Neutralization of Acid Mine Drainage Using Stabilized Flue Gas Desulfurization Material W. Wolfe 1, C.-M. Cheng 1, R. Baker 1, T. Butalia 1, J. Massey-Norton 2 1 The Ohio State University, 2 American Electric Power
Stingy Run Fly Ash Impoundment
Reclamation of Fly Ash Impoundment
Highwalls and Pits in Stingy Run Impoundment
Sources of AMD into Stingy Run AMD Weir #4 North Pond AMD Weir #3 AMD Weir #1 AMD Weir #2 South Pond Weir # 4 10 8 6 ph 4 OGS- UGMs GA-031, GA-011 2 0 Weir #1 Weir #2 Weir #3 Weir #4 North Pond South Pond Location
Reclaiming using Fixated FGD Material Utilizing large volume of fixated flue gas desulfurization materials FGD by-product (calcium sulfite) stabilized with fly ash and lime Goals Encapsulate acid mine drainage (AMD) producing materials Neutralize AMD Re-contour highwalls Approaches Year I: field investigation; laboratory test; bench-scale study; numerical analysis of design approaches; background water monitoring Year II and III: permitting, water quality monitoring, construction of the demonstration project
Full-scale Demonstration N MW-96155 4000 ft 3000 ft Drainage-way for AMD Discharge during Excavation 2000 ft Proposed Road Entrance from Plant 1000 ft Proposed Pomeroy Monitoring Well Sites MW-96159 Start Point Proposed Deep Monitoring Well Site Scale: Approximate Highwall Location 1000 ft Approximate Measurement of Distance
Establishing Background Groundwater Quality
Groundwater Quality Monitoring
Establishing Background Surface Water Quality
Surface Water Quality Monitoring
Bench Scale Testing 1 4 ~2.5 tons
Bench Scale Testing Assessment of FGD saturation with tap and AMD waters in the absence and presence of geo-composite intrusion Optimizing geo-composite placement design to maximize contact between AMD and stabilized FGD material Monitoring change of water quality as tap/amd water percolates through the FGD mass under different hydraulic heads AMD was transported to the lab the day before each batch of test and continuously purged with nitrogen gas to prevent oxidation and carbonation
Bench Scale Testing
12 Change of AMD ph after Contacting Fixated FGD Material 2.2 2.0 10 1.8 ph 8 6 4 LL1 LL2 LL3 Outlet Hydraulic Head AMD ph 1.6 1.4 1.2 1.0 0.8 Hydraulic Head, ft 0.6 2 0 200 400 600 800 1000 1200 1400 1600 1800 0.4 Accumulative testing time, minutes
Change of AMD ph after Contacting Fixated FGD Material at Different L/S ratio 12 10 ph 8 6 LL1 LL2 LL3 Outlet 4 AMD ph=3.14 2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 L/S Ratio
Mineral Composition of Gavin Fixated FGD Material Hannebachite (CaSO 3 0.5 H 2 O) Portlandite (Ca(OH) 3 ) Hematite (Fe 2 O 3 ) Magnetite (Fe 3 O4 ) Quartz (SiO 2 ) Mullite (3Al 2 O 3 2SiO 2 ) Maghemite (Fe 2 O 3 ) Ettringite (Ca 6 Al 2 (SO 4 ) 3 (OH) 12 26H 2 O)
Chemical Reactions between AMD and Fixated FGD Material Neutralization of AMD Portlandite + 2+ Ca( OH ) 2 + 2H Ca + 2H 2O Ettringite C6 2 4 3 12 2 + Al (SO ) (OH) 26H O + 12H 2 4 3+ 2+ 2 Al + 6Ca + 3SO + 38H Iron oxides + 3+ Fe2O3 + 6 H 2Fe + 6H 2O + 3+ 2+ Fe O + 8 H 2Fe + Fe + H 2O 3 4 8 Carbonates 2 O Fixated FGD (g)/ AMD (L) Formation of potential secondary minerals Iron hydroxides, Chrysotile (Mg 3 Si 2 O 5 ), diaspore (AlHO 2 ), bixbyite (Mn 2 O 3 ), barite (BaSO 4 )
Neutralization Capacity Estimated by Geochemical Modeling 14 12 3.7% Lime 4.7% Lime geochemical model 10 ph 8 6 4 AMD 3.18 2 0 20 40 60 Gallon AMD/Pound Fixated FGD
