Geochemical Modeling to Evaluate Remediation …...Geochemical Modeling to Evaluate Remediation...

ldquo

ldquo

ndashndash

Geochemical Modeling to Evaluate Remediation Charles Cravottandash1 Options for Iron-Laden Mine Discharges

Geochemical Modeling to Evaluate Remediation Options for Iron-Laden Mine Discharges

Charles Chuckrdquo Cravotta III US Geological Survey

Pennsylvania Water Science Center cravottausgsgov

AlAl3+3+

FeFe2+2+ Fe Fe3+3+

MnMn2+2+ ActiveActivePassivePassive

TREATMENT OF COAL MINETREATMENT OF COAL MINE DRAINAGEDRAINAGE

Increase pHIncrease pHoxioxidatdatiionon withwith nnaatuturalral susubbsstratestrates ampamp mmiicrobial activitycrobial activity

ReactReactiions slons slowow

LarLargge area fe area footprintootprint

LoLow mainw maintentenaannccee

Summary Aqueous geochemical tools using PHREEQC have been developed by USGS for OSMRErsquos AMDTreatrdquo cost-analysis software

Iron-oxidation kinetics model considers pH-dependent abiotic and biologgical rate laws pplus effects of aeration rate on the pH and concentrations of CO2 and O2

Limestone kinetics model considers solution chemistry plus the effects of surface area of limestone fragments

Potential water quality from various treatments can be considered for feasibility and benefitscosts analysis

ACTIVE TREATMENTACTIVE TREATMENT

28 ndash aeration no chemicals (Ponds) 21 caustic soda (NaOH) used 40 lime (CaO Ca(OH)2) used 6 ndash flocculent or oxidant used 4 ndash limestone (CaCO3) used

Increase pHIncrease pHoxioxidatdatiionon withwith aeratioaerationn ampoamporr iindustndustrriiaall chemchemiicalcalss

Reactions fReactions faastst efefffiicientcient

MModeratoderatee areaarea ffootootpriprinntt

HiHigh mgh maaiinntteenancenance

Vertical Flow Limestone BedsVertical Flow Limestone Beds Bell CollieryBell Colliery

PPAASSIVESSIVE TREATREATMENTTMENT Limestone Dissolution

O2 Ingassing CO2 Outgassing

Fe(II) Oxidation amp Fe(III) Accumulation

PPiinene FFoorestrest ALALDD ampamp WWeettllaandsnds SilvSilverer CreekCreek WWeetlantlanddss

PASSIVE TREATMENT

Pine Forest ALD amp WetlandsPine Forest ALD amp Wetlands Silver Creek WetlandsSilver Creek Wetlands

p

A Anthrac te M ne D scharges

B B tum nous M ne Discharges

AMDTreat


i i i

0

5

10

15

20

25

30

35

40

2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5

Fre

quency

in p

erc

ent

N=41

pH field

pH lab (aged)

BIMODAL pH FREQUENCY DISTRIBUTION

pH increases after ldquooxidationrdquo of net alkaline

water (CO2 outgassing) HCO3

- = CO2 (gas) + OH-

Anthracite AMD

20 25 30 35 40 45 50 55 60 65 70 75 80 85

i i i

0

5

10

15

20

25

30

35

40

20 25 30 35 40 45 50 55 60 65 70 75 80 85

pH

Fre

quency

in p

erc

ent

N=99 pH field

pH lab (aged)pH decreases after ldquooxidationrdquo

of net acidic water (Fe oxidation and hydrolysis)

Fe2+ + 025 O2 + 25 H2O rarr Fe(OH)3 + 2 H+

Bituminous AMD

ldquoPHREEQ-N-AMDTREATrdquo httpamdosmregov

AMDTreat is a computer application for estimating abatement costs for AMD (acidic or alkaline mine

drainage)

AMDTreat is maintained by OSMREby OSMRE

The current version of AMDTreat 50+ is being recoded from FoxPro to

C++ to facilitate its use on computer systems running

Windows 10 The PHREEQC geochemical models described below

will be incorporated to run with the recoded program

consideration of kinetics of gas exchange rates and

ignores effects of changing pH on iron oxidation rate

AMDTreatAMDTreat 50+50+

CausticCaustic AdditionAdditionmdashmdash

StSt MichaelsMichaels DischargeDischarge

AMDTreat 50+lnk

Escape Presentation

ldquoNewrdquo PHREEQC Kinetics Models for AMDTreat 50+

FeII oxidation model that utilizes established rate equations for gas exchange and pH-dependent iron oxidation and that can be associated with commonly

sed aeration de icessteps (incl ding decarbonation)used aeration devicessteps (including decarbonation)

Limestone dissolution model that utilizes established rate equation for calcite dissolution and that can be adjusted for surface area of commonly used aggregate particle sizes

AMDTREAT 50+ bull With the ldquoPHREEQC chemical titration toolrdquo

AMDTreat 50+ has capability to estimate

Quantity and cost of caustic chemicals to attain a target pH (without and with pre-aeration)

Chemistry of treated effluent after reactions and

Volume of sludge produced as the sum of precipitated metal hydroxides plus unreacted chemicals

AMDTREAT 50+ bull PHREEQ-N-AMDTreat ldquochemical titration

toolrdquo accurately relates caustic addition pH and metals solubility hellip but

assumes instantaneous complete reactions without


KINETICS OF IRON OXIDATIONKINETICS OF IRON OXIDATION ndashndash pH amppH amp GASGAS EXCHANGEEXCHANGE EFFECTSEFFECTS

(1996)

Iron Oxidation Kinetics are pH Dependent (abiotic and microbial processes can be involved)

(Kirby et al 1999)

Cbact is concentration of iron-oxidizing bacteria in mgL expressed as dry weight of bacteria (28E-13 gcell or 28E-10 mgcell )

The AMDTreat FeII oxidation kinetic model uses most probable number of iron-oxidizing bacteria per liter (MPNbact)

Cbact = 150 mgL is equivalent to MPNbact = 53E11 where Cbact = MPNbact middot(28E-10)

Minutes

Hours

Days

Months

Abiotic Homogeneous Fe(II) Oxidation Rate (model emphasizes pH)

Between pH 5 and 8 the Fe(II) oxidation rate increases by

100x for each pH unit increase

At a given pH the rate increases by 10x for a 15 degC increase Using the activation energy of 23 kcalmol with the

Fe2+Fe(OH)2 0

Fe(OH)1+

Years

log kT1 = log kT2 + Ea (2303 R) middot (1T2 - 1T1)

At [O2] = 026 mM (pO2 = 021 atm) and 25degC Open circles (o) from Singer amp Stumm (1970) and solid circles (bull) from Millero et al (1987)

Dashed lines are estimated rates for the various dissolved Fe(II) species

energy of 23 kcalmol with the Arrhenius equation the rate

can be adjusted for temperature

Extrapolation of homogeneous rate law -d[Fe(II)]dt = k1middot[Fe(II)]middot[O2]middot[H+]-2

k1 = 3 x 10-12 molLmin

Effects of O2 Ingassing and CO2 Outgassing

on pH and Fe(II) Oxidation Rates

Batch Aeration Tests at Oak Hill Boreholes

(summer 2013)(summer 2013)

Control Not Aerated Aerated H2O2 Addition

PHREEQC Coupled Kinetic Model of CO2 Outgassing amp Homogeneous Fe(II) OxidationmdashOak Hill Boreholes

pH FeII

kLCO2a = 000056 s-1

Dissolved CO2 Dissolved O2

kLCO2a = 000011 s-1

kLCO2a = 000022 s-1

kLO2a = 000023 s-1

kLO2a = 00007 s-1kLO2a = 00012 s-1kLCO2a = 000001 s-1

kLO2a = 000002 s-1

CO2 Outgassing is Proportional to O2 Ingassing (model specifies first-order rates for outin gassing)

-d[C]dt = kLCamiddot([C] - [C]S) exponential asymptotic approach to steady state

Atmospheric equilibrium

kLCO2a = 000056 s-1

kLCO2a = 000011 s-1

kLCO2a = 000022 s-1

kLCO2a = 000001 s-1


Aerated

Not Aerated

00014

00012

00010

00008

00006

00004

00002

00000

y = 243x + 000 Rsup2 = 096

kLa [O2] vs kLa [CO2]

00000 00001 00002 00003 00004 00005 00006

1st Order CO2 outgassing rate constant (1s)

1st

Ord

er O

2 in

gass

ing

raate

con

stan

t (1

s)


New Iron Oxidation Rate Model for ldquoAMDTreatrdquo (combines abiotic and microbial oxidation kinetics)

The homogeneous oxidation rate law (Stumm and Lee 1961 Stumm and Morgan 1996) expressed in terms of [O2] and H+ (=10-pH) describes the abiotic oxidation of dissolved Fe(II)

-d[Fe(II)]dt = k1middot[Fe(II)]middot[O2]middotH+-2

The heterogeneous oxidation rate law describes the catalytic abiotic oxidation of sorbed Fe(II) on precipitated Fe(III) oxyhydroxide surfaces where (Fe(III)) is the Fe(III) oxyhydroxide concentration expressed as Fe in mgL (Dempsey et al 2001 Dietz and Dempsey 2002)

-d[Fe(II)]dt = k2 (Fe(III)) middot[Fe(II)]middot[O2]middotH+-1

The microbial oxidation rate law describes the catalytic biological oxidation of Fe(II) by acidophilic microbes which become relevant at pH lt 5 (Pesic et al 1989 Kirby et al 1999)

