Infrastructure

Sydney Desalination Plant is a large scale reverse osmosis desalination plant. The site covers 45 hectares and is located on the coast of Kurnell, 25 kilometres from Sydney's CBD.

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Seawater Intake

  • Four intake risers are located approximately 300 metres offshore and 25 metres below the sea surface
  • Deliver around 600 million litres per day of seawater to site via the 2 .5 kilometre long concrete intake tunnel 
  • Inflow is gravity fed and its velocity does not exceed prevailing currents. The intake velocity of 0.1 metres per second ensures that marine life is not drawn into the structure
  • Artificial reefs created around the structures
  • Take a look at the seawater intake during operations to see how fish can easily swim in and around the structures

 

Screening

  • A penstock or gate valve is used to permit flow into the plant
  • Drum screens filter out material down to around 3 millimetres in diameter
  • Sacrificial anodes prevent corrosion of the metal screening

Filtration

  • 12 Dual Media filters are used as an added refining process to remove more solids
  • Seawater is dosed with a flocculant to improve filtration
  • Seawater is filtered by gravity through layer of filter coal and a layer of sand
  • The filtration rate, filter bed depth and size of filtering media are all carefully selected to give the optimum compromise between filtered water quality and filter 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
  • From overall production only 0.05% becomes solid waste
  • Solids from the Dual Media filters are thickened by gravity and then dewatered in a centrifuge prior to disposal in landfill

Reverse Osmosis

  • Centrifugal pumps are used to elevate water pressure to approximately 5 bar
  • High Pressure pumps elevate water pressure further to approximately 50 - 60 bar to prepare for reverse osmosis
  • Pressure required is seasonal as salinity and temperature change
  • Filtered seawater is pushed through the reverse osmosis membranes under high pressure
  • 36,000 reverse osmosis 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) devices are placed at the end of each first pass train
  • 90% of energy is recovered from the seawater concentrate and transferred to the incoming seawater
  • Reduces the required size of pumps

Treatment 

  • Fluoride and minerals are added to the fresh water to meet Australian Drinking Water Guidelines and NSW Health's requirements
  • To ensure water quality standards are met, there is continuous online water quality monitoring throughout the entire plant process
  • These processes meet the same qualities as drinking water from other water filtration plants
  • Lime waste is thickened and de-watered and sent for beneficial reuse in agriculture
  • Water quality tests are conducted after re-mineralisation - if water meets the guidelines it is transferred to the Drinking Water Holding Tank 
  • The Drinking Water Holding Tank holds 40 million litres of drinking water
  • 2 large variable speed pumps are used to transfer the water to the pipeline
  • 4 large shock absorbers are used to reduce the effects of water hammer during the start up and shutdown of these 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 under Botany Bay

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