The proposed desalination plant at Port Bonython on SA's Spencer Gulf should not be allowed to dump its waste brine back into the already hypersaline Gulf.

Spencer Gulf is an arm of the sea that stretches about 300km into the dry interior of South Australia. It receives very little run-off, there are no rivers worth the name that run into it; a few creeks carry water more saline than sea water. Evaporation concentrates the salinity of the sea water in the Gulf, which has limited tidal mixing with the ocean.

Spencer Gulf is a breading ground for prawns, fish, squid and the famous Australian Giant Cuttlefish. It is also one of the most southern mangrove areas in the world. It should not be put at risk by economically driven developments.

The proposed desalination plant will take 320ML each day from the Gulf, extract from that 120ML of fresh water (to be piped to the Olympic Dam mine) and dump 200ML (200 000 tonnes) of brine back into the Gulf every day.

This will compound the increasing salinity in the Gulf due to (climate change) rising temperatures. There will be future developments that will also be needing desalinated water from the Gulf; the state government will take a third of the water from the plant to supply Spencer Gulf cities and the Eyre Peninsula - this requirement will only increase with time as rainfall declines. Other mines that are likely to be developed will also want water. All these things will increase the problem of high salinity in the Gulf.

I have written a page on this at http://au.geocities.com/daveclarkecb/GulfDesal.html.

Perhaps we could put this in some perspective. On my calculations the gulf is about 20000sqkm or 2million hectares. At 3mm/day of evaporation(1m/year approx) this equates to a loss of 60 000ML/day. Will 120ML extra be significant?

No in no way.

Dave Clarke,

I tend to be fairly dismissive of these sort of apparently general objections to desalination of seawater, but your link has earned you a hearing. In it you make a good case for not returning the relatively more concentrated saline water into this particular part of Spencer Gulf, as opposed to a more general case of brine 'back into the sea' in more open waters.

The text link 'Lincoln Gap wind farm' in your linked page section headed 'A more workable alternative?' that takes you to the page titled 'Wind power and wind farms in South Australia' is excellent. I had no idea there was so much capacity already installed.

It is not clear what method of desalination is proposed at the BHP Billiton Port Bonython facility. I suspect that it may be a process that depends upon only taking a small part of total seawater throughput to become desalinated water. If your 'more workable alternative' of desalinating at Olympic Dam depends upon the same technique, then BHP Billiton would probably see that as requiring a lot of pumping of seawater for nothing, and consequently of adding to the final cost of the desalinated product.

There may be tremendous potential being overlooked in this part of South Australia. That is for using solar powered multi-effect reduced-pressure desalination near Lake Torrens. It would appear possible to desalinate as much as 90% of pumped seawater using this method, as opposed to the 37.5% proposed at Port Bonython. See this link http://www.globalwarmingsolutions.co.uk/large_scale_solar_desalination_using_multi_effect_humidification.htm

If there is significant waste heat available from coal burning power generation at Port Augusta, then perhaps even greater cost reductions in desalinated water are achievable, but in any case the steady accumulation of solar pondage near dry salt lakes that solves the brine disposal problem will provide a large future energy supply.

The need for a coordinated approach to desalination that integrates with other and future energy supplies is very apparent. Pumped storage on the nearby Flinders Ranges seems potentially relevant.

Dave Clarke,

It should be noted that cost-effective collection of solar energy in solar ponds holding accumulated brine resulting from desalination would very soon mean that multi-effect reduced-pressure desalination could be 100% sustainably self-powered. Not only that, but electricity generation from the ponds using low boiling point working fluids could mean that significant quantities of solar generated power eventually becomes available to the grid around the clock.

I also note in your webpage at http://www.geocities.com/daveclarkecb/SusElectricity.html#Levelling%20the%20peaks%20and%20troughs a slightly dismissive reference to the possible use of pumped storage as a means of balancing the electrical power grid in SA. Given the increasing proportion of wind-generated electricity supplied to the grid, the need for such a quick response load levelling capability is becoming more apparent.

The proximity of possible storage sites for pumped seawater on ground over 500m above sea level in the Flinders Ranges near to the head of Spencer Gulf is fortuitous. Was a storage for seawater to be built there, the prospect would then exist for hydrostatic pressure-driven reverse-osmosis desalination, as well as effective electricity storage. RO may be used to start with for the Olympic Dam desalination requirements, with reduced-pressure desalination progressively taking over as operational solar pondage comes on line.

A coordinated approach involving more than just BHP Billiton could see other prospective customers for water and the electricity generation industry in general benefit from including a pumped storage facility in any plan to desalinate seawater from Spencer Gulf.

Prohibiting the return of brine to Spencer Gulf from the outset may stimulate such coordination. Long term, the cost of electricity may be significantly reduced, and the proportion of it obtained from sustainable sources dramatically increased.

First, a quick answer to Rojo. Yes, the total area of the Gulf is about 200 000km^2, but the water in the northern part of the Gulf does not mix well with the remainder. The area of the part of the Gulf north of Port Pirie is about 1600km^2. Then there is the point that the brine will go to the bottom, it will not form a homogenious mix with the rest of the water. Finally, this increase in salinity is on top of the increase due to rising temperatures from climate change.

Second; how to answer Forrest Gumpp?

I gather that they intend to use reverse osmosis. I'm not sure of this, but the proposed proportion of brine and product water seems to support it.

The cooling for the Northern Power Station is by pumping water from the Gulf and returning it to the Gulf. There must be scope for using the heat in a more creative way.

I did not intend to be dismissive of pumped storage as a means of balancing power generation/demand, but I am a bit cautious about its potential in South Australia because the state is generally pretty flat. However, there may well be some potential between the Flinders Ranges and the Lake Torrens plain - as you suggest.

You seem to be full of good ideas (I'm not being sarcastic, I mean it); why don't you email your suggestions to Richard.Yeeles@bhpbilliton.com. But don't expect a quick answer.

I will look into your other points.

Dave,
I agree that it is a smaller area that will really be affected. This 1600km2 will still lose 5000ML/day to evaporation.
Your concern about brine pollution is absolutely valid. The brine will be 60% saltier than the gulf water and will need to be discharged in a way that ensures mixing. This may be achieved by pressure injection into the gulf from a series of holes in the discharge pipe, to prevent a homogenous hypersaline solution which would sink.
Good luck with it all.

Rojo; I'm sure BHP will try to mix the brine with Gulf water, but how effective will that be? If their brine is 60% saltier than the water in the Gulf, and then they mix 1 volume of brine with, say, 5 volumes of Gulf water the resultant mix will still be 10% saltier (if my calculations are correct) than Gulf water and will still go to the bottom.