Selenium Removal from Mine Waters

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• Selenium Removal from Mine Waters
• Raymond J. Lovett, Ph.D.
• Environmental Chemist
• ShipShaper, LLP
• Morgantown, WV

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SUPPORT

• National Mine Land Reclamation Center, West
  Virginia University
• United States Office of Surface Mining
• Magnum Coal Company
• Catenary Coal

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Typical Southern West Virginia Mine Water

• Se 13 ug/L
• Fe 0.15 mg/L
• SO4-2 980 mg/L
• Alkalinity 235 mg/L as CaCO3
• pH 7.1

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Problems

• Overriding Concern
• Regulatory limit near 5 ug/L
• Specific Problems for Treatment
• Low level of Se
• Differing chemistries
• Selenate, SeO4-2, Se(VI)
• Selenite, SeO3-2, Se(IV)

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Selenium Removal Difficulties

• Different dissolved species
• No direct precipitation chemistries
• Reduction of selenate is difficult (slow)
• Sulfate may interfere

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Treatment System Objectives

• Effluent maximally 5 ug/L Se
• Low installation cost
• Low operating cost
• Passive

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Demonstrated Chemistries

• Adsorption or co-precipitation by Fe(III)
  hydroxides
• Biological (bacterial reduction)
• Reverse osmosis
• Reduction by Fe(0)

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Reduction with Iron Metal

• SeO4-2 Fe(0) gt Fe(II,III) Se(0)
• SeO3-2 Fe(0) gt Fe(II,III) Se(0)

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Selenium Species on Iron
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Field TrialCatenary Coal

• Test in a real setting
• Real, variable input chemistry
• Continuous Se Input

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Field Trial System
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Field Trial System
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Catenary Post Trial 1
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Catenary Post Trial 2
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Catenary Post Trial 3
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Catenary Post Trial 4
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Catenary Post Trial 5
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Reduction with Iron Metal

• Potential
• Removal of selenate and selenite
• Passive
• Problems
• Iron Oxides/ Dissolved Fe, Mn
• Exhaustion
• Passivation
• Expense (surface area)

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BacterialEstimated Cost

• Flow 285 gpm
• Capital Cost 7.2 to 10 million
• OM Unknown

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Reverse OsmosisEstimated Cost

• Flow 200 gpm
• Capital Costs 1.2 million
• OM 5.85 million/year

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Iron HydroxideEstimated Cost

• Flow 200 gpm
• Capital Cost 0.69 to 1.03 million
• OM 1.39 million/year

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Zerovalent IronEstimated Cost

• Flow 250 gpm
• Capital costs 478,000
• OM 150,000 to 300,000
• Gravity flow, includes surge

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Conclusions

• Iron metal removes selenate and selenite, but
  currently requires long contact times
• Manganese and iron generated
• Temperature sensitive (?)
• Less expensive than other methods