology and biochemisty of the processes need to be understood in detail so that gene expression can be correlated to activity. For example, using green fluorescent protein fusions, Holden et al.

Instead, adherence to the hydrocarbon-water interface was more important for biodegradation. Aside from isolating and identifying microorganisms present in hydrocarbon-impacted environments, descriptions of microbial communities have been based solely on functional characteristics.

Normally based on MPN assays, dividing communities into physiological types is best served if numerous selective media are used and associated with relevant site characteristics. The MPN has appeared to be particularly useful for studying anaerobic systems, as it is sensitive, even when slow-growing anaerobes are being studied. Both groundwater and soil samples were taken with the aim of correlating microbiological and chemical data to assess bioremediation potential.

Microorganisms were divided into the following classes: In addition, 3, bacterial isolates While this is an impressive number of isolates, there is no indication of how important these isolates are in that particular environment. A separate study of a crude oil-contaminated aquifer 51 used a similar MPN approach to study ecological succession, microbial nutrient demands, and the importance of free-living versus attached populations.

MPN determinations of aerobes, denitrifiers, iron reducers, heterotrophic fermenters, sulfate reducers, and methanogens were used. The dominant physiological types were consistent with the known geochemical evolution of the contaminant plume, from iron-reducing to methanogenic. In Antarctica, Delille et al. Total bacteria acridine orange saphrophytes, and hydrocarbon-utilizing bacteria MPN were assayed.

Following crude oil or diesel fuel contamination, bacterial counts increased, with increases in oil-degrading bacteria from 0. Both saprophytic and oil-degrading bacteria increased with Inipol addition. In contrast, the underlying seawater showed limited variation between control and contaminated plots.

In lieu of MPN assays, direct immunofluorescence and enzyme-linked immunosorbent assay have been used for nearly real-time quantification of hydrocarbon-degrading organisms Immunodetection was shown to be applicable to complex sample matrices for rapid field evaluation.

Antibody mixtures of sufficient specificity could potentially be developed to target specific microbial groups, although, in most situations, tracking the expression of specific genes involved in hydrocarbon metabolism would be of greater utility.

The most effective uses of an MPN approach, or indeed any approach to characterize a petroleum-impacted microbial community, has been realized when evaluating the role of a particular microbial group during remediation. For example, during enhanced oil recovery by water flooding, wells are often contaminated with hydrogen sulfide-producing sulfate-reducing bacteria that result in the souring of sweet crude oils.

Biocides have often been found to be ineffective in controlling this problem, while nitrate addition has been used with some success , , Eckford and Fedorak , undertook an MPN-based study of some western Canadian oil field waters to show that nitrate addition stimulates the growth of heterotrophic nitrate-reducing bacteria that outcompete sulfate-reducing bacteria, presumably due to more favorable metabolic energetics. Nitrate-reducing bacteria have been neglected in the study of petroleum reservoirs , which illustrates that a circular approach to community studies, whereby non-culture-based approaches lead to the development of new isolation techniques and vice versa, is recommended.

Total community analyses have been carried out with phospholipid fatty acid analysis profiles and Biolog substrate utilization patterns. In Australia, phospholipid fatty acid analysis profiles were evaluated as a method to provide insight into the monitoring-only approach during management of a gasoline-contaminated aquifer Principal-component analysis did not reveal any clear groupings with respect to an aromatic hydrocarbon plume, and phospholipid fatty acid profiles were rejected as expensive and technically difficult for their purpose.

A similar study used total phospholipid fatty acid profiles to evaluate microbial community structure and biomass levels in a JP-4 jet fuel-contaminated aquifer. Aerobic and anaerobic zones were examined, and specific fatty acids were used in an attempt to draw conclusions with respect to the presence of aerobes and anaerobes, but overall, phospholipid fatty acid patterns are not sufficiently powerful to provide solid data about the presence of specific microorganisms in a community, let alone provide insight into their function.

Protein banding pattern analysis as a method to infer the function of isolates from a contaminated aquifer was found to suffer from the same limitations when evaluated by Ridgway et al.

A total of isolates were screened for the ability to use gasoline vapor as a sole carbon and energy source and were pooled into groups based on the usage pattern of 15 different volatile organic hydrocarbons.

