DESALINATION TECHNOLOGY
The Victorian Desalination Project will use reverse osmosis (membrane based) desalination technology to turn seawater into freshwater.
There are several steps to this process. Firstly, seawater will be drawn in from an underground and undersea tunnel. Fine particles are then removed during an initial screening before the water passes through the reverse osmosis membrane.
Once converted, the water from Victoria’s desalination plant will be treated to Australian drinking water standards and blended with current drinking water supplies.
The following text and accompanying diagram (JPG 1.8mb) explains the process in more detail:
- Seawater enters the desalination plant through a specially designed intake system, including a tunnel approximately 1.2km long. Water enters at a low speed to avoid impacts on the marine environment. Even small fish will be able to swim against the intake current and a protective grill will ensure larger marine life can’t swim into the structure.
- Seawater passes through an initial screening to remove fine particles including sand and sediment. Seawater is then filtered to remove finer particles.
- The filtered seawater passes though two stages of reverse osmosis, where it is pushed through more than 55,000 ultra-fine membranes under high pressure. Fresh water will pass through, leaving sea water concentrate behind.
- Desalinated water is treated to meet Australian drinking water standards and Victorian health requirements.
- Drinking water may be stored in tanks before it is distributed into the Melbourne and regional water networks where it may be blended with water from existing catchments.
- Seawater concentrate will be safely returned to Bass Strait though an underground and undersea tunnel approximately 1.5km long and discharge structures. The salt content and temperature will return to normal seawater salinity and temperature a short distance from the discharge nozzles, which act as diffusers. Ocean currents dilute the concentrate within seconds.
Why reverse osmosis technology?
All recent and proposed large Australian seawater desalination plants have adopted reverse osmosis technology because:
- it is typically more energy efficient and cost effective.
- it has lower environmental effects relating to the discharge of salty concentrate
- it has less odour and visual intrusion to impact on its surroundings.
Analysis conducted during extensive studies on the Victorian Desalination Project confirmed that the reverse osmosis approach was the most efficient and effective desalination process and would produce the best environmental outcomes for this project.