Tim Danehy and Bruce Leavitt, Consulting Hydro-geologist, BioMost, “Passive Aeration Using a Trompe“ Water aeration is needed at many mine drainage treatment facilities to oxidize ferrous iron or to remove dissolved carbon dioxide. Typical aeration accomplished through surface diffusion, cascade aeration, mechanical aeration, or with chemical reagents such as hydrogen peroxide. Using an ancient device known as a Trompe, it is possible to achieve the benefits of mechanical aeration without the need for electricity, motors, or any moving parts.

1. Use of TROMPEs in Mine
Drainage Treatment
Bruce Leavitt1, Tim Danehy2, and Bryan Page2
1 Consulting Hydrogeologist 2776 S-Bridge Rd Washington, Pa. 15301
2 BioMost Inc. 434 Spring Street Ext. Mars, PA 16046

2. What is a TROMPE?
 Water powered air compressor
 Has no moving parts
 Can be built from available plastic pipe
 Does not require any electricity
 Does not need much maintenance.
 Produces about 1 cfm / 25 gpm

3. Principals of Operation
Falling water in a pipe entrains air.
The high velocity water carries the air down the
pipe to an air separation chamber.
Compressed air is separated from the water by
gravity.
The air is collected for use.
The water is discharged.

4. What is a TROMPE? continued

5. Trompe History
• Discovered in 17th
century Italy.
• Defining component
of the Catalan Forge
• Developed 1 to 16 oz
pressure

6. Trompe History Continued
• Rediscovered by Charles
Taylor, Canada
• Ragged Chutes Compressor
delivered 128 psi to the area
mines
• Was in continuous operation
for over 70 years with only
two maintenance shutdowns.

7. When is Aeration Needed?
 When ferrous iron is present and
 When the raw water has a low dissolved
oxygen content.
 When the raw water has elevated carbon
dioxide.

8. Ferrous Iron Oxidation
 Many mine drainage treatment facilities
require aeration for iron oxidation.
 Fe2+ + ¼ O2 + H+ → Fe3+ + ½ H2O
 Based on this equation 1 mg of DO will
oxidize 7 mg of ferrous iron.
 The time required for this reaction to occur
is dependent on oxygen transfer to the water
and the pH of the water.

9. Effect of pH
After Dietz 2008
• The higher the pH the
faster iron is oxidized.
• As iron is oxidized the
pH is lowered
lengthening the time
required for oxidation.
• This increase in
detention time requires
a commensurate
increase in pond size.

10. Effect of Carbon Dioxide
 Mine drainage from underground mines
frequently contains excess carbon dioxide.
 The effect of this excess carbon dioxide is
to lower the pH of the raw water.
 Aeration of mine water will remove the
excess carbon dioxide and could increase
pH (Kirby et al., 2009).

11. Aeration Removes CO2
and Increases pH
H+ + HCO3
-
↔ H2O + CO2 (g)

12. Aeration Tests

13. Aeration Tests

14. Aeration Tests

15. Aeration Tests

17. TROMPE Design
 TROMPES operate in a narrow flow range
 Flow is dependent on pipe diameter
 Four feet of head is required between inlet
and outlet
 Maximum pressure is dependent on the
length of the return pipe
 TROMPES can be constructed in parallel or
series to meet flow and air requirements
 TROMPES generate about 1 cfm / 25 gpm

18. 3 TROMPES in Series

19. North Fork Montour Run
Aeration of Pond 2 at 125 gpm flow
with 3 TROMPES in series

20. Oxygen Transfer
 Oxygen transfer to water is dependent on:
– Air flow
– Bubble size (fine bubbles have more surface
area)
– Depth of aeration (10 feet is recommended)
Disc aeration heads used in sewage
treatment produce fine bubbles.
Periodic cleaning is required.

21. Single TROMPE Cost
Gallons per
Minute
Approximate
Pipe Cost
Approximate
Installation Cost
Total Cost
20 to 100 $3,000 $9,400 $12,400
500 - 1000 $15,700 $16,800 $32,500
500 - 3000 $21,800 $24,268 $46,068

22. Semi-Active Lime Dissolution
 Water powered Lime Dosers.
 Long Dissolution Channel.
 Lime Buildup in Channel or Ponds.
 Carbon Dioxide Reacts to Form Calcite.

23. Add Pebble Quicklime

24. MixWell
patent pending
 Raw water is feed to
the bottom of the
MixWell.
 Lime or lime slurry
is added to the
annulus and sinks to
the bottom.
 The lime is agitated
by the raw water.
 Only small particles
rise to the discharge.

25. MixWell

26. Lime Particles from MixWell

27. A-Mixer
patent pending
 Compressed Air
supplied by Trompe.
 Airlift created in 12
inch pipe.
 Circulation in tank
keeps small particles
suspended.
 Airlift provides oxygen
for iron oxidation.

28. A-Mixer

29. Lime Particles from A-Mixer

30. Pebble Quicklime

31. Significant Cost Reduction
$30,000/yr.
$13,900/yr. est.

32. Acknowledgments
 Office of Surface Mining
 PA DEP – Moshannon DMO
 Montour Run Watershed Association
 Allegheny Count Airport Authority
 Gongaware Environmental Services
 Kathy Leavitt (for allowing me to trompe
around the back yard!)

33. Questions