The document summarizes replacing an aged lime treatment plant for acid rock drainage (ARD) with passive and semi-passive treatment techniques. It describes analyzing alternatives including a new active lime plant versus a hybrid passive treatment train. The proposed semi-passive system includes quicklime dosing at ARD sources, passive mixing/aeration, and passive aeration using Trompes. Field pilot testing was conducted and economic analysis found the hybrid passive approach to have lower total costs over 30 years compared to a new active treatment plant. Source control methods were also discussed to potentially treat ARD at its source and eliminate long-term water treatment needs.

1. Replacing an Aged Lime Treatment
Plant with Passive and Semi-Passive
Treatment Techniques
Presented by:
Tyler Chatriand, PE
Sovereign Consulting Inc.

2. Mine Water Treatment Options
 Active Treatment
 Uses chemicals, energy, labor, & infrastructure to produce clean water in the
shortest time & smallest possible footprint
 Passive Treatment
 Capitalizes on the low-energy dynamics employed in natural biological and
geochemical processes at ambient temperatures





No moving parts or power requirements => Simple to operate
Resilient to quantity variations (flow rates, temp, chemistry)
Blends into landscape, wildlife habitat
Low O&M
Large footprint, long HRT, high capital
 Semi-Passive Treatment
 Utilizes moving parts and chemicals WITHOUT continuous power and labor
required for active treatment systems

3. The Problem - Acid Rock Drainage (ARD)

ARD is formed by the oxidation of sulfide minerals
when exposed to air and water.

Acidithiobacillus
ferrooxidans –
metabolizes iron and
sulfur to produce
sulfuric acid
Gusek, 2004
Stumm and Morgan, 1981

4. Project Background
 Inactive Coal Mine in Western PA
 Surface Mine
 2 Underground Mines


Upper Freeport coal seam
Kiskiminetas coal seam
 3 Coal Refuse Disposal Areas

Waste rock piles – Acid Rock Drainage (ARD)

5. Vicinity Map

6. Active Mining - 1993

7. Post Mining - 2006
Coal Refuse Area #5
Coal Refuse Area #4
Coal Refuse Area #6
Treatment Plant

8. Existing ARD Treatment
Hydrated Lime Feed Plant
• 25+ yrs old
• Weak structural integrity
• Inadequate pump system
• Single stage treatment
• Insufficient Mn/Al removal
• Clean stormwater routed
below compliance point


Treatment Alternatives Analyses
 Passive vs. Active?  Hybrid

9. Site Characterization





Review Historical Data
Inventory ARD Sources
Establish Monitoring and Gaging
Stations
Evaluate Water Chemistry and
Contaminant Loadings
Identify Treatment Alternatives

10. ARD Sources

11. Conceptual Site Model

12. Proposed Semi-Passive System

13. Alternatives Analysis
 Economic Analyses
 New Active Plant vs. Semi-Passive
Treatment
Option
Capitol
Cost
Annual
O&M
Total Cost
Year 1
Total Cost
Year 5
Total Cost
Year 10
Total Cost
Year 20
Total Cost
Year 30
Hybrid Passive
Train
$2,419,568
$120,360
$2,539,928
$3,021,367
$3,623,167
$4,826,766
$6,030,364
Lime Treatment
Plant
$1,922,845
$400,000
$2,322,845
$3,922,845
$5,922,845
$9,922,845
$13,922,845

14. Pebble Quicklime at ARD Source
 Aquafix – water wheel driven
chemical feed system

15. Pond 14 Lime Dosing Footprint
400 sf

16. Passive Mixing/Aeration – BioMost, Inc
MixWell
BioMost, Inc
A-Mixer
BioMost, Inc

17. Passive Aeration - Trompe
 Water-powered air compressor

For every 4’ TDH,
= 1 cfm/25 gpm

Pond 14 Outfall = 13’

3 Trompes in series
= 4 CFM at base flow

18. Field Pilot Testing

19. Source Control

Back to the ARD Tetrahedron

Remove the Source
 Circulating Fluidized Bed Combustion
Impermeable cap – high cost
 In-situ treatment

 pHoamTM injection technology

Waste milk, Biosolids, Surfactants (SLS)
 Biochemical reactor (BCR) effluent

20. Source Control – BCR Effluent

BCR - uses sulfate-reducing bacteria to produce sulfide and bicarbonate, allowing metals to
precipitate as metal sulfides.
 Excess alkalinity generated by sulfate reducing bacteria and limestone dissolution in the
BCR substrate
 Excess dissolved sulfide ion, which can bind with dissolved ferrous iron to form iron
mono-sulfide coatings/deposits, and
 Dissolved manganese which could coat pyritic refuse in deeper, more aerobic zones of the
refuse area with manganese oxide.

21. Recap

Semi-Passive Treatment is a viable, cost-effective
alternative to solely active or passive treatment

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
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


Treat at the source - reduce SW impacts, flow flux, reclaim stream
Small footprint
Increased chemical utilization
No power required - reliable
Minimal labor – periodic inspections
Low capital and O&M
Effective – meet stringent discharge permit limits
Innovative Source Control Methods
 Water treatment in perpetuity
 Eliminate the source  Only walk-away solution
 Stage 3 Reclamation Bond Release

22. Questions?
Tyler Chatriand, PE, CFM
Environmental Engineer | email: tchatriand@sovcon.com
Office: 206.812.8265
Cell: 406.471.0436
Sovereign Consulting Inc.
2101 Fourth Ave, Suite 2130
Seattle, WA 98121
www.sovcon.com