The GWR treatment process
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The Trial will use world class technologies to treat the water before it is pumped into the aquifer.
These technologies are applied here in Australia for drinking water treatment, including in regional areas of WA to improve drinking water quality and, used in the treatment of recycled water for drinking in Singapore, the United States, Namibia and Belgium.
These technologies have been chosen because they will remove virtually all contaminants of concern from the already treated wastewater and produce a water quality similar to that of distilled water.
The water used for injection into the aquifer has already passed through the normal stages of wastewater treatment at the Beenyup Plant. These are: screening, primary sedimentation and secondary treatment, followed by further sedimentation. From the plant, the water is then purified through a three step treatment process of membrane filtration, reverse osmosis and ultraviolet radiation.
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Membrane filtration
The first treatment process is called membrane-filtration, which involves passing wastewater through very fine hollow fibre membranes, filtering out all the particles and micro-organisms from the water before it undergoes treatment through reverse osmosis.
After passing through the membrane, the filtered water contains only dissolved salt and organic molecules.
Reverse osmosis
Reverse osmosis is a treatment that involves forcing filtered water through a specially engineered membrane at high pressure to remove impurities such as dissolved salts, viruses, pesticides and other organic compounds.
Reverse osmosis is the same process used to desalinate water at the Perth Seawater Desalination Plant. Often bottled drinking water has undergone treatment using reverse osmosis technology.
Ultraviolet disinfection
Following reverse osmosis, ultraviolet light is used as a final precaution to disinfect the water. This process would destroy any trace levels of microbiological organisms.
All 'reject' water or water not meeting the quality requirements is sent back to the start of the wastewater treatment plant for further processing.
This treatment process produces a quality of water that exceeds standards set by the World Health Organisation and the Australian Drinking Water Guidelines.
The Groundwater Replenishment Trial takes an extra precautionary step, injecting the water underground to let natural processes at work in the aquifer make doubly sure it’s safe to drink.
Research has shown that while the water is in the ground for a period of time, the groundwater environment assists in breaking down any organic chemicals that remain in the injected water.
When the water is taken out for use many years later, it would be treated again as part of standard drinking water treatment processes.