Limits to petroleum degradation
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Limits to Petroleum Degradation. Name the 3 most common things that most often limit in situ petroleum hydrocarbon degradation. Nitrogen Phosphorus Oxygen. Oxidation/Reduction Reactions. Hydrocarbon biodegradation is essentially an oxidation/reduction reaction

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Limits to Petroleum Degradation

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Limits to petroleum degradation

Limits to Petroleum Degradation

Name the 3 most common things that most often limit in situ petroleum hydrocarbon degradation

  • Nitrogen

  • Phosphorus

  • Oxygen


Oxidation reduction reactions

Oxidation/Reduction Reactions

  • Hydrocarbon biodegradation is essentially an oxidation/reduction reaction

  • Hydrocarbon is oxidized and Electron acceptor is reduced

hydrocarbon + electron acceptor + microorganisms + nutrients  carbon dioxide + microorganisms + waste products

Electron acceptors include: O2, NO3-, iron oxides (Fe(OH)3), SO42-, H2O


Aerobic degradation

Aerobic Degradation

  • Aerobic bacteria use O2 as their terminal electron acceptor

  • Water saturated with air contains 6 – 12 mg/L dissolved O2

  • Complete conversion of hydrocarbons to CO2 and H2O requires ~3 mg/L of O2 for each 1 mg/L hydrocarbon

  • Maximum of 12 mg/L dissolved O2 = maximum 4 mg/L hydrocarbon degradation

  • Unlikely to have saturated dissolved O2


Organic chemistry

Organic Chemistry

polycyclic aromatic hydrocarbon

monocyclic aromatic hydrocarbons

primary alkane

biphenyl type benzenoid ring

organohalide

nitro compound


Limits to petroleum degradation

BTEX

Benzene, Toluene, Ethylbenzene, Xylene

  • Volatile monoaromatic hydrocarbons

  • Commonly found together in crude petroleum and petroleum products such as gasoline

  • Major cause of environmental pollution

  • LUSTs: leaking underground storage tanks

    • ~35% of 1.4 million gas storage tanks in the US are leaking


Biocatalysis biodegradation database

Biocatalysis/Biodegradation Database

http://umbbd.ahc.umn.edu

Microbial biocatalytic reactions and biodegradation pathways primarily for xenobiotic, chemical compounds.


Aerobic btex degradation

Aerobic BTEX Degradation

  • Pseudomonads: chemoorganotrophs, aerobic, rod-shaped bacteria

  • Important genera are: Pseudomonas, Burkhoderia, and sometimes Xanthomonas

  • Isolated from the environment

  • Some are pathogenic

  • 1968: strain of Pseudomonas putida isolated

    • grew on ethylbenzene, benzene, and toluene

    • toluene dioxygenase!


Toluene dioxygenase

Toluene Dioxygenase

-Catalyzes over 108 reactions

1. Monocyclic aromatics2. Fused Aromatics

3. Linked aromatics4. Miscellaneous


Anaerobic btex degradation

Anaerobic BTEX Degradation

  • Wide variety of microorganisms

  • Denitrifiers, example is Thauera aromatica

  • Iron Reducers

  • Sulfate reducers, examples are Desulfovibrio, Desulfobacter

  • Methanogens

  • Usually requires a consortium


Field studies

Field Studies

  • Crude oil study in MN in 2000

  • Buried oil pipeline ruptured in 1979 = 3200 barrels of oil spilled into subsurface

  • Growth of aquifer microbial populations (dominated by aerobes, iron reducers, methanogens)

  • Biodegradation caused a number of FOOTPRINTS near the plume = geochemical changes

What might FOOTPRINTS be???


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