-d[Fe(II)]dt = kbio middot Cbact middot[Fe(II)]middot[O2]middotH+

where kbio is the rate constant in L3mgmol2s Cbact is the concentration of iron-oxidizing bacteria in mgL (dry weight) [ ] indicates aqueous concentration in molL

New Iron Oxidation Rate Model for ldquoAMDTreatrdquomdash PHREEQC Coupled Kinetic Models of CO2 Outgassing

amp Fe(II) Oxidation

CO2 outgassing rate in sec-1

Duration of aeration (time for reaction) TimeSecs 28800 is 8 hrs

Kinetic variables can be adjusted including CO2 outgassing and O2

ingassing rates plus abiotic and microbial FeII oxidation rates Constants are temperature corrected

Adjustment CO2 outgassing rate

Adjustment O2 ingassing rate (x kLaCO2)

Adjustment abiotic homogeneous rate

Adjustment abiotic heterogeneous rate FeIIexe Iron oxidizing bacteria microbial rate

Calcite saturation limit

Hydrogen peroxide added

1 Aer3 kLCO2a = 000056 s-1

Aer1 kLCO2a = 000011 s-1 Aer2 kLCO2a = 000022 s-1

Aer0 kLCO2a = 000001 s-1

User may estimate Fe2 from Fe and pHAdjustment to H2O2 rate

plus TIC from alkalinity and pH And Option to specify FeIII recirculation

specify H2O2 or recirculation of FeIII Output includes pH solutes net acidity TDS SC and precipitated solids

multiply Femg by 00090 to get [H2O2]

Estimated CO2 Outgassing amp O2 Ingassing Rate Constants for Various Treatment Technologies

Slow

Fast

Slow

kLa_20 = (LN((C1-CS)(C2-CS))t) (10241(TEMPC - 20)) where C is CO2 or O2 Dissolved O2 temperature and pH were measured using submersible electrodes Dissolved CO2 was computed from alkalinity pH and temperature data

New Module For AMDTreat mdash PHREEQC Coupled Kinetic Models of CO2 Outgassing

amp Fe(II) Oxidation with Caustic Pre-Treatment

CO2 outgassing rate

Option to adjust initial pH with caustic Variable CO2 outgassing and O2

ingassing rates apply Can choose to adjust initial pH with caustic The required quantity of caustic is reported in units used by AMDTreat


Adjustment O2 ingassing rate (x kLaCO2) Caustic+FeIIexe


Adjustment abiotic heterogeneous rate

Iron oxidizing bacteria Kinetic variables including CO2 Calcite saturation limit

Hydrogen peroxide added outgassing and O2 ingassing rates plus Adjustment to H2O2 rate abiotic and microbial FeII oxidation

Option to specify FeIII recirculation rates can be adjusted by user In addition to caustic chemicals hydrogen peroxide and recirculation of FeIII solids

multiply Femg by 00090 to get [H2O2] can be simulated

Fast

Revised AMDTreat Chemical Cost Module mdash Caustic Titration with Pre-Aeration (Decarbonation) PHREEQC Coupled Kinetic Models of CO2 Outgassing amp Fe(II) Oxidation

Original option for no aeration plus new option for kinetic pre-aeration (wwo hydrogen peroxide) that replaces original equilibrium aeration

Duration of pre-aeration in sec Dropdown kLa

Allows selection and evaluation of key variables that affect chemical usage efficiency

Adjustment CO2 outgassing rate (x kLaCO2)


CO2 outgassing rate constant in sec-1


Adjustment to H2O2 rate


PHREEQTitration_StMichaelsexe


Dropdown kLa

KINETICS OFKINETICS OF LIMESTONELIMESTONE DISSOLUTIONDISSOLUTION ndashndash pH COpH CO22 and and

SURFACE AREASURFACE AREA EFFECTSEFFECTS


Limestone Dissolution Rate Model for AMDTreat (ldquoPWPrdquo model emphasizes pH and CO2)

r = (k1bullaH+ + k2bullaH2CO3 + k3bullaH2O) - k4bullaCa2+bullaHCO3shy

According to Plummer Wigley and Parkhurst (1978) the rate of CaCO3

dissolution is a function of three forward (dissolution) reactions

CaCO3 + H+ rarr Ca2 + + HCO3 - k1

CaCO3 + H2CO3 rarr Ca2 + + 2 HCO3 - k2

CaCO3 + H2O rarr Ca2 + + HCO3 - + OH- k3

and the backward (precipitation) reaction

Ca2 + + HCO3 -rarr CaCO3 + H+ k4

Although H+ H2CO3 and H2O reaction with calcite occur simultaneously the forward rate is dominated by a single species in the fields shown More than one species contributes significantly to the forward rate in the gray stippled area Along the lines labeled 1 2 and 3 the forward rate attributable to one species balances that of the other two

Limestone Dissolution Rate Model for AMDTreat (generalized expression corrects for surface area)

