Project Description
This project will use a Reverse Osmosis
(R.O.) process to desalinate the brackish scour water
from Wellington dam into high grade potable water for
domestic supply to Perth. It will use the pressure (hydraulic
head) produced from the elevation difference (150m)
between Wellington dam and a reverse osmosis desalination
plant located at the foot of the Darling escarpment.
After a careful review of all factors,
it is concluded that the above project is technically
viable and the scheme is commercially viable without
factoring in social and environmental benefits.
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Currently brackish scour water is
discharged from Wellington dam during the winter
months. The timing and duration of this scouring
is then limited by the availability of the Collie
river downstream of Wellington dam to transport
this scour water to the Leschenault estuary but
usually occurs between June and the end of October.
The Collie River is unavailable at other times
due to its use in transferring irrigation water
from Wellington dam to Burekup weir. This rapid
scouring rate has limitations in that it can cause
breakthrough (vortex) where fresher water is drawn
into the scour stream from the top strata's in
the dam in preference to the saline layer on the
bottom of the dam. This also causes mixing of
the different strata's (layers) in the dam. A
much slower and continuous withdrawal, as would
be the situation if the scour water was withdrawn
for desalination purposes, would be expected to
produce better scouring of the saline layer from
the dam because the breakthrough and mixing of
the strata's would not occur. Additional sources
of brackish water that are available from the
Collie Catchment at the top of the escarpment
may also be able to be combined into this feed
water stream to provide continuity of supply in
the event of reduced quantities of scour water
from the dam.
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Significant advances in reverse
osmosis membrane technology are such that the
quality of the water produced more than meets
required Australian and World potable and drinking
water standards and guidelines. In addition recreational
and other activities on Wellington dam will not
have to be curtailed and will have no effect on
the final quality of the water produced by the
reverse osmosis plant.
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The potable water produced would
then be piped approx 20 km to Harvey to connect
into the Integrated Water Supply Scheme (IWSS)
connection point at Harvey. The energy required
for this transfer could have 15 - 25% supplemented
by energy recovered from the Desalination plant.
Therefore total power requirements for this process
will be low.
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The concentrate stream (waste discharge)
from the R.O. plant will be less salty than seawater
(20 - 25%) and can be discharged under gravity
from the desalination plant to the ocean.
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