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
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


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 aromatics 2. Fused Aromatics

3. Linked aromatics 4. 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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