Selenium Removal from Mine Selenium Removal from Mine WatersWaters

Raymond J. Lovett, Ph.D.Raymond J. Lovett, Ph.D.Environmental ChemistEnvironmental Chemist

ShipShaper, LLPShipShaper, LLPMorgantown, WVMorgantown, WV

SUPPORTSUPPORT

National Mine Land Reclamation Center, National Mine Land Reclamation Center, West Virginia UniversityWest Virginia University

United States Office of Surface MiningUnited States Office of Surface Mining

Magnum Coal CompanyMagnum Coal Company Catenary CoalCatenary Coal

Typical Southern West Typical Southern West Virginia Mine WaterVirginia Mine Water

[Se] = 13 ug/L[Se] = 13 ug/L[Fe] = 0.15 mg/L[Fe] = 0.15 mg/L[SO[SO44

-2-2]] = 980 mg/L= 980 mg/L

Alkalinity = 235 mg/L as CaCOAlkalinity = 235 mg/L as CaCO33

pH = 7.1pH = 7.1

ProblemsProblems

Overriding ConcernOverriding ConcernRegulatory limit near 5 ug/LRegulatory limit near 5 ug/L

Specific Problems for TreatmentSpecific Problems for TreatmentLow level of SeLow level of SeDiffering chemistriesDiffering chemistries

Selenate, SeOSelenate, SeO44-2-2, Se(VI), Se(VI)

Selenite, SeOSelenite, SeO33-2-2, Se(IV), Se(IV)

Selenium Removal Selenium Removal DifficultiesDifficulties

Different dissolved speciesDifferent dissolved speciesNo direct precipitation chemistriesNo direct precipitation chemistriesReduction of selenate is difficult Reduction of selenate is difficult

(slow)(slow)Sulfate may interfereSulfate may interfere

Treatment System Treatment System ObjectivesObjectives

Effluent maximally 5 ug/L Effluent maximally 5 ug/L SeSe

Low installation costLow installation costLow operating costLow operating costPassivePassive

Demonstrated ChemistriesDemonstrated Chemistries

Adsorption or co-precipitation by Adsorption or co-precipitation by Fe(III) Fe(III) hydroxides hydroxides

Biological (bacterial reduction)Biological (bacterial reduction) Reverse osmosisReverse osmosis Reduction by Fe(0) Reduction by Fe(0)

Reduction with Iron MetalReduction with Iron Metal

SeOSeO44-2-2 +Fe(0) => Fe(II,III) +Se(0) +Fe(0) => Fe(II,III) +Se(0)

SeOSeO33-2-2 +Fe(0) => Fe(II,III) +Se(0) +Fe(0) => Fe(II,III) +Se(0)

Selenium Species on IronSelenium Species on Iron

Field TrialField TrialCatenary CoalCatenary Coal

Test in a real settingTest in a real setting

Real, variable input chemistryReal, variable input chemistry

Continuous Se InputContinuous Se Input

Field Trial SystemField Trial System

Field Trial SystemField Trial System

0

0.005

0.01

0.015

0.02

0.025

0.03

0 50 100 150 200 250

Removal of Selenium with Iron

Influent SeEffluent SeRegulatory Limit

Se

, m

g/L

Days

0

0.005

0.01

0.015

0.02

0.025

0.03

0 5 10 15 20

Selenium Removal versus Flow

Influent SeEffluent SeRegulatory Limit

Se

, m

g/L

Flow, gpm

0

0.005

0.01

0.015

0.02

0.025

0.03

0 5 10 15 20

Selenium Removal versus Residence Time

Influent SeEffluent SeRegulatory Limit

Se

, m

g/L

Residence Time, hr

45

50

55

60

65

70

75

80

85

0 50 100 150 200 250

Temperature Profile for Trial Period

Te

mp

era

ture

, F

Days

0

0.005

0.01

0.015

0.02

0.025

0.03

45 50 55 60 65 70 75 80 85

Selenium Removal versus Temperature

Influent SeEffluent SeRegulatory Limit

Se

, m

g/L

Temperature, F

Catenary Post Trial 1Catenary Post Trial 1

Catenary Post Trial 2Catenary Post Trial 2

Catenary Post Trial 3Catenary Post Trial 3

Catenary Post Trial 4Catenary Post Trial 4

Catenary Post Trial 5Catenary Post Trial 5

Reduction with Iron MetalReduction with Iron Metal

PotentialPotentialRemoval of selenate and seleniteRemoval of selenate and selenitePassivePassive

ProblemsProblemsIron Oxides/ Dissolved Fe, MnIron Oxides/ Dissolved Fe, MnExhaustionExhaustionPassivationPassivationExpense (surface area)Expense (surface area)

BacterialBacterialEstimated CostEstimated Cost

Flow = 285 gpmFlow = 285 gpm Capital Cost = $7.2 to $10 millionCapital Cost = $7.2 to $10 million O&M = UnknownO&M = Unknown

Reverse OsmosisReverse OsmosisEstimated CostEstimated Cost

Flow = 200 gpmFlow = 200 gpm Capital Costs = $1.2 millionCapital Costs = $1.2 million O&M = $5.85 million/yearO&M = $5.85 million/year

Iron HydroxideIron HydroxideEstimated CostEstimated Cost

Flow = 200 gpmFlow = 200 gpm Capital Cost = $0.69 to 1.03 millionCapital Cost = $0.69 to 1.03 million O&M = $1.39 million/yearO&M = $1.39 million/year

Zerovalent IronZerovalent IronEstimated CostEstimated Cost

Flow = 250 gpm*Flow = 250 gpm* Capital costs = $478,000Capital costs = $478,000 O&M = $150,000 to $300,000O&M = $150,000 to $300,000

* Gravity flow, includes surge* Gravity flow, includes surge

ConclusionsConclusions

Iron metal removes selenate and Iron metal removes selenate and selenite, but currently requires long selenite, but currently requires long

contact timescontact times Manganese and iron generatedManganese and iron generated Temperature sensitive (?)Temperature sensitive (?) Less expensive than other methodsLess expensive than other methods