Desalination

WaterSecure supplies South East Queensland with safe, pure, climate-resilient sources of water. One of these new sources is desalinated water. Desalination is a climate-independent source of water. Even during periods of drought it can continue to deliver high quality drinking water, making our supply less vulnerable to interruption.  The Gold Coast Desalination Plant is located at Tugun and includes the 12 buildings on site as well as intake and outlet tunnels that run about 1.5 kilometres out to sea. A pipeline owned by Linkwater connects the desalination plant to existing water infrastructure on the Gold Coast. The desalinated water mixes with dam water at reservoirs and water treatment plant tanks before it is supplied to the SEQ Water Grid.

The Gold Coast plant is one of the most energy efficient desalination facilities in the world. The plant uses energy recovery devices and has also purchased Reusable Energy Certificates for 100 per cent of the power it uses. Read more about energy use at the desalination plant including how it stacks up against everyday household appliances.

The desalination process
Seawater is drawn from the ocean through an inlet structure 1.4 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.

Reverse osmosis 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.