A sewage treatment facility in [Nagano prefecture,] central Japan has recorded a higher gold yield from sludge than can be found at some of the world’s best mines. [T]he high percentage of gold found at the Suwa facility was probably due to the large number of precision equipment manufacturers in the vicinity that use the yellow metal. The facility recently recorded finding 1,890 grammes of gold per tonne of ash from incinerated sludge [far higher than the 20-40 grammes per tonne] of Japan’s Hishikari Mine, one of the world’s top gold mines.
The prefecture [...] expects to earn about 15 million yen [US$ 168,000] for the fiscal year to the end of March from the gold it has retrieved from the ashes of incinerated sludge.
Source: Miho Yoshikawa, Reuters, 30 Jan 2009