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SILICON
CHIP
www.siliconchip.com.au
Publisher & Editor-in-Chief
Leo Simpson, B.Bus., FAICD
Production Manager
Greg Swain, B.Sc.(Hons.)
Technical Editor
Peter Smith
Technical Staff
John Clarke, B.E.(Elec.)
Ross Tester
Jim Rowe, B.A., B.Sc, VK2ZLO
Reader Services
Ann Jenkinson
Advertising Enquiries
Phil Benedictus, Laurence Smith
Benedictus Smith Pty Ltd
Phone (02) 9211 9792
Fax: (02) 9211 0068
info<at>benedictus-smith.com
Regular Contributors
Brendan Akhurst
Rodney Champness, VK3UG
Julian Edgar, Dip.T.(Sec.), B.Ed,
Grad.Dip.Jnl
Mike Sheriff, B.Sc, VK2YFK
Stan Swan
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Publisher’s Letter
Desalination a sensible approach
for Perth’s water supply
This summer has certainly highlighted the ongoing water shortages faced by most Australians,
whether they live in the cities or rural areas. One
way or another, we need more fresh water, whether
it is obtained by more careful use of our existing limited water resources or by obtaining new
sources. For the cities, the problems are possibly
more urgent than in rural areas which are always
subject to periods of drought.
Perth has the most pressing problems, followed
by Sydney, Melbourne and Adelaide. Perth has had declining rainfall over
the last 30 years or so and has much reduced run-off into its dams. So Perth
is taking the immediate approach of building a sea-water desalination plant,
located next to the Kwinana power station. This makes sense, since it is close
to the sea and the power source.
The plant will use the reverse osmosis process whereby sea-water under
high pressure is applied to semi-permeable membranes to remove salt and
other dissolved solids.
Reverse osmosis is the favoured process because it is one of the most energy
efficient, although all desalination processes use large amounts of energy –
hence the need to site the plant next to a power station.
Perth’s proposed plant has an annual capacity of 45 gigalitres or 130 million litres/day. It is estimated to cost $346 million to build and $24 million
a year to run. That sounds like a lot of money but it pales into insignificance
compared to the much higher cost to build the mooted pipe-line or canal
from the Kimberley region in the north of Western Australia down to Perth.
Not only will it cost billions to build such a pipeline but it will need some
very big pumping stations to get the water from the Kimberley down to Perth.
Projections by Perth’s Water Corporation indicate that the energy cost
for water from the desalination plant will be 5kWh/litre while that via the
pipeline will be 15kWh/litre. Compare that with the price typically charged
to domestic consumers in Australian cities – around $1 per thousand litres
– and you wonder if our water shortage problems would suddenly disappear
if the present water price was doubled!
Really, when you think about the large energy cost of our present water
supplies, for pumping, filtering, chlorination (don’t forget the high energy cost
of chlorine production), fluoridation and so on, we should be making every
attempt to be frugal in water use. And maybe the water authorities could do
much to foster this by increasing the price!
No doubt there will be many people who would be opposed to any increase
in price for water but let’s face it, it is the most effective measure, requiring
no new technology, no heavy consumption restrictions and no need for draconian policing – you use the water, you pay.
Leo Simpson
ISSN 1030-2662
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