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

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

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

Problems Overriding Concern Specific Problems for Treatment 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)

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

Treatment System Objectives Effluent maximally 5 ug/L Se Low installation cost Low operating cost Passive

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

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

Selenium Species on Iron

Field Trial Catenary Coal Test in a real setting Real, variable input chemistry Continuous Se Input

Field Trial System

Field Trial System

Catenary Post Trial 1

Catenary Post Trial 2

Catenary Post Trial 3

Catenary Post Trial 4

Catenary Post Trial 5

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

Bacterial Estimated Cost Flow = 285 gpm Capital Cost = $7.2 to $10 million O&M = Unknown

Reverse Osmosis Estimated Cost Flow = 200 gpm Capital Costs = $1.2 million O&M = $5.85 million/year

Iron Hydroxide Estimated Cost Flow = 200 gpm Capital Cost = $0.69 to 1.03 million O&M = $1.39 million/year

Zerovalent Iron Estimated Cost Flow = 250 gpm* Capital costs = $478,000 O&M = $150,000 to $300,000 * Gravity flow, includes surge

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