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Bench Scale Tests of Selenium Removal from Mine Waters

This article presents bench scale tests conducted to investigate the removal of selenium from mine waters. The study identified the difficulties in removing low levels of selenium and explored various chemistries and technologies for effective removal. The results showed that reduction with iron metal has potential for removing selenite and selenate, although contact efficiency needs improvement.

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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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