1. Formation and Treatment
Acid Mine Drainage
Formation and Treatment

2. Introduction AMD is an environmental concern many states face
2nd largest polluter in PA streams
PA has over miles of streams impacted
1910—AMD research began
1977—passage of Surface Mine Control and Reclamation Act (SMCRA)

5. AMD Formation
AMD occurs due to the exposure of overburden during mining
Function of geology, hydrology and mining technology
Neutralizing compounds are absent from soil and the water becomes acidic
Contaminated with high concentrations of Fe, Mn, Al, and SO4

8. Chemistry Pyrite + Oxygen + Water  “Yellowboy” + Acid
4FeS2 + 15O2 + 14H2O  4Fe(OH)3 + 8H2SO4

9. Effects of AMD Oxygen removal Depletes buffering capacity
Decreases light penetration
Smothers bottom dwellers
Directly toxic
Economic: PA loses $67 million each year

12. Treatment of AMD 1968—PA instituted strict effluent discharge limits
Coal companies used chemical treatment to meet standards
Calcium carbonate, sodium hydroxide, anhydrous ammonia
Raise pH and precipitate metals

13. Active Treatment
Mechanized procedure for addition of alkaline material
Needs constant monitoring and maintenance
Can exceed $200,000 per year at one site
Produces large volumes of sludge
Potentially harmful chemicals are used
Caustic soda, soda ash, sodium hydroxide

15. Passive Treatment Mid 1980s No input of manufactured chemicals
Lower operation costs
Longer retention times and larger treatment areas
First passive system was natural Sphagnum wetland

16. Constructed Wetland
Encourage oxidation processes to precipitate metals and increase pH
Aerobic
Rely on oxidation
Shallow, vegetated
Surface flow
Anaerobic
No oxygen
Organic layer with sulfate reducing bacteria

19. Anoxic Limestone Drain
Alkalinity produced by AMD reacting with calcium carbonate
Constructed as shallow channel sealed from atmosphere
Used of oxidation basin after for metals to precipitate

21. Vertical Flow Wetland Combine ALDs and anaerobic wetlands
Constructed as ponds with grid like piping system, 3’ of limestone, 2’ of mushroom compost, and 2-3’ of standing water
Adds alkalinity through limestone dissolution and sulfate reduction

23. Open Limestone Channels
Simplest passive treatment method
Construct drainage ditch and fill with limestone
Or, add limestone directly to the stream
High velocity and turbulence enhance performance, steep slopes

25. Diversion Wells Well of limestone
Hydraulic force of the water causes the limestone to mix and abrade particles of limestone
Diverted back to the stream

29. Problems Use depends on water chemistry and flow rates
Must calculate loadings!
High Fe may “coat” limestone, less efficient
High Al will precipitate and plug pore space

30. Other Solutions Remining Reclamation Removal of “spoil” piles
Injection of alkaline material into mines
Sealing of deep mine portals
Fix at source instead of band-aid!