Desalination, perhaps; dumping brine in Spencer Gulf, no

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The state government has proposed to increase the size of the plant so that it can take water to supply the north and west of the state.

As the brine discharged from the desalination plant will be significantly heavier than 'normal' Gulf water it will go to the bottom. (One ML of fresh water weighs a thousand tonnes, one ML of sea water weighs about 1030 tonnes, one ML of this brine would weigh about 1050 tonnes.) The expected power consumption (for the BHP Billiton proposal) is 30MW; the sourcing of this power is part of the subject of the upcoming Evironmental Impact Statement (EIS); it should be sustainably generated.

Chemicals used in the water pretreatment and in the reverse osmosis process itself can also be problematic when they are released, with the brine stream, back into the sea. Coaguants like ferric- or aluminium-chloride can be used to improve the initial filtration process and both alkaline and acidic solutions are used in the RO plants to remove silt deposits, biofilms, metal oxides and scales. However, I believe that reverse-osmosis seawater desalination plants can be designed and operated without needing such undesirable chemicals, or at least without releasing them into the waste stream. More can be read on the Clean Ocean Internet site, the full URL for what is probably the most relevant page is http://www.cleanocean.org/index_general.asp?menuid=040.090.010.

The upper Spencer Gulf already becomes hypersaline in summer due to the high evaporation rates and poor mixing with the open ocean. The addition of 200 000 tonnes of brine to the upper Gulf each day, I believe, would have to have significant adverse effects on the health of the Gulf. The additional salt load to the Gulf would be similar to increasing the area of water available for evaporation by 22km² without the increased tidal flushing that an extra 22km² would bring (Calculations).

The brine will be released into water greater than 20m deep, too deep for seagrass to grow (see Correspondence with BHP Billiton), but it will go to the bottom where it will be swept backward and forward by the tides. By increasing even further the salinity in the Gulf, it must place more stress on the plants, the fish, prawns, cuttlefish and squid. The Spencer Gulf prawn industry alone is worth $20 million dollars per year. Also the spawning ground of the Giant Cuttlefish is important environmentally and as a growing tourist industry. These species, and others, should not be put at risk.

The SA state government and the federal Rudd opposition have each promised $160 million dollars for the construction of this desalination plant. One wonders why they seem to have completely overlooked several more environmentally friendly alternatives (see Links, below).

Climate change is already increasing the salinity of Spencer Gulf. Research has confirmed that increasing temperatures due to climate change has significantly increased surface salinities in the world's tropical oceans. (See OLPA. The research was done by Ruth Curry of the Woods Hole Oceanographic Institution.) Temperatures are increasing in South Australia, so it follows that salinities will also be increasing in Spencer Gulf.

The only way that I can see that this desalination plant should be allowed to happen is if the brine is kept out of the Gulf. It could be pumped to evaporation basins, the salt harvested and sold. The evaporation basins, which would need to be something like 35 square kilometres in size, should be located in an existing salt lake so that no land needs to be degraded and to minimise vegetation clearing. The most conveniently placed such site could be the southern end of Lake Torrens, seventy kilometres north of Port Augusta and close to where any pipeline from the Gulf to Olympic Dam mine will have to go.

The proceeds from the sale of the salt would go some way toward covering the additional cost.

Flinders University marine ecologist professor Peter Fairweather has been reported to have warned that the proposed plant could make the upper Spencer Gulf "much, much more salty" and turn it into "something like the Dead Sea". He is reported to have said that "It would become a very nasty place for a lot of organisms."

Alternatives

An alternative configureation for BHP

In this case sea water would be piped to Lake Torrens, the desalination would take place there, and the fresh water would then continue on to Olympic Dam.

Sea water at Port Augusta - especially in summer - is more saline than it is at Port Bonython and this would increase the cost of desalination (this point would have to be balanced against the financial savings due to the shorter pipeline needed). Obviously a third alternative would be to take the water from Port Bonython and pipe it to Lake Torrens before desalination.

Alternatives for South Australia

Other prospective sites would be Ceduna, Port Lincoln and Adelaide. This is discussed further in SA Water.

Economies of scale apply to desalination plants, but information I have received indicates that economies of scale flatten out for reverse osmosis plants when they reach about a seventh of the size of the proposed BHP-Billiton plant; that is at about 6GL/yr.