Following identification, sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns were used to regroup the isolates. Fifty-one groups were resolved that partitioned into two broad classes metabolically diverse and metabolically restricted , but catabolic activity could not be predicted. Berthe-Corti and Bruns 57 used Biolog substrate utilization patterns to evaluate the functional diversity of microbial communities in continuous-flowthrough cultures treating C 16 -contaminated intertidal sediments.

Standard dissolved oxygen and dilution rate effects typically used in in situ remediations were implemented because it is desirable to determine if adaptations to low oxygen are due to changes in microbial community structure or metabolic adaptations of specific populations. Measurements of C 16 degradation, product formation, oxygen consumption, total heterotrophs, and MPN determinations of nitrate reducers, sulfate reducers, and C 16 -utilizing bacteria were combined with Biolog data.

It was observed that substrate utilization became more limited, especially at low dissolved oxygen 0. Other parameters C 16 degradation, protein production, and oxygen consumption increased with dilution independently of dissolved oxygen. Lindstrom et al. No differences in total bacterial numbers or soil carbon mineralization were detected, while hydocarbon degraders based on the sheen-screen assay were elevated at the oil-contaminated site.

Nitrogen mineralization and metabolically active microorganisms were abundant at the contaminated site. A kinetic analysis of the Biolog results was used to avoid problems with inoculum density and time-of-reading effects. Taken together, the evidence was interpreted to conclude that the oil resulted in diminished microbial population diversity and selection for metabolic generalists even after extended exposure times. However, the importance of the observations in terms of overall ecosystem function is difficult to determine.

At this time, we are beginning to understand the astonishing diversity of microbial populations and communities in the environment. Coming to grips with the inherent variability in microbial communities over space and time, even in the absence of petroleum hydrocarbons, remains a major challenge. Culture-independent approaches to microbial community analyses have recently enjoyed a surge in popularity as new techniques have been developed and are available in most major research institutions.

Molecular descriptions of microbial communities now dominate the literature in all areas of microbial ecology, not just petroleum microbiology. To be successful in the future, rapid automated systems will be required to process and evaluate vast quantities of data in order to subtract background variability.

Even then, care must be taken to realize that, while molecular methods are powerful and attractive, the genetic composition of a community cannot be used to extrapolate ecosystem function. Kent and Triplett summarized the current state of microbial community analysis succinctly: A few of the recent studies will be discussed here, and it is important to note that most studies involving culture-independent characterization of petroleum-impacted microbial communities have included other measures of microbial activity with culture-dependent methods.

This is a requirement for making sense of data generated from culture-independent methods and to allow the development and evaluation of new methods.

Bulk measurements of total community DNA in a manner analogous to phospholipid fatty acid analysis and protein banding patterns have been used in an attempt to detect perturbations and changes in petroleum-impacted environments. Unlike phospholipid fatty acid analysis, specific microorganisms can be identified if the genetic material is extracted from each individual band following elecrophoresis and then sequenced. This practice is time-consuming, and identification results, while intriguing, are often left without further attempts to isolate the observed organisms.

Shi et al. Physical-chemical data and the lack of members of the Archaea suggest that methanogenesis was not occurring in the aquifer. MacNaughton et al. Complex banding patterns and low reproducibility were encountered, along with some disagreements between phospholipid fatty acid analysis and DGGE analysis.

However, two novel bands, closely related to Flexibacter-Cytophaga-Bacteroides were detected in all nutrient-amended sites. Their contribution to enhanced degradation remains speculative. Roony-Varga et al. Increased diversity at contaminated sites was observed along with higher phospholipid fatty acid contents.

This may be an indication that, while phospholipid fatty acid analysis can be useful for identifying isolated microorganisms, its utility as a tool for extrapolating the identity of individual community members from a total phospholipid fatty acid pattern is limited.

To date, community characterizations have been, for the most part, applied to field situations. Hydrocarbon-contaminated or impacted sites rather than fermentor-based treatment systems have been the target of characterization. Thus, this type of system may be useful for developing methods in a more controlled environment.

Colores et al. They found that surfactant levels close to the critical micellization in soil inhibited mineralization and shifted the community from Rhodococcus and Nocardia populations to Pseudomonas and Alcaligenes species able to degrade both surfactant and hydrocarbon. Of 60 isolates, 11 unique DGGE banding patterns were obseved, three of which Rhodoccocus , Psuedomonas , and Alcaligenes corresponded to major bands from the whole-community analysis.

