Frequently asked questions
- Pre-treatment - seawater is pumped through intake screens and filters to remove particles, before passing through an ultrafiltration membrane.
- Reverse osmosis - semi-permeable membranes allow water molecules to pass through but block larger salt molecules, resulting in the removal of impurities and salt in the water.
- Post-treatment - desalinated water is disinfected and re-mineralised to increase alkalinity to reduce the potential for corrosion in the pipe network and customers’ plumbing. Treated water meets the Australian Drinking Water Guidelines (2011), ensuring it’s safe to drink.
- Storage - clean drinking water is then stored and supplied to homes and businesses.
- Outfall - the remaining concentrated seawater is returned to the ocean through the outfall pipe and diffusers to ensure it reaches the natural salinity levels of the environment.
- It is in close proximity to existing water and electricity networks, requiring a short, 4 km powerline route and a short transfer main of 7.4 km, therefore reducing the construction timeframes and costs associated with building the plant further away from the network.
- It is large enough to accommodate for future growth in demand across the Eyre Peninsula. The 5.3 gigalitre a year plant will be able to be scaled up to an 8 gigalitre a year capacity if required, while ensuring its visual and environmental footprint is minimised.
- The location is on industrial-zoned land that is relatively sheltered and flat, helping to reduce construction risks and challenges.
- Sleaford West sits a fair distance from our existing water network, meaning there would be significant additional costs to construct a new water pipeline and electricity transmission line, as well as costs and timeframes associated with managing landowner agreements and reducing the environmental footprint of the new pipes.
- Construction feasibility and timeframes would likely have been subject to the challenging oceanographic conditions in Sleaford Bay. Higher energy wave movements would require marine equipment large enough to safely build a desalination plant at that location. This increased the risks around the construction timeframe, overall cost and personnel safety during construction in high tide periods.
- Geological investigations revealed the existence of extremely hard 140 megapascal (MP) granite and a rare geological rock formation.
- Sleaford Bay is seasonally home to internationally protected whale aggregations, resulting in additional restrictions and limits to construction timeframes to ensure there are no impacts to the whales that visit the bay.
- A rare species of native flora was found in the local coastal zone, creating additional environmental challenges to ensure this important species (along with other State protected species also recorded) was not impacted.
- Cultural heritage areas of interest were identified along the coast of Sleaford, making it extremely difficult to find a suitable entry point into the marine environment from the coast.
Where does the Eyre Peninsula currently get its water from?
Drinking water supply for the majority of the Eyre Peninsula is sourced from a range of local groundwater aquifers – including the Southern Basins Prescribed Wells Area (Uley South, Uley Wanilla, Lincoln and Coffin Bay) and Elliston – as well as the River Murray, via the Morgan to Whyalla and Iron Knob to Lock pipelines.
Currently, the region’s primary source is Uley South Basin. Other groundwater aquifers are used for high-demand summer period contingency and emergency use only due to elevated salinity and sustainability management. Water is pumped from Uley South Basin to North Side Hill storage tanks near Port Lincoln (151 metres above sea level) and then distributed through a network of pipes across the Eyre Peninsula, largely by gravity.
Why do we need a desalination plant?
Uley South Basin has experienced low natural recharge in the past several years due to low rainfall in the region. Water quality monitoring has also indicated there are some bores within the basin which need to be rested to help maintain their ongoing health.
Without a desalination plant, we are unlikely to be able to provide a long-term supply of safe, clean drinking water to Eyre Peninsula customers at current volumes. Uley South Basin is the last remaining major productive groundwater source on the Eyre Peninsula, and while it will continue to be used to supply drinking water for our customers, a desalination plant will reduce the amount of water we need to take from the aquifer.
In 2007, we began working with the Eyre Peninsula community as we prepared a long-term water plan for the region. The plan identified seawater desalination as the preferred future water supply option to ensure ongoing water security for 35,000 customers living and working on the Eyre Peninsula.
How does the desalination process turn seawater into drinking water?
Desalination uses reverse osmosis to transform seawater into safe, clean drinking water. The broader water treatment process includes:
After desalination, clean, fresh water will be pumped to the North Side Hill storage tanks near Port Lincoln. The water from the tanks is distributed through our network to ensure it reaches regional and remote communities across the Eyre Peninsula for use in homes, businesses, schools and hospitals.
Why does the desalination plant need to be at Billy Lights Point?
Billy Lights Point is the preferred location for a desalination plant because:
Why wasn’t the Site Selection Committee’s recommendation of Sleaford West accepted?
Following the Site Selection Committee recommending the site at Sleaford West to the government, the project team undertook several preliminary site investigations to develop a cost comparison to the base case site at Billy Lights Point.
Throughout these investigations, several design, construction and environmental challenges were identified at the Sleaford West site including:
As a result of these factors, the cost estimate for building a plant at Sleaford West was significantly higher than the base case. Attempts to secure the additional funding required were unsuccessful.
How much water will the desalination plant produce?
The desalination plant at Billy Lights Point will produce up to 16 megalitres (16 million litres) of safe, clean drinking water per day.
When will the desalination plant start supplying water to the Eyre Peninsula?
Subject to all required approvals being in place, construction of the plant is planned to begin in late-2024, with first water to be delivered from the end of 2025.
Who will receive the desalinated water?
The desalinated water will be pumped to our North Side Hill storage tanks and mixed with Uley South Basin water, before being supplied to homes and businesses across the Eyre Peninsula through our existing network.
How much will the desalination plant cost to build? How is the project being funded?
The budget for the project is being finalised and the state government is not contributing any funding to the project. As with all of our major projects, the cost of the desalination plant will be shared by our customers across South Australia through our state-wide pricing.
