The Gold Coast Desalination Plant, located at Tugun, uses reverse osmosis to produce drinking water for the Gold Coast, Logan and Brisbane. The plant’s intake and outlet structures are located approximately 1.5 kilometres out to sea and have become artificial reefs, which are home to a variety of local sea creatures.
- 1 megalitre (ML) of water = 1,000,000 litres (L) of water
- Desalinated water was blended with treated dam water and used to supplement drinking water supplies in the final years of the Millennium drought in 2009 and 2010, and during flood events in 2011 and 2013.
- The plant was also used to supply water to areas of the Gold Coast during the Mudgeeraba Water Treatment Plant upgrade in 2015.
- The Gold Coast Desalination Plant operates in a 'hot standby' mode
- The plant can supply around 125 megalitres (ML) of water a day, that’s equivalent to around 50x Olympic sized swimming pools
The desalination process
Seawater is drawn from the ocean through an inlet structure 1.5 kilometres out to sea. The water is gravity fed to the plant. The water entering the tunnel actually flows at a lower rate than the surrounding currents meaning fish and marine life will not be pulled into the inlet structure.
The seawater first passes through a drum screen to remove particles larger than three millimetres.
The water is then pre-treated to remove minute suspended solids. A coagulant is added to the water causing the solids to clump together. The water then slowly passes through settlement tanks containing coal and sand, which filter out the solids.
The reverse osmosis process forces seawater through layers of synthetic membranes at high pressure (about 60 times atmospheric pressure) to remove salt, minerals and other microscopic particles. The plant uses a two-pass system, which means that while some water is completely stripped of salts and minerals after the first pass the rest is put through a second set of reverse osmosis. The plant has approximately a 40 per cent recovery rate, so for each 100 litres of water taken in 40 litres becomes pure water and the other 60 litres is returned to the ocean with a higher concentration of salt.
After reverse osmosis the water contains no minerals and is very soft. The water is remineralised by adding lime and carbon dioxide, and chlorine is also added for disinfection. Drinking water in Queensland is fluoridated, so before water leaves the desalination plant fluoride is added to ensure optimum levels across the region.
Desalinated water is blended with other Gold Coast water supplies and joins the South East Queensland Water Grid to supply homes and businesses on the Gold Coast and in Brisbane.