This article was taken from the February 2014 issue of Wired
magazine. Be the first to read Wired's articles in print before
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Alfredo Zolezzi's low-cost purifier could transform the lives of
some of the planet's most deprived people. Once, Alfredo Zolezzi
invented technologies to help corporations refine their oil
more efficiently. But in 2009, he refocused on water. "Science and
technology are advancing quickly, but our innovations are not
always helping the poor," says Zolezzi, 55, founder of the Advanced
Innovation Center in Viña del Mar, Chile.
With the Plasma Water Sanitation System (PWSS), contaminated
water is pressurised and then pumped into a 32cm-long tube. There
it is accelerated to 320m/s to achieve a pressure drop, which
transforms the water into a liquid-and-gas steam. A 5,000-volt
electrical field ionises it, transforming it briefly into plasma --
a state in which the external structures and genetic material of
micro-organisms are destroyed. Finally, the plasma is decelerated
and returned to water. "The whole process takes just a few
milliseconds," says Zolezzi. It has been in use since August 2011
in the San José de Cerrillos slum in Santiago, Chile, where Zolezzi
says it has reduced the incidence of waterborne illness. In tests
performed by the US National Sanitation Foundation, the PWSS killed all bacteria and viruses in
heavily contaminated water.
Each full-size PWSS device, housed alongside a pump and a water
tank in a shipping container, can clean 2,500 litres of water a
day: enough for 125 people. Zolezzi says each full-size unit will
cost £320 when mass-produced. "But I am not a philanthropist," he
says. Instead, by developing compact versions of the PWSS to be
sold as kitchen appliances, Zolezzi plans to build a business that
makes a profit while helping to solve one of humanity's toughest
The contaminated water enters the Plasma Water Sanitation System
in a continuous stream.
The water is rapidly pressurised and then pumped into a
narrow, 32cm-long tube.
Once inside the tube, the water is accelerated to 320m/s - that's
close to the speed of sound.
This acceleration causes a sudden drop in pressure, and the
water becomes a stream of liquid and gas.
A 5,000v electrical field is turned on, ionising the steam
and turning it into plasma.
The water is returned to normal pressure and is now drinkable. The
entire process takes milliseconds.
Watch Alfredo Zolezzi discuss the PWSS at WIRED2013.