by Neil Palmer, CEO, National Centre of Excellence in Desalination Australia
Stretching all the way back to 1895, the Mammoth Condenser at Coolgardie, completed by the Public Works Department, was, at the time, the largest in the world and could produce 500kL/d. A condenser was built at Cook on the Trans Australia Railway in 1917 for boiler water. A reverse osmosis (RO) plant, thought to be Australia’s first, was built in 1968, but it only operated for a short time as it was cheaper to haul water from Port Augusta. Many remote areas in Australia have brackish or saline water and there are an estimated 600 desalination plants of reasonable scale across the nation.
Historically, evaporation by boiling salt water followed by condensation has been the most common form of desalination. Many large distillation plants have been built in the oil states of the Middle East to provide drinking, recreation and industrial water. Since its commercial development in the 1960s, RO has come to dominate the world market. All of Australia’s major desalination plants use this process.
The Millennium drought and climate change
Observed most strongly in south-west Western Australia since 1970, the impact of climate change has seen a modest reduction in rainfall with a very large reduction in runoff. This has virtually ended reliable water supplies from Perth’s dams. A CSIRO study completed in 2008 into climate change and water across the whole of Australia found that, while overall rainfall is likely to be slightly less, climatic variability is increasing dramatically. This means longer droughts interspersed with more intense rainfall events. Knowing this, provision of climate resilient water sources (like seawater desalination) as insurance against water shortages is recognised as good policy.
Australia has a long history of experience in desalination. While the Millennium Drought may have broken, there’s many compelling reasons as to why desalination plants will continue to play an important role in the supply of water across the country.
Seawater desalination projects were constructed in all mainland state capitals during the 13-year Millennium Drought – the worst in Australia’s recorded history. From the first (Perth Seawater Desalination Plant – Kwinana) in WA in 2004, all six projects were completed by 2012 – an eight-year construction period including environmental approvals. The total cost of around $12billion was a huge water security project and the delivery of such a large infrastructure package in such a short time was impressive by world standards.
The Millennium Drought was severe and it could well have continued for several more years. Adelaide was within weeks of running out of potable water as the River Murray became more saline, and Melbourne could have run out of water had the drought continued for another year or so.
The crisis precipitated decisions to build desalination infrastructure, naturally with some cost premium due to the tight project delivery time frames.
However, the drought broke in 2010 and floods came to the eastern states in 2011. Not so in Western Australia, where the two desalination plants at Kwinana (140ML/d) and Binningup (300ML/d) operate at 100 per cent and supply half of Perth’s drinking water. Fresh water from the sea will continue to be the main source of drinking water in Perth for the foreseeable future.
Where governments changed (after the drought had broken), incoming governments were often critical of decisions taken by their predecessors, and desalination infrastructure became the subject of political debate. However, in Queensland and Victoria, the new conservative governments were defeated after only one term. It is my belief that one of the reasons for this was that voters grew weary of the politicking and were smart enough to realise that water security is too important an issue to be left entirely to chance.
Advances in desalination
The National Centre of Excellence in Desalination Australia (NCEDA) was established in 2009 as a policy response to the drought. Given the challenges of Australia, being the driest inhabited continent, it was logical that a centre to develop Australia’s capability in desalination be established and funded to provide water solutions and to develop an export industry.
In the six years since its inception, the NCEDA has established itself as a world-leading research organisation that has established an excellent reputation and extensive networks throughout Australia and internationally. The centre has delivered five competitive funding rounds converting an initial investment of $23million into $81million of research activity across 50 projects, involving input from over 400 national and international researchers. The centre has also awarded over 40 PhD and honours scholarships and developed laboratory, pilot-scale testing and education facilities.
