Neutralization of Acid Mine Drainage Using Stabilized Flue Gas Desulfurization Material W. Wolfe1, C.-M. Cheng1, R. Baker1, T. Butalia1, J. Massey-Norton2 1The Ohio State University, 2American 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

Weir # 4

Location

Weir #1Weir #2

Weir #3Weir #4

North PondSouth Pond

pH

0

2

4

6

8

10

AMD Weir #1 AMD Weir #2

AMD Weir #3

AMD Weir #4

South Pond

North Pond

OGS- UGMs GA-031, GA-011

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

1000 ft

2000 ft

3000 ft 4000 ft

Approximate Highwall Location

Start Point

1000 ft Approximate Measurement of Distance

Drainage-way for AMD Discharge during Excavation

Scale:

N Proposed Road Entrance from Plant

MW-96155

MW-96159 Proposed Pomeroy Monitoring Well Sites

Proposed Deep Monitoring Well Site

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

Accumulative testing time, minutes

0 200 400 600 800 1000 1200 1400 1600 1800

pH

2

4

6

8

10

12

Hyd

raul

ic H

ead,

ft

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

LL1LL2LL3OutletHydraulic HeadAMD pH

Change of AMD pH after Contacting Fixated FGD Material

L/S Ratio

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

pH

2

4

6

8

10

12

LL1LL2LL3Outlet

Change of AMD pH after Contacting Fixated FGD Material at Different L/S ratio

AMD pH=3.14

Mineral Composition of Gavin Fixated FGD Material

Hannebachite (CaSO3 0.5 H2O) Portlandite (Ca(OH)3 )

Hematite (Fe2O3 ) Magnetite (Fe3O4 ) Quartz (SiO2 )

Mullite (3Al2O3 2SiO2 ) Maghemite (Fe2O3) Ettringite (Ca6Al2(SO4)3(OH)12·26H2O)

Chemical Reactions between AMD and Fixated FGD Material

Fixated FGD (g)/ AMD (L)

Neutralization of AMD

OHCaHOHCa 22

2 22)( +→+ ++

Portlandite

OHSOCaAl

12HO·26H(OH))(SOAlC 2123426

22

423 38362 +++

→+−++

+

Ettringite

OHFeHOFe 23

32 626 +→+ ++

Iron oxides

OHFeFeHOFe 223

43 828 ++→+ +++

Formation of potential secondary minerals

Iron hydroxides, Chrysotile (Mg3Si2O5), diaspore (AlHO2), bixbyite (Mn2O3), barite (BaSO4)

Carbonates

Neutralization Capacity Estimated by Geochemical Modeling

Gallon AMD/Pound Fixated FGD

0 20 40 60

pH

2

4

6

8

10

12

14

AMD 3.18

3.7% Lime4.7% Limegeochemical model

Laboratory Column Testing

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)

Simulating AMD neutralization process under similar percolation process as reclamation

Date/Time

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

pH

7.0

7.5

8.0

8.5

9.0

9.5

10.0

Column IColumn II

delay depletion of portlandite/enttringite

Change of AMD pH after Contacting Fixated FGD Material in Flow Through Column Test

L/S Ratio

0 20 40 60 80 100 120 140 160 180

pH

6

7

8

9

10

pH a

t inl

et

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Gallon of AMD/pound of Fixated FGD

0 3 6 9 12 15 18

Column IColumn IIColumn I inletColumn II inlet

Change of AMD pH after Contacting Fixated FGD Material in Flow Through Column Test

as a Function of L/S Ratio

L/S Ratio

0 20 40 60

Sul

fate

, mg/

L

1000

2000

3000

4000

5000

6000

Column IColumn IIColumn I inletColumn II inlet

Change of Sulfate in AMD

Independent of flow rate

due to change of AMD chemical property

Constituent

K B Mo Sr Sulfate Ca Ba V pH

Nor

mal

ized

Con

cent

ratio

n (C

i/CA

MD)

0.1

1

10

100

1000

Column IIColumn I

Bench Scale Outlet

Constituents with Elevated Levels

Constituent

Cr Cd Si Co Zn Ni Al Mn Fe

Nor

mal

ized

Con

cent

ratio

n (C

i i/CA

MD)

0.00001

0.0001

0.001

0.01

0.1

1

10

Column IIColumn I

Bench Scale Outlet

Elements with Decreased Concentration

Constituent

Na Cl Hg Sb Tl Se As Cu Be Pb

Nor

mal

ized

Con

cent

ratio

n (C

i i/CA

MD)

0.01

0.1

1

10

100

1000

Column IIColumn I

Bench Scale Outlet

Elements Showing First Flush Phenomenon

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

Future Works Full-scale demonstration 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

L/S Ratio

0.0 0.5 1.0 1.5 2.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0

Ars

enic

, mg/

L

0.008

0.010

0.012

0.014

0.016

0.018

0.020

0.022

Column 1Column 2Inlets (under detection limt)Bench Scale LL1Bench Scale LL2Bench Scale LL3Bench Scale Outlet

First Flush of Arsenic

L/S Ratio

0.0 0.5 1.0 1.5 10.0 20.0 30.0 40.0 50.0 60.0 70.0

Mer

cury

, ng/

L

0

10

20

30

40

50

Column 1Column 2L/S ratio_Full vs Hg L/S ratio Half vs Hg Bench Scale LL1Bench Scale LL2 Bench Scale LL3 Bench Scale Outlet

First Flush of Mercury