Finnish engineers have poured pig manure into a contaminated pond next to an old mine, saying the bacteria in the slurry will clean up metals in the water.

Mining company Outokumpu dumped 450 cubic metres of pig slurry into the waste water near the closed Kangasjarvi mine, which once produced zinc, copper and sulphur.

"Pig slurry contains bacteria that bind metals that are in the mine water and they will sink to the bottom. We have used this system to clean mine waters at various mines", Eero Soininen, Outokumpu's mine reclamation manager, told Reuters.

"Around 15 years ago we noticed mine water got cleaned by itself at our Foldal mine in Norway. We studied the water and found bacteria that eat sulphides."

It takes around 2 to 4 years for sulphide-eating bacteria to get their job done.

Story credit: Reuters and Planet Ark Environmental Foundation, 24 July 2006. Helsinki, Finland