Why do we need purified recycled water?

View the Purified Recycled Water Questions and Answers fact sheet (PDF, 189 KB) .

Purified recycled water is vital to securing South East Queensland’s water supply because it addresses two main issues facing our region:

Climate variability and climate change
Currently, 95% of our water supply is dependent on dams and weirs, which are susceptible to long droughts, such as the one we are experiencing now. South East Queensland’s climate is already highly variable, and when combined with increasing uncertainty regarding global climate change, this may adversely affect rainfall and dam storage levels. This creates significant risks to our supply.

Purified recycled water enables us to diversify the sources from which we obtain water, it provides a climate resilient source of supply and helps ensure the region’s water security.

Increased demand for water
South East Queensland continues to experience the fastest growth rate of any urban region in Australia. Currently, almost 2.8 million people live in South East Queensland and this figure could increase to more than 6 million by 2056. Even with significant new efficiency measures to reduce water consumption, this sustained level of population growth is substantially increasing the region’s demand for water.

Purified recycled water, along with desalination, is expected to provide up to 30% of our water supply by 2056. It is an important element of the draft South East Queensland Water Strategy, which aims to provide long term water security.

What is purified recycled water?

Purified recycled water is wastewater that has been treated to a very high standard using world’s best technology through a 7-barrier process.

Why is a 7-barrier process used for purified recycled water?

The 7-barrier process is designed to be a fail-safe system to ensure the quality and purity of the water.

The system uses world class technology and a strict testing regime to ensure the safety of the water. The process provides multiple opportunities to identify and fix any problems that might occur. For example, reverse osmosis (barrier 4) is very effective in purifying waste water. However, advanced oxidation (barrier 5) has been added to further guarantee the safety of the water. The dam (barrier 6) provides further time and environmental buffers to ensure water quality standards are met. The water then passes through the existing treatment process currently used to produce drinking water. Multiple barrier processes are standard practice in any manufacturing process where the safety of human health is paramount.

Read more in our fact sheet – How is purified recycled water made? (PDF, 473 KB)

How do you ensure it is safe?

Purified recycled water must meet strict water quality and health standards before it can be added to drinking water supplies.

Queensland Health has developed health-based water quality criteria for purified recycled water, based on national guidelines and recommendations from peak health bodies such as the World Health Organisation and the National Health and Medical Research Council.

The standards set quality control levels to ensure the water is safe. Using world class technology, the water goes through a number of high level engineering and filtering processes to meet these stringent health standards.

The water is subject to water quality monitoring and testing at all stages of the 7-barrier process.

Once added to Wivenhoe Dam, purified recycled water mixes with dam supplies before being transported 60km along the Mid Brisbane River where it is treated by the Mt Crosby Treatment Plant before being supplied to households.

Purified recycled water has a long history of safe use for drinking in countries such as the United States, Belgium, England and Singapore.

How are bacteria and viruses removed from the water?

Bacteria and viruses are reduced during a number of different stages of the 7-barrier process. Some are removed during secondary treatment. Following this, as part of the advanced water treatment process, recycled water goes through various steps including microfiltration, reverse osmosis and advanced oxidation processes. Microfiltration involves forcing water through bundles of tiny plastic straws with microscopic pores which are much smaller than bacteria and some viruses. This step removes most of the bacteria and even some viruses, particularly those that adhere to particles in the water.

Reverse osmosis involves forcing the filtered water through an even finer membrane made of sheets of synthetic material (cellulose acetate) which is tightly wound into a roll. This will remove any remaining bacteria and viruses. Advanced oxidation, the final step of the advanced water treatment process, uses hydrogen peroxide (a powerful oxidant) and ultraviolet light that provide an extra level of disinfection should it ever be required. The combination of these steps ensures no viruses and bacteria are found in purified recycled water and that it is safe to add to drinking water supplies.

