Penneshaw Desalination Plant

The small community of Penneshaw on Kangaroo Island has no local natural fresh water sources. SA Water had to find an innovative solution to provide drinking water to the town.

The answer was to build a $4 million desalination plant - which converts seawater into high quality, crystal clear, fresh drinking water to meet Penneshaw’s needs. The plant uses conventional reverse osmosis technology. No chemicals are added to the seawater feed, helping to minimise the impact of the brine on the marine environment.

Improvements to the plant since 1999 have increased its output to about 300 kilolitres of fresh water every day.

Penneshaw Desalination Process:

• Seawater is drawn into the plant through an intake pipe and pumped to a holding tank.
• The water is prescreened to remove seaweed and other objects.
• Chemical free UV disinfection is used to minimise biological growth in the downstream multi-media filters. Multi-media filters remove most of the particles that block the reverse osmosis membranes.
• The filtered seawater is again treated with UV before entering the desalting process to control biological growth.
• The filtered seawater is forced under high pressure through reverse osmosis membranes. These membranes allow fresh water to pass through, but very little salt - about 30 litres of fresh water is produced from every 100 litres of saltwater.
• The desalinated water from the membrane process is conditioned to make it fit for human consumption.
• The fresh water is dosed with carbon dioxide before passing through two marble chip filters. The carbon dioxide helps to dissolve the marble chips, adding calcium and alkalinity to the water.
• The water is stored in a holding tank then pumped either to the reticulation network or the reservoir located near Penneshaw.
• From here it is disinfected and piped to customers.
• The water containing the concentrated salt solution (brine) is returned to the sea through an outlet pipe.