Bench Scale Tests of Bench Scale Tests of Selenium Removal from Selenium Removal from

Mine WatersMine Waters

Raymond J. Lovett*Raymond J. Lovett*ShipShaper, LLPShipShaper, LLPMorgantown, WVMorgantown, WV

West Virginia Mine Drainage Task Force West Virginia Mine Drainage Task Force SymposiumSymposium

April 10-11, 2007April 10-11, 2007

SupportSupport

National Mine Land Reclamation Center, National Mine Land Reclamation Center, West Virginia University, Paul ZiemkiewiczWest Virginia University, Paul Ziemkiewicz

United States Office of Surface MiningUnited States Office of Surface Mining

via OSM-WVU Cooperative Agreementvia OSM-WVU Cooperative Agreement

ProblemsProblems

Overriding ConcernOverriding Concern The new regulatory limit is 5 ug/L.The new regulatory limit is 5 ug/L.

Specific ProblemsSpecific Problems Removing such low levels of SeRemoving such low levels of Se Differing chemistries of aqueous formsDiffering chemistries of aqueous forms

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

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

Typical Southern West Virginia Typical Southern West Virginia Mine WaterMine Water

pH = 7.1pH = 7.1 [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

Selenium Removal Selenium Removal DifficultiesDifficulties

Different dissolved speciesDifferent dissolved species No direct precipitation chemistriesNo direct precipitation chemistries Reduction of selenate is difficultReduction of selenate is difficult Sulfate may interfereSulfate may interfere

ObjectivesObjectives

Low installation costLow installation cost Removal to 5 ug/L or lessRemoval to 5 ug/L or less Low operating costLow operating cost PassivePassive

Demonstrated ChemistriesDemonstrated Chemistries

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

Reduction by Fe(0) Reduction by Fe(0) Reduction (adsorption) by Fe(II,III) Reduction (adsorption) by Fe(II,III)

mixed hydroxides (green rust)mixed hydroxides (green rust) Biological (bacterial Biological (bacterial

reduction/metabolism)reduction/metabolism)

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)

Iron FormsIron Forms

Apparatus 1Apparatus 1

Operation, SideOperation, Side

Operation, TopOperation, Top

Iron AfterwardsIron Afterwards

Selenium RemovalSelenium Removal

0

20

40

60

80

100

0 5 10 15 20 25

Selenium Total, ug/L

Selenium Dissolved, ug/L

Sel

eniu

m T

ota

l, u

g/L

Time (hrs)

Exponential DecayExponential Decay

20

30

40

50

60

70

0 2 4 6 8 10 12 14

Se

len

ium

To

tal,

ug

/L

Time (hrs)

Se Removal, 6-12 HoursSe Removal, 6-12 Hours

0

5

10

15

20

25

30

0 2 4 6 8 10 12 14

Se

len

ium

To

tal,

ug

/L

Time (hrs)

Rate of Se RemovalRate of Se RemovalIntervalInterval ug Se/hrug Se/hr

0-1 hour0-1 hour 2424

0-8 hours0-8 hours 5.85.8

0-12 hours0-12 hours 4.94.9

6-12 hours6-12 hours 33

Other ChangesOther ChangesTrial 1Trial 1

Time (hrs)Time (hrs) Iron (mg/L)Iron (mg/L) Manganese Manganese (mg/L)(mg/L)

00 <0.05<0.05 <0.01<0.01

2424 6.76.7 0.290.29

Apparatus 2Apparatus 2

Packed, beforePacked, before

Packed, duringPacked, during

Pipe FilterPipe Filter

RecycleRecycle

Selenium Removal 2Selenium Removal 2

0

10

20

30

40

50

60

70

0 2 4 6 8 10 12 14

Se

Co

nce

ntr

atio

n (

ug

/L)

Time (hrs)

Other ChangesOther ChangesTrial 2Trial 2

Time (hrs)Time (hrs) Iron (mg/L)Iron (mg/L) Manganese Manganese (mg/L)(mg/L)

00 0.070.07 <0.01<0.01

2424 3.03.0 0.480.48

Iron After Trial 2Iron After Trial 2

Catenary Field SystemCatenary Field System

Reduction with Iron MetalReduction with Iron Metal

PotentialPotential Removal of selenate and seleniteRemoval of selenate and selenite BarrierBarrier PassivePassive

ProblemsProblems Iron Oxides/ Dissolved Fe, MnIron Oxides/ Dissolved Fe, Mn ExhaustionExhaustion PassivationPassivation Expense (surface area)Expense (surface area)

ConclusionsConclusions

Iron metal removes selenite and Iron metal removes selenite and selenate, but currently requires long selenate, but currently requires long contact timescontact times

Contact efficiency needs to be improvedContact efficiency needs to be improved

Iron and manganese release complicatesIron and manganese release complicates