Electro-Biochemical Reactor (EBR) Technology for Treatment of

Electro‐Biochemical Reactor (EBR) Technology for Treatment of Leach Pad Waters at the Landusky Mine
A. Ola Opara, Michael J. Peoples, D. Jack Adams*, & William C. Maehl
Mine Design, Operations & Closure Conference 2014
Landusky Mine ‐ Background
• The Landusky Mine is a closed gold mine located in the Little Rocky Mountains in north‐central Montana. • Cyanide leaching was used to extract the precious metals. • The mine operated until 1998, when its owner, Pegasus Gold Corporation, declared bankruptcy.
Landusky Mine ‐ Background
• Spectrum Engineering of Billing, MT, performed the reclamation and is currently managing the site and its water treatment plants, including the Landusky
Biotreatment System (LBS). • The LBS system was comissioned in 2002; based on a patented advanced biological wastewater treatment process to treat contaminants not readily treatable by chemical precipitation.
– nitrate‐N at 100‐350 mg/L
– selenium at 0.8‐1.5 mg/L
Landusky Conventional Biotreatment
Treatment Conditions
• Water temp. <2 ‐ 12° C
• pH~4.0 adjusted to ~6.5
• NO3‐N ‐ 100 to 340 mg/L
• Hardness >2,100 mg/L
• Broad spectrum of metals (Se, Cd, Cu, Fe, Mn, Ni, Zn)
EBR – ORP Fundamental Concepts (Electron Availability)
Wastewater
+
Substrate
+800
E
N
E
R
G
Y
ORP
(mV)
-250
Y
I
E
L
D
O 2  H 2O
Aerobic Respiration
NO3  N2
Denitrification
SeO4 
Se0
Selenium Reduction
SeO42‐ + 3H+ + 2e‐ <‐> HSeO3‐ + H2O
HSeO3‐ + 5H+ + 4e‐ <‐> Se(s) + 3H2O SO4--  HS-
Sulfate Reduction
CCl4  Cl-
Reductive
Dechlorination
CO2  CH4
Methanogenesis
EBR Technology
•
EBR technology utilizes nutrients to provide required
component for cell growth
•
Low voltage (1-3 Volts potential) provides:
1. Electrons and electron acceptor
environments for controlled
contaminant removal environment
2. Compensation for inefficient and
fluctuating electron availability
through nutrient metabolism
•
•
1 mA provides ~6.24 x 1015 electrons/second
to the EBR system.
– Replaces excess nutrients
– Better contaminant removal
– Produces less TSS (bio-solids)
The Electro‐Biochemical Reactor
Electromicrobiology
High-performing EBR technologies have been
demonstrated within the precious metals, base
metals, and coal mining sectors to remove
target and co-contaminants to low ppb levels.
ADAPTED FROM
MAY 2013
Electro‐Biochemical Reactor Technology
ORP [mV]
Providing electrons directly has numerous benefits including
better ORP control and stability.
200
150
100
50
0
‐50
‐100
‐150
‐200
‐250
‐300
1
22
43
64
Data Points
85
106
127
148
1 STAGE EBR
169
190
211
2 STAGE CBR
Landusky Conventional Biotreatment System
(3) – 250,000 gallon (946 m3)
Bioreactors in series
BR1
14‐hr
BR2
14‐hr
BR3
14‐hr
Landusky EBR Pilot System
EBR1
8‐hrs
EBR2
8‐hrs
Nitrate/Nitrite ‐ LBS
NO3‐N + NO2‐N [mg/L]
400
350
300
250
200
150
100
50
0
Aug‐10
Dec‐10
May‐11
Sep‐11
Date
Feb‐12
Jul‐12
Influent
Influent
Influent
BR1 BR1 BR1
BR2 BR2 Limit
BR3 LimitLimit
Nov‐12
Results: Nitrate/Nitrite ‐ EBR
NO3‐N + NO2‐N [mg/L]
Inoculation
450
400
350
300
250
200
150
11
100
50
0
7/17
Validation
Temp. Stress (1.2 oC)
Nutrient Stress
44
33
22
7/29
8/10
8/22
9/3
Date
9/15
Influent
Influent EBR1EBR1 EBR2Limit Limit
9/27
Selenium ‐ LBS
Total Selenium [mg/L]
1.20
1.00
0.80
0.60
0.40
0.20
0.00
Aug‐10
Feb‐11
Influent
Jul‐11
BR1
Dec‐11
Date
BR2
May‐12
BR3
Nov‐12
Limit
Results: Selenium ‐ EBR
Inoculation
Total Selenium [mg/L]
1.2
Validation
Temp. Stress (1.2 oC)
Nutrient Stress
1.0
0.8
0.6
4
1
3
2
0.4
0.2
0.0
7/17
7/29
8/10
Influent
8/22
Date
EBR1
9/3
EBR2
9/15
Limit
9/27
Results: Other Contaminants (Average)
Influent
LBS
Effluent
EBR
Effluent
Discharge
Limit
CN1 (TOTAL)
0.084
NA
<0.005
0.005
CN1 (WAD)
0.012
0.072
<0.005
NA
Al [mg/L]
0.34
1.99
0.04
NA
Cd [mg/L]
0.135
0.125
<0.001
0.005
Cu [mg/L]
0.061
0.122
0.014
0.031
Mn [mg/L]
57
55
29
NA
Ni [mg/L]
0.832
0.893
0.007
NA
Se [mg/L]
0.858
0.417
0.039
0.050
Zn [mg/L]
2.26
2.94
0.04
0.388
TSS [mg/L]
<18
NA
<16
NA
1After EBR system aerobic step.
EBR Water Sampling
EBR Water Sampling
Microbial Metal Precipitates
Biofilm
Metal precipitate
formation and
growth on bacteria
Biofilm with
Se precipitate
Al Mattes 2007
Refurbishment & Conversion of the Landusky Biotreatment System to an EBR
EBR Pilot System
1
Combined EBR/In Situ Biotreatment
Irrigation
Groundwater
Injection
Reaction Zone:
•Denitrification
•Se+6 reduction
•Adsorption, precipitation (Se0, Se2-)
SEMI PASSIVE TREATMENTS
SEMI PASSIVE TREATMENTS
• Reconfigure water collection system for (additional amendments) and partial redistribution from the EBR active treatment system to in situ heap treatment
• Approaches have been proven in full‐scale applications at several US hard rock mines at elevations >3,200 meters
EBR – Yukon Mine
• The EBR system consistently removed selenium from an average of 2.73 mg/L to an average of 0.002 mg/L ‐ well below the discharge requirement of 0.020 mg/L.
• An ~8 hour EBR HRT will be required to achieve the lowest levels of selenium removal at full‐scale with temperatures down to <5° C at this site. www.inotec.us
Thank You
Jack Adams
Cell: 801‐712‐2760 Office: 801‐966‐9694
[email protected]

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