Biodegradation study of diesel and surrogate compounds of

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A laboratory study of biodegradati

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Biodegradation study of diesel and surrogate compounds of

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

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