This document discusses acid mine drainage (AMD), its causes, effects, and treatment methods. AMD is highly acidic water formed through chemical reactions between oxygen, water and sulfide minerals exposed during mining. It causes environmental issues by increasing acidity in water resources and releasing metals. The main chemical reaction involves pyrite oxidizing to produce sulfuric acid. Passive treatment methods for AMD include using calcium oxide, ammonia, wetlands, or open limestone channels to neutralize acidity and precipitate metals. The best prevention approach is proper mine reclamation to restrict air and water contact with pyritic materials.

1. Acid Mine Drainage And Its
Control Measures
Submitted By:
Sachchidanand Singh
109MN0504
Email Id: sachchi1991@gmail.com

2. Introduction: What is
Acid Mine Drainage (AMD)?
• Highly acidic water with elevated levels of
dissolved metals.
• Drainage from surface or deep coal or metal
mines and coal refuse piles.
• An important environmental issue in many
areas where mining has taken place.

3. Sources of Acid Mine Drainage
• Mining of gold, silver, copper, iron, zinc,
lead (or combined metals), and coal
– During exploration, operation, and closure of
mine, from the mine’s:
• dewatering system
• tailings disposal
• waste heaps

4. Process of Acid Mine Drainage
• Geochemical and microbial reactions during
weathering of sulfide minerals (pyrite) in
coal, refuse, or mine overburden
– Oxidation of sulfide minerals in the presence of
air, water, and bacteria
– Formation of sulfuric acid and increase in
acidity
– Solubilization of metals due to low pH

5. Effects of Acid Mine Drainage
• Water resources
– Increased acidity
– Depleted oxygen
– Increased weathering of minerals ⇒ release of
heavy metals/toxic elements into stream
– Precipitation of Fe(OH)3 ⇒ bright orange color
of water and rocks

6. Effects of AMD (cont’d)
• Biological resources
– Low pH and oxygen content ⇒ water
unsuitable for aquatic life
– Precipitation of Fe(OH)3
• Increased turbidity and decreased photosynthesis
• Clogging of interstitial pore space in coars aquatic
substrate habitat

7. Effects of AMD (cont’d)
• Biological resources
– Elimination of aquatic plants ⇒ change in
channel hydraulics
– Stress on other biota associated with aquatic
habitats
• Human resources
– Corrosion of pipes, pumps, bridges, etc.
– Degradation of drinking water supplies
– Harm to fisheries

8. Chemistry of Acid Mine Drainage
Reaction 1
2FeS2 + 7O2 + 2H2O → 4Fe 2+
+ 4SO4 + 4H+
• weathering of pyrite in the presence of oxygen and water to
produce iron(II), sulfate, and hydrogen ions
Reaction 2
4Fe2+
+ 7O2 + 2H2O → 4Fe3+
+ 2H2O
• oxidation of Fe(II) to Fe(III)
• rate determining step

9. Chemistry of AMD (cont’d)
Reaction 3
2Fe3+
+ 12H2O → 4Fe(OH)3 + 12H+
• hydrolysis of Fe(III)
• precipitation of iron(III) hydroxide if pH > 3.5
Reaction 4
FeS2 + 14Fe3+
+ 8H2O → 15Fe2+
+ 2SO4
2-
+ 16H+
• oxidation of additional pyrite (from steps 1 and 2) by Fe(III) --
here iron is the oxidizing agent, not oxygen
• cyclic and self-propagating step

10. Chemistry of AMD (cont’d)
Overall Reaction
4FeS2 + 15O2 + 14H2O → 4Fe(OH)3 + 8H2SO4

11. Treatment
• Chemical Treatment
1. Calcium Oxide
2. Anhydrous Ammonia
• Passive Treatment
1. Wetlands
2. Open Limestone channel

12. Calcium Oxide
• Its Alkaline in nature
• Addition of calcium oxide increase the PH
level of AMD.
• Cause many of the metals present in
solution to precipitate as hydroxides and
carbonates.
• It has the lowest material cost and is the
safest and easiest to handle.

13. Anhydrous Ammonia
• In the gaseous state, ammonia is extremely
soluble and reacts rapidly.
• It behaves as a strong base and can easily
raise the pH of receiving water.
• Injection of ammonia into AMD is one of
the quickest ways to raise water pH.
• It should be injected into flowing water at
the entrance of the pond to ensure good
mixing because ammonia is lighter than
water.

14. Wetlands
• Wetlands have several functions that aid in
the removal of metals in drainage
• It acts on filtering mechanism of the dense
plant root system which catches any of the
suspended solid and flocculated particles as
they pass through the wetland.
• There are two types of wetland which are
used: 1. Aerobic wetlands 2. Anaerobic
wetlands

15. • Aerobic wetlands are shallow (1- to 3-foot
deep) ponds; they filled with soil or organic
matter. They facilitate natural oxidation of
the metals and precipitate iron, manganese,
and other metals.

16. • Anaerobic wetlands are shallow ponds
filled with organic matter, such as compost,
and underlain by limestone gravel. It used
to neutralize acidity and reduce metals to
the sulfide form.

17. Open Limestone Channel
• Its an open, free-flowing channel lined with
coarse limestone.
• These systems oxidize and precipitate
metals and add alkalinity to the water.

18. The best method to treatThe best method to treat
AMD is preventionAMD is prevention
This can be done by
using proper
reclamation
methods, which
prevents air and/or
water from
reaching the pyritic
materials.

19. References
1. Acid mine drainage remediation options: a review D.
Barrie Johnson*, Kevin B. Hallberg,School of
Biological Sciences, University of Wales, Bangor
LL57 2UW, UK
2. The Science of Treating Acid Mine Drainage and
Smelter Effluents By Bernard Aubé, P. Eng.,
M.A.Sc. EnvirAubé 361 Aumais, Ste-Anne-de-
Bellevue Québec, Canada, H9X 4A9
3. en.wikipedia.org/wiki/Acid_mine_drainage
4. www.wvu.edu/~agexten/landrec/water.htm

20. THANK YOU