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Minewater Treatment for Direct Discharge Using Media-based Engineered Treatment SolutionsSeptember 12, 2012
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Direct Discharge under NPDES Permit
NPDES Program requirements now include specific contaminant limits based on the receiving water in-stream water quality criteria. Recent initiatives are directed toward ensuring
pollution discharge levels are met on a watershed basis.
This means that Federal, State and Tribal derived limits for some constituents can be, and many times are, specified lower than typical drinking water standards. Extreme examples are trace level requirements for
arsenic, radium and selenium below the allowable drinking water concentrations for these metals.
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Sorption Media Treatment
Primary Targeted Contaminants suitable for media sorption. Metals: Arsenic, Molybdenum, Lead, Mercury, Selenium,
Copper, Chromium, Cadmium, Thallium Radionuclides: Uranium, Radium, Gross Alpha emitters
Why. Concentrations of these constituents in most waste
waters are low enough to provide reasonable service volumes between media exchanges.
Media sorption provides the best opportunity to reduce effluent concentrations to extremely low trace levels.
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Zeolite-based Media Systems
Natural zeolite ion exchange properties are well documented and studied. Cation exchange directly allows removal of lead, zinc,
cadmium and copper. Raw natural zeolites for once-through processing of
waste water is very cost effective compared to synthetic ion exchange materials or other adsorbants where removal performance is similar.
Surface modified zeolites have shown effective removal of oxy-anion metal complexes of selenium, manganese, arsenic and chrome from waste streams.
Natural zeolites are easily processed to facilitate their use in water treatment systems.
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Natural Zeolite-based Media Systems
Natural zeolites are readily available. The resources are large, well tested and consistent in performance.
There are a number of available technologies that improve sorbent selectivity or increase capacity for specific contaminants.
Technology is proven in municipal and drinking water, nuclear, and industrial water treatment applications and is becoming more common in polishing mine effluents prior to discharge.
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Applications
Water Treatment Products Clinoptilolite and chabazite
based products for ion exchange applications
SCM proprietary functionalized mineral based zeolites are fast, reliable, low-cost water treatment alternatives to chemical treatment and activated carbon
NSF 60 Certified for Potable Water Treatment Systems
NSF 50 products for swimming pools
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Types of Zeolites
7
St. Cloud Mining Company
Bowie Chabazite
Ash Meadows Clinoptilolite
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TYPICAL PROPERTIES
Form Powder or Granules
Color Dark Brown (Dry Brightness 40)
Ring Members 8
Crystal Size - Chabazite Less than 1 micron
Crystallinity + 90%
Density 1.73 g/cm3
Pore Size 4.1 by 3.7 Angstroms
Effective Pore Diameter 4.3 Angstroms
Cavity Size 11.0 by 6.6 Angstroms
Total Pore Volume .468 cm3/g
Surface Area 520.95 m2/g
Crystal Void Volume .47 cm3/cm3
Packing Density Approx. 513kg/m3 (32 lbs/ft3)
SiO2/Al2O3 Ratio Approx. 4:1
MOH's Hardness -5
Moisture as packaged Less than 12% by weight
pH of 1% Dispersion 8.5
Stability pH of 3 through 12
Ion Exchange Capacity 2.50 meq/g
Sorption Capacity Greater than 15 wt.% H2O at 10% R.H.
Anhydrous Sodium Aluminosilicate-Chabazie Zeloite (Powder and Granules)
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TYPICAL CHEMICAL ANALYSIS
EXCHANGE OF HEAVY METAL IONS
Weight Percent of Heavy Metals Retained in anhydrous CABSORB After Ion Exchange from a .10 mg/ml solution AgNO3, Pb(NO3)2, CoSO4 and a 0.025 mg/ml solution of CuSO4 at the initial pH indicated for each solution.
SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O DominantCation
68.10 18.59 2.84 0.27 0.75 8.32 1.12 Na
EXCHANGE SELECTIVITIES
Tl+>Cs+>K+>Ag+>Rb+>NH4+>Pb2+>Na+ = Ba2+>Sr2+>Ca2+>Li+
Anhydrous Sodium Aluminosilicate-Chabazie Zeloite (Powder and Granules)
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Hydrous Sodium AluminosilicateClinoptilolite Zeolite
TYPICAL PROPERTIES
Form Granules Color Tan – Green Pore Diameter 4.0 Angstroms Pore Volume 15% Specific Surface Area 40m.2/g. Bulk 45-80 lbs/ft3
760 - 1283 Kg/m3
Solid Density 100 lbs/ft3 1603 Kg/m3
Alkali Stability pH of 7 - 10 Acid Stability ph of 3 - 7 Thermal Stability 1202 degrees F
650 degrees C Ion Exchange Capacity 1.85 milliequivalents/g.
