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

3. Problems Overriding Concern Overriding Concern The new regulatory limit is 5 ug/L. The new regulatory limit is 5 ug/L. Specific Problems Specific Problems Removing such low levels of Se Removing such low levels of Se Differing chemistries of aqueous forms Differing chemistries of aqueous forms Selenate, SeO 4 -2, Se(VI) Selenate, SeO 4 -2, Se(VI) Selenite, SeO 3 -2, Se(IV) Selenite, SeO 3 -2, Se(IV)

6. Typical Southern West Virginia Mine Water pH = 7.1 pH = 7.1 [Se] = 13 ug/L [Se] = 13 ug/L [Fe] = 0.15 mg/L [Fe] = 0.15 mg/L [SO 4 -2 ] = 980 mg/L [SO 4 -2 ] = 980 mg/L Alkalinity = 235 mg/L as CaCO 3 Alkalinity = 235 mg/L as CaCO 3

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

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

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

10. Reduction with Iron Metal SeO 4 -2 +Fe(0) => Fe(II,III) +Se(0) SeO 4 -2 +Fe(0) => Fe(II,III) +Se(0) SeO 3 -2 +Fe(0) => Fe(II,III) +Se(0) SeO 3 -2 +Fe(0) => Fe(II,III) +Se(0)

12. Iron Forms

13. Apparatus 1

14. Operation, Side

15. Operation, Top

16. Iron Afterwards

17. Selenium Removal

18. Exponential Decay

19. Se Removal, 6-12 Hours

20. Rate of Se Removal Interval ug Se/hr 0-1 hour 24 0-8 hours 5.8 0-12 hours 4.9 6-12 hours 3

21. Other Changes Trial 1 Time (hrs) Iron (mg/L) Manganese (mg/L) 0<0.05<0.01 246.70.29

22. Apparatus 2

23. Packed, before

24. Packed, during

25. Pipe Filter

26. Recycle

27. Selenium Removal 2

28. Other Changes Trial 2 Time (hrs) Iron (mg/L) Manganese (mg/L) 00.07<0.01 243.00.48

29. Iron After Trial 2

30. Catenary Field System

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

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