31 August 2006:
A team of Australian scientists is
trailblazing new ways to clean up cancer-causing chemicals that
have been lurking in groundwater under the nation’s cities
for up to 50 years.
Researchers in the Cooperative Research
Centre for Contamination Assessment and Remediation of the
Environment are pioneering a range of techniques to make safe
chlorinated and petroleum compounds and other toxins produced by
industries a generation and more ago.
“Virtually anywhere there has been a
fuel dump, a munitions store, an old chemical factory or heavy
manufacturing plant, there is potential for toxic substances to
leak into groundwater underneath,” says Associate Professor
‘Megha’ Mallavarapu, who leads CRC CARE’s
remediation research programme.
“Today, with urban growth, these sites
are often in the heart of our cities – prime residential real
estate. And the water may be used to irrigate gardens and parks,
sometimes for food production and even for drinking, exposing the
population to a risk from the past.”
CRC CARE researchers are now testing a range
of methods for breaking down toxins underground, without the high
cost and risk of having to excavate or pump and treat the site.
A range of techniques including manipulation
of naturally-occurring microbes, introduction of specially-selected
microbes, physical dispersal, physical lock-up, oxidation and
volatilization are being tested at CRC CARE’s labs at the
University of South Australia.
“Every site presents unique
challenges. No two places are the same, either in the type of
pollutants, the type of soil or the pattern of groundwater flow.
This means we have to tailor a special solution from the range of
techniques available,” Megha explains.
A world-first development is the use of
tracers and monitors to measure the ‘flux’ – or
variation – in the polluted underground water in real time
and over a long period. This enables the researchers to
predict accurately how the pollution will behave, what risk it
poses to humans and to devise the best way to deal with it.
“The preferred solution is natural
attenuation, in which microbes break down the chemical into
harmless fractions or in which it is diluted into
insignificance.
“However in cases where the pollution
is very toxic, is relatively immobile or just not breaking down, we
have to take other measures. These include stimulating the microbes
with fertilizer or oxygen or introducing new mixes of microbes
better able to handle the toxic substance.
The new approach to making pollution safe
begins with establishing the history of what has gone on at the
site over the previous century or so, the exact cocktail of
pollutants and their byproducts which remains, and the soil, water
and biological conditions that are working on them. The next step
is to assess whether the contaminants can reach people via the
water, air, soil or the food supply – their
‘bioavailability’.
This done a tailored plan can be drawn up
for the best way to treat the site and make it safe, he says.
“With the growth in our cities, demand
for remediation services is growing very fast, as new suburbs
overlap old industrial areas,” Megha explains.
“The problem is even greater in Asia, where there are
literally millions of polluted sites, many of them
unknown.”
CRC CARE scientists are already working with
colleagues in China, Korea and the United States to develop ways to
save populations round the world from the epidemic of disease which
many now fear may be the outcome of prolonged exposure to toxic
substances like TCE, PCBs, benzene and other carcinogens.
One of the CRC’s major efforts is to
find ways to make safe the fluorine-based chemicals which are
commonly used in fire-fighting foams. These compounds are highly
persistent and very carcinogenic, yet still in wide use in many
countries including Australia, Megha says.
“We are working on a permeable reactor
technique that allows water to pass through but actively removes
toxic substances,” he says.
Research into techniques for cleaning up the
mistakes of the past also means that industry in future will be far
safer and cleaner – because the same techniques can be used
to cleanse wastes before they enter the environment, he adds.
More information:
Associate Professor Megharaj Mallavarapu, CRC CARE and University
of SA, ph 08 8302 5044 or 0411 035 757
Professor Ravi Naidu, CEO, CRC CARE, ph 08 8302 5041 or 0407 720
257
Kim Sinclair, CRC CARE communication, ph 08 8302 3933 or 0416 095
324
Kim.sinclair@crccare.com
About CRC CARE:
CRC CARE is an Australian partnership of
scientific, industry and government organisations set up to devise
new ways of dealing with and preventing contamination of soil,
water and air.
Its goals include:
- Cleaner, safer food supplies, water
and living conditions leading to a reduced toll of disease due to
toxic contamination of our food, water, air and living
conditions
- Benefits of up to $1.8 billion per year
from direct savings in remediation and improved values or
remediated land
- A cleaner natural environment for Australia
and its neighbours.
CRC CARE is part of the Australian
Government’s Cooperative Research Centres Program.
