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Low-pH Fe(II) oxidation can improve passive treatment of acid mine drainage

Low-pH Fe(II) oxidation can improve passive treatment of acid mine drainage. Bill Burgos Civil and Environmental Engineering Pennsylvania State University. Acknowledgements.

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Low-pH Fe(II) oxidation can improve passive treatment of acid mine drainage

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  1. Low-pH Fe(II) oxidation can improve passive treatment of acid mine drainage Bill Burgos Civil and Environmental Engineering Pennsylvania State University

  2. Acknowledgements John Senko, Melanie Lucas, Trinh DeSa, Mickey Adelman (Lafayette) – Penn State University, Civil and Environmental Engineering Mary Ann Bruns, Pauline Wanjugi – Penn State University, Crop and Soil Sciences Project Number PA DEP_AMD 42(0420)102.1 NSF EMSI Program CHE-0431328

  3. Research Objectives • study the microbial communities and mineral precipitates associated with low-pH Fe(II) oxidation in Appalachian coal mine drainage • transfer knowledge to the design and operation of more effective passive treatment systems • engineer the system to produce minerals for industrial reuse

  4. Presentation Outline • Field chemistry • Microbial characterizations • Laboratory experiments • Field implementation

  5. Low-pH Fe(II) Oxidation Field Sites Gum Boot: “high rate” Rapid Fe(II) oxidation Fridays-2: “low rate” Little Fe(II) oxidation

  6. Emergent water chemistry

  7. Gum Boot AMD Emergence X 18 m AMD flows underground X X 30 m AMD re-emerges X 79 m X AMD Flow X X To Gum Boot Creek X = sampling point

  8. Gum Boot – view from bottom of hill

  9. Gum Boot – top of “aeration terrace”

  10. AMD Emergence Fridays-2 X AMD Flow X = sampling point X 3 m X 10 m X X Creek Flow 10 m X

  11. Fridays-2 – view upstream towards iron mound

  12. Seasonal Water Chemistry Blue markers – winter Red markers – fall Dark green – spring Light green – summer Arrows at Fridays-2 are upstream and downstream locations downstream distance (m)

  13. Presentation Outline • Field chemistry • Microbial characterizations • Laboratory experiments • Field implementation

  14. 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 Enumeration of Fe(II)-oxidizing bacteria Serial dilution of a soil suspension Spread on solid medium Count number of colonies formed Assume 1 CFU = 1 cell So, 20 colonies on 10-4 plate = 2 x 105 CFU/ml

  15. ln(C/Co) Air Fe(II) (mM) Time (d) AMD w/ Fe2+ Time (d) Determination of first-order rate constants for Fe(II) oxidation at Gum Boot and Fridays-2 y = -1.6x - 0.08 R2 = 0.96 Fridays-2 or Gum Boot sediment

  16. Microbial Enumeration and Activity Fe(II)OB most abundant in regions where most Fe(II) oxidation is occurring Fastest rates of Fe(II) oxidation at Fridays-2 comparable to fastest rates at Gum Boot

  17. Bacteria with DNA Iron mound sample with four different kinds of bacteria Fridays-2 After PCR, each kind of bacteria yields a different band in the “community DNA fingerprint” DNA fingerprint with four different bands Gumboot Down Up kbp stream MWM 0 m 2 m 60 m 127 m 10 m stream 3 m 0 m 3000 1 2000 RISA profiles DNA bands 1 1 1500 2 1 2 2 3 1 3 1 1 2 4 2 3 4 2 1000 1 2 3 5 5 3 4 1 3 2 3 4 6 700

  18. DNA-based bacterial community characterization Microbial communities are distinctly different, yet potential for low-pH Fe(II) oxidation ~same. Therefore, relatively small fraction of community may be responsible for Fe(II) oxidation. 2% 9% 2% 6% 3% 6% 28% n = 34 n = 39 59% 74% 5% 3%

  19. Presentation Outline • Field chemistry • Microbial characterizations • Laboratory experiments • Field implementation

  20. Gas Mix Sampling Port Septum Headspace purged with O2, CO2, and N2 Air out Air in 500 mL synthetic AMD Sediment 25 grams sediment Batch Reactor Experiments Air out

  21. Batch Reactor Experimental Matrix

  22. Batch Reactor Results FR 10m sediments – 0.7% O2, 1.1% CO2, 98.2% N2

  23. Batch Reactor Results – Gum Boot

  24. Batch Reactor Results – Fridays-2

  25. Enumeration of Fe(II) Oxidizing Bacteria

  26. Rate Comparisons Abiotic and Biological Fe(II)(aq) Oxidation Rimstidt, 2004

  27. Batch Reactor Experimental Matrix 27

  28. Presentation Outline • Field chemistry • Microbial characterizations • Laboratory experiments • Field implementation

  29. Limestone ChannelPassive Treatment System • Mine operators must meet effluent standards • Fe <7, Mn< 5, pH 6-9 • Two type of treatment • Active Treatment (chemical) • Passive Treatment (limestone) Active Treatment Passive Treatment CaCO3 + H+ = Ca2+ + HCO3- Ca(OH)2 +2H+ = Ca2+ + 4H2O

  30. “emergent” AMD pH = 4.0 Fe(II) = 100 mg/L DO = 0 mg/L “aerated” AMD pH = 4.0 Fe(II) remains Fe(II) in absence of bio-catalyst DO > 2 mg/L “aerated” AMD pH = 4.0 Fe(II)  Fe(III) via bio-oxidation DO > 2 mg/L “aerated” AMD pH = 7.0 Fe(II)  Fe(III) rapid abiotic oxidation DO > 2 mg/L Spatial separation of iron oxidation/precipitation from alkalinity addition can improve performance

  31. Gum Boot – top of “aeration terrace”

  32. Upstream overview of Fridays-2, February 2006. Mound flow disrupted May 2006 – Thanks Jon!

  33. Upstream overview of Friday-2 05/09/07 mine pool “Original” Flowpath “Fresh” Flowpath new precipitates since 05/06

  34. All samples collected 05/09/07

  35. October 2006 Hughes Borehole discharge: 800 – 1,500 gallons per minute

  36. October 2006 Hughes Borehole

  37. October 2006 Hughes Borehole

  38. April 2008 Hughes Borehole

  39. May 2008 Hughes Borehole

  40. May 2008 Hughes Borehole

  41. On-Mound Channels Laboratory “Gutter” Reactors Hughes Borehole Sackett Building Penn State University

  42. Construction of “Aeration Terraces” • Design to mimic hydrologic characteristics of Gum Boot Run iron mound. • Maximize aeration and surface area. • Maximize residence time (ca. 15 – 60 min?) over iron mound sediments. • Construct as series of roughened steps. • Control system to produce minerals for industrial reuse.

  43. Thanks for your attention.

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