NEWCASTLE UPON TYNE, England, Feb. 6 (UPI) -- British researchers say llama droppings may soon help villagers in the Andes fight water pollution from silver and tin mines.
The scientists say their time-tested method, already in use in England with horse and cow manure, can empower small, local groups to create "bioreactors" from bacteria in the dung to purify the extremely acidic water from abandoned mines.
"We're doing this to try and give help to people who would otherwise be stuck with an environmental nightmare," said lead researcher Paul Younger, a hydrogeochemical engineer at the University of Newcastle upon Tyne. "We're hoping this will help provide low-cost solutions that can really empower local communities to take the environment into their own hands."
The bioreactors are simply ponds that contain limestone gravel buried under a layer of compost with manure in it. Bacteria living in the bioreactors use dissolved sulphate -- which is always found in mine water in abundance -- as an energy source, much the same way humans use oxygen.
This microbial activity produces sulphide molecules that trap and precipitate out dissolved metals. The limestone helps the bacteria neutralize the acidic mine water while the compost serves as the bacteria's food source.
The bioreactor technique developed by Younger was originally designed to help former coal and iron mining communities in northeast England. It has proven so successful that the researchers are now trying to customize it for similar problems in other countries -- in this case, Bolivia.
"From the day I took up my first university post," Younger explained, "I instinctively sought opportunities to place my technological insights and skills at the disposal of grass roots organizations and individuals who are striving to take control of their own destinies, to the long-term benefit of the ecosystems on which we all ultimately depend."
Damage from an abandoned mine named Mina Milluni in the Andes is seriously polluting the main water supply of Bolivia's capital, La Paz. Mina Milluni closed abruptly in 1985 as a consequence of the global slump in tin prices which occurred that year.
"The former mining company has neither the financial resources nor the legal responsibility to remediate the polluted drainage," Younger said. "The problem will continue indefinitely unless some local champions decide to find solutions of their own."
While the city's waterworks efficiently cleans the water, some of it is used untreated by impoverished local residents for domestic and agricultural purposes. Younger is working with Bolivian engineers to see if bioreactors can help, but the natural obstacles are considerable. The mine lies well above sea level, so at night temperatures dip below freezing for much of the year, impairing water flow into the bioreactors.
Bioreactors in Britain also depend on cows or horses for manure, animals that do not do well in the thin air of the Andes.
However, any herbivorous mammal appears to do the trick, and llama droppings do just as well than cow manure, if not better, Younger told UPI.
The researchers experimented with four small llama-based bioreactors for a five-month period in 2000. A continuous flow of acid drainage was filtered through the tanks between June and November, the coldest time of the year in the Bolivian Andes.
The findings from the experiment were extremely encouraging, Younger said. The bacteria generate enough heat to counteract freezing, and the llama droppings promoted bacterial activity as hoped, making the water significantly less acid. The water entering the bioreactors was roughly as acidic as vinegar, or pH 3.2, and upon leaving was about pH 6.3, less acidic than rainwater.
"That's good -- that's exactly what you hope to hear," said Bob Kleinmann, director of the environmental science and technology division for the National Energy Technology Laboratory in Pittsburgh. "That gives hope for the system."
Younger and his colleagues are trying to find funding to support the Bolivian engineers to develop larger bioreactors.
(Reported by Charles Choi in New York.)