"I'm particularly concerned about them at that Point Lowly, Port Bonython area because that's where they aggregate," she said.

"We do know that they breed in other places but nowhere near the hundreds and thousands that they do at Point Lowly."

Ms Gillanders says unlike fish, increased salt levels may be disastrous for cuttlefish.

"Squids and cuttlefish are generally short-lived," she said.

"They live a year. They breed only once. So if you damage the eggs or affect their reproductive ability then potentially that will have devastating consequences for the population."

Already the South Australian government has stated that it wants to take a third of the water from the proposed BHP Billiton desalination plant for northern SA and the Eyre Peninsula.

If this development is allowed to dump its brine in the Gulf it will be only the first stage.

What happens if the desalination plant is unable, for whatever reason, to run at full capacity for some period of time. Will the existing pipelines from the Murray be sufficient to make up the loss, and if not, who will have to suffer reduced water supplies? Will BHP Billiton supply Olympic Dam and the water consumers of northern SA and Eyre Peninsula go without? Would this be fair considering that the tax payers of Australia will have put so much money into the development?

Oil spills have occurred from Port Bonython, which is very close to the proposed desalination plant. An oil spill could seriously damage the desalinator.

Wouldn't several smaller quite independent desalination plants in different places be a better option for these reasons?

I would like to thank Eric Barro for bringing up this point.

Thursday, 1 March, 2007 1:18:59 PM Subject: Letter to BHP Billiton David You suggest re-cycling of water used at Olympic Dam from the GAB rather than desalination. To the extent it is able to do so, Olympic Dam does re-cycle water used in its operations. However, there is a limit to how much re-cycling can be achieved. The cost of water to Olympic Dam is high. Olympic Dam has paid the full cost of the GAB infrastructure necessary to supply water. This is now in excess of $100 million. Olympic Dam also pays all operational and maintenance costs. As a result, the cost of water to Olympic Dam exceeds that available at locations closer to metropolitan and regional cities and towns. Owing to the high cost of supply, the processing facilities at Olympic Dam were designed and built, and are being operated to be efficient in the use of water. However, the continuous re-use of process water results in the build up of salts (particularly chlorides) and other contaminants, which originate either from the initial water source or from the ore or process chemicals used. Eventually, the concentrations of some salts and other contaminants become so high that they have detrimental effects on process efficiency. BHP Billiton is continuing to research and develop methods to reduce consumption and to encourage water conservation. In relation to the proposed desalination plant, this is still subject to a pre-feasibility study. In this work, intensive research is being undertaken to assess the impact of brine disposal to the gulf. Development of desalination plants typically focus on the following issues - - brine discharge and the potential impactss on the marine environment - energy use and greenhouse impacts - community and economic impacts In preparing an Environmental Impact Statement, BHP Billiton is continuing to undertake detailed ecotoxicity testing of marine species in the gulf (Yellow Tail Kingfish, Western King Prawn, Cuttlefish, etc) and has gathered the most comprehensive data ever assembled on tidal flow, plume dispersion modelling and site location. The results of this work will be reported in the Environmental Impact Statement to be released later this year. I trust this information is of assistance. Richard Yeeles Base Metals Australia

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As this did not really answer my original question (perhaps I was unclear) I wrote again; as below:

1 March 2007 Dear Richard; What I was really wondering is that if desalination of Spencer Gulf water plus piping all the way from Port Bonython to Olympic Dam is economically viable, why is not desalination of process water at Olympic Dam? You mention build up of chloride; I know that chloride is readily removed by reverse osmosis (while some other ions such as boron are not). Does the chloride get to levels that are too high for economic desalination? Do you do any desalination for the mine at OD? David Clarke

A reply was received on 2007/04/12 (apparently my email of 1st March did not get to Richard):

The acid waste water stream at Olympic Dam has low pH. The cost of neutralisation is prohibitive and RO is not possible before neutralisation. In addition, there are other contaminants in solution after the leaching process that will not be rejected, such as fluorine and boron - these would quickly destroy an RO membrane and make the process uneconomic. Minewater is not desalinated on site but is shandied back into the process. The waters are low in chlorides compared to seawater desalination so this is not the issue - it is a combination of a low pH and contaminants in solution that prohibit recovery of acid water by desalination. At the proposed expanded capacity of the operation, we will reuse as much of this acid water back in the process as possible, limited only by contaminant build up. Richard Yeeles

As Richard mentioned that ecotoxicity testing was done for marine species including Yellow Tail Kingfish, Western King Prawn, Cuttlefish, but did not mention whether any testing was done on plants at the bottom of the food chain, I asked him whether BHP Billiton had done such testing.

