Overviews of Two Advanced AMD Overviews of Two Advanced AMD Treatment Technologies: Semi-passive Treatment Technologies: Semi-passive Sulfate Reducing Bioreactors and Sulfate Reducing Bioreactors and the Rotating Cylinder Treatment the Rotating Cylinder Treatment System System July 2008 July 2008 Timothy K. Tsukamoto, Ph.D. Timothy K. Tsukamoto, Ph.D. RCTS™
Semi-passive Bioreactors Timothy K. Tsukamoto, Ph. D Semi-passive Bioreactors Timothy K. Tsukamoto, Ph.D. (775) 321-8100 www.iwtechnologies.com
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Overviews of Two Advanced AMDOverviews of Two Advanced AMDTreatment Technologies: Semi-Treatment Technologies: Semi-
1.1. Higher capital costHigher capital cost2.2. Requires some O&MRequires some O&M
Types of Bioreactors Passive BioreactorsPassive Bioreactors
-The carbon or energy source is part of the substrate.-The carbon or energy source is part of the substrate.-Once the degradable carbon sources are depleted, -Once the degradable carbon sources are depleted, treatment efficiency falls off.treatment efficiency falls off.-Metals are precipitated within the matrix.-Metals are precipitated within the matrix.-Plugging and short circuiting leads to decreased -Plugging and short circuiting leads to decreased treatment efficiency.treatment efficiency.
Semi-Passive BioreactorsSemi-Passive Bioreactors-The carbon source is added to the influent water-The carbon source is added to the influent water-The majority of the metals are precipitated outside of -The majority of the metals are precipitated outside of the bioreactor.the bioreactor.-Flushing built into the matrix.-Flushing built into the matrix.-All three contribute to a longer lasting system-All three contribute to a longer lasting system
Passive BioreactorsPassive Bioreactors-The carbon or energy source is part of the -The carbon or energy source is part of the
substrate.substrate.-Once the degradable carbon sources are -Once the degradable carbon sources are
-Metals are precipitated within the matrix.-Metals are precipitated within the matrix.-Plugging and short circuiting leads to -Plugging and short circuiting leads to
-The carbon source is added to the influent -The carbon source is added to the influent waterwater
-The majority of the metals are precipitated -The majority of the metals are precipitated outside of outside of the bioreactor.the bioreactor.
-Flushing built into the matrix.-Flushing built into the matrix.-All three contribute to a longer lasting system-All three contribute to a longer lasting system
Sulfate-reducing Activity
Passive Bioreactors Passive Bioreactors 0.3 moles per cubic meter per day0.3 moles per cubic meter per day
limited to about 1 meter deeplimited to about 1 meter deepso 0.3 moles per square meter per dayso 0.3 moles per square meter per day
Semi-passive BioreactorSemi-passive Bioreactor0.56 moles per cubic meter per day0.56 moles per cubic meter per daycan go much deepercan go much deeperSo for Leviathan Bioreactor 3 meters deep So for Leviathan Bioreactor 3 meters deep 1.68 moles per square meter per day1.68 moles per square meter per day
Leviathan MineOriginal Manure Substrate at the Leviathan Mine.
-down-flow reactor approximately 3ft deep. -ineffective at treating AMD after 1 year. -the source of manure substrate for the column experiments that
follow.
Leviathan Mine
Six Weeks of Treatment
One Year of Treatment
7-27-93 7-1-94
Influent Effluent Influent Effluent
pH 4.78 6.97 4.7 6.45
Temperature C 9.9 15.6 8.4 13.1
alkalinity - 1458.00 - 269
Al 41.0 <0.02 48 0.24
As 0.41 0.023 0.28 0.015
Fe 310 2.8 380 260
Ni 1.8 0.01 2.1 0.01
Sulfate 1690 1190 2070 1910
Leviathan MineSulfate concentrations vstime for Leviathan underdrain site4-3-97 to 7-10-98.
Time (Days)
0 100 200 300 400 500
Sul
fate
con
c. (m
g/L)
0
500
1000
1500
2000
2500
3000
influenteffluent
Iron concentrations vstime for Leviathan underdrain site4-3-97 to 7-10-98.
All information delivered in this presentation relating to the Rotating Cylinder Treatment System (“RCTS”), US Patent No. 7,011,745 is patented technology proprietary to Ionic Water Technologies, Inc. The presentation’s content related to IWT’s technologies shall not be used for any purpose by any recipient or viewer hereof without the express written consent of Ionic Water Technologies, Inc.
RCTS CONCEPTRotating perforated cylinders add oxygen from the atmosphere to the water
Energy efficient 10 hp system treats up to 500 gpm
Low maintenance rotor maintenance on most sites2 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
Chemistry and Chemistry and StoicheometryStoicheometry
For Hydrated Lime
Ca(OH)2 + M 2+ M(OH)2 (s) + Ca 2+ Ca 2+ + SO4 2- CaSO4
Gypsum generally precipitates to ~ 2,000 mg/L
For Sodium Hydroxide
2 NaOH + M 2+ M(OH)2 (s) + Na + Sodium remains soluble
Chemistry and Chemistry and StoicheometryStoicheometry
CaO=1 Na(OH)=1.43Ca(CO)3=1.78
If 2000 mg/L acidity then need= 1120
mg/L of CaO and 1600 mg/L of NaOH and 920 mg/L will be Na
Lime Precipitation
Add lime (CaO) or Ca(OH)2 to raise the pHPrecipitate metals as hydroxidesPrecipitate sulfate as gypsumRequires oxygen addition if there is significant dissolved iron, manganeseOxygen 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 tanksLabor and energy demanding
Iron Hydroxide Solubility with Respect to pHpH 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).