Appelo and Postma (2005) give a generalized rate expression for calcite dissolution that considers physical characteristics of the system as well as solution chemistry

R = k bull ( A V ) bull ( 1 ndash Ω )n

where A is calcite surface area V is volume of solution Ω is saturation state (IAPK = 10SIcc) and k and n are empirical coefficients that are obtained by fitting observed rates

For the ldquoPWPrdquo model applied to 1 liter solution the overall rate becomes

R = (k1bullaH+ + k2bullaH2CO3 + k3bullaH2O) bull ( A ) bull (1 - 10(n bull SIcc))

Plummer and others (1978) reported the forward rate constants as a function of temperature (T in K) in millimoles calcite per centimeter squared per second (mmolcm2s)

log k1 = 0198 ndash 444 T


log k3 = -586 ndash 317 T for T lt 298 log k3 = -110 ndash1737 T for T gt 298

Limestone Dissolution Rate Model for AMDTreat (surface area correction for coarse aggregate)

Plummer Wigley and Parkhurst (1978) reported unit surface area (SA) of 445 and 965 cm2g for ldquocoarserdquo and ldquofinerdquo particles respectively used for empirical testing and development of PWP rate model These SA values are 100 times larger than those for typical limestone aggregate Multiply cm2g by 100 gmol to get surface area (A) units of cm2mol used in AMDTreat rate model

New Module For AMDTreat mdash PHREEQC Kinetic Model of Limestone Dissolution

TimeSecs 7200 is 2 hrs

Surface area cm2mol

Equilibrium approach

Mass available

Multiply surface area (SA) in cm2g by 100 to get SAcc in cm2mol

Calcite dissolution rate model of Plummer Wigley and Parkhurst (PWP 1978) Empirical testing and development of PWP rate model based on ldquocoarserdquo and ldquofinerdquo calcite particles with surface areas of 445 and 965 cm2g respectively

LimestonePWPexe

Surface area and exponential corrections permit application to larger particle sizes (045 to 144 cm2g) used in treatment systems

New Module For AMDTreat mdash PHREEQC Coupled Kinetic Models of Limestone

Dissolution amp Fe(II) Oxidation Rate models for calcite dissolution CO2

outgassing and O2 ingassing and FeII oxidation are combined to evaluate possible reactions in passive treatment systems

CO2 outgassing rate

Surface area


Mass available





Iron oxidizing bacteria

Limestone+FeIIexeAdjustment O2 ingassing rate (x kLaCO2)



Can simulate limestone treatment followed by gas exchange and FeII oxidation in an aerobic pond or aerobic wetland or the independent treatment steps (not in sequence)

Sequential steps Variable detention times adjustable CO2 outgassing rates limestone surface area temperature and FeIII

PHREEQC Coupled Kinetic Models Sequential Steps Limestone Dissolution + Fe(II) Oxidation

Pine Forest ALD + Aerobic Wetlands

Can simulate passive treatment by anoxic or oxic limestone bed open (limestone) channels or spillways aerobic cascades ponds and wetlands

Next slide

Limestone+FeIIseqexe


PHREEQC Coupled Kinetic Models Sequential Stepsmdash Pine Forest ALD + Aerobic Wetlands

77

33

44

55 66

88 99

00

11

22

33

Step Treatment 1 ALD 2 Riprap 3 Pond 4 Cascade 5 Wetland 6 Cascade 7 l dWetland 8 Cascade 9 Wetland

Limestone+FeIIseq_PineFor151212exe

LS+FeIIseq_kineticssel - Shortcutlnk

PineForest_Field_151212txlsx - Shortcutlnk

Sequential steps Pre-treatment with caustic andor peroxide and for each subsequent step variable detention times adjustable CO2 outgassing rates limestone surface area temperature and FeIII

PHREEQC Coupled Kinetic Models Sequential Steps Caustic + Limestone Dissolution + Fe(II) Oxidation

Silver Creek Aerobic Wetlands

Can simulate active treatment including chemical addition or aeration or passive treatment including anoxic or oxic limestone bed open (limestone) channels or spillways aerobic cascades ponds and wetlands

Next slide

Caustic+Limestone+FeIIseqexe

1122

33 44

55

00

Step Treatment 1 Pond 2 Aeration 3 Pond 4 Aeration 5 Pond 6 Riprap 7 Wetland 8 Riprap 9 Wetland

88

66 77

SilverCrk_Field_160808txlsx - Shortcutlnk

99

Caustic+LS+FeIIseq_SilCr160808exe

9 Wetland

Caustic+LS+FeIIseq_kineticssel - Shortcutlnk

References Burrows JE Cravotta CA III Peters SC (2017) Enhanced Al and Zn removal from coal-mine drainage during rapid oxidation and precipitation

of Fe oxides at near-neutral pH Applied Geochemistry 78 194-210 Cravotta CA III (2003) Size and performance of anoxic limestone drains to neutralize acidic mine drainage Journal of Environmental Quality