Many of the centre’s projects have concentrated on pre-treatment, essential for sustainable desalination. Much has been learned about the microbiology of biofilms which inevitably build up in all RO membrane systems, increasing the energy required to desalinate water, and reducing membrane life. Better scientific understanding helps prevention, control and removal. Another new idea is to eliminate fouling organisms by allowing them to grow in a membrane bioreactor pre-treatment system rather than on the RO membranes. Robust ceramic membranes with ozone pre-treatment have been used prior to RO of recycled water to greatly improve pre-treatment performance.
A new polysaccharide coating on RO membranes has been found to prevent biofouling by making it difficult for bacteria to attach and grow. This idea has been patented and is approaching commercialisation. A comprehensive guide has been developed for cleaning membranes. Another project that is underway is using aquaporins (nature’s salt separation membranes) for the next generation of productive and efficient membranes.
Centre researchers have developed an operating forward osmosis system that has been trialled on a mine site to supply ‘fertigated’ water to a turf farm in NSW. Fertigated water is formed from concentrated fertiliser solution using forward osmosis to dilute it with, in this case, mine tailings wastewater. A solar powered membrane distillation system has been used in a remote community in WA to produce freshwater from hypersaline groundwater. Another centre-funded project used solar powered membrane-free capacitive deionisation to desalinate brackish water in remote Northern Territory. Further projects have examined the use of graphene to improve capacitive deionisation.
Concentrate minimisation is essential for efficient desalination of inland waters. A project undertaken in partnership with an Australian desalination system manufacturer and a coal seam gas company in NSW has seen an improvement of recovery from 80 to 95 per cent treating coal seam gas produced formation saline water. This has resulted in a huge reduction of the downstream infrastructure required to evaporate or crystallise the concentrate.
A centre project has thoroughly tested an operating concentrate outfall and diffuser in Queensland to understand any risk that might exist to the marine environment. The results confirm that a properly designed diffuser returns the concentrate (about double seawater salinity) to near background salinity in a very short time and poses no risk. This is confirmed by the operating experience at the Water Corporation’s Kwinana Desalination Plant, which has run at 100 per cent flow for eight years and discharged concentrate to Cockburn Sound without adverse impact on the marine environment.
Another project surveyed more than 3,000 Australians to determine their views on desalination. Most were happy with desalination as a water source in times of shortage, although the survey confirmed the rapid implementation of the projects did not allow for adequate conversation and consultation with the community. A further economic study into all the capital city desalination projects revealed some surprising results – a portfolio of water sources including major desalination plants removes some of the costs associated with increasingly costly alternative supplies and the high cost of restrictions, and actually leads to lower overall costs.
The future for desalinated water
In 2011, National Geographic magazine ran a feature on water. It proposed three potential disruptive technologies to enable cheaper and more plentiful fresh water from saline sources: biomimetics (use of aquaporins for example); forward osmosis and carbon nanotubes. The NCEDA has had projects in all areas of new technology, and it is evident that they are all some way off commercial reality.
It is likely that RO will remain the workhorse of desalination in the near future. Research efforts by the major manufacturers are high and the performance and efficiency of RO membranes continues to improve.
The big six Australian desalination plants are effectively wind and solar powered. It is more expensive, but they have virtually no operating carbon footprint. The NCEDA is of the view that improvements in efficiency for collection of energy (particularly photovoltaics), coupled with improved RO membranes, will enable the cost of seawater desalination to fall. Couple this with population and demand growth, and the higher cost of alternative and increasingly hard-to-reach sources, and the option of sourcing some base load supply from the inexhaustible supplies adjacent to our coastal cities (where most of the people live) makes increasing sense.
It is our view that the improving unit cost of both photovoltaics and RO membranes will enable much larger scale renewable desalination, especially in areas of high sunshine, substantial availability of cheap land and abundant seawater. Australia has an abundance of all of these. A developer (Sundrop Farms) is using these resources in Port Augusta with a 20 hectare greenhouse powered by solar energy deriving fresh water from Spencer Gulf. The success of this enterprise will lead to other similar developments and there is plenty of scope for sustainably producing high quality horticultural products for the very large Asian market nearby.