16th-Century Method May Ease Mine Drainage
24 June 2013
By Don Hopey
A technology dating to the 16th century and built with PVC piping
available at any Home Depot or Lowe's will soon be used to enhance
and possibly revolutionize the treatment of abandoned mine
drainage, still Pennsylvania's biggest water quality problem.
The technology, called "trompe," an old French word meaning
trumpet, is a water-powered air compressor with no moving parts.
It has been adapted and developed by Bruce Leavitt, a mining
hydrologist and professor of mining engineering at West Virginia
University, to provide enhanced aeration of polluted mine water,
which speeds the cleanup process.
Use of trompe technology is especially applicable to the hundreds
of mine discharges flowing out of the Pittsburgh coal seam in
Western Pennsylvania, said Mr. Leavitt, during a walking tour of a
trompe-enhanced passive treatment system on the North Fork of
Montour Run in Findlay, 2 miles south of the Pittsburgh
"Trompe can reduce the size and cost of passive treatment systems
for mine drainage," he said, "And it can take a treatment system
that's not working, or not working well, and clean the water
PG graphic: Passive aeration of mine water
(Click image for larger version)
A trompe is a device that uses falling water to compress air.
According to a paper submitted by Mr. Leavitt at a mine discharge
symposium in March 2011 in Morgantown, W.Va., mine discharge can
be collected into a trompe system where it is allowed to fall down
a vertical pipe. The water falls faster than the air bubbles
trying to escape up the pipe and so traps and compresses the air.
At the bottom of the vertical pipe the water enters a horizontal
separation chamber where water flows into a discharge pipe and the
air escapes into vertical chambers and from there is piped up to
the first mine discharge pool.
That compressed air is piped through submerged heads to aerate the
mine discharge water in a bubbling pond, oxidizing the suspended
iron and causing it to form heavier, rusty-orange particles that
fall out of the water column and collect on the bottom of the
Last week, approximately 65 gallons of water a minute was flowing
through the three trompes installed on the North Fork treatment
project, generating 5 cubic feet a minute of compressed air, Mr.
Leavitt said. Those trompes, each with a four-foot vertical fall
pipe, can handle almost twice that flow.
It's long been known that aeration speeds up the oxidation of iron
and chemical reactions that occur during the treatment of mine
water drainage, which pollutes more than 2,500 miles of streams
and rivers in Pennsylvania. Through the years aeration has been
accomplished by cascade aeration, mechanical aeration using
electricity or expensive chemical treatments.
By using the ancient trompe technology it's now possible to get
the benefits of mechanical aeration without the use of expensive
motors, electricity or any moving parts, Mr. Leavitt said.
"Anyplace you would need aeration, whether an active or passive
system, can use something like this," Mr. Leavitt said. "It's
going to generate a lot of oxygen transfer."
In the 17th century, a trompe was used instead of a bellows by the
Spanish to introduce compressed air into medieval Catalan forges
for iron production. Use of trompe technology peaked in the late
19th century and early 20th century when it was used to provide
compressed air to cotton mill forges and other industrial
In 1910, the Ragged Chute trompe, the biggest ever built -- it had
a 345-foot-long vertical fall -- began operation near Cobalt,
Ontario, where it generated compressed air to run rock drills at a
silver mine and, Mr. Leavitt said, "as a side benefit provide
ventilation to the miners."
Tim Danehy, principal of BioMost Inc., a mining reclamation
services company and project designer and consultant on the North
Fork site, said the passive treatment system, involving a series
of five ponds and a wetland, cost $674,000 in 2008, and was built
to last 25 years. The cost of adding the three trompes to make the
treatment system more efficient was about $30,000.
"You could go to Lowe's and buy all that stuff and that's part of
the idea; to keep it all low-tech and low-cost. Of course the
bigger the trompe the more it costs," he said.
In addition to the Findlay passive treatment site, trompe aeration
units have been installed at the Curley site in Fayette County and
the Manner site in Clearfield County, where it is used to drive an
air lift mixer for mine drainage treatment.
Industry representatives on the North Fork tour were impressed.
Jim Kelly, from Arch Coal, said the technology has potential if
the mine drainage contains significant carbon dioxide, and Greg
Mergenthaler, manager of environmental compliance at Carter Roag
Coal Co. in Randolph, W.Va., said the demonstration project is
producing "excellent results," noting, "That's water that will
support aquatic life."
Lois Uranowski, chief of the Ecological Services and Technology
Transfer Branch at OSM, said the development of the trompe
technology grew out of the federal office's 2010 Applied Science
"That year we asked the question, 'How do we improve water
treatment?' And we received this proposal from Bruce Leavitt that
is practical, simple and easily installed. We've had a lot of
interest from Appalachian states and all over."
Don Hopey: email@example.com or 412-263-1983.