32 1277-1289 Cravotta CA III (2015) Monitoring field experiments and geochemical modeling of Fe(II) oxidation kinetics in a stream dominated by net-

alkaline coal-mine drainage Pennsylvania USA Applied Geochemistry 62 96-107 Cravotta CA III Means B Arthur W McKenzie R Parkhurst DL (2015) AMDTreat 50+ with PHREEQC titration module to compute caustic

chemical quantity effluent quality and sludge volume Mine Water and the Environment 34 136-152 Davison W Seed G (1983) The kinetics of the oxidation of ferrous iron in synthetic and natural waters Geochimica et Cosmochimica Acta 47

67-79 Dempsey BA Roscoe HC Ames R Hedin R Byong-Hun J (2001) Ferrous oxidation chemistry in passive abiotic systems for the treatment of

mine drainage Geochemistry Exploration Environment Analysis 1 81-88 Dietz JM Dempsey BA (2002) Innovative treatment of alkaline mine drainage using recirculated iron oxides in a complete mix reactor

American Society of Mining and Reclamation 19th Annual Meeting p 496-516 Geroni JN Cravotta CA III Sapsford DJ (2012) Evolution of the chemistry of Fe bearing waters during CO2 degassing Applied Geochemistry

27 2335-2347 Kirby CS Elder-Brady JA (1998) Field determination of Fe2+ oxidation rates in acid mine drainage using a continuously-stirred tank reactor

Applied Geochemistry 13 509-520 Kirby CS Thomas HM Southam G Donald R (1999) Relative contributions of abiotic and biological factors in Fe(II) oxidation in mine

drainage Applied Geochemistry 14 511-530 Kirby CS Dennis A Kahler A (2009) Aeration to degas CO2 increase pH and increase iron oxidation rates for efficient treatment of net

alkaline mine drainage Applied Geochemistry 24 1175-1184 Langmuir D (1997) Aqueous environmental geochemistry Prentice Hall New Jersey USA 600 p (especially p 58-62) Parkhurst DL Appelo CAJ (2013) Description of input and examples for PHREEQC version 3mdashA computer program for speciation batch-

reaction one-dimensional transport and inverse geochemical calculations USGS Techniques Methods 6-A43 497 p Pesic B Oliver DJ Wichlacz P (1989) An electrochemical method of measuring the oxidation rate of ferrous to ferric iron with oxygen in the

presence of Thiobacillus ferrooxidans Biotechnology and Bioengineering 33 428-439 Plummer LN Wigley ML Parkhurst DL (1978) The kinetics of calcite dissolution in CO2-water systems at 5o to 60oC and 00 to 10 atm CO2

American Journal of Science 278 179-216 Rathbun RE (1998) Transport behavior and fate of volatile organic compounds in streams USGS Professional Paper 1589 151 p Singer PC Stumm W (1970) Acidic mine drainage the rate-determining step Science 167 121-123 Stumm W Lee GF (1961) Oxygenation of ferrous iron Industrial and Engineering Chemistry 53 143-146 Stumm W Morgan JJ (1996) Aquatic chemistry--chemical equilibria and rates in natural waters (3rd) New York Wiley-Interscience 1022 p

(especially p 682-691)

SOLUBILITY AND SORPTIONSOLUBILITY AND SORPTION CONTROL OF TRACE ELEMENTSCONTROL OF TRACE ELEMENTS

PHREEQC Coupled Kinetic Models Sequential Stepsmdash Silver Creek Aerobic Wetlands Conclusions

Geochemical kinetics tools using PHREEQC have been developed to evaluate mine effluent treatment options

Graphical and tabular output indicates the pH and solute concentrations in effluent

By adjusting kinetic variables or chemical dosing various passive andor active treatment strategies can be simulated

AMDTreat cost-analysis software can be used to evaluate the feasibility for installation and operation of treatments that produce the desired effluent quality

100

10

1

20


Solubilities of Metal Hydroxides Fe Limited by FeII-Carbonate and FeIII-Hydroxide and Sulfate SolubilitiesAl(OH)3 0

10000000 Dissolved Fe is Solid phaseFe(OH)3 FeII(OH)2predominantly FeII 1000000 Fe(OH)2 2

100000 MnO2METALS HAVE FeIICO3

Co

nc

en

tra

tioo

n

Me

TO

T (

mg

L)

-lo

g [

Fe T

FeeI

I amp

FeI

II (m

ol

L)]

