Semi-Passive Bioreactors and RCTS Lime Treatment of Acid Mine Drainage

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1 Semi-Passive Bioreactors and RCTS Lime Treatment of Acid Mine Drainage Timothy K. Tsukamoto, Ph.D. TKT Consulting, LLC

2 Bridging the Gap Between Passive and Active PASSIVE ACTIVE Limestone channels SAPPS HDS Organic bioreactors Semi-Passive bioreactors RO RCTS Lime Treatment

3 Solubility Products for Metal Complexes Complex K sp Complex K sp HgS 6.38 x Zn(OH) x Fe(OH) x Ni(OH) x CuS 1.28 x Cd(OH) x CdS 1.4 x MnS 4.55 x PbS 8.81 x Mn(OH) x ZnS 2.91 x PbCO x NiS 1.08 x CdCO x Pb(OH) x FeCO x FeS 1.57 x MnCO x Fe(OH) x NiCO x 10-7

4 Treatment Process Sulfate-reducing Bioreactors Sulfate-reduction 4 A H 2 + S O H + 4 A - + H S H 2 O Ethanol + Sulfate + Acidity Bicarbonate + Hydrogen sulfide + Water Sulfide Precipitation of Metals H 2 S + M 2 + M S + 2 H + Hydrogen sulfide + Metals Metal sulfides

5 Leviathan Bioreactors

6 Constructed fall 2002 Spring 2003 Pretreat by raising ph over 4 2 rock SRB cells 1 pretreat and 2 post treat ponds Design flow gpm, Peak 40 gpm Average flow Aspen Seep 12 gpm Climate cool (snow in April) During UNR operation: visits 1 to 2 times per month in winter visits weekly in summer

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8 Comparison Gravity- Recirculation

9 Constituent Aspen Seep Bioreactor 1 effluent Bioreactor 2 effluent Discharge Discharge objectives ph SO NA Al < Fe Ni Cu <0.01 < Zn

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13 Constituent Aspen Seep Bioreactor 1 effluent Bioreactor 2 effluent Discharge Discharge objectives ph SO NA Al 28 <0.5 <0.5 < Fe Ni Cu Zn

14 Residence Time and Working Volume for Leviathan Bioreactor System Component Working Volume Calculated Residence Time (38 Lpm) Pretreatment Pond 100 ft days Pond 1 5,300 ft days Pond 2 3,000 ft days Settling Pond 1 16,500 ft days Settling Pond 2 18,000 ft days Totals 42,900 ft 3 23 days

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16 Nacimiento Mine US Forest Service, New Mexico Up to 120 gpm, Rock Substrate, Recycle Construction Completed 2009

17 Nacimiento Mine

18 Nacimiento Mine Well Field Pump Transfer Station Recycle Line Settling Pond Bioreactor Aeration Aeration Transfer Tanks Sodium Hydroxide Ethanol Delivery Delivery Discharge

19 Nacimiento Mine

20 Nacimiento Mine

21 Nacimiento Mine

22 Nacimiento Mine

23 Nacimiento Mine

24 Calculated Residence Time and Working Volume for Nacimiento Bioreactor at 240 LPM Settling Pond 117,000 ft3 7.5 days Bioreactor 50,000 ft3 3.2 days Aeration Ponds 134,000 ft3 8.6 days

25 Comparison Between Nacimiento and Leviathan (mg/l) Sample Location No samples ph Sulfate Al Cu Fe Ni Zn Leviathan Mine Influent* ** ** ** ** ** Leviathan Mine Effluent* ** ** ** ** ** Leviathan Discharge Objective* Nacimiento Mine Influent Nacimiento Mine Effluent Nacimiento Discharge Objective < NA NA *Data from EPA 2006 **Standard deviation

26 Lime Precipitation Add lime (CaO) or Ca(OH) 2 to raise the ph Precipitate metals as hydroxides Precipitate sulfate as gypsum Requires oxygen addition if there is significant dissolved iron, manganese Oxygen addition is typically accomplished with large compressors and air diffusers and tanks Lime addition requires thorough mixing due to it s low solubility and slow dissolution rate. Mixing is typically accomplished with large mixers inside reaction tanks Labor and energy demanding

