As South East Queensland (SEQ) faced the combined challenges of climate change, population growth and its toughest drought on record, the Queensland state government looked for innovative solutions which would solve the region’s water crisis. In 2007, dam levels dropped below 17%, and with a population projected to reach more than 5 million by 2056, the government knew it had to act quickly. In response to the worsening drought conditions and growing population, a AUS$6.9 billion dollar Water Grid was constructed. The SEQ Water Grid is Australia’s largest water infrastructure project and the first system in the world to manage, source, treat, store and supply treated water on such a large scale. The SEQ Water Grid provides a secure source of water to meet the challenges of population growth and climate change.
 

The AUS$2.5 billion Western Corridor Recycled Water Scheme was designed as the backbone of the SEQ Water Grid, to diversify South East Queensland’s water sources. The project won an Honour Award at the 2010 International Water Association Project Innovation Awards [see table below]. The SEQ Water Grid has increased climate resilient water sources from 5 to 25% of the total supply. 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 water supply. Purified recycled water enables a diversification of sources from which water is obtained and provides a climate resilient source of supply to help ensure the region’s water security.
 

With the capacity to produce up to 232 megalitres (ML) of water per day, the Western Corridor Recycled Water scheme is the largest in the Southern Hemisphere and the third largest in the world. It provides water to three power stations located at Tarong and Swanbank. In future, the scheme will supply water to industry, potentially to agricultural users, and to Wivenhoe Dam when the region’s drinking water supplies fall below 40%.

The scheme includes a network of more than 200 kilometres (kms) of large-diameter underground pipes, three advanced water treatment plants, nine storage tanks and 12 pumping stations. It also provides significant environmental benefits by removing nutrients from water released to waterways which flow to environmentally sensitive Moreton Bay.

Western Corridor Recycled Water is owned by Queensland Government statutory authority WaterSecure, which also owns the Gold Coast Desalination Plant. WaterSecure provides a safe and sustainable source of pure water for South East Queensland, with the capacity to produce up to 365 ML of pure water each day; providing water security for the region as part of the SEQ Water Grid.

Scheme overview

Three advanced water treatment plants located at Luggage Point, Gibson Island and Bundamba, are central to the Western Corridor’s successful operation. The facilities use multi-barrier treatment processes to purify water. Each plant uses technologies which have been applied successfully in Singapore, Europe and the United States, but the combination of technologies used in Queensland is unique and provides the most stringent safeguards to public health.

More than 200 kms of pipelines, pump stations and balance tanks link the system. The pipeline starts at Luggage Point and Gibson Island advanced water treatment plants at the mouth of the Brisbane River. It travels through Brisbane’s eastern and southern suburbs and meets the Bundamba Advanced Water Treatment Plant at Ipswich. Purified recycled water pipelines travel in multiple directions from Bundamba. One pipeline leads to the Swanbank power station. A second pipeline continues north to Caboonbah at the top of Wivenhoe Dam, where it taps into an existing pipeline and takes water to power stations at Tarong.

Purifying water

Testing has demonstrated that water produced by the scheme meets the Public Health Regulation standards set by Queensland Health