Sydney
SYRINGES, infectious body parts, and other types of hospital waste are being
turned into an inert pulp using a disposal system developed by Australian
chemists. The result can then be disposed of safely at a landfill site.
Cairns Base Hospital in Queensland has been testing the new disposal system,
called Matrix. In trials, the hospital found that the system could successfully
sterilise even the tough bacteria that cause tuberculosis and leprosy.
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Waste material is tipped into a chute and sprayed with dilute hydrogen
peroxide to kill airborne bacteria. It is then shredded into a mixture
resembling muesli. After this, it passes into a container where it is mixed for
five minutes with calcium oxide and bentonite clay. The mixture is then sprayed
with sodium silicate. The calcium oxide kills the bacteria by breaking down cell
walls. 鈥淚t literally dissolves the beasts,鈥� says Matrix鈥檚 inventor Stephen
Webb.
The bentonite absorbs moisture and traces of pharmaceuticals. The sodium
silicate has two functions. It fixes some heavy metals, which prevents them
leaching into watercourses once the material has been dumped in a landfill site.
It also reacts with the calcium oxide to produce a cement that binds the
material while it is being disinfected.
After 48 hours in a skip, the result, which shrinks by 80 per cent during
processing, is sterile enough to be used for landfill. 鈥淭he bugs are dead, the
lime reacts with carbon dioxide in the air to form calcium carbonate and the
peroxide breaks down to water and oxygen,鈥� says Webb. While plastics, such as
PVC, are not destroyed, they degrade quickly in the ground, Webb says, because
they are so finely shredded. Matrix can handle 200 kilograms of waste an hour.
The process can cope with most items found in hospital waste, with a few
exceptions such as large quantities of pharmaceuticals and radioactive
material.
An Australian government grant of $200 000 (拢100 000) and a
partnership with the Cairns-based engineering company NQEA, which put in
$1 million, turned the initial idea into a going concern. The unit costs
7 cents per kilogram of waste to run and is now in commercial operation.
Matrix鈥檚 only disadvantage is that its end product is relatively heavy and
Australian landfill charges are based on weight. Despite this, Webb thinks it
will catch on. 鈥淭he product is non-odorous and non-identifiable as hospital
waste,鈥� he says. 鈥淚t鈥檚 very economical to run and purchase and is
environmentally friendly. It鈥檚 got a lot going for it.鈥�
