The Reverse Osmosis
technique of desalinating seawater produces Trihalomethanes (THM's) which are a known
carcinogen and pass through the membranes
into the product water (refer U.S.A.I.D. Manual by IDCAOE US Gov't 1980 page
5-36, a study by SWCC of Saudi Arabia, epidemiological studies and various other academic literature).
According to the NHMRC in the
Australian
Drinking Water Guidelines, a number of studies have suggested an association
between various cancers such as bladder and rectum cancers. There are no safe
levels for THM's (p 6-4).
Low levels of THM's have also been linked to miscarriages and birth defects in a number of other epidemiological studies.
The Water Corporation advised the KEP that the desalination benchmark cost that had to bettered by other competing sources such as Kimberley water was $1.16 per kilolitre.
The latest Report on desalination for the QLD gov't puts the cost at $ 2.55 per kilolitre for a similar sized plant to the WA one at Kwinana.
The seawater desalination plant at Kwinana has a capital cost according to the Water Corporation of $387 million. The discount rate that the KEP (p57) have been told to use is 6%.
The Water Corp (Metropolitan Desalination Proposal : EPA Submission ,p1) estimates that the plant will last 20 years.
The variable cost of running the desalination plant has been budgeted at $ 24 million per year (Water Corporation, The West Australian,20-1-07, page 6).
The budgeted output of the plant is estimated at 45 million m3 of fresh water.
The actual output of the plant has in the first 14 weeks of operation has been 6.5 million m3 (Water Corporation, The West Australian,10-3-07, page 62 ). This annualises to 25 million m3 per annum, or 55 % stated capacity.
The actual cost of this desalinated seawater calculates as follows:
| Interest on $ 387 million @ 6 % | $ 23.22 million |
| Depreciation @ 5 % on $ 387 million | $ 19.35 million |
| Annual running costs | $ 24.00 million |
| TOTAL | $ 66.57 million |
to produce 25 million m3 per year at $ 2.66 per kilolitre !
This is a lot more expensive than the Water Corp's estimate of seawater desalination cost in 1987 of $ 1.45 per kilolitre (WAWA, Planning Future Sources For Perth's Water Supply, ISBN 0 7244 6743 2).
The fact that the desalinated product water is more expensive than claimed comes as no surprise to anyone with experience in water supply economics. Desalination is a very energy intensive process that is inherently unreliable. The companies selling these plants typically estimate that they will produce at 80 % plant capacity and yet they achieve significantly less than this in practice. The average in Kuwait for example is 54 % (Marafie and Darwish, Desalination, Elsevier Science Publishers, vol 71, 1989 page 49 ).
The argument advanced by the people selling these plants is to ignore the poor track record of desalination plants as now the technology is now much more improved. This is the same argument that has been used for the last 30 years. The track record of desalination speaks for itself.
Given that there are so many anomalies in the various figures supplied by the Water Corporation in this whole area of water supply planning we need independent outside people to investigate all costs and claims by them so the public can be given more realistic information.
We should be told how the claimed 4.5 KWH per m3 compares to actual results. We should also be told how much the plant is paying for its electricity and how this compares to other large users in the State. We should also be told what the State will have to pay to generate additional electricity due to the desalination plant using up some of its installed capacity. The Government's claim that the plant is running on wind power would blow the above costs out even further if the real dollar cost of the wind power was paid for by the plant. The desalination plant is using very significant amounts of electricity from the State's interconnected grid at a time when we are regularly experiencing blackouts and power shortages because Western Power does not have enough generating capacity to provide for us.
Environmentalists such as the World Wildlife Fund are concerned about the impact of desalination on the environment.
