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Biodegradation study of diesel and surrogate compounds of

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A laboratory study of biodegradati

A laboratory study of biodegradati

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  • 1. Biodegradation Study of Diesel and Surrogate Compounds of Diesel Todd R. Crawford Crawford Independent Analysts
  • 2. Biodegradation
    • …the biologically catalyzed reduction in complexity of chemicals… (Alexander 1994)
    • Organic compounds are frequently biodegraded to inorganic chemicals – mineralization
    • A desirable approach to site remediation
  • 3. Incomplete Biodegradation
    • A threshold concentration is reached
    • Remaining material cannot be biodegraded by:
      • Aeration, or
      • Addition of nutrients
    • This phenomenon is seen for most organic chemicals biodegrading in soil
  • 4. Causes of Incomplete Biodegradation
    • Contaminant may be adsorbed into micropores
    • Contaminant may be adsorbed into soil organic carbon
    • Microorganisms may be inhibited by some biodegradation byproduct
    • Amount of contaminant may not be sufficient to support biological activity
    • Remaining contaminant may not be composed of biodegradable material
  • 5. Diesel Fuel
    • Several thousand chemicals
    • Mostly carbon and hydrogen (hydrocarbons)
    • Aliphatics
      • Straight chain alkane
      • Branched chain alkane
    • Aromatics
      • Polycyclic Aromatic Hydrocarbons (PAHs)
  • 6. GC-FID trace of diesel fuel
  • 7. Site
    • Rhode Island
    • Former petroleum distribution terminal
    • Approximately 100 acres
    • Approximately 150,000 cy diesel contaminated soil
    • Remediation goal 500 ppm TPH
    • Ex situ biodegradation
  • 8. Incomplete Biodegradation
    • Biodegradation ceased around 1000 ppm TPH
    • Weekly tilling (aeration) did not stimulate biodegradation
    • Soil amendments did not stimulate biodegradation
    • Holding up the project!
  • 9. Soils
    • U2A – treatment soil
      • Silty sand from shore area
      • Initial TPH concentration ~3000 ppm
      • Final TPH concentration ~1000 ppm
      • Air-dried for 24 hours
      • Sieved
      • Air-dried for 24 hours
      • Stored in 1-Liter glass jars in refrigerator until used
  • 10. Biodegradation Study
    • Is the petroleum sequestered in the soil – not available to biodegradation?
    • Is the remaining petroleum not biodegradable?
  • 11. TPH Redistribution Experiment
    • If petroleum is sequestered in soil, then let’s redistribute it…
    • Out of soil pores onto soil surface where it is bioavailable…
    • Out of soil onto another soil where it may be more bioavailable…
  • 12. Redistribution setup
    • U2A soil
    • U2A soil shaken with methylene chloride and evaporated at room temperature
    • U2A soil extract (methylene chloride) transferred to sandy soil and evaporated at room temperature
    • Diesel fuel in sand
  • 13.  
  • 14. Indications
    • Little or no significant biodegradation of the remaining diesel in:
      • U2A soil without redistribution
      • U2A soil with redistribution
      • Sand with U2A soil extract
    • Biodegradation did occur for diesel in sand – the setup should biodegrade the contaminant
  • 15. Surrogate Biodegradation Experiment
    • Is the remaining petroleum non-biodegradable – not bioavailable?
    • Add surrogates of diesel to soil
    • Add surrogates of diesel to soil extract in another soil
  • 16. Selected Diesel Surrogates
    • Hexadecane – straight C-16 alkane
    • Octacosane – straight C-28 alkane
    • Pristane – branched C-19 alkane
    • Squalane – branched C-30 alkane
    • Phenanthrene – C-14 PAH
    • 100 ppm of each surrogate added to soils
  • 17.  
  • 18.  
  • 19.  
  • 20. Observations
    • Branched alkanes are biodegrading slowly
    • Longer alkanes are biodegrading slower than shorter alkanes
    • Phenanthrene is biodegrading faster than other surrogates!?
  • 21. Conclusions
    • Biodegradation is inhibited in the site soils by a chemical that is transferred with the methylene chloride extract
    • And/Or
    • Most of the remaining material is branched alkanes
  • 22. Acknowledgements
    • Jim Smith and Les Eng, Trillium Inc.
    • John E. Ross, CTEH LLC
    • José A. Amador, URI

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