Why can’t the Adelaide Desalination Plant supply water to the Eyre Peninsula?
Water weighs one tonne per kilolitre and therefore requires immense energy to pump. Consequently, the water distribution network is not set up to be operated like the power grid and requires significant additional assets like pump stations to push water through the network.
Currently, there is no pipeline large enough connecting Eyre Peninsula to the rest of the network. This was previously considered and discounted on the basis that it is impractical due to the cost to construct and operate such a pipeline. Ultimately, it would be far more expensive than the cost of a new desalination plant on the Eyre Peninsula.
Will the desalination discharge affect the marine environment? What research has been conducted regarding salinity in the bays and dispersion of the discharge?
The wider potential impacts on Boston Bay and Proper Bay from the long-term operation of the desalination plant have been modelled by the South Australian Research and Development Institute (SARDI), with extensive validation of the model against newly-collected tidal and current data.
The preliminary outputs have demonstrated that if the required dilution is met at the discharge point, the project will have minimal impact on the bays, with the discharge (after mixing) remaining well within background salinity variability and well below the Australian and New Zealand water quality guidelines (ANZECC & ARMCANZ 2000) relating to changes in salinity.
An independent Marine Science Review Panel – comprising of internationally recognised experts, with membership having been supported by the Site Selection Committee and the Environment Protection Authority (EPA) – reviewed and supported the research conclusions. Their role continues and review of the marine science data generated by the project is ongoing, with SA Water committed to publishing marine science reports on Water Talks.
Why don’t you store the desalination discharge on land and harvest the salt through evaporation?
For the saline discharge to be used, there needs to be a commercial demand. To date, there has been no demand demonstrated for this product on the Eyre Peninsula. Additionally, a considerable amount of land is needed to evaporate the discharge and produce salt, and management of evaporation ponds has significant environmental constraints.
Will the intake pull in fish and mussels like a vacuum cleaner?
Any extraction of water from a marine system will remove some particles (including larvae and spat) present within the water, and our design engineers are working to minimise this impact. In addition, habitat mapping studies and particle tracking modelling are helping to identify which areas are likely to be of greater importance to the aquaculture industry. Our design engineers will use this information to place the intake in a location that minimises the entrainment (taking in) of marine species, along with practical measures such as reducing the speed of the water being taken in, which will help small fish swim away.
Our preliminary modelling shows that at Billy Lights Point, fewer than 0.1 per cent of the particles in the water, such as larvae, are at risk of coming within a 25m zone around the intake pipe.
As the design for the plant progresses, we will continue to work with industry and marine specialists to optimise the intake location and ensure it is not located adjacent to an area where large numbers of mussels are likely to occur.
What happens to desalination discharge during dodge tides?
The term ‘dodge tide’ refers to a neap tide, which occurs just after the first or third quarters of the moon phase. During this period, there is minimal rise and fall of tides over the course of a day or two. This tidal cycle is well understood through many years of studies and modelling throughout the Spencer Gulf.
The desalination plant design must meet a minimum 40:1 dilution by the time the discharge meets the seabed under all conditions, including when there is minimal tidal difference. This will be achieved through careful design of the discharge diffusers, pipeline length and its location.
Modelling of the discharge plume both locally to the diffuser (often referred to as ‘near-field’) and over a wider area (‘far-field’) will continue to be developed and validated during the detailed design. Validation monitoring and reporting to regulatory agencies post-construction will also form part of the licence conditions to ensure these key environmental criteria are monitored and met.
How will salinity levels at the outfall location be monitored?
The discharge from the desalination plant will be licensed by the Environment Protection Authority (EPA) and subject to strict conditions. The project is not yet at the approvals and licensing stage, however, conditions of the licence for the desalination plant are likely to include implementation of an EPA-approved monitoring plan and compliance with reporting requirements.
The desalination plant will be located near the wastewater treatment plant and stormwater outlets, will that affect the safety and quality of desalinated water?
Water provided to our customers must meet Australian Drinking Water Guidelines (2011). We undertake regular monitoring across the state of all our water, from the source (River Murray, groundwater, reservoir or desalination plant) through to customers’ taps.
Discharge of treated wastewater is licensed by the Environment Protection Authority (EPA) and managed to minimise the risk of negative impacts to the receiving environment. Conditions of SA Water’s licence for the wastewater treatment plant include implementation of an EPA-approved monitoring plan and compliance with reporting requirements.
SA Water will also have a responsibility, as a licence holder, to comply with obligations under all State and Federal Environment Protection legislation. Ultimately, the aim of licencing and legislation is to avoid environmental harm and ensure that marine life and the supporting ecosystem is protected and maintained.
With respect to the location of the desalination plant intake, from an operational efficiency point of view, consistent and suitable intake water quality will be essential (i.e., sufficiently low levels of salt and suspended solids, access to warmer water, etc.). The project team is in the early stages of design, with mid and near-field modelling of the local marine environment underway to inform the location and design of the intake and outlet structures for the desalination plant.
What’s happening with the Northern Water project?
In September 2023, the State Government confirmed the Northern Water project is not a viable option to supply Port Lincoln with drinking water, due to the time it will take to build and the prohibitive cost.
Northern Water is limited in its ability to be part of the solution to Eyre Peninsula’s water security needs, as it is not yet a committed project. Additionally, if Northern Water proceeds, the earliest water would be available is in 2028.
Regular monitoring and expert scientific modelling of the Uley South Basin show there is a very real risk of irreversible damage if current extraction rates continue beyond 2025, creating an urgent need to augment the region’s water supply with a climate-independent source and ensure the aquifer remains a viable resource for the long-term.
More information on Northern Water can be found at the project website.