Scientists are using microbes to clean up the problem of corrosive acid pollution left over as mining waste.
Pollution left at industrial sites is an ongoing issue
Microbes are micro-organisms, especially bacteria which cause disease or fermentation.
Dr Barrie Johnson, from the University of Wales, Bangor, is leading research into their use for cleaning up mine effluents.
Some of the microbes being used were found in the Caribbean and America.
Dr Johnson outlined his work at a conference of the Society for General Microbiology at Heriot-Watt University, Edinburgh on Wednesday.
Microbes which break down minerals are already being used by miners to extract gold, copper and other metals from their ores.
By discovering microbes which can survive in this environment, Dr Johnson aims to build on these developments to address serious environmental hazards at abandoned mines and spoil heaps.
"We work with the mining industry to get metals from ores in more environmentally-friendly ways," he said.
"We tend to work with micro-organisms which can clean up liquid wastes in mines, which tend to be acidic."
Some of the microbes discovered have come from sites in Wales, America and the Caribbean island of Montserrat. "We are using organisms that no-one has seen or worked with before."
He said their techniques were different from others, because their microbes could produce metals ready to be recycled, rather than metal-rich sludges, which he described as "effectively toxic waste".
"Our ongoing research is focussing on extending the applications of biomining technology, and on using newly-discovered extremophile bacteria to simultaneously recover metals and clean up mine effluents from abandoned mines, streams that pass through them and their waste tips," he said.
Bill Keevil, professor of Environmental Healthcare at the University of Southampton, said the potential for microbes to be used in this way had been known for some time.
"The challenge has been to find the strains which can be used to carry out this work," he said.
He said the need was to find microbes which could survive at very high or very low pH values (which express its acidity or alkalinity), and often high temperatures as well.
"The ideal would be a thermo tolerant bug that can survive at a low pH - you can then put it in mine workings where it doesn't mind being...and clean up as they go."