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