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TYPICAL CHEMICAL ANALYSIS
MAJOR EXCHANGEABLE CATIONS
Hydrous Sodium AluminosilicateClinoptilolite Zeolite
SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O MnO TiO2
69.1 11.9 .7 .8 .4 3.5 3.8 0.02 0.1
Rb+ Na+ Ba+2 Mg+2 Li+ Ag+ Sr+2 Fe+3 K+ Cd+2
Cu+2 Co+3 Cs+ Pb+2 Ca+2 Al+3 NH+4 Zn+2 Hg+2 Cr+3
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Typical removal rates for Copper and Zinc.
0.98
0.982
0.984
0.986
0.988
0.99
0.992
0.994
0.996
0.998
0 5 10 15 20 25 30 35 40 45
Volume (L)
Per
cen
t A
dso
rbed
(%
)
Copper Zinc
Adsorption from solution of copper and zinc obtained with Chabazite in once through column operation
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Media Sorption Treatment Systems
Media sorption systems are well suited to mining water treatment. Conceptually the process selectively removes
contaminants onto a solid phase media material for safe and convenient disposal, creating no or minimal additional waste streams.
Can be designed to treat small and large (greater than 10.0 MM gal/day treatment streams.−Designs can accommodate long-term and temporary
installations Media sorption can implemented as a complimentary
treatment to existing or additional treatment processes as BACT to assure very low compliance requirements.
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Project Oriented Approach to Water Treatment Problems
Implementing a project approach to particular water treatment objectives. We use typical project cost estimates for determining
whether sorptive media systems are an effective alternative for specific mine water treatment.− Costs associated with initial equipment installations.− Costs of operations and maintenance of the system.− Costs for media disposal.
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The Project Approach to Media-based Treatment
System Configuration Media process vessels
−Flow configurations to match process specific needs• Upflow and Downflow• Pressure vessels and atmospheric vessels• Vertical and horizontal cylindrical vessels
−Media retaining systems• Hydraulic distribution • Uniform media contaminant loading • Bed-depth and media contact time
−Single and multiple treatment stages• Sensitivity of discharge excursions• Maximizing media loading rates
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The Project Approach to Media-based Treatment
Operating and Maintenance Minimal pressure requirements Pretreatment to control water quality at inlet to the
process media vessel−Total Suspended Solids handling.• Disposition and disposal of collected solids.
−pH and oxidation/reduction potential.• Changes can drastically affect media removal efficiency and
metal compound solubilities.
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The Project Approach to Media-based Treatment
Media disposal Residuals management
−RCRA requirements for Arsenic, Cadmium, Chromium (total), Lead, Mercury and Selenium.• Leachate testing using TCLP
−California disposal options are more stringent.• California WET test procedure for toxicity leachate.
−Media disposal preparation meeting dewatering criteria.• Disposal of solid media generally must meet no free moisture
requirement.• Paint filter test
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Getting a Project Started
Testing various media systems for selection in full-scale. Laboratory-scale tests
−Equilibrium sorptive capacity testing• Stirred batch tests• CEC Testing for select cation contaminants
−Purpose:• Determine the relative sorptive capacity for removal of select
contaminants from solution under equilibrium conditions.• Determines the removal ability of the selected media using
actual test water sampled from the source.−Limitations:• Will not determine the kinetic removal capacity for the media.
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Laboratory Testing
Small-scale column testing Column tests for removal capacity and to determine
potential break-through volumes. Testing is performed by operating a simulated column
and sampling discharge treated water at various throughput increments.
To accelerate the laboratory testing, Rapid Small-scale Column Tests (RSSCT) can be used to reduce total testing times in many cases.−Depending upon the specific media being tested, smaller
size particles are used to duplicate similar diffusion rates for contaminant mass transfer onto the solid phase.
Tests can usually be completed within a weeks time frame to obtain results.
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Small-scale Column Tests
Water In
Feed
1.4
4m
0.4
2m
0.4
2m
E-4
0.4
2m
0.0
7m
0.4
1m
Outlet Tank
F
Distributor plate
Solids Drain
Rotameter
RecycleWater from tap
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Small-scale column Tests
Test results can determine expected sorption capacity, removal efficiency under specific contact time, and develop isotherm curves with expected break-through volumes. The data obtained through laboratory column tests is
used to develop scale-up testing to conduct on-site pilot testing.
The data can eliminate media types not suitable for further testing.
Can help to establish the expected dynamic removal rate using a packed column. −This rate is usually the best removal the media will be
expected to achieve in controlled conditions.
21
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On-site Pilot Testing
Pilot-scale testing is best performed on site Provides site specific results using real-time raw water
samples from the source. Volume requirements for testing a pilot-scale unit usually
prohibit remote testing. Testing of media systems that appear to offer the
best option design of full-scale system. The pilot test should be designed to resemble and partially
simulate full-scale conditions including:−Media operating contact time and hydraulic loading rates.−Number of operating stages to allow comparative data to
estimate full-scale bed depths.− Column design should include media retaining screen design
similar to that envisioned for the full-scale design. −Pretreatment systems operated to provide expected media inlet
conditions.22
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On-site Pilot Testing
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On-site Pilot Testing
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On-site Pilot Testing
Total media contact time estimated from laboratory small-scale column tests. Using isotherm curves developed from the testing, bed depths
can be estimated using design effluent concentrations. On-site pre-treatment used to maximize removal
efficiency of contaminant(s). This usually includes some type of filtration to remove
suspended material from the water stream that will potentially foul sorption media systems.
