Post on 03-Jan-2016
description
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