SELENIUM TREATMENT ARCH-EASTERN, BIRCH MINE€¦ · 12/01/2016 · Arch-Eastern, Birch Mine In...
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SELENIUM TREATMENT ARCH-EASTERN, BIRCH MINE WEST VIRGINIA MINE DRAINAGE TASK FORCE SYMPOSIUM March 27, 2012 Conestoga-Rovers & Associates Arch Coal, Inc.
Transcript of SELENIUM TREATMENT ARCH-EASTERN, BIRCH MINE€¦ · 12/01/2016 · Arch-Eastern, Birch Mine In...
SELENIUM TREATMENT
ARCH-EASTERN, BIRCH MINE
WEST VIRGINIA MINE DRAINAGE TASK FORCE SYMPOSIUM
March 27, 2012
Conestoga-Rovers & Associates
Arch Coal, Inc.
Conestoga-Rovers & Associates (CRA)
• Al Meek
Arch Coal, Inc.
• Keith Odell
Bratton Farm
• Ben Faulkner
Arch-Eastern, Birch Mine
In March of 2011 a Consent Decree was entered by WVDEP requiring corrective action to comply with Selenium standard (i.e., 4.7 µg/l (average) and 8.2 µg/l (maximum )) at 10 discharge points on the Knight Ink surface mine.
A corrective action plan developed by Arch and CRA to establish the following:
• Establish design criteria for treatment of waters associated with discharge points identified in the Consent Decree
• Determine applicability of new and existing selenium treatment technologies
• Complete alternatives analysis of selenium treatment system options.
• Select Treatment Alternative
• Design and construct system
• Initial compliance by August 2012
Establishing Design Criteria
• Design Flow Rates • Hydrologic Modeling of Surface Runoff, Infiltration,
Evapotranspiration and Shallow Ground Water (pit floor discharge) — Developed Base Model (calibrated with weir data)
— Applied Base Model to 2010 rainfall
— Inserted 10yr, 24 hr. rain event in 2010 model year
• Design Selenium Concentration • Historical review of NPDES outfall monitoring
• Surface water runoff analysis
• Surface runoff and seep flow components of outfall concentrations
Hydrologic Modeling
Consisted of Three Separate Models
• Surface Runoff
• Infiltration/Evapotranspiration
• Pit Floor (Seepage flow)
Utilized the EPA developed Storm Water Management
Model (PCSWMM)
Conducted on-site flow monitoring to calibrate model.
Utilized 2010 rainfall data and inserted a 10 yr, 24 hour
event.
Hydrologic Modeling- Model Calibration
Input Parameters
90 deg. V-NotchV-Notch Rectangular Weir
Formula Q=4.28 C Tan (v-angle deg./2) (H + K)5/2Q=C(L-0.2H)H3/2
Q= Flow in CFS Q= Flow in CFS
K= Head correction Factor= 0.002903 C= Reference MSHA 3.33
Design ManualManual
H= head (ft)above bottom of V-Notch H= head (ft)
Tan (90/2) = 1 L= width rect.weir(FT) 4
C= Discharge Coeficient=0.5779
Head adjustment Factor (ft)0.49791
Weir Id-- Discharge 006 V-notch Rect Notch Total Total
Date Time Flow Flow Flow Flow
H (head ft) CFS CFS CFS GPM
2/13/2012 2:51:26 PM 0.242 0.073 0.000 0.073 32.9
2/13/2012 3:21:26 PM 0.237 0.070 0.000 0.070 31.4
2/13/2012 3:51:26 PM 0.246 0.076 0.000 0.076 34.3
2/14/2012 4:21:26 PM 0.247 0.077 0.000 0.077 34.8
2/14/2012 4:51:26 PM 0.245 0.076 0.000 0.076 34.1
2/14/2012 5:21:26 PM 0.251 0.080 0.000 0.080 36.1
2/15/2012 5:51:26 PM 0.250 0.079 0.000 0.079 35.6