It is apparent that total community approaches such as 16S rRNA DGGE banding patterns are not the end-all in understanding microbial communities or providing sufficient power to address specific hypotheses More information is often available when gene probes for specific isolates, genotypes, or metabolic activities are used, and approaches to achieve this are being applied in both aerobic and anaerobic systems , , , , , , , , An excellent example of this has come out of Voordouw's laboratory at the University of Calgary.

That group has published extensively on the use of molecular methods for the quantitative analysis of sulfate-reducing bacterial communities in oil fields , , Sulfate-reducing bacteria play a key role in anaerobic corrosion in oil and gas fields, and elucidating their modes of action is important to oil companies.

To this end, metabolic activity tests are useful but do not provide information about specific species. The observation that many specific hydrogenase probes failed to hybridize with sulfate-reducing bacterial isolates led to the development of reverse-sample genome probing This technique allows the total DNA from a community to be quantitatively analyzed in a single step.

The proportion of the community being analyzed is related to the quantity of probe in the master filter, and a quantitative approach has been developed , and adding probes for non-sulfate-reducing bacteria to a filter is straightforward Biofilm formation , nitrate injection , and diamine biocide effects with respect to community composition and functional properties have been described.

The approach has also been used for evaluating hydrocarbon-degrading bacteria in soil exposed to dicyclopentadiene , although it must be kept in mind that important groups of organisms may be missed with this method and that the presence of a specific microorganism does not indicate that it is active. From a remedial perspective, tracking specific genes expected to be present in isolates from hydrocarbon-impacted environments may be more useful at this time, especially if workable methods for mRNA can be developed.

Early work with gene probes following the Exxon Valdez spill revealed that bacterial populations containing both the xylE and alkB genes could be deteced in environemental samples In laboratory columns, proportions of xylE and ndoB polycyclic aromatic hydrocarbon degradation populations from an aquifer community were monitored during degradation of creosote-related PAHs Isolates grown on tryptone-yeast extract medium were probed, and it was found that p -cresol addition resulted in a fold increase in total culturable bacteria, with a threefold increase in xylE- and ndoB -positive populations.

Langworthy et al.

Laurie and Lloyd-Jones recently used competitive PCR to illustrate that the newly descibed phn genes of Burkolderia sp. The phn genes, while encoding the identical biodegradation pathway, have low sequence homology to nah , a different gene order, and are present in the organisms that are rarely cultured in the laboratory.

If the biochemistry and genetic diversity are known, gene probe suites have greater potential for accurately evaluating bacterial degradative potential , , although the application of a small number of probes may be effective if meaningful hypotheses are tested Recent advances in characterizing alkane metabolism in a number of organisms have allowed the production of a variety of primers to detect, for example, the alkB gene from P.

As more strains are tested and more probes are produced, it is becoming clear that, while different alkane hydroxylases can be found in phylogenetically distant microorganisms 19 , many probes will only provide information on the presence of a similar gene in closely related strains. Thus, the usefulness of such gene probes will grow as the diversity of genes responsible for hydrocarbon metabolism is better appreciated , , , , , This field will be greatly advanced if genome projects are initiated to sequence environmentally important microorganisms, including fungi, if the diversity of hydrocarbon metabolic pathways is better characterized, and if tools to monitor gene expression on a large scale are developed Finally, the most important point to recall when embarking on a community-based study is that a clear, testable hypothesis be framed at the outset.

The general importance of relying on the indigenous microbial population, which presumably resists tidal washing by association with oily surfaces rather than on inocula, has been emphasized.

Environmental impacts from the petroleum industry derive from recovery, transport, refining, and product usage. In various operations of production, processing, and storage, large volumes of waste are generated as oily sludges Hydrocarbons bind strongly to solid surfaces, including soils, and remediation of these materials represents a significant challenge.

The lighter and often toxic hydrocarbon components tend to volatilize into the atmosphere, reducing air quality and threatening human and animal health. High levels of sulfur compounds are also emitted in petrochemical waste streams, which require treatment.