10000 LOW SOLUBLITY Mn(OH)2 4 AT NEUTRAL TO Cu(OH)21000 ALKALINE pH

6

8

Pb(OH)2

FeIII 8O8(OH)45(SO4)175Ni(OH)2

Zn(OH)2Zn(OH)2

Co(OH)2

01 Cd(OH)2

8

FeIII(OH)3

10 Fe(OH)3 (amorph) FeIIIOOH Goethite FeOOHAlIII001 Mg(OH)2

FeII MnII Ca(OH)2 12 Schwertmannite x=175 Aqueous phase0001 FeIII

Temp = 25oCSiderite FeCO300001 FeIII amp MnIV ARE LEAST SOLUBLE000001

pSO4 TOT = 23

MnIV 14 Fe(OH)2 pK+ = 430

OXIDATION RATE 0000001 IS LIMITING

00000001 0 2 4 6 8 10 12 14

pH

SORPTION OF CATIONS ON ldquoSORPTION OF CATIONS ON ldquoHHFOrdquoFOrdquo 100 0

90 10

2080

70 30

pCO2 = 20 AMD140 [FeTOT]

16 2 4 6 8

pH

SORPTION OFSORPTION OF ANIONS ON ldquoANIONS ON ldquoHHFOrdquoFOrdquo 100 0

90 10

80 20

70 30

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T D

ISSS

OLV

ED

PE

RC

EN

T D

ISSS

OLV

ED 60 40 60 40

50 5050 50

40 60 SO4-2

30 70AsO4-3

Pb+2

CrIII50 5050 50

Cu+2

Zn+240 60

Cd+2 30 70Co+2

Ni+2 SeO3-280 20Mn+2

10 Ba+2 90 10 CrO4-2

90 Sr+2 PO4-3

0 3 4 5 6 7 8 9 10

100 11

0 3 4 5 6 7 8 9 10

100 11

pH pH

10

80

p

A Anthrac te M ne D scharges

B B tum nous M ne Discharges

AMDTreat


i i i

0

5

10

15

20

25

30

35

40

2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5

Fre

quency

in p

erc

ent

N=41

pH field

pH lab (aged)

BIMODAL pH FREQUENCY DISTRIBUTION

pH increases after ldquooxidationrdquo of net alkaline

water (CO2 outgassing) HCO3

- = CO2 (gas) + OH-

Anthracite AMD

20 25 30 35 40 45 50 55 60 65 70 75 80 85

i i i

0

5

10

15

20

25

30

35

40

20 25 30 35 40 45 50 55 60 65 70 75 80 85

pH

Fre

quency

in p

erc

ent

N=99 pH field

pH lab (aged)pH decreases after ldquooxidationrdquo

of net acidic water (Fe oxidation and hydrolysis)

Fe2+ + 025 O2 + 25 H2O rarr Fe(OH)3 + 2 H+

Bituminous AMD

ldquoPHREEQ-N-AMDTREATrdquo httpamdosmregov

AMDTreat is a computer application for estimating abatement costs for AMD (acidic or alkaline mine

drainage)

AMDTreat is maintained by OSMREby OSMRE

The current version of AMDTreat 50+ is being recoded from FoxPro to

C++ to facilitate its use on computer systems running

Windows 10 The PHREEQC geochemical models described below

will be incorporated to run with the recoded program

consideration of kinetics of gas exchange rates and

ignores effects of changing pH on iron oxidation rate

AMDTreatAMDTreat 50+50+

CausticCaustic AdditionAdditionmdashmdash

StSt MichaelsMichaels DischargeDischarge

AMDTreat 50+lnk

Escape Presentation

ldquoNewrdquo PHREEQC Kinetics Models for AMDTreat 50+

FeII oxidation model that utilizes established rate equations for gas exchange and pH-dependent iron oxidation and that can be associated with commonly

sed aeration de icessteps (incl ding decarbonation)used aeration devicessteps (including decarbonation)

Limestone dissolution model that utilizes established rate equation for calcite dissolution and that can be adjusted for surface area of commonly used aggregate particle sizes

AMDTREAT 50+ bull With the ldquoPHREEQC chemical titration toolrdquo

AMDTreat 50+ has capability to estimate

Quantity and cost of caustic chemicals to attain a target pH (without and with pre-aeration)

Chemistry of treated effluent after reactions and

Volume of sludge produced as the sum of precipitated metal hydroxides plus unreacted chemicals

AMDTREAT 50+ bull PHREEQ-N-AMDTreat ldquochemical titration

toolrdquo accurately relates caustic addition pH and metals solubility hellip but

assumes instantaneous complete reactions without



(1996)


(Kirby et al 1999)




Minutes

Hours

Days

Months





Fe2+Fe(OH)2 0

Fe(OH)1+

Years














pH FeII

kLCO2a = 000056 s-1


kLCO2a = 000011 s-1

kLCO2a = 000022 s-1

kLO2a = 000023 s-1


kLO2a = 000002 s-1




kLCO2a = 000056 s-1

kLCO2a = 000011 s-1

kLCO2a = 000022 s-1

kLCO2a = 000001 s-1


Aerated

Not Aerated

00014

00012

00010

00008

00006

00004

00002

00000

y = 243x + 000 Rsup2 = 096


00000 00001 00002 00003 00004 00005 00006


1st

Ord

er O

2 in

gass

ing

raate

con

stan

t (1

s)






