Laboratory Column Testing Simulating AMD neutralization process under similar percolation process as reclamation Two columns with different L/S flow rates Column I: ~1.0 L/S per day Column II: ~2.0 L/S per day Monitoring change of AMD water quality with extended L/S ratio Column I: ~74 (9 gallons AMD/lb fixated FGD) Column II: ~147 (17 gallons AMD/lb fixated FGD)
Change of AMD ph after Contacting Fixated FGD Material in Flow Through Column Test 10.0 9.5 Column I Column II 9.0 ph 8.5 8.0 delay depletion of portlandite/enttringite 7.5 7.0 6/24/14 7/1/14 7/8/14 7/15/14 7/22/14 7/29/14 8/5/14 8/12/14 8/19/14 8/26/14 9/2/14 Date/Time
Change of AMD ph after Contacting Fixated FGD Material in Flow Through Column Test as a Function of L/S Ratio 10 5.0 9 Column I Column II Column I inlet Column II inlet 4.5 4.0 ph 8 3.5 ph at inlet 3.0 7 2.5 6 2.0 0 20 40 60 80 100 120 140 160 180 L/S Ratio 0 3 6 9 12 15 18 Gallon of AMD/pound of Fixated FGD
Change of Sulfate in AMD 6000 5000 Column I Column II Column I inlet Column II inlet Sulfate, mg/l 4000 3000 2000 Independent of flow rate due to change of AMD chemical property 1000 0 20 40 60 L/S Ratio
Constituents with Elevated Levels Normalized Concentration (C i /C AMD ) 1000 100 10 1 Column I Column II Bench Scale Outlet 0.1 K B Mo Sr Sulfate Ca Ba V ph Constituent
Elements with Decreased Concentration 10 Normalized Concentration (Ci i /C AMD ) 1 0.1 0.01 0.001 0.0001 Column I Column II Bench Scale Outlet 0.00001 Cr Cd Si Co Zn Ni Al Mn Fe Constituent
Elements Showing First Flush Phenomenon Normalized Concentration (Ci i /C AMD ) 1000 100 10 1 0.1 Column I Column II Bench Scale Outlet 0.01 Na Cl Hg Sb Tl Se As Cu Be Pb Constituent
Summary Mitigating AMD using fixated FGD material Re-contour unreclaimed highwalls and highwall pits Based on laboratory leaching study and geochemical model, one pound of Gavin fixated FGD material is able to neutralize approximately 20 gallons of AMD (~160 L/S) Change of AMD water quality Based on available data from column and bench-scale tests Constituents with elevated concentrations ph, sulfate, Ca, K, B, Mo, Ba, Sr, and V Elements with decreased concentrations Fe, Mn, Zn, Cd, Co, Cr, Ni, Si, and Al Elements with first flash phenomenon Na, Cl, Hg, Sb, As, Cu, Se, Tl, Li, and Pb
Future Works Laboratory column test Examining the environmental response beyond the neutralization capacity of the fixated FGD material Geochemical kinetic model Bench-scale reclamation module Optimizing placement of geocomposite drainage layer and fixated FGD material in the reclamation design Establishing AMD flow model Finalizing reclamation design
Full-scale demonstration Future Works Continuing on water quality monitoring Carrying out statistical and hydrogeochemical analyses of background water quality data Permit application Project site preparation/construction Backfilling of fixated FGD material Post reclamation water monitoring
First Flush of Arsenic Arsenic, mg/l 0.022 0.020 0.018 0.016 0.014 Column 1 Column 2 Inlets (under detection limt) Bench Scale LL1 Bench Scale LL2 Bench Scale LL3 Bench Scale Outlet 0.012 0.010 0.008 0.0 0.5 1.0 1.5 2.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 L/S Ratio
First Flush of Mercury 50 Mercury, ng/l 40 30 20 Column 1 Column 2 L/S ratio_full vs Hg L/S ratio Half vs Hg Bench Scale LL1 Bench Scale LL2 Bench Scale LL3 Bench Scale Outlet 10 0 0.0 0.5 1.0 1.5 10.0 20.0 30.0 40.0 50.0 60.0 70.0 L/S Ratio