By filtration...
"A small French start-up company is selling a technology with a hint of alchemy: turning water into gold.
It does so by extracting from industrial waste water the last traces of any rare -- and increasingly valuable -- metal..."
http://uk.finance.yahoo.com/news/modern-alchemy-leaches-gold-water-120603193.htmlIgnorance is bliss, bliss is happiness, I am happy...to draw your attention to the possible connectivity in the foregoing.