How are chemicals such as pharmaceuticals (including chemotherapy drugs), hormones, endocrine-disrupting compounds and pesticides removed from the water?

Conventional sewage treatment in Queensland (barrier 2) is so effective that most pharmaceuticals (including chemotherapy drugs), hormones and endocrine-disrupting chemicals have already been reduced to concentrations below health guideline values. The advanced wastewater treatment process that follows conventional sewage treatment (particularly reverse osmosis and advanced oxidation) reduces the remaining chemicals that, if detectable, are much too low to pose a risk to people’s health, according to the strict requirement laid down by the Australian Guidelines for Water Recycling: Augmentation of Drinking Water Supplies. Those guidelines are based on the Australian Drinking Water Guidelines which were used as a model for theWorld Health Organisation’s Drinking Water Guidelines. Queensland Health’s drinking water criteria are also based on these guidelines.

For more information on water and health, visit the Queensland Health website.

What other countries are using purified recycled water?

Purified recycled water has been added to drinking water supplies for the last 40 years in various parts of the world. Examples of other countries using purified recycled water are Orange County USA, Upper Occoquan USA, Montebello USA, Singapore, Belgium and Essex, UK. Studies of the direct effect on human health carried out as part of these projects have shown that water containing purified recycled water is safe to consume. For more information, refer to the fact sheet, Water Recycling – examples from other countries.

What are the benefits of using purified recycled water?

Purified recycled water is a climate resilient source of water that can be added to existing sources to assist in securing South East Queensland’s water supply.

The additional water supply provided by purified recycled water reduces the risk of severe water restrictions being imposed on households, businesses and industry in the future.

The purification process for purified recycled water will significantly reduce the release of nutrients and other environmentally detrimental compounds to Moreton Bay.

How much additional water will purified recycled water create?

Purified recycled water will provide us with a significant alternative water supply. Once complete, the Western Corridor Recycled Water Project has the capacity to provide up to 232 million litres per day. Some of this purified recycled water will be supplied directly to industry and power stations, and some will be provided for rural production when not required for urban use. The amount that is released into Wivenhoe Dam will vary over time depending on rainfall, dam levels and water usage.

What percentage of our water supply will be purified recycled water?

The percentage will vary depending on the dam level. The percentage will be higher in dry times when dam levels are low. However, when rain is plentiful, the percentage of purified recycled water supply will be low. The percentage of purified recycled water as a water supply will have no affect on the quality of water in our taps.

Will the purified recycled water taste or smell different from the reticulated water that I currently use?

No. It is clear and odourless. The water will taste or smell no different from the drinking water that is currently being supplied. The purified recycled water will meet all water quality criteria contained in the Australian Drinking Water Guidelines and the Australian Drinking Water Guidelines before it is added into the environmental buffer. There it will mix with water from the dam and travel to the point where it is collected and treated by the drinking water treatment plant before being supplied to the consumer.

After the water treatment plant (barrier 7), water will be required to meet the standards contained in the Australian Drinking Water Guidelines.

Will the purified recycled water process benefit the environment?

Yes. The purified recycled water process will benefit the environment by significantly reducing the discharge of nitrogen and phosphorous into Moreton Bay.

Currently, six water treatment plants discharge effluent into local waterways that flow into Moreton Bay. These treatment plants discharge 1235 kilograms of nitrogen per day and 1313 kilograms of phosphorous per day into the bay. Through the Western Corridor Recycled Water Project, there will be a 57 per cent reduction in nitrogen and a 40 per cent reduction in phosphorous discharges into Moreton Bay.

The removal of these nutrients and other environmentally detrimental compounds will help protect sensitive waterways like Moreton Bay.

Purified recycled water also requires less energy to operate than desalination. The Western Corridor Recycled Water Project will use about one megawatt hour of electricity to produce one megalitre of purified recycled water. The desalination plant that is being constructed at Tugun on the Gold Coast will use about five megawatt hours of energy to produce the same amount of drinking water.