Bench scale tests of selenium removal from mine waters
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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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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

  • United States Office of Surface Mining

    via OSM-WVU Cooperative Agreement


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)


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


Selenium Removal Difficulties

  • Different dissolved species

  • No direct precipitation chemistries

  • Reduction of selenate is difficult

  • Sulfate may interfere


Objectives

  • Low installation cost

  • Removal to 5 ug/L or less

  • Low operating cost

  • Passive


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)


Reduction with Iron Metal

  • SeO4-2 +Fe(0) => Fe(II,III) +Se(0)

  • SeO3-2 +Fe(0) => Fe(II,III) +Se(0)


Iron Forms


Apparatus 1


Operation, Side


Operation, Top


Iron Afterwards


Selenium Removal


Exponential Decay


Se Removal, 6-12 Hours


Rate of Se Removal


Other ChangesTrial 1


Apparatus 2


Packed, before


Packed, during


Pipe Filter


Recycle


Selenium Removal 2


Other ChangesTrial 2


Iron After Trial 2


Catenary Field System


Reduction with Iron Metal

  • Potential

    • Removal of selenate and selenite

    • Barrier

    • Passive

  • Problems

    • Iron Oxides/ Dissolved Fe, Mn

    • Exhaustion

    • Passivation

    • Expense (surface area)


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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