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The follolwing sections will focus on treatment of petroleum-contaminated solids, biofiltration of volatile compounds from air streams, and removal of sulfur compounds from waste streams. Hence, in contrast to earlier reviews which focused on clean-up of contaminated sites, the main emphasis here is on bioprocessing of waste streams.

However, abiotic losses due to evaporation, dispersion, and photooxidation also play a major role in decontamination of oil spill environments , In the case of in situ subsurface bioremediation processes, the greatest challenges relate to engineering of the subsurface environment so that microbes can thrive there and effectively degrade the contaminants present.

The rate of microbial degradation of crude oil or oil waste depends on a variety of factors, including the physical conditions and the nature, concentration, and ratios of various structural classes of hydrocarbons present, the bioavailability of the substrate, and the properties of the biological system involved , , , , A generalized sequence of petroleum components in order of decreasing biodegradability is represented as follows Predictive models for estimating the extent of petroleum hydrocarbon biodegradation and diffusion-controlled bioavailability of crude oil components have been developed.

Properly chosen chemical surfactants may enhance biodegradation 79 , 80 , , , The efficiency of processes for degradation of hydrocarbons will also depend on the nature of the hydrocarbon-contaminated material, the environmental conditions, and the characteristics of the microbial population that is present.

Assuming that microbes are present, nutrient availability, especially of nitrogen and phosphorus, appears to be the most common limiting factor , Laboratory and field experiments with inorganic nitrogen and phosphate fertilizers and organic fertilizers, including fish bones, fish or animal meal, biosurfactants, and bulking agents, have shown success 68 , , , , , , , , , Strategies for microbial degradation of petroleum contaminants or wastes manifest themselves in processes having different degrees of complexity and technological requirements.

Bioremediation of contaminants in soil by natural attenuation requires no human intervention, whereas implementation of accelerated and controlled bioreactor-based processes may be directed to exploiting microbial technology and bioprocess engineering to optimize the rates and extents of contaminant degradation.

In simple bioremediation systems, which require little or no microbiological expertise, process-limiting factors often relate to nutrient or oxygen availability or the lack of relatively homogeneous conditions throughout the contaminated medium. Microbial growth and degradation processes operating under such conditions are typically variable and suboptimal, leading at best to prolonged degradation cycles Processes are often unreliable, and required contaminant degradation endpoints are often not achieved throughout the medium.

These processes tend to ignore the realities of enzyme and cell substrate saturation kinetics, where rates of degradation slow as contaminant concentrations fall, with resulting reductions in the viable microbial population. When contaminants are degraded by cometabolism, early elimination of the cosubstrates, necessary for degradation of these contaminants, can halt the degradation processes. The nonhomogeneous and unpredictable nature of these processes makes them intensive in terms of sampling and analytical activities, as patterns of contaminant removal have to be monitored throughout a three-dimensional grid.

The need for intensive monitoring represents a major justification for the implementation of more optimized biodegradation processes, which ensure contaminants are efficiently biodegraded to defined criteria.

Short-term real estate development plans or measures to afford greater protection to the environment or to comply with increasingly stringent environmental regulations require accelerated remediation of contaminated sites.

Increasing levels of microbial expertise may be exploited in processes for accelerated transformation of petroleum contaminants and wastes. Several laboratory and field investigations have indicated that the addition of commercial microbial cultures bioaugmentation , , , did not significantly enhance rates of oil biodegradation over that achieved by nutrient enrichment biostimulation of the natural microbial population , , The Exxon Valdez bioremediation experience, in particular, has been viewed by many as a general rule that bioaugmentation is ineffective in petroleum and other biodegradation processes.

This begs two questions: Is there ever a role for inocula in petroleum degradation processes? Is there any potential to exploit recombinant organisms in the practice of environmental bioremediation and waste treatment?