2/15/2012 6:21:26 PM 0.255 0.084 0.000 0.084 37.5
2/15/2012 6:51:26 PM 0.256 0.084 0.000 0.084 37.9
2/16/2012 7:21:26 PM 0.252 0.082 0.000 0.082 36.6
2/16/2012 7:51:26 PM 0.253 0.082 0.000 0.082 36.8
2/16/2012 8:21:26 PM 0.254 0.083 0.000 0.083 37.0
Hydrologic Model- Model Calibration
ICG-Eastern- Weir Data
Blue-007, Yellow 021
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
20-A
pr
21-A
pr
22-A
pr
23-A
pr
24-A
pr
25-A
pr
26-A
pr
27-A
pr
28-A
pr
29-A
pr
30-A
pr
1-May
2-May
3-May
4-May
5-May
6-May
7-May
8-May
9-May
10-M
ay
11-M
ay
12-M
ay
13-M
ay
14-M
ay
15-M
ay
16-M
ay
17-M
ay
18-M
ay
19-M
ay
20-M
ay
21-M
ay
22-M
ay
23-M
ay
24-M
ay
25-M
ay
26-M
ay
27-M
ay
28-M
ay
29-M
ay
30-M
ay
31-M
ay
1-Ju
n
2-Ju
n
3-Ju
n
4-Ju
n
5-Ju
n
6-Ju
n
7-Ju
n
8-Ju
n
9-Ju
n
10-Jun
11-Jun
12-Jun
13-Jun
14-Jun
15-Jun
16-Jun
17-Jun
18-Jun
19-Jun
20-Jun
21-Jun
22-Jun
23-Jun
24-Jun
25-Jun
26-Jun
27-Jun
28-Jun
29-Jun
30-Jun
1-Ju
l
2-Ju
l
3-Ju
l
4-Ju
l
5-Ju
l
Date/time
Rain
fall
(in
ch
es)
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
1000.0
Flo
w (
GP
M)
Model Output- surface/seep flow (2010 rainfall)
by discharge
Date/Time Precipitation W002 W002 W002
Runoff Seep Flow Total Flow T. Acre Ft % runoff
M/d/yyyy (in) gpm gpm gpm per day of T. Flow
5/8/2010 0.28 0.0 43.9 43.9 0.19 0.00%
5/9/2010 0 20.4 84.2 104.5 0.46 19.47%
5/10/2010 0 0.0 57.2 57.2 0.25 0.00%
5/11/2010 0 0.0 39.8 39.8 0.18 0.00%
5/12/2010 0.22 0.0 29.0 29.0 0.13 0.00%
5/13/2010 1.66 14.2 53.7 67.9 0.30 20.91%
5/14/2010 0 2460.7 150.0 2610.8 11.54 94.25%
5/15/2010 0.47 0.0 145.4 145.4 0.64 0.00%
5/16/2010 0 60.9 217.2 278.2 1.23 21.90%
Modeling Summary by Discharge
10 yr 24 hr storm
Discharge Average Average Average Peak runoff Peak seep flow Total Peak
I.D. runoff (gpm) seep flow (gpm) total flow (gpm) gpm gpm gpm
001 77.5 86.8 164.3 5462.0 1041.5 6503.5
002 88.1 72.7 160.8 6810.7 167.6 6978.3
005 41.6 67.1 108.8 3602.7 225.5 3828.2
006 13.4 192.4 205.8 1032.9 429.3 1462.2
007 31.1 97.4 128.5 3582.1 472.9 4055.0
014 14.0 26.6 40.6 1057.3 102.4 1159.7
021 22.7 68.4 91.0 1525.4 168.9 1694.3
031 22.6 77.7 100.3 1281.1 894.7 2175.8
034**
036 19.3 23.6 42.9 719.6 239.5 959.2
Totals 330.3 712.7 1,043.0 25,073.9 3,742.4 28,816.3
** Discharges into 001, flow included in 001
Modeling Summary of Contributing Precipitation
Rainfall (2010)
Total inches
Runoff
Inches (%)
Seepage
Inches (%)
Evapotrans.
Inches (%)
45.87 10.10 (22%) 26.47(58%) 9.30 (20%)
Surface Runoff Pit Floor Total
Average
Gal/min./a
cre 0.5 1.4 1.9
Modeling Summary of Contributing Precipitation
Determining Design Se Concentrations
From 2010 DMR Data
Discharge Average Se Conc. 95th Percentile Se Conc. Maximum. Se Conc.
I.D. ug/l ug/l ug/l
001 4.59 11.13 17.50
002 8.38 20.03 34.90
005 6.97 10.40 11.60
006 2.10 5.95 15.10
007 6.21 13.34 20.50
014 2.47 6.80 9.00
021 9.66 16.34 32.90
031 6.72 15.94 21.00
034 3.82 9.50 10.60
036 13.25 20.45 21.20
µg/l µg/l µg/l
Basis-- 2010 rainfall Modeled (W. 10yr-24hr) and DMR Selenium Conc.Average Average Selenium (2010)
Average Flow Surface Runoff Seepage Flow Design Conc.
Discharge ID. gpm gpm gpm ug/l **
001 164.29 77.5 86.8 11.1
002 160.82 88.1 72.7 20
005 108.79 41.6 67.1 10.4
007 128.48 31.1 97.4 13.3
021 91.03 22.7 68.4 16.3
031 100.31 22.6 77.7 15.9
036 42.88 19.3 23.6 20.5
Totals 796.59 302.88 493.71
Weight Average 14.88
** 95 th Perentile Se concentrations
Treatment Design Basis
µg/l**
Arch-Eastern, Birch Mine
In March of 2011 a Consent Decree was entered by WVDEP
requiring corrective action to comply with Selenium standard at 10
discharge points on the Knight Ink surface mine.
A corrective action plan developed by Arch and CRA to establish
the following:
• Design criteria for discharge points identified in the Consent Decree
• Determine applicability of new and existing selenium treatment
technologies
• Complete alternatives analysis of selenium treatment system options.
• Select Treatment Alternative
• Design and construct system
• Initial compliance by August 2012
Treatment Design Considerations, Centralized
vs. Independent
Property access, permitting time requirements and jurisdictional
wetlands immediately downstream of discharges, dictated that a
centralized treatment approach be employed.
Centralized Collection and Transfer System
• Water level in ponds will be kept low via level controlled pump.
• Pumps will deliver water to a centralized location for treatment
Benefits of Centralized Collection and Treatment
• Flow equalization is achieved in existing ponds
• Treatment system can be constructed in most favorable location
• Combining of flow allows for a lower Se. design concentration i.e., 95th
percentile vs. max concentration
Centralized Collection and Transfer System
(20,000 ft. Pipeline Transfer System)
Centralized Collection and Transfer System
Key System Details
• 2200 GPM pumping capacity via seven pumps
• Surface Runoff Selenium concentrations found to
be low, during precipitation events
• Pump capacity nearly three times avg. flow,
equivalent to 9.7 acre-ft./day
• Level Controlled Automatic pump operation
• 60 acre feet of storm water storage and flow
equalization volume
• System Owning and Operating cost is estimated
at $0.48/1000 Gallons 10 yr. period, 8% NPV
Selenium Treatment Alternatives Evaluation
Completed Bench Scale Testing of the Following Technologies
• Electro-Coagulation
• Adsorbent Media
• Iron Co-Precipitation
Completed Pilot or Demonstration Scale Testing of the Following Technologies
• Phyto -Remediation
• Bio-Augmentation -in-situ pond treatment
• Zero-Valent Iron Treatment
• Ion-Exchange
• Biological Reactor (Anaerobic Wetland) Treatment
— With and Without Bio-Augmentation
Selenium Treatment Alternatives Evaluation
Bench Scale Results • Electro-Coagulation- Bench scale tests had favorable results, equipment
issues prevented further investigation of the technology
• Adsorbent Media- Removal rates were insufficient to warrant further evaluation
• Iron Co-Precipitation- Iron addition requirements were very high, did not move to pilot testing of the technology
Pilot Scale Results • Phyto -Remediation – Some removal during active growing season, not
effective for higher Se loading
• Bio-Augmentation (in pond) –Effective during low load, summer months, Not effective during winter months
• Zero-Valent Iron Treatment- Effective Selenium Removal, High Iron generation
• Ion-Exchange-Effective Selenium Removal, Large Brine disposal requirement
• Biological Reactor (Anaerobic Wetland) Treatment-Effective Selenium removal, No Apparent Issues.
Results of Focused Feasibility of Selected
Technologies
Estimated O&O Cost Pro's Con's
Treatment Technology $/1000 Gal. 10yr
Semi-Passive Biological Reactor $0.38 Low Maintenance, No Residual Large footprint required, initial
Material Handling Issues, Self startup equilibrium period,
Sustaining, Low Cost Operation Reaction to higher Se concentration
Have installed simular systems is time consuming
that have shown long term
success
Ion Exchange $3.90 Small Footprint required, Labor intensive, Residual Brine
Reaction period for higher Se handling issue, Active mechanical
Concentrations short. maintenance issues. High Cost
Operation, Treatment materials
require storage, spill control
Zero Valent Iron $3.00-$5.00 Small Footprint required, Labor intensive, Residual Iron
Reaction period for higher Se handling issue, Active mechanical
Concentrations short. maintenance issues. High Cost
Operation, Treatment materials
require storage, spill control
Iron sludge handling and cost
Determination of Treatment
In November, 2011 ARCH-Eastern Indicated to WVDEP
that Centralized Collection & Transfer and Biological
Reactor Treatment Would be Implemented in Accordance
with the Site Consent Decree
• Final sizing of the biological treatment system would occur after
winter operation of the demonstration project.