Many mine water systems are outside nominal range of pH ideally suited to sorption media.
−pH reagents should be carefully selected to reduce the potential for scale formation, of insoluble salts. • Insoluble salt formation invariably co-precipitates metal complexes and
will ultimately reduce sorption on media systems.
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On-site Pilot Testing
Length of test should be sufficient to establish an operating expectation for changes in water conditions throughout the operating season. Impoundment temperature inversions Blending changes between potential sources Variations in:
−Ambient temperature−Contaminant concentrations−General water quality
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On-site Pilot Testing
Test results establish the expected full-scale performance of the media for contaminant removal and in many cases the media expected break-through volume. Results are analyzed with two primary objectives:
−To compare and verify original expected results from laboratory based data
−Develop full-scale design parameters for use in system design
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Results from Third Zeolite Pilot Test for Thallium Removal at Hilger Mine
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Tl Conc. (mg/L)
Date Influent Col. 1 Col. 3
5-Dec 1.4 0.005 0.002
10-Dec 2.4 0.015 0.002
16-Dec 0.48 0.75 0.056
17-Dec 0.75 0.86 0.086
19-Dec 1.4 0.96 0.13
22-Dec 2.9 1.2 0.27
24-Dec 3.2 0.87 0.13
26-Dec 2.4 1.3 0.26
29-Dec 1.5 1.7 0.4
31-Dec 0.68 1.7 0.48
2-Jan 1 1.6 0.56
5-Jan 0.5 1.3 0.77
1-Mar
AVERAGE 1.8 0.850 0.148
% RED. 53 92
Det. Limit1 0.003
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Pilot Testing for SR-90 Removal
Filter Flow Technology Inc CPFM SystemFlow Rate = 5.7 Liters/minuteResidence = 9.9 minutes
.5 C/Co breakthrough
0
0.5
1
1.5
2
0 500 1000 1500 2000 2500 3000
Column Volume
C/Co
90Sr C/Co
Ca C/Co
Mg C/Co
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Pilot Testing for Zinc and Copper Removal
Adsorption results obtained with column when operated in re-circulating mode
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0 50 100 150 200 250
Volume Processed (L)
Rel
ati
ve
Co
nce
ntr
atio
n (
C/C
o)
Copper - Clinoptilolite Zinc - Clinoptilolite
Copper - Chabazite
Zinc - Chabazite
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Full-scale Media Removal System Design
Full-scale media designs usually include various features: Multiple treatment stages for consistent water treatment
discharge results Service vessels sized for requisite media contact time and
recommended hydraulic loading rates Service vessels are configured for either upflow or downflow
depending upon specific process requirements Vessels designed to facilitate media removal and
replacement. Many applications are a part of a complete water
treatment system to compliment other treatment technologies or further “polish” treated water to assure trace level effluent values
31
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Full-scale Media Treatment System
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Thallium removal setup at CR Kendall Hilger Mine Montana
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Full-scale Media Removal System Design
Pretreatment equipment is incorporated into the design to meet specific media system inlet conditions. Typically pH adjustment and suspended solids removal
systems are employed.
34
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Spent Media Removal Operation
Media-based treatment systems generally require minimal monitoring and process input changes to maintain consistent operating performance.
Regular effluent sampling for compliance and system performance is used to assess the on-going operation. Obtaining operating data to anticipate future media
exchange frequency. Develops long-term operating trends and notifies
changes to inlet conditions Establishes data necessary to estimate future cost
assessments.
35
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Media Exchange and Disposal
Media exchanges accomplished with direct transfer of wetted media from service vessel to transport container using pressure or vacuum.
Replacement media fill using similar conveyance systems as removal
Most cases require an up-flow and downflow pre-service rinse operation. Pre-service rinsing accomplished at or near service
flow rate.
36
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Media Unloading
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Media Replacement and Fill
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Media Exchange and Disposal
Preparation of media for transport Suitable DOT container with linings depending upon
site disposal requirements−Bag liners−Roll-off dumpsters−Dewatering bins
Waste acceptance criteria documentation Includes TCLP testing results to verify non-hazardous
waste disposal Manifest of media contents
39
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Preparation for Transportation
Dewatering Packaging
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Media Exchange and Disposal
No free moisture requirement for land fill disposal less than 1 percent by volume water
Dewatering Moisture lock and absorbents can be used On-site free moisture draining
41
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Media Exchange and DisposalRadionuclide Laden Media
Radionuclide laden media disposal requires additional preparation Estimated radionuclide activity determinations Disposal is limited to select disposal locations Special DOT requirements for radioactive waste
material transportation −DOT Class 7 for waste material exceeding specific
radionuclide activity and total activity thresholds
42
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Media Transportation and Disposal
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Thanks for Attending.
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Questions and Contact Information
James Arnold, P.E.WRT, [email protected]
Daniel T. EydeSt. Cloud [email protected]