Most of us might think sewage is just a waste product, but a group of scientists in Belgium are seeing it very differently. They've launched a project to recover precious metals like gold and silver from what we're all flushing away.
ADVERTISEMENTYou and I might not see a goldmine in the sewage water from the city of Brussels, but a team of scientists are hunting for gold and silver here.
"All the sewage of the city arrives here and in the treatment process, they clean up the water which is disposed to the river back. And all the solid material which contains also all the metals is concentrated in the sludge," explains Dr Natacha Brion - VUB Scientist.
Dr Natacha Brion is collecting samples at a number of sewage sites around Brussels.
They're 6 months into a 3 year project. Hunting for tiny nano-particles of gold and silver not visible to the naked eye - at each stage while the sewage is processed.
Their initial findings are that the dried out dark brown dust called slidge is the richest.
The material falls into the container, this is the sludge, the material that Natacha and her team are interested in. It smells disgusting.
Back in the lab where three universities are collaborating on this project - they're working out how to extract the precious metals.
"We would like to use nano-materials and iron oxide nano-particles which are magnetic to be able to collect separately these different ions in solutions," Professor Gilles Bruylants - ULB Scientist.
Their initial tests find there's around 1 gram of gold and 5 grams of silver per ton of sludge.
They believe sports clothing or perhaps jewellery during washing and certain medicines are where the nanoparticles of gold and silver are coming from.
"Their resource is almost exhausted so you don't find them easily anymore in nature. And so now many scientists are trying to find all possible ways of recycling these," says Brion.
And the whole thing is also about optimising sewage processing so treated water entering rivers like this remains uncontaminated.