• Construction of the collection and transfer system would occur
beginning in December 2011 (and it has)
Chemistry of Selenium Treatment
Most Treatment Strategies (except Ion exchange
& Reverse Osmosis) Reduce Selenate (+6) to
Selenite (+4) Elemental (0) or Selenide (-2) form.
Reducing Condition can be created either
chemically or biologically.
Chemically by a reducing agent (e.g., -ZVI),
biologically through decomposing organic matter
and/or microbial respiration processes
Chemistry of Selenium Treatment in Bio-Reactor
4CH3C0- + 3SeO2 Se°+ 8CO2 +4H20 + 4H+
Selenium (Selenate/Selenite) is reduced to its elemental state, where it precipitates out of solution and remains in the bio-reactor substrate.
Key Factors to Removal • Form of Selenium, Arch-Eastern waters are > 95% Selenate
• Eh (oxidation/Reduction) potential of the system
— Affected by Temperature, Biological Activity, Flow Rate
• Hydraulic Retention Time (detention time in the system)
— Affected by Theoretical HRT (volume of the Bio-Reactor)
— Affected by Actual HRT (Flow patterns within the system).
Chemistry of Selenium Treatment in Bio-Reactor
Key Components of Bio-reactor Design • Gravel Sub-Drain- Acts as a Biological Media and Principle
Flow Path.
• Hay Substrate- Acts as a Biological Media and Carbon Source for microbial activity. Reduces Eh of the System through decomposition
• Mushroom Compost- Serves as a source of Nutrients to Microbes. Serves as growth media for cattails.
• Cattails- Provides cover. Dying cattails replaces decomposing hay.
• Microbes- Consumes available Oxygen, creates reducing conditions. (Some forms consume Oxygen associated with Selenate and Selenite ions)
Bioreactor Demonstration Project-Key Features
Lined System
Fixed Bed-Plug Flow Biological Reactor
Horizontal and Downward Flow
Volume and Theoretical Hydraulic Retention Time (HRT) measured upon initial filling of the system
Pumped, Measured inflow to the system
Ability to increase Se concentrations to the influent
Weekly analysis of daily composite samples
Daily field reading of flow, pH, eH, Temp. and DO
Continual operation from Mid-August thru February
Demonstration Bio-reactor Results
Arch-Eastern, Bioreactor # 1
05
1015202530
8/29
/2011
9/1/20
11
9/8/20
11
9/15
/2011
9/22
/2011
9/29
/2011
10/6/2011
10/13/201
1
10/20/201
1
10/27/201
1
11/3/2011
11/10/201
1
11/17/201
1
12/1/2011
12/8/2011
12/15/201
1
12/22/201
1
12/29/201
1
1/5/20
12
1/12
/2012
1/19
/2012
1/26
/2012
2/2/20
12
2/9/20
12
2/16
/2012
2/23
/2012
Date
Sele
niu
m C
on
c.
(ug
/l)
Bio #1 influentBio #1 Effluent SeDischarge Criteria
Arch-Eastern, Bioreactor #1
Dementration Project
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
0.3000
0.0 500.0 1000.0 1500.0 2000.0 2500.0
Influent Se, mg/day
Se r
em
oval,
mg
/day/c
ub
ic f
t.
Y=. 0 0 0 13 5 X+. 0 0 9 6 7
r 2 = . 9 8
I n f l e c t i o n P o i n t i n
r e mo v a l r a t e @
. 2 2 mg / d a y / f t3
r2
= . 9 4 5
Arch-Eastern, Bioreactor #1
Demonstration Project
Arch-Eastern, Bioreactor #1
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
0.0000 0.0500 0.1000 0.1500 0.2000 0.2500 0.3000
Influent Se, (mg/day/cub.ft.)
Se R
em
oval,
(mg
/day/c
ub
.ft.
