SOME of the bacteria that live in aquifers may destroy dangerous viruses. If
they do, this could allow these natural reservoirs to be used to store sewage or
even to help convert it into drinking water.
Worldwide, aquifers hold immense quantities of water. For example, the
Ogallala aquifer that lies beneath parts of Texas, Kansas, Nebraska and South
Dakota contains as much as 4 trillion tonnes of water. Hydrologists believe they
could use such natural formations as a cheap way to store sewage, storm water
run-off and other types of contaminated water that can have a devastating impact
if they are allowed to drain into rivers.
At the moment, health fears prevent such water being used for irrigation
because it contains viruses and protozoa such as Cryptosporidium, which
causes life-threatening diarrhoea. So Simon Toze and his colleagues at the CSIRO
Centre for Groundwater Studies in Perth, are investigating how those
microorganisms fare in water from the aquifer at Bolivar, near Adelaide.
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Toze seeded sterilised and unsterilised samples of Bolivar water with
poliovirus. To some samples, he added sterilised sewage as a tasty food for any
bacteria. Within 40 days, the poliovirus was undetectable in the unsterilised
samples containing sewage.
The virus also was also destroyed in the other samples, but at a slower rate.
The virus disappeared fastest under conditions that allowed the bacteria to
flourish. Toze believes this could be a metabolic effect.
鈥淓ither the bacteria are using the virus as food or they are producing
something else that is killing the virus off,鈥� he says. Bacteria are less of a
threat than viruses because they can be easily killed off with chlorine or other
treatments.
The CSIRO team and the American Water Works Research Foundation are looking
at using aquifers to reduce the cost of producing drinking water. Whether this
will be feasible isn鈥檛 clear.
鈥淲e鈥檙e running blind at the moment,鈥� says Nicholas Ashbolt, a water
microbiologist at the University of New South Wales in Sydney. 鈥淲e don鈥檛 know
the ecology of these subsurface environments.鈥