Improved Oxygen Addition
O2 = Qw x Fe x 7.14 x 10 -5O2 = Theoretical O2 demand (lb O2/hr)Qw = Acid mine drainage flow rate (gal/min)Fe = Fe 2+ initial concentration (mg/L)
U.S. Environmental Protection Agency (USEPA). 1983. Design Manual: Neutralization of Acid Mine Drainage. EPA-600/2-83-001.
Type of Aeration Pounds of O2 delivered per horsepower-hour
Results from StartupResults from StartupTable 1. Results for samples taken at various pH with and without settling. All samples were taken at an influent flow rate of
approximately 32 gpm.
Sample ID Initial pH FeT Fe2+ Mn Al Cu Zn 24 hour pH
K (sampled from unit and filtered immediately no settling ) 9.80 0.20 0.00 0.20
Pond 7-26 (not filtered) 7.51 0.36 0.26 1.80
Pond 7-27 (filtered) 0.05 0.04 0.70
Pond 7-28-08 (not filtered) 7.54 0.10 0.03
Iron and Manganese Iron and Manganese OxidationOxidation
The Effect of pH on Oxidation Rates for Iron and Manganese. All experiments were conducted at dissolvediron and manganese concentrations of less than 5 x 10-4 M. (a) oxygenation of Fe 2+ in bicarbonate solutions(b) oxygenation of Mn 2+ in bicarbonate solutions (c) oxidation of Mn 2+ in bicarbonate solutions (autocatalytic plot)(d) Effect of pH on oxidation rates (taken from Faust and Aly 1981)
Sunshine Mine
Residence time in RCTS 1 to 2 minutes
Mn ppm after treatment
0
2
4
6
8
10
12
14
16
18
8 8.5 9 9.5 10 10.5 11
operating pH
Mn
ppm
1 hr settle
3 hr settle
1 hr filter
1 day
2 day
Figure 1
LEVIATHAN MINE, NORTHERN CALIFORNIALEVIATHAN MINE, NORTHERN CALIFORNIAATLANTIC RICHFIELD SITE 2007ATLANTIC RICHFIELD SITE 2007
HydraulicCapacity(gallons)
AverageFlowRate(gpm)
SystemResidence
Time(minutes)
InfluentpH
EffluentpH
FilterBagpH
EffluentDO mg/l
AverageLime
per Day
Conventional Tank Reactor
System 4000 30.38 131.67 4.73 7.88 8.12 4.22 398
Rotating Cylinder Treatment
System
1600 *includes
dosing tank 27.33 58.54 4.86 8.12 8.11 7.86 233
Comparison of RCTS with Conventional SystemLeviathan Mine
EMERGENCY TREATMENT AT THE LEVIATHAN MINE
2006Plowed the road April 9 and let the road dry.Mobilized the lime on April 12 and 13 via 4 wheel drive equipment.Mobilized the entire treatment system on April 13Started treating on April 14 and by 10 a.m April 15 the average pH of the pond was 8.4.Treated 24 hours/day with 2 man crew onsite an average of 4.6 hours/dayMet USEPA directivesTreated 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.Removed ~ 180 m3 of sludge from the lined pond in 2 days
Comparison of RCTS with Conventional SystemLeviathan Mine
RCTS vs Conventional RCTS vs Conventional System Leviathan MineSystem Leviathan Mine
Water Treated per ton of lime
RCTS 150,000 gallonsConventional System 73,000 gallons
Empire Mine
Goals: To oxidize and precipitate the iron and co precipitate arsenic from solution. It was initially proposed that sodium hydroxide would be added to raise the pH from 6.6 approximately 8.0. The addition of base was not necessary (Degassing of carbon dioxide from the water)
HCO3- + H+ H2O + CO2
Nevada Pit Lake
Nevada Pit Lake•6 Billion gallon pit lake pH~2.9
•Utilize CaO fed through a silo
Utilize the RCTS and IWT lime grinder to slake the lime and dissolve it
•Add CaO at ~ 2.8 lbs/ min and slake with ~ 2 to 10 gpm to obtain a slurry of 3.5% to 17.5%
•Mix with between 50 and 300 gpm of water in the RCTS unit (lime dissolvesCompletely)
•Reintroduce with the ~6,000 gpm of water feeding the pit lake
•It will take ~ 1,000,000 lbs of CaO to neutralize 1 B gallons
•2.8 lbs/min ~ 120,000 lbs per month so we would neutralize ~ 1.5 B gallons per year
Cost ComparisonCost ComparisonCost to treat 1Bg of water
$ units Gallons tons Material Delivery Total Caustic $0.13 poundCaustic $1.66 gal 263,158 1,679 $436,842 $31,413 $468,255 12.76 #/galQuickLime $76.00 ton 2,000,000 533 $40,508 $15,015 $55,523 1.66 gallonKiln Dust* $8.00 ton 2213 $17,704 $63,535 $81,239 Delivery $ 18.71 tonNote* Kiln dust usage is ~4x Quicklime usage for equivilant CaOH
Cost to treat current lake volume of 5.6 Bg 3990 elev. Quick lime 76.00 tonMaterial Infrastructure Labor* Total Delivery $ 28.17 ton