27 RCTS CONCEPT Rotating perforated cylinders add oxygen from the atmosphere to the water Energy efficient 10 hp system treats up to 500 gpm Aggressive agitation near 100% reagent efficiency Reduced lime costs and sludge handling costs Low maintenance rotor maintenance on most sites 2 to 3 times per year (takes 3 to 4 hours) Small footprint most units are mobile Effective Aeration and Oxidation Less Sludge produced Faster sludge settling

28 Iron Hydroxide Solubility with Respect to ph ph vs Total Iron Solubility Diagram for Ferrous and Ferric Hydroxide Precipitation. Note the Minimum Solubility for Manganese Precipitation is Between ph 9 and 10. (Taken from USEPA 1983).

29 Iron and Manganese Oxidation

30 Early Spring Treatment Leviathan Mine 2006

31 Removed ~ 180 yd3 of sludge from the lined pond in 2 days TKT Consulting, LLC Early Spring Treatment Leviathan Mine 2006 Plowed the road & mobilized the entire system including lime in approximately 1 week. Treated 24 hours/day with 2 man crew onsite an average of 4.6 hours/day Met USEPA directives Treated and actively discharged ~7.5 million gallons of water containing iron as high as 610 mg/l and aluminum as high as 490 mg/l.

32 Early Spring Treatment Leviathan Mine 2006 Hydraulic Capacity (gallons) Maximum Flow Rate (gpm) Average Flow Rate System Residence Time Minutes Max Flow (Ave Flow) Effluent ph Ave Gallons water Treated per ton lime Conventional System 40, (200) ,700 Rotating Cylinder Treatment System (2.36) ,700

33 Early Spring Treatment 2011

34 -Plowed the road April 1 and 2 and let the road dry. -Mobilized the treatment system on April 4 and 5 via 4 wheel drive equipment. -Treatment began at 1:30 p.m. on April 5 -By 3:30 p.m. April 8 the average ph of the pond was The first discharge began at 8:10 a.m. on April 9. -Treated for 56 days 24 hours/day with 2 man crew onsite an average of 6.9 hours/day for operations and discharge -Treated AMD containing iron as high as 648 mg/l and aluminum as high as 345 mg/l. -Actively discharged ~8.18 million gallons of water that met USEPA discharge criteria except for one discharge with iron slightly above the maximum -Average treatment rate over the 56 days (101 gpm) -Removed ~ 260 yd 3 of sludge from the lined pond TKT Consulting, LLC Mobilization and Treatment Summary

35 Elizabeth Mine Dry Feed System

36 Elizabeth Mine Dry Feed System

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39 Results from Startup and 2010 Season Elizabeth Mine Elizabeth Mine 2010 Field Data Iron Concentrations Iron concentration (mg/l) Influent total iron Sed pond total iron Sed pond ferrous iron Iron Concentration (mg/l) Apr May Jun Jul Aug Sep Date Time (Days) Influent iron Effluent iron

40 Alaska Connex System System

41 Alaska Connex System Utilize bagged hydrated lime, hand mix Operated at 10 to 20 gpm intermittently Sample # Test ph Date Lime Dose (mg/l) 24 Hr ph Alaska Project Beaker Tests Fe mg/l Mn ug/l Influent 2.931/15/ /28/ /28/ /28/ < 500 < /28/ < 500 < /27/ < 500 < /27/ < < /27/ < < < /27/ < < < /27/ < <50 < < /27/ < <50 < < /27/ <0.01 < 50 <50 < <0.98 < /27/ <0.01 < 50 <50 < <0.98 < /27/ <0.01 < 50 <50 < <50 Ni ug/l Zn ug/l Al ug/l Cd ug/l Cu ug/l ph Modification Pond Outflow Bold= certified samples run by ICP

42 Alaska Connex System

43 Alaska Connex System

44 QUESTIONS?