1 Aer3 kLCO2a = 000056 s-1


Aer0 kLCO2a = 000001 s-1






Slow

Fast

Slow




CO2 outgassing rate











Fast













Dropdown kLa




























Surface area cm2mol


Mass available



LimestonePWPexe





CO2 outgassing rate

Surface area


Mass available














Next slide




77

33

44

55 66

88 99

00

11

22

33









Next slide


1122

33 44

55

00


88

66 77


99


9 Wetland
























100

10

1

20





Co

nc

en

tra

tioo

n

Me

TO

T (

mg

L)

-lo

g [

Fe T

FeeI

I amp

FeI

II (m

ol

L)]


6

8

Pb(OH)2


Zn(OH)2Zn(OH)2

Co(OH)2

01 Cd(OH)2

8

FeIII(OH)3




pSO4 TOT = 23



00000001 0 2 4 6 8 10 12 14

pH


90 10

2080

70 30


16 2 4 6 8

pH


90 10

80 20

70 30

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T D

ISSS

OLV

ED

PE

RC

EN

T D

ISSS

OLV

ED 60 40 60 40

50 5050 50

40 60 SO4-2

30 70AsO4-3

Pb+2

CrIII50 5050 50

Cu+2

Zn+240 60

Cd+2 30 70Co+2

Ni+2 SeO3-280 20Mn+2

10 Ba+2 90 10 CrO4-2

90 Sr+2 PO4-3

0 3 4 5 6 7 8 9 10

100 11

0 3 4 5 6 7 8 9 10

100 11

pH pH

10

80



(1996)


(Kirby et al 1999)




Minutes

Hours

Days

Months





Fe2+Fe(OH)2 0

Fe(OH)1+

Years














pH FeII

kLCO2a = 000056 s-1


kLCO2a = 000011 s-1

kLCO2a = 000022 s-1

kLO2a = 000023 s-1


kLO2a = 000002 s-1




kLCO2a = 000056 s-1

kLCO2a = 000011 s-1

kLCO2a = 000022 s-1

kLCO2a = 000001 s-1


Aerated

Not Aerated

00014

00012

00010

00008

00006

00004

00002

00000

y = 243x + 000 Rsup2 = 096


00000 00001 00002 00003 00004 00005 00006


1st

Ord

er O

2 in

gass

ing

raate

con

stan

t (1

s)






















1 Aer3 kLCO2a = 000056 s-1


Aer0 kLCO2a = 000001 s-1






Slow

Fast

Slow




CO2 outgassing rate











Fast













Dropdown kLa




























Surface area cm2mol


Mass available



LimestonePWPexe





CO2 outgassing rate

Surface area


Mass available














Next slide




77

33

44

55 66

88 99

00

11

22

33









Next slide


1122

33 44

55

00


88

66 77


99


9 Wetland
























100

10

1

20





Co

nc

en

tra

tioo

n

Me

TO

T (

mg

L)

-lo

g [

Fe T

FeeI

I amp

FeI

II (m

ol

L)]


6

8

Pb(OH)2


Zn(OH)2Zn(OH)2

Co(OH)2

01 Cd(OH)2

8

FeIII(OH)3




pSO4 TOT = 23



00000001 0 2 4 6 8 10 12 14

pH


90 10

2080

70 30


16 2 4 6 8

pH


90 10

80 20

70 30

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T D

ISSS

OLV

ED

PE

RC

EN

T D

ISSS

OLV

ED 60 40 60 40

50 5050 50

40 60 SO4-2

30 70AsO4-3

Pb+2

CrIII50 5050 50

Cu+2

Zn+240 60

Cd+2 30 70Co+2

Ni+2 SeO3-280 20Mn+2

10 Ba+2 90 10 CrO4-2

90 Sr+2 PO4-3

0 3 4 5 6 7 8 9 10

100 11

0 3 4 5 6 7 8 9 10

100 11

pH pH

10

80






















1 Aer3 kLCO2a = 000056 s-1


Aer0 kLCO2a = 000001 s-1






Slow

Fast

Slow




CO2 outgassing rate











Fast













Dropdown kLa




























Surface area cm2mol


Mass available



LimestonePWPexe





CO2 outgassing rate

Surface area


Mass available














Next slide




77

33

44

55 66

88 99

00

11

22

33









Next slide


1122

33 44

55

00


88

66 77


99


9 Wetland
























100

10

1

20





Co

nc

en

tra

tioo

n

Me

TO

T (

mg

L)

-lo

g [

Fe T

FeeI

I amp

FeI

II (m

ol

L)]


6

8

Pb(OH)2


Zn(OH)2Zn(OH)2

Co(OH)2

01 Cd(OH)2

8

FeIII(OH)3




pSO4 TOT = 23



00000001 0 2 4 6 8 10 12 14

pH


90 10

2080

70 30


16 2 4 6 8

pH


90 10

80 20

70 30

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T D

ISSS

OLV

ED

PE

RC

EN

T D

ISSS

OLV

ED 60 40 60 40

50 5050 50

40 60 SO4-2

30 70AsO4-3

Pb+2

CrIII50 5050 50

Cu+2

Zn+240 60

Cd+2 30 70Co+2

Ni+2 SeO3-280 20Mn+2

10 Ba+2 90 10 CrO4-2

90 Sr+2 PO4-3

0 3 4 5 6 7 8 9 10

100 11

0 3 4 5 6 7 8 9 10

100 11

pH pH

10

80


























Surface area cm2mol


Mass available



LimestonePWPexe





CO2 outgassing rate

Surface area


Mass available














Next slide




77

33

44

55 66

88 99

00

11

22

33









Next slide


1122

33 44

55

00


88

66 77


99


9 Wetland
























100

10

1

20





Co

nc

en

tra

tioo

n

Me

TO

T (

mg

L)

-lo

g [

Fe T

FeeI

I amp

FeI

II (m

ol

L)]


6

8

Pb(OH)2


Zn(OH)2Zn(OH)2

Co(OH)2

01 Cd(OH)2

8

FeIII(OH)3




pSO4 TOT = 23



00000001 0 2 4 6 8 10 12 14

pH


90 10

2080

70 30


16 2 4 6 8

pH


90 10

80 20

70 30

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T D

ISSS

OLV

ED

PE

RC

EN

T D

ISSS

OLV

ED 60 40 60 40

50 5050 50

40 60 SO4-2

30 70AsO4-3

Pb+2

CrIII50 5050 50

Cu+2

Zn+240 60

Cd+2 30 70Co+2

Ni+2 SeO3-280 20Mn+2

10 Ba+2 90 10 CrO4-2

90 Sr+2 PO4-3

0 3 4 5 6 7 8 9 10

100 11

0 3 4 5 6 7 8 9 10

100 11

pH pH

10

80



77

33

44

55 66

88 99

00

11

22

33









Next slide


1122

33 44

55

00


88

66 77


99


9 Wetland
























100

10

1

20





Co

nc

en

tra

tioo

n

Me

TO

T (

mg

L)

-lo

g [

Fe T

FeeI

I amp

FeI

II (m

ol

L)]


6

8

Pb(OH)2


Zn(OH)2Zn(OH)2

Co(OH)2

01 Cd(OH)2

8

FeIII(OH)3




pSO4 TOT = 23



00000001 0 2 4 6 8 10 12 14

pH


90 10

2080

70 30


16 2 4 6 8

pH


90 10

80 20

70 30

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T D

ISSS

OLV

ED

PE

RC

EN

T D

ISSS

OLV

ED 60 40 60 40

50 5050 50

40 60 SO4-2

30 70AsO4-3

Pb+2

CrIII50 5050 50

Cu+2

Zn+240 60

Cd+2 30 70Co+2

Ni+2 SeO3-280 20Mn+2

10 Ba+2 90 10 CrO4-2

90 Sr+2 PO4-3

0 3 4 5 6 7 8 9 10

100 11

0 3 4 5 6 7 8 9 10

100 11

pH pH

10

80

100

10

1

20





Co

nc

en

tra

tioo

n

Me

TO

T (

mg

L)

-lo

g [

Fe T

FeeI

I amp

FeI

II (m

ol

L)]


6

8

Pb(OH)2


Zn(OH)2Zn(OH)2

Co(OH)2

01 Cd(OH)2

8

FeIII(OH)3




pSO4 TOT = 23



00000001 0 2 4 6 8 10 12 14

pH


90 10

2080

70 30


16 2 4 6 8

pH


90 10

80 20

70 30

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T A

DDS

OR

BE

D

PE

RC

EN

T D

ISSS

OLV

ED

PE

RC

EN

T D

ISSS

OLV

ED 60 40 60 40

50 5050 50

40 60 SO4-2

30 70AsO4-3

Pb+2

CrIII50 5050 50

Cu+2

Zn+240 60

Cd+2 30 70Co+2

Ni+2 SeO3-280 20Mn+2

10 Ba+2 90 10 CrO4-2

90 Sr+2 PO4-3

0 3 4 5 6 7 8 9 10

100 11

0 3 4 5 6 7 8 9 10

100 11

pH pH

10

80

Geochemical Modeling to Evaluate Remediation …...Geochemical Modeling to Evaluate Remediation...

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Transcript of Geochemical Modeling to Evaluate Remediation …...Geochemical Modeling to Evaluate Remediation...