SCIENTISTS DISCOVER HAZARDOUS WASTE EATING BACTERIA
Tiny single-cell
organisms discovered living underground could help with the problem of nuclear
waste disposal, say researchers involved in a study at The University of
Mancheste
Although bacteria with
waste-eating properties have been discovered in relatively pristine soils
before, this is the first time that microbes that can survive in the very harsh
conditions expected in radioactive waste disposal sites have been found. The
findings are published in the ISME
(Multidisciplinary Journal of Microbial Ecology) journal.
The disposal of our
nuclear waste is very challenging, with very large volumes destined for burial
deep underground. The largest volume of radioactive waste, termed 'intermediate
level' and comprising of 364,000m3 (enough to fill four Albert
Halls), will be encased in concrete prior to disposal into underground vaults.
When ground waters eventually reach these waste materials, they will react with
the cement and become highly alkaline. This change drives a series of chemical
reactions, triggering the breakdown of the various 'cellulose' based materials
that are present in these complex wastes.
One such product
linked to these activities, isosaccharinic acid (ISA), causes much concern as
it can react with a wide range of radionuclides -- unstable and toxic elements
that are formed during the production of nuclear power and make up the
radioactive component of nuclear waste. If the ISA binds to radionuclides, such
as uranium, then the radionuclides will become far more soluble and more likely
to flow out of the underground vaults to surface environments, where they could
enter drinking water or the food chain. However, the researchers' new findings
indicate that microorganisms may prevent this becoming a problem.
Working on soil
samples from a highly alkaline industrial site in the Peak District, which is
not radioactive but does suffer from severe contamination with highly alkaline
lime kiln wastes, they discovered specialist "extremophile" bacteria
that thrive under the alkaline conditions expected in cement-based radioactive
waste. The organisms are not only superbly adapted to live in the highly
alkaline lime wastes, but they can use the ISA as a source of food and energy
under conditions that mimic those expected in and around intermediate level
radwaste disposal sites. For example, when there is no oxygen (a likely
scenario in underground disposal vaults) to help these bacteria
"breath" and break down the ISA, these simple single-cell microorganisms
are able to switch their metabolism to breath using other chemicals in the
water, such as nitrate or iron.
The fascinating
biological processes that they use to support life under such extreme
conditions are being studied by the Manchester group, as well as the
stabilizing effects of these humble bacteria on radioactive waste. The ultimate
aim of this work is to improve our understanding of the safe disposal of
radioactive waste underground by studying the unusual diet of these hazardous
waste eating microbes.
One of the
researchers, Professor Jonathan Lloyd, from the University's School of Earth,
Atmospheric and Environmental Sciences, said: "We are very interested in
these Peak District microorganisms. Given that they must have evolved to thrive
at the highly alkaline lime-kiln site in only a few decades, it is highly
likely that similar bacteria will behave in the same way and adapt to living
off ISA in and around buried cement-based nuclear waste quite quickly.
"Nuclear waste
will remain buried deep underground for many thousands of years so there is
plenty of time for the bacteria to become adapted. Our next step will be to see
what impact they have on radioactive materials. We expect them to help keep
radioactive materials fixed underground through their unusual dietary habits,
and their ability to naturally degrade ISA."
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