His reply (received 2007/04/13) is below:

Impacts of the brine discharge on the general Upper Spencer Gulf ecosystem have been assessed via ecotoxicology studies using a technique called Whole of Effluent Toxicity (WET) testing. During these studies various concentrations of simulated brine were tested against seven indicator organisms from a range of taxa that included two species of marine algae. The algae tested were the microalgae Nitzschia closterium and the macroalga Hormosira banksii. The technique is used to derive a species protection value or "safe" dilution of effluent to protect 99% of marine flora and fauna species. Hydrodynamic modelling of the dispersion of the brine plume have indicated the "safe" dilution of the brine would generally only be exceeded within hundreds of metres of the outfall, and up to 1.5 km for a short time during dodge tides. The marine plant species of greatest interest is the seagrass Posidonia spp., which covers extensive areas Upper Spencer Gulf, but only to a depth of about 10 metres. There is no seagrass in the vicinity of the brine outfall as the water is too deep (> 20 m). The nearest extensive seagrass communities occur in False Bay and Fitzgerald Bay, 5-10 km from the outfall. Furthermore, Posidonia spp. is adapted to highly saline conditions - extensive communities occur near Port Auggusta where salinities reach 47-48 ppt in summer. It's therefore extremely unlikely that the discharge of brine would have adverse effects on seagrass communities in Upper Spencer Gulf.

Mr Foley said the Government's information was there would be "no impact on any of the fishing grounds" but they would continue to monitor the situation closely throughout the Environmental Impact Study process, which is expected to take 12 to 18 months.

Update 2007-04-02

It has been claimed that no site has definitely been chosen. Yet the pilot plant is to test pre-filtration equipment that is specific to the Port Bonython site!

Kevin Rudd has committed a future federal Labor Government to $160 million toward this desalination plant. There was no mention that I heard of any environmental conditions placed on the money.

Natural salt content at the head of the Gulf can reach 4.8% in summer, CSIRO. Ocean water is typically around 3.5% salt, Wikipedia. From these three figures we can calculate that the density of 4.8% Gulf water would be about 1037kg/m³.

The Olympic Dam desalination proposal includes the release of water at 6.5% salt into the Gulf near Port Bonython. The density of this water would be around 1050kg/m³.

Pan evaporation at Adelaide is about 1600mm/yr. It would be considerably higher in upper Spencer Gulf; for the calculation of the additional evaporative area that the adding of the brine from the proposed desalination plant would equal, I have assumed 2000mm/yr.

Calculations

The desalination plant will take about 44GL of water from the Gulf each year. At 2m evaporation per year, this is equivalent to the evaporation from an additional 22 square kilometres of exposed water, without the additional tidal flushing that 22km² would bring. (44GL = 44 000 000m³
Evaporation is 2m/yr, so 44 000 000m³/2m gives 22 000 000m² = 22km² of evaporative area.)

A solar powered desalination plant at Port Augusta (northern end of Spencer Gulf) has been proposed by Acquasol. This proposition is preferable environmentally to the BHP plant (this should be greenhouse neutral and will not dump brine in the Gulf), Michael J. Fielden, Managing Director of Acquasol Pty Limited informed me by email that "... our company is listing in July, and construction on our project will commence early next year (2008)." (He also promised me more information on the proposal. I didn't ever receive this.)

A page on the BHP proposal is at Olympic Dam EIS Project.

"A Water Supply for Regional South Australia: Reducing Reliance on the River Murray Feasibility Assessment Report", a 2.5MB pdf file, can be downloaded from TheLivingMurray site. (The full URL for the report is
http://www.thelivingmurray.mdbc.gov.au/__data/page/195/ SA_desalination_Feasibility_Final_Report_for_web.PDF).

Renfrey Clarke discusses the proposal on Green Left On Line.

The US Department of the Interior - Water Treatment Engineering and Research Group has a comprehensive, if difficult to navigate, 3.6MB document titled Desalting Handbook for Planners at the full URL of http://www.usbr.gov/pmts/water/publications/reportpdfs/report072.pdf

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