Groundwater in the grainbelt of WA is a useful resource for on-farm water. However, in this environment it is often saline and unsuitable for livestock or other on-farm uses.
Desalination can remove much of the salt from groundwater and produce suitable water for livestock, crop spraying, horticulture and domestic uses. This may be achieved using reverse osmosis (RO) systems.
Compliance with regulations
Disposal of saline reject water from desalination is covered by the Soil and Land Conservation Regulations 1992. This requires prior notification on a prescribed form to the Commissioner of Soil and Land Conservation before any discharge takes place. You must lodge this at least 90 days before intended discharge. Note that land degradation caused by operating a desalination plant is covered under the Soil and Land Conservation Act 1945, and could attract a Soil Conservation Notice. It is an offence to proceed without notification, and penalties and prosecutions may be applied.
Submit notice to the Commissioner
It is a legal requirement for owners or land occupiers to submit written notice to the Commissioner at least 90 days before intended draining of surface or subsurface water to control salinity and discharging that water onto other land, into other water or a watercourse, including on the same property. Submit the notice of intent to drain or pump water – desalination via the form supplied below, together with the neighbour comments required.
Notice of intent to drain or pump – desalination
Reverse osmosis (RO) desalinisation is technology farmers are adopting to improve water self-sufficiency when other sources are compromised, especially in low rainfall years or where better quality is required. The number of farmers seeking fresh water, and companies supplying units, has increased rapidly in recent drier than average seasons.
Most farms in the agricultural areas of WA have bores into saline groundwater that could be suitable for RO desalination.
Conditions favouring an RO system
- you have an urgent water deficiency
- you run out of water frequently
- your demand from the bore is less than 30 kL/day
- you have bores producing brackish water
- water from off-farm sources is limited or costs too much
- you have a safe place to dispose of the reject water.
Bore suitability for attaching an RO system
Ideally, bores should be able to sustain yields of greater than 30 kL/day and be able to reject water safely to disposal points such as reject wells, evaporation basins, saline waterways and lakes. Bores high in the landscape into brackish aquifers can also use gravity to enable low-cost reticulation to tanks and disposal points.
RO plants require less energy and cost less to desalinate brackish water (< 8,000 mg/L). Salt water RO plants have different membranes, and can desalinate water up to 30,000 mg/L.
Small RO plants using 10 to 30 kL of water a day, cost $20,000 to $40,000. Small units can be operated by solar photovoltaic panels, though most are single-phase grid connected. Larger RO plants producing 50 to 100 kL of water a day cost significantly more and require 3-phase power or stand-alone diesel generators. Note: the effectiveness of solar systems will depend on the number of panels, orientation, and power storage.
Water treatment is less complex for neutral acidity (pH), low silica and iron waters. Water chemistry will affect the efficiency of the RO membranes. Detailed water chemistry samples should be taken and analysed by an RO business.
Technical requirements of an RO plant
- The Commissioner must have no objection to the proposed reject water discharge before operating the RO plant. See Groundwater desalination and regulation for farm water supply in Western Australia and use the correct notice of intent to drain form (supplied above).
- Have the power supply organised before installing the RO plant.
- We recommend that you obtain technical support before purchasing and operating the RO plant. RO plants need careful design, regular maintenance and planning for disposal of the reject water management systems.
Designing the system for desalination
The department strongly recommends that you take these steps in designing an RO system that is suitable for your location and your farm needs.
Assess your water quantity and quality requirements, by ensuring the bores are located in the most suitable areas, with appropriate salinity and where the resource can be sustained.
Test aquifer/bore yield by pumping and analysing water chemistry through a reliable drilling or RO service, by pump-testing bores to ensure they are capable of meeting expected demand, and ensuring water quality is acceptable. Pumping over an extended period of days to weeks may be required to confirm sustained yield and reliable water chemistry.
Get quotes and basic designs from suppliers. Designs should include water sampling and assessment of reject water disposal options. There are several major suppliers, with some in WA offering field and design services. Check that the supplier has experience in the WA grainbelt, knowledge of water chemistry and design issues, and provides maintenance and after-sales service.
Assess disposal options – into purpose-built reject bores, evaporation basins, creeks, salt lakes – before going to final design of the RO system. Complete and submit the correct Notice of Intent to Drain (NOID) form (supplied on this page) to the at least 90 days before the intended discharge. Add enough information for the Commissioner to properly assess the proposal, and to show that downstream neighbours have been fully advised. The proposal may be referred to other agencies and your Local Government for comment.
Develop a final RO system design to confirm operability, power and disposal operations.
Reassess the total costs of water from the RO system, and whether this is still your preferred option for additional water when compared to other options (e.g. rebuilding dams and roaded catchments).
Go ahead and invest in your selected RO system after following all steps.
Find more information on desalination technologies
- Reverse osmosis (RO)
- Electrodialysis reversal (EDR)
For explanations, see the American Membrane Technology Association
- Multi stage flash distillation (MSF).
- Multiple-effect distillation (MEF).
- Vapour compression (METC, MVC).
- There are several ion exchange systems.