Saturday, 26 December 2015

Sewage Sludge good as Gold

Precious metals worth an estimated £13m are flushed down UK sinks and drains each year.

Gold, silver and platinum end up in sludge with the washing of hands (rubbing gold rings) and brushing of gold teeth. Cars deposit traces of platinum in drains from catalytic converters and precious metals are increasingly used in shampoos, detergents and even in nanoparticles in clothes. The result is a level of gold in sewage systems comparable to that found in working mines.
Earlier this year, researchers from Arizona State University found that a city of a million people can produce around $13m worth of precious metals annually, including $2.6m in silver and gold. They found that amounts of the 13 most valuable elements, including silver, copper, gold and platinum, were worth about $280 US ($350 Cdn) per tonne of sludge. Researchers noted that cities currently pay about $300 to $400 per tonne to get rid of their sewage sludge or biosolids.

At a sewage treatment facility in the industrial town of Suwa, north-west of Tokyo, they’re incinerating sludge and processing the molten ash. In 2009 the plant reported a yield of gold to rival production levels at the world’s leading mines. It collected nearly two kilograms of gold in every ton of ash.
About 60% of the sewage sludge in the United States is spread on fields and forests as fertilizer. The remaining sludge is burned in incinerators or dumped in landfills.

Cost is one of the chief barriers keeping sewage treatment plants from going for the gold.
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All that glitters is gold in the sewers of Chickpet
The streets may not be paved with gold but the gutters of Chickpet, Bangalore is an El Dorado. At least for the workers who, at the break of dawn, descend on a maze of lanes near the K R Market area to slip into the murky pits that receive the overnight and morning ablutions of the locals. They are looking for gold.

In the early hours, manholes with covers removed are guarded by boys to warn drivers of vehicles. One might assume the band is on a cleanliness drive or mistake them for manual scavengers hired by civic agencies to clean the sewers.

The area is a major hub for goldsmiths and jewellers. There are more than 300 goldsmiths in this area who are the design supply chain for some of the top jewellers in the city.

The gold dust from these workshops lands in the drains when the goldsmiths wash up at the end of the day or gets strewn on pathways as powder. That is the mother lode for the young boys are purposefully hunting for gold.
Once it is collected, the gold is sold to dealers in the same area.

A goldsmith for the past 45 years explains "When we're melting gold, there's a small amount of wastage -- for every 10 gm, at least 1 gm is lost.