Replacing an Aged Lime Treatment Plant with Passive and Semi-Passive Treatment Techniques

Replacing an Aged Lime Treatment Plant with Passive and Semi-Passive

Treatment Techniques

Presented by:

Tyler Chatriand, PE

Sovereign Consulting Inc.

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

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

The Problem - Acid Rock Drainage (ARD)

Stumm and Morgan, 1981 Gusek, 2004

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)

Vicinity Map

Active Mining - 1993

Post Mining - 2006

Treatment Plant

Coal Refuse Area #5

Coal Refuse Area #4

Coal Refuse Area #6

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

Existing ARD Treatment

Treatment Alternatives Analyses

Passive vs. Active? Hybrid

Site Characterization

Review Historical Data

Inventory ARD Sources

Establish Monitoring and Gaging Stations

Evaluate Water Chemistry and Contaminant Loadings

Identify Treatment Alternatives

ARD Sources

Conceptual Site Model

Proposed Semi-Passive System

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

Pebble Quicklime at ARD Source

Aquafix – water wheel driven chemical feed system

Pond 14 Lime Dosing Footprint

400 sf

Passive Mixing/Aeration – BioMost, Inc

MixWell A-Mixer

BioMost, Inc BioMost, Inc

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

Field Pilot Testing

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

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.

Recap

Semi-Passive Treatment is a viable, cost-effective alternative to solely active or passive treatment 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

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