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University of Nebraska - Lincoln

I. Impact of Ethanol Releases: Long-Term Monitoring Results. Roy F. Spalding. Nebraska Ethanol Safety and Environmental Coalition Meeting Aurora, NE February 4, 2010. University of Nebraska - Lincoln. Collaborators. Kansas Dept of Health & Environment Greg Hattan

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University of Nebraska - Lincoln

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  1. I Impact of Ethanol Releases: Long-Term Monitoring Results Roy F. Spalding Nebraska Ethanol Safety and Environmental Coalition Meeting Aurora, NE February 4, 2010 University of Nebraska-Lincoln

  2. Collaborators Kansas Dept of Health & Environment Greg Hattan Minnesota Pollution Control Agency Mark Toso Tom Higgins Adam Sekely University of Nebraska-Lincoln Mary Exner, co-PI Dave Fitzpatrick, graduate student

  3. Ethanol Properties Influencing Fate and Transport • Cosolvency • Surface tension • Specific gravity • Interfacial tension • Phase separation • Bioremediation

  4. Pi (mm Hg) 27–28 0.8–0.9 2.8 0.2 0.7–0.8 Gasoline Constituent MTBE Benzene Toluene Ethylbenzene Xylenes % by Volume 11% 1% 10% 2% 10% Vapor Pressure (mm Hg) If vapor pressure > 100 mm Hg • Volatilization from free phase (NAPL) • Vaporization of residual product from dry soil • Law of Partial Pressure • Ptotal = PMTBE + Pother constituents • PMTBE = XMTBE PoMTBE Iso-octane (49) (NSTC, OSTP Report, June 1997) Arulanantham et al., 1999

  5. Ethylbenzene Benzene Toluene Xylene BTEX

  6. COSOLVENCY 100,000 Benzene Toluene Xylenes 10,000 1,000 Aqueous Phase Concentration (mg/L) 100 10 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Volume Fraction of Ethanol in the Aqueous Phase Powers (2001)

  7. Properties Impacting Ethanol & Gasoline in Capillary Fringe 80 70 60 50 Surface / Interfacial Tension (dyne/cm) 40 Surface Tension 30 20 Interfacial Tension 10 60 70 10 20 40 50 30 Percent Ethanol in Aqueous Phase Powers (2001)

  8. Mixing Ethanol-Blended Fuels with Water(Adapted from B.P. Stafford, 2007) ethanol E95 1 phase field E85 25 50 50 75 75 2phasefield E10 50 75 25 gasoline water

  9. Attenuation in the Capillary Fringe water gasoline and/or ethanol Water Table groundwater • Contaminant spreading in thin layer in collapsed capillary fringe due to decreased interfacial tension. • Predominately anaerobic microbial degradation within the capillary fringe and conversion tomethane.

  10. Ethanol Attenuation Mechanisms • Degradation by sulfate reduction: CH3CH2OH + 1.5 SO4-2 = 2 CO2 + 3 H2O + 1.5 S-2 144 mg SO4-2 /liter consumes 46 mg ethanol /liter • Fermentation: CH3CH2OH + H2O →CH3COOH + 2 H2 CH3COOH→ CO2 + CH4

  11. Balaton, Minnesota July 28, 2004 ~90,000 Gs of d-ethanol released ~10,000 Gs residual ethanol after product removal and soil excavation

  12. Balaton, Minnesota

  13. D. Oxygen: 4.3 Years After Derailment

  14. Methane: 2.8 Years After Derailment

  15. Methane: 4.3 Years After Derailment

  16. Benzene: 4.3 Years After Derailment SOURCE ZONE C2H5OH: never detected by us CH3CO2H: 5-100 mg/L NO3-N: ND in most wells SO42-: 2 – 3 mg/L Fe2+: >10 mg/L Mn2+: ND H2S: ND

  17. Cambria, Minnesota November 22, 2006 ~24,877 Gs of d-ethanol released 12,500 Gs recovered No soil excavation

  18. Methane: 0.5 Years After Derailment

  19. Methane: 2 Years After Derailment SOURCE ZONE C2H5OH : 120 µg/L – 0.16% CH3CO2H : <3,090 mg/L C6H6: ~50 – 900 µg/L D.O.: < 2 mg/L SO42-: generally < 5 mg/L Fe2+: > 10 mg/L H2S: ND

  20. South Hutchinson, Kansas August 31, 2005 Tanker held 28,488 Gs of ethanol 28,000 Gs were released

  21. South Hutchinson, Kansas

  22. D. Oxygen: 1 Year After Derailment

  23. D. Oxygen: 3.5 Years After Derailment

  24. Methane: 1 Year After Derailment

  25. Methane: 1.3 Years After Derailment

  26. Methane: 2 Years After Derailment

  27. Methane: 2.8 Years After Derailment

  28. Methane: 3.5 Years After Derailment SOURCE ZONE C2H5OH : <5 - 240,000 µg/L C6H6: 100 – 560 µg/L

  29. Acetate: 3.5 Years After Derailment SOURCE ZONE H2: 3 – 50 nmoles Fe2+: >10 mg/L Mn2+: ND H2S: usually ND NO3-N: <1.5 mg/L SO42-: ~45 – 100 mg/L

  30. Observations of and Explanations for Ethanol’s Unconventional Behavior • Ethanol accumulates & persists in the collapsed capillary fringe (CF) and some may be released to gw after 2 years. • Buoyant ethanol (sg = 0.79 g/cc) floats above the water table. • A protective biofilm coating develops around the ethanol delaying anaerobic degradation and production of methane. • Ethanol concentrations may remain toxic to microbial attenuators within the envelope. • Methane continues to be produced years after the release.

  31. Hypothesis for Ethanol’s Persistence in the Source Zone

  32. Future Research • A controlled ethanol release test site with about 10 feet to groundwater is needed. • The site should be fully instrumented with volatile traps, gas probes, lysimeters, neutron probe tubes, down-hole camera tubes, and multilevel samplers. • The study will focus on reactions in the CF. • Concentrations of ethanol, methane & hydrogen will be measured routinely by students. • Geoprobe™ cores and biotraps will be used to monitor changes in the microbial community as indicated by chemical indicator changes. • The site will allow improved quantification of the ethanol leached to the CF and its persistence in the CF.

  33. Acknowledgements Bruce Bauman, API John Landwehr, Pinnacle Engineering Shane Jensen, UNL Nebraska Ethanol Board

  34. Thank You! rspalding1@unl.edu

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