)
Data Linear Regression Line
Y=.818 X -.0029
r2 =.985
.22 mg/ day/ f t3
.26 mg/ day/ f t3
Arch-Eastern, Bioreactor #1
0
0.05
0.1
0.15
0.2
0.25
0.3
0 5 10 15 20 25 30
Temperature (C)
Se R
em
oval
(mg
/day/c
ub
ic f
t.) R e mo v a l r a t e d u r i n g
l o w e s t e f f l u e n t
t e mp s . t h r o u g h o u t
t h e e x p e c t e d r a n g e ,
d o n o t a p p e a r t o b e
e f f e c t e d b y t e mp s .
d o w n t o 5 d e g r e e s CHi gher temper atur e ef f l uents al so
coor esponds to l ower i nf l uent Se
l oadi ng
Arch-Eastern, Bio-reactor #1
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
0.3000
0 10 20 30 40 50 60 70 80 90 100
Theoretical HRT (Hours)
Se R
em
oval, (
mg
/day/c
ub
ic f
t
Effective Removal seen at
Theoretical HRT as low as
eleven hours
Removal more dependent on incoming
load than HRT
)
Arch-Eastern, Bio-Reactor #1
0
0.05
0.1
0.15
0.2
0.25
0.3
-350 -300 -250 -200 -150 -100 -50 0
Efflluent Eh (mv)
Se
Rem
ov
al,
mg
/da
y/c
ub
ic f
t.
Eh varied between minus 155 and minus
340. Variation appears to be dependent
on system flow and effluent temperature.
Acceptable Selenium removal throughout
the range of effluent Eh.
Initial start up period
Full Scale Implementation
Full Scale Design Criteria (Established earlier in the project). • Flow 800 gpm
• 95th Percentile Se concentration- 14.88
• Effluent Concentration -2.35 µg/l (1/2 discharge criteria)
• Yields a required Se removal of - 54635 mg Se/day
Selenium removal rates of bio-reactor treatment established during demonstration testing • 0.22 mg/day/ft3
Full Scale Bio-Reactor Size
• 54635 mg/day / .22 mg/day/ft3 = 248,340 ft3
Arch-Eastern, Full Scale Bio-Reactor
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
0 200 400 600 800 1000 1200 1400 1600
Influent Flow (GPM)
Th
eo
reti
cal H
RT
(h
ou
rs)
Arch-Eastern, Full Scale Bio-reactor
250,000 cubic foot, of Media
Design Se Removal Rate= .022 mg/day/ft3
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
0.3000
0.0000 0.0500 0.1000 0.1500 0.2000 0.2500 0.3000 0.3500 0.4000 0.4500
Influent Se, mg/day/cub.ft.
Se
Rem
ov
al, m
g/d
ay
/cu
b.f
t
Data
Linear Equation
Y=.818 X - .0029
r2 = .985
Linear Equation
Design Removal
rate=.22 mg/day/ft3
95th percentile
Influent load.=.26
Avg. Removal
Avg. influent
Average operational
Range
Quality Predictive Tool
The linear equation developed during the demonstration
projects allows us to model expected effluent concentrations at
various incoming loads
• Incoming Concentration 14.88 µg/l (95th percentile) at 800 gpm =
effluent concentration of 2.35 µg/l
• Incoming Concentration 7.24 µg/l (average conc.) at 800 gpm =
effluent concentration of 1.5 µg/l
• Incoming Concentration 19.7 µg/l at 800 gpm=
effluent concentration of 3.7 µg/l
• Incoming Concentration 7.24 µg/l (average conc.) at 1150* gpm =
effluent concentration of 1.45 µg/l
* HRT at 10 hr.
Full scale Bio-reactor Design, Plan View
Full scale Bio-reactor Design, Inlet section
Full scale Bio-reactor Design, Outlet section
Full scale Bio-reactor Design
Conclusions, Completed Objectives
• Establish design criteria for treatment of waters associated with
discharge points identified in the Consent Decree- 800 GPM, 14.88
mg/l
• Determine applicability of new and existing selenium treatment
technologies – Bench and/or Pilot testing of 8 technologies
• Complete alternatives analysis of selenium treatment system
options. -Three Technologies Analyzed
• Select Treatment Alternative- Collection and Transfer to Central
Bio-reactor Treatment
• Design and construct system- Design Completed, Construction
underway
• Initial compliance by August 2012
