Australia ramps up desalination deployment
The Water Corporation of Western Australia (WCWA) is on schedule to commission the southern hemisphere's largest desalination plant, in Perth, early next year. Gary Crisp of WCWA reports on how the plant has addressed the challenges of environmental sustainability and technological feasibility and heralds increased uptake of reverse osmosis technology in Australia.
Gold Coast City, Sydney, Adelaide, Brisbane and Gosford-Wyong are among other coastal Australian cities that are considering seawater desalination. Some of these cities are in advanced stages of acquiring large seawater desalination plants.
In the face of the driest winter on record, the Perth Seawater Desalination Plant (PSDP) is on track to deliver 45 million m3 much needed new drinking water into the Integrated Water Supply Scheme (IWSS) commencing December 2006. The PSDP, located at Cockburn Sound, Western Australia could be regarded as a world-leading model for future sustainable seawater desalination plants.
The plant will be completed in December 2006 and commissioned in early 2007. At a peak capacity of 144,000m3/d, the US$290 million plant will be the largest seawater desalination plant outside the Middle East, and Australia's first large-scale desalination facility.
"The PSDP will also hold the title of the largest desalination plant in the southern and eastern hemispheres into the foreseeable future," said the WCWA's chief operating officer, Jim Gill. "Its capacity will make it the biggest single water source feeding into the IWSS, providing 17% of Perth's water needs, but most importantly, it will provide a secure supply of water that does not depend on rainfall."
Climate change has contributed to a 10-20% reduction in rainfall in the south-west of the state over the past 30 years, significantly reducing run-off into dams supplying the IWSS. Building this plant on an extremely tight time schedule and budget has come with its own set of challenges.
The key environmental challenges were: approvals and regulations, energy, concentrate management, marine monitoring, aesthetics and community involvement. Construction works on the plant site are now around 90% complete.
Pipelines to transport the desalinated water into the distribution network have been laid. In addition, the new Nicholson Road Pump Station - which will move the water into the IWSS - is currently being commissioned. The desalination plant is being built by Multiplex-Degremont Joint Venture, in alliance with the Water Corporation.
This joint venture is registered as the Pro Alliance (Perth Reverse Osmosis Alliance). It will be operated for 25 years by French environmental engineering group Degremont in alliance with the WCWA. A six-month commissioning process has commenced.
The associated 82MW wind farm, which will be injecting over 272GWh/y into the grid from which the PSDP will be abstracting 185GWh/y, has recently been commissioned. This will make the PSDP the world's largest desalination plant using renewable energy.
Coupling this energy with the low specific energy consumption achieved from the plant's novel design, incorporating isobaric energy (PX) recovery devices from ERI, ensures that it is the world's greenest plant. Taking this into account and considering its small physical footprint, this plant has to be one of the most sustainable water sources in Australia.
Gold Coast City, Sydney, Adelaide, Brisbane and Gosford-Wyong are among other coastal Australian cities that are considering seawater desalination. Desalination is a key component of both the Gold Coast Waterfuture Strategy and the Southeast Queensland Regional Drought Strategy Contingency Supply Plan, and is being investigated as an emergency water source in the region's fight against continuing drought conditions.
Early works have commenced following the State Government's commitment of a further US$60 million funding for the Gold Coast desalination project. This funding is to support 'early works' for the development of the proposed expansion of the desalination plant at Tugun to an operational capacity of 125,000m3/d for regional supply purposes.
Gold Coast City Council has committed a further US$15 million to the early works program. The proposed expansion of the desalination facility will supply water to the South East Queensland water grid. Early works include:
- Procurement of major plant items with long lead times
- Investigation and preparation of the Tugun site
- Progression of detailed designs.
The desalination plant will be built by Veolia-John Holland Joint Venture, in alliance with Gold Coast Water and the State Government. This joint venture is registered as the Gold Coast Alliance; it will be operated for 10 years by Veolia, in alliance with Gold Coast Water and the State Government.
The Central Coast of New South Wales (NSW), located 100km north of Sydney and comprising the Gosford and Wyong local government areas, is facing its worst water supply drought in history. Storages are down to 16% of capacity, representing less than 16 months' supply for a population of over 305,000.
The Council's plans for a 20,000m3/d desalination plant are on hold while conditions associated with a development application submitted in July 2005 are being negotiated with the State Government. With the deteriorating water supply situation, it is unlikely that this size of plant could be constructed in time even if immediate development approval was granted.
The local authorities are therefore pursuing the option of installing temporary portable desalination plants at a number of beach and estuary locations. The plants, nominally 1000m3/d in capacity, could be operating within 3-4 months of any decision to proceed, provided that the necessary preconstruction activities (including approvals) are in place.
Planning for up to 10,000m3/d capacities from such plants is well advanced with the development application currently on exhibition. A total of 20,000m3/d capacity may eventually be required.
Should drought conditions continue or worsen, the first of these plants could be operational by March 2007. No decision to proceed to construction has yet been made; however the water supply situation is under constant review.
In the unlikely event of extreme drought and dam levels falling below 30%, desalination is an important, non-rainfall dependent option in the NSW Government's new approach to drought management. Sydney, Australia's largest city has completed preliminary studies to build what could be the world's largest desalination plant.
To ensure that they are in a position to deploy desalination quickly, if necessary, Sydney Water will invest approximately US$92 million in preparatory works to reduce the lead-time needed for a plant to start supplying water. Sydney Water has prepared an environmental assessment for the construction, operation and maintenance of a SWRO plant at Kurnell, as well as the infrastructure associated with connecting the desalination plant to Sydney's water distribution network.
The Kurnell site has already been secured. The desalination plant is intended to be sized so that it has the capacity to provide up to 500,000m3/d into the water supply.
This additional supply will afford current and future drought relief and cater for future population growth. The plant would be capable of providing up to a third of Sydney's drinking water needs. This equates to fresh water for around 1.4 million Sydneysiders.
There are three key components to the project:
- The desalination plant
- The seawater intakes and seawater concentrate outlets
- The delivery infrastructure (pipes, tunnels and pumping stations) that will distribute water to the existing water network.
Mining company BHP Billiton, is expanding production at its Olympic Dam mining and processing plant near Roxby Downs, South Australia. The company aims to significantly increase production from the deposit and additional water resources are required.
The preferred water supply involves the following infrastructure:
- Seawater desalination plant with a capacity of 120,000m3/d. Infrastructure includes offshore intake and outfall structures, pre-treatment facilities, desalination plant development and post treatment/storage. The preliminary plant location is adjacent to Whyalla, South Australia.
- Transfer pipeline system capable of transferring potable water to Olympic Dam. The estimated pipeline length is 320km, with a nominal pipeline diameter in excess of 1.0m.
- Three or four potable water booster pumping stations with power capacities up to 6MW.
- Construction of additional water storage facilities in the region of 1 million m3. The most likely form of construction will be lined and covered water storage dams.
Of further interest is the full-scale pilot plant that the Water Corporation of Western Australia is currently conducting in conjunction with OsmoFlo, an Australian-based desalination company with the licence to produce high-efficiency RO (HERO) plants capable of high recovery from silica-infested brackish groundwater.
If proved successful it will pave the way to a water-supply solution for numerous towns in Australia, as most inland brackish groundwater sources have high silica contents. There are multitudes of small desalination plants being constructed in Australia, which are not discussed in this article. These exclude water reuse plants.