Electro Biochemical Reactor (EBR) Technology for Treatment of Leach Pad Waters at the Landusky Mine

Transcription

1 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

2 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.

3 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 mg/l selenium at mg/l

4 Landusky Conventional Biotreatment Treatment Conditions Water temp. <2 12 C ph~4.0 adjusted to ~6.5 NO 3 N 100 to 340 mg/l Hardness >2,100 mg/l Broad spectrum of metals (Se, Cd, Cu, Fe, Mn, Ni, Zn)

5 EBR ORP Fundamental Concepts (Electron Availability) Wastewater + Substrate +800 E N E R G Y ORP (mv) Y I E L D -250 O 2 H 2 O NO 3 N 2 SeO 4 Se 0 SO 4 -- HS - CCl 4 Cl - CO 2 CH 4 Aerobic Respiration Denitrification Selenium Reduction SeO H + + 2e < >HSeO 3 + H 2 O HSeO 3 + 5H + + 4e < >Se (s) + 3H 2 O Sulfate Reduction Reductive Dechlorination Methanogenesis

6 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 electrons/second to the EBR system. Replaces excess nutrients Better contaminant removal Produces less TSS (bio-solids)

7 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

8 Electro Biochemical Reactor Technology ORP [mv] Providing electrons directly has numerous benefits including better ORP control and stability Data Points 1 STAGE EBR 2 STAGE CBR

9 Landusky Conventional Biotreatment System (3) 250,000 gallon (946 m 3 ) Bioreactors in series BR1 14 hr BR2 14 hr BR3 14 hr

10 Landusky EBR Pilot System EBR1 8 hrs EBR2 8 hrs

11 Nitrate/Nitrite LBS NO 3 N + NO 2 N [mg/l] Aug 10 Dec 10 May 11 Sep 11 Feb 12 Jul 12 Nov 12 Date Influent Influent Influent BR1 BR1 BR1 BR2 BR2 Limit BR3 Limit Limit

12 Results: Nitrate/Nitrite EBR NO 3 N + NO 2 N [mg/l] Inoculation Validation Nutrient Stress Temp. Stress (1.2 o C) /17 7/29 8/10 8/22 9/3 9/15 9/27 Date Influent InfluentEBR1EBR1EBR2Limit Limit

13 Selenium LBS 1.20 Total Selenium [mg/l] Aug 10 Feb 11 Jul 11 Dec 11 May 12 Nov 12 Date Influent BR1 BR2 BR3 Limit

14 Results: Selenium EBR 1.2 Inoculation Validation Nutrient Stress Temp. Stress (1.2 o C) Total Selenium [mg/l] /17 7/29 8/10 8/22 9/3 9/15 9/27 Date Influent EBR1 EBR2 Limit

15 Results: Other Contaminants (Average) Influent LBS Effluent EBR Effluent Discharge Limit CN 1 (TOTAL) NA < CN 1 (WAD) <0.005 NA Al [mg/l] NA Cd [mg/l] < Cu [mg/l] Mn [mg/l] NA Ni [mg/l] NA Se [mg/l] Zn [mg/l] TSS [mg/l] <18 NA <16 NA 1 After EBR system aerobic step.

16 EBR Water Sampling

17 EBR Water Sampling

18 Microbial Metal Precipitates Biofilm Metal precipitate formation and growth on bacteria Biofilm with Se precipitate Al Mattes 2007

19 Refurbishment & Conversion of the Landusky Biotreatment System to an EBR EBR Pilot System 1

20 Combined EBR/In Situ Biotreatment Irrigation Groundwater Injection Reaction Zone: Denitrification Se +6 reduction Adsorption, precipitation (Se 0, Se 2- ) 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

21 EBR Yukon Mine The EBR system consistently removed selenium from an average of 2.73 mg/l to an average of mg/l well below the discharge requirement of 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.

22 Thank You Jack Adams Cell: Office: