Technical Details

Learn more detail about Sydney's Desalination Process

Seawater Intake 

  • Seawater is drawn from the ocean under gravity, via four intakes that are approximately 300 metres offshore
  • The intakes are 5.2 metres high and 8.5 metres wide. They sit on the seabed about 25-30 metres below the surface and can deliver around 600 million litres of seawater per day via a 2 .5 kilometre long pipeline
  • The inflow rate is less than the prevailing current (about 0.1 metres per second) so that marine life can easily swim around the intake without being caught
  • Artificial reefs have been created around the structures
  • Click here to see video of the seawater intake in operation

Screening 

  • A Penstock or gate valve is used to permit flow into the plant
  • Drums screens then filter out material to 3 millimetres in diameter, such as kelp from the seawater
  • Sacrificial anodes prevent corrosion of the metal screening
  • Usually less than one cubic metre of material is collected per week

 Pre-treatment filtration 

  • 12 Dual Media filters are used as an added refining process to remove more solids
  • Seawater has a flocculant added to encourage particles to bind together to improve filtration
  • Seawater is filtered by gravity through a layer of filter charcoal and sand
  • Filtration rate, filter bed depth and size of filtering media are carefully selected to give the optimum compromise between filtered water quality and run times
  • In normal operation all filters will be operating with one being taken offline for backwashing or planned maintenance
  • Cartridge filters are used to refine the filtered seawater to prepare it for the reverse osmosis process
  • Centrifugal booster pumps are used to elevate water pressure to about 5 bar

Waste treatment  

  • From overall production only 0.05% becomes solid waste
  • Lime waste is thickened and dewatered and sent for beneficial reuse in agriculture
  • Solids from the Dual Media filters are thickened by gravity and then dewatered in a centrifuge prior to disposal in landfill

Reverse osmosis 

  • High pressure centrifugal pumps increase the water pressure to 50 – 60 bar
  • Filtered seawater is pushed through the reverse osmosis membranes under high pressure
  • The presure required is seasonal as salinity and temperature change
  • Each pressure vessel contains 8 membranes
  • There are around 36,000 membranes
  • There is a 2 pass reverse osmosis system, with 13 first pass trains and 7 second pass trains
  • Automatic Clean In Place (CIP) system

Dual Work Exchange Energy Recovery (DWEER) 

  • Dual Work Exchange Energy Recovery (DWEER) devices are placed at the end of each first pass train
  • 90% of energy is recovered from the seawater concentrate and is used to pressurise the incoming seawater
  • This reduces the plant's energy needs by up to 60%
  • This reduces the required size of pumps and improves efficiency

Re-mineralisation 

  • Fluoride and minerals are added to the fresh water to meet Australian Drinking Water Guidelines and NSW Health requirements
  • There is continuous online water quality monitoring throughout the entire plant process
  • Water quality test are also conducted after remineralisation to ensure standards are met

Drinking Water Holding Tank and pump station 

  • Drinking Water Holding Tank holds 40 million litres water which is four hours of water production
  • Two large variable speed pumps are used to transfer the water to the pipeline
  • Four large shock absorbers reduce the effects of water hammer during start up and shut down of the pumps

Water supply - pipeline 

  • Drinking water is discharged to the Sydney Water network along an 18 kilometre pipeline that runs from the plant to the main water supply at Erskineville

Seawater Concentrate Outlet 

  • Specially designed outlet nozzles ensure that water returns to normal seawater salinity and temperature within 50 - 75 metres of the oultet
  • Approximately 58% of intake water is returned to the ocean
  • Seawater concentrate is twice the salinity and about 1 degree warmer
  • Click here to see video of the seawater outlet in operation