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Bench Scale Tests of Selenium Removal from Mine Waters

Bench Scale Tests of Selenium Removal from Mine Waters. Raymond J. Lovett* ShipShaper, LLP Morgantown, WV West Virginia Mine Drainage Task Force Symposium April 10-11, 2007. Support. National Mine Land Reclamation Center, West Virginia University, Paul Ziemkiewicz

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Bench Scale Tests of Selenium Removal from Mine Waters

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  1. Bench Scale Tests of Selenium Removal from Mine Waters Raymond J. Lovett* ShipShaper, LLP Morgantown, WV West Virginia Mine Drainage Task Force Symposium April 10-11, 2007

  2. Support • National Mine Land Reclamation Center, West Virginia University, Paul Ziemkiewicz • United States Office of Surface Mining via OSM-WVU Cooperative Agreement

  3. Problems • Overriding Concern • The new regulatory limit is 5 ug/L. • Specific Problems • Removing such low levels of Se • Differing chemistries of aqueous forms • Selenate, SeO4-2, Se(VI) • Selenite, SeO3-2, Se(IV)

  4. pH = 7.1 [Se] = 13 ug/L [Fe] = 0.15 mg/L [SO4-2]= 980 mg/L Alkalinity = 235 mg/L as CaCO3 Typical Southern West Virginia Mine Water

  5. Selenium Removal Difficulties • Different dissolved species • No direct precipitation chemistries • Reduction of selenate is difficult • Sulfate may interfere

  6. Objectives • Low installation cost • Removal to 5 ug/L or less • Low operating cost • Passive

  7. Demonstrated Chemistries • Adsorption or co-precipitation by Fe(III) hydroxides • Reduction by Fe(0) • Reduction (adsorption) by Fe(II,III) mixed hydroxides (green rust) • Biological (bacterial reduction/metabolism)

  8. Reduction with Iron Metal • SeO4-2 +Fe(0) => Fe(II,III) +Se(0) • SeO3-2 +Fe(0) => Fe(II,III) +Se(0)

  9. Iron Forms

  10. Apparatus 1

  11. Operation, Side

  12. Operation, Top

  13. Iron Afterwards

  14. Selenium Removal

  15. Exponential Decay

  16. Se Removal, 6-12 Hours

  17. Rate of Se Removal

  18. Other ChangesTrial 1

  19. Apparatus 2

  20. Packed, before

  21. Packed, during

  22. Pipe Filter

  23. Recycle

  24. Selenium Removal 2

  25. Other ChangesTrial 2

  26. Iron After Trial 2

  27. Catenary Field System

  28. Reduction with Iron Metal • Potential • Removal of selenate and selenite • Barrier • Passive • Problems • Iron Oxides/ Dissolved Fe, Mn • Exhaustion • Passivation • Expense (surface area)

  29. Conclusions • Iron metal removes selenite and selenate, but currently requires long contact times • Contact efficiency needs to be improved • Iron and manganese release complicates

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