Cattails for cleanup of acidic mine water
New Alexandria, Pa. — Something is happening to the water that seeps from an abandoned coal mine here. At the mine entrance, the water is reddish-brown, acidic, and polluted with iron and other minerals. Downstream it is clear and much cleaner.
Ralph Gray, an engineer for the coal company that owns this western Pennsylvania mine, is trying to explain the phenomenon. He tugs vigorously at a cattail.
``That is what does the work,'' he says, pulling out the tall plant and turning it upside down to expose its roots. For reasons even scientists don't fully understand, cattails and other aquatic plants in shallow-water wetlands can help clean up one of Appalachia's most vexing water problems - acid mine drainage. It causes streams and rivers to run brown with iron and other pollutants.
The natural cleanup process is so promising that mining companies throughout Appalachia are racing to create new wetlands. The number of wetlands built to control acid mine drainage has doubled every year since 1985, mostly in the East. The process is also being used to handle municipal waste in several states around the country.
``I can't believe it,'' says Robert Kleinmann, a supervisor for the US Bureau of Mines research center in Pittsburgh. ``It's the first time we have seen the mining industry jump on a technology this way.'' Dr. Kleinmann expects the current 300 projects to double again next year.
The reason for the enthusiasm is economic.
Since 1977, federal law has required mine companies to clean up polluted waters that flow from their mines, even abandoned ones. The mine drainage is 30 to 300 times more acidic than acid rain and can kill fish and vegetation. It has affected more than 5,000 miles of Appalachian waterways, virtually killing West Virginia's popular Cheat River and even affecting upper reaches of the Potomac River.
The mining industry spends an estimated $1 million a day to clean up this mess. And it is anxious to try any alternative to the expensive chemical treatments now in use.
At this abandoned mine outside New Alexandria, for example, it would cost the North Cambria Fuel Company nearly $8,000 a month to treat the problem with chemicals, Mr. Gray says.
Instead, the company last year built several wetland areas stair-stepping down two sides of the abandoned mine. Upkeep is virtually zero. And if the project eliminates the need for chemicals, it will pay for itself in five or six years, he says.
So far, the project seems to be working.
Acid mine drainage is caused when mining equipment moves soil or rock and exposes pyrite, or ``fool's gold,'' to air or water. This forms iron-laden sulfuric acid. At this mine entrance, the water is very acidic (pH 2.8) and so loaded with iron (400 parts per million) that it looks a rusty red.
But the water gradually clears as it flows into the successive wetlands.
By the fifth shallow-water area, it tests a much better pH of 4.8. The water does not yet meet state standards. Pennsylvania requires a minimum pH of 6 (7 pH is a neutral reading). But the iron content does meet state requirements.
Gray thinks the results will improve even more by next summer, substantially reducing the company's needs for chemical treatment.
Scientists are more guarded in their optimism.
``We think there's tremendous potential for it,'' says Don Hammer, project manager for the Tennessee Valley Authority's wetlands wastewater treatment. ``But there's a lot to be learned.... We don't have very good knowledge about how to build these things.''
In fact, many wetlands built so far have failed to clean up acid mine drainage satisfactorily, he says.
A recent Bureau of Mines survey in Pennsylvania, for example, found that very few wetlands sites brought water quality all the way up to state standards. Iron concentrations were brought within acceptable limits at one-third of the sites; only a fifth neutralized acidity. Manganese remained a problem at all but two of the survey sites.
Research continues at the Bureau of Mines and at the Tennessee Valley Authority. Gray himself has begun experimenting with other methods to clean up the mine's manganese problem.
``We certainly pray that it does do the job,'' he says. ``It would be a boon.''