The low water solubilities of the majority of petroleum hydrocarbon compounds have the potential to limit the capacity of microbes, which generally exist in aqueous phases, to access and degrade these substrates. These biosurfactants and added chemical surfactants enhance removal of petroleum hydrocarbons from soil or solid surfaces. However, both enhancement and inhibition of biodegradation of hydrocarbons have been observed 35 , , Suppression of their production, by use of inhibitors or mutagens, retards the ability of these bacteria to degrade oil 41 , The low-molecular-weight biosurfactants glycolipids, lipopeptides are more effective in lowering the interfacial and surface tensions, whereas the high-molecular-weight biosurfactants amphipathic polysaccharides, proteins, lipopolysaccharides, and lipoproteins are effective stabilizers of oil-in-water emulsions 41 , 97 , , , , Many studies have characterized the roles of biosurfactants in biodegradation by observing the effects of fractionated preparations 42 , , , , , , , , , , , , , However, the successful application of biosurfactants in bioremediation of petroleum pollutants will require precise targeting to the physical and chemical nature of the pollutant-affecting areas.

Although many laboratory studies indicate the potential for use of biosurfactants in field conditions, a lot remains to be demonstrated in cost-effective treatment of marine oil spills and petroleum-contaminated soils compared to chemical surfactants.

Recent Advances in Petroleum Microbiology

Chemical surfactants have the ability to emulsify or pseudosolubilize poorly water-soluble compounds thus potentially improving their accessibility to microorgansims. Properties of chemical surfactants that influences their efficacy include charge nonionic, anionic or cationic , hydrophilic-lipophilic balance a measure of surfactant lipophilicity , and critical micellar concentration the concentration at which surface tension reaches a minimum and surfactant monomers aggregate into micelles.

Surfactants with hydrophilic-lipophilic balance values from 3 to 6 and 8 to 15 generally promote formation of water-in-oil and oil-in-water emulsions, respectively. Biodegradation of certain poorly soluble petroleum hydrocarbons may be inhibited by surfactants as a result of i toxicity by high concentration of surfactant or soluble hydrocarbon; ii preferential metabolism of the surfactant itself; iii interference with the membrane uptake process; or iv reduced bioavailability of miceller hydrocarbons , , Much of the surfactant added to soil is ineffective as it becomes sorbed to soil particles.

Micellarization of the contaminant at or above the surfactant critical micellar concentration may prevent access to the contaminant by the microorganism. Diluting the contaminated medium to get the surfactant concentration below its critical micellar concentration can facilitate microbial accession and contaminant degradation When the effects of surfactant physicochemical properties hydrophilic-lipophilic balance and molecular structure on the biodegradation of crude oil by a mixed bacterial culture were examined, hydrophilic-lipophilic balance nonylphenolethoxylate substantially enhanced biodegradation at surfactant concentrations of more than critical micellar concentration value Surfactants from other chemical classes with hydrophilic-lipophilic balance values of 13 had no effect or were inhibitory.

The range of stimulatory and inhibitory effects of surfactants on hydrocarbon degradation reported in the literature may not be contradictory but simply describe unique cases based on the nature of the hydrocarbon contaminants, characteristics of the contaminated medium, surfactant properties and the physiology of the organisms involved , Understanding how these four elements interact may enable us to design surfactant-enhanced bioremediation systems on a more rational basis 36 , , , In the following section, the variety of petroleum biodegradation processes will be reviewed, starting with the processes requiring the least microbial expertise and moving on to processes with increasing levels of microbial technological complexity.

Natural attenuation, the least invasive approach to bioremediation, requires no intervention other than to demonstrate the progress of the degradation mediated by the indigenous microbial population, and its efficacy remains controversial Plants and their rhizospheric microorganisms phytoremediation can participate in hydrocarbon remediation 47 , , , , , , , , , , , , Plant root exudates can supply carbon and nitrogen sources for microbial growth 12 , , raising the densities of rhizospheric bacteria by orders of magnitude more than the population in the surrounding soil 12 , , , and enzymes may be produced that degrade organic contaminants 69 , , Phytoremediation is not a suitable method for remediation of high-volume oily wastes.

Volatile organic carbons can be taken up by plants and transpired to the atmosphere without transformation in a process known as phytovolatilization, which is not an acceptable environmental solution. There is limited plant uptake of more hydrophobic and larger petroleum components. Wetland use in the petroleum industry for removal of inorganic and organic contaminants and toxicity from hydrocarbon wastes was reviewed by Knight et al.

Contaminant removal effectiveness depended more on hydraulic loading and influent concentrations than on internal plant communities and water depth. Often biodegradation is accompanied by other removal mechanisms Aerobic processes generally predominate, and the toxicity of contaminants or metabolites is often a problem.

The availibility of fertilizer and oxygen is often rate limiting , , , , While landfarming of refinery and wellhead oily sludges is no longer considered environmentally acceptable, it is still being used as an oily sludge treatment and disposal method in many parts of the world 29 , 44 , As a starting point, large uncontaminated tracts of land are first deliberately contaminated, followed by bioremediation of the less recalcitrant oil fractions.

Petroleum microbiology

Large refineries, having capacities of , to , barrels per day can produce as much as 10, cubic meters of sludge per annum. These landfarming operations can therefore result in tying up large areas of land which will later have to be decommissioned when more environmentally desirable processes are implemented.

Large quantities of volatile organic carbons present in these wastes, which are hazardous to health and which cause tropospheric ozone production, are typically transferred to the atmosphere rather than biodegraded, facilitated by spraying the waste on the land and then routinely tilling the soil to promote gas transfer. Lack of control over the parameters affecting microbial activity temperature, pH, moisture, aeration, mixing, and circulation prolongs treatment time 62 , , , , , , , , , Maximum contaminant degradation occurs in the tilled surface, typically amounting to 10 to 20 cm of depth, although deeper aeration and mixing with ploughing and rotovating equipment has also been effectively implemented.

The following examples indicate that typical degradation rates of 0. Oxygen availability appeared to be a limitation in this project. During intensive landfarming of petroleum waste, a gradual accumulation of petroleum hydrocarbons occurred in the soil over time, amounting to Of the total PAHs applied to the soil in the waste, the percentages remaining at the end of treatment were 1. Residual soil concentrations for pyrene and benzo[ a ]pyrene were and 28 ppm, respectively, representing extents of degradation of Because of the trend to ban landfarming of petroleum sludges and because thery are considered hazardous wastes, oil companies are seeking other disposal solutions.

Most of the rate-limiting and variability factors observed in landfarming of oily sludges may be eliminated in employing simple bioreactors where optimal performance can be achieved by controlling factors affecting rates and extents of microbial growth and oil transformation Through break up solid aggregates and dispersion of insoluble substrates, hydrocarbon desorption and contact with the aqueous phase is promoted, resulting in increased biodegradation Bioreactor-based petroleum sludge degradation processes also allow management of volatile organic carbons.

By creating reactor conditions which accelerate the process of bioremediation of volatile organic carbons, the biodegradation process rather than volatilization becomes the dominant volatile organic carbon removal mechanism , Retaining the more volatile components, which are generally more biodegradable and more supportive of microbial growth and cell energy, supports degradation of the less volatile components, which may rely on cometabolic processes.

In more prolonged hydrocarbon biodegradation processes, for example, landfarming, where volatile materials are lost to the atmosphere, the development of microbes on these substrates, containing the catabolic enzymes with relaxed substrate specificities to transform the more recalcitrant compounds, is not facilitated.

Diesel fuel stimulated cometabolic mineralization of benzo[ a ]pyrene in culture and in soil , The volatile components also help solubilize the more recalcitrant molecules, making them more bioavailable.

The ability of paraffin oil to promote mineralization of pyrene was attributed to its solubilizing action Examples 1 to 3 below describe bioreactor processes having reactor cycle durations of 1 to 4 months , Example 1: French Limited, Crosby, Tex. Example 2: Gulf Coast Refinery, a 1-million-gallon bioreactor was used to treat petroleum-impounded sludges The inoculum was hydrocarbon-degrading organisms from a refinery wastewater activated sludge system. Other operating parameters were an average temperature of Example 3: Sugar Creek, Mo.

The inoculum was activated sludge and prepared hydrocarbon cultures. A float-mounted aeration and mixing system was used. Example 4: This process, employing eight bioreactors with a total capacity of 1. What is petroleum microbiology http: Microbial enhanced oil recovery http: Petroleum microbiology: Sintef http: Petroleum microbiology http: Microbial enhanced oil recovery: Oil spill: Wikipedia http: Bioremediation for marine oil spills http: Oil cleanup directory http: Microbes and oil spills: ASM http: Microbes eating Gulf oil spill http: Oil spills: Microbe Wiki http: Oil spill cleanup: EPA http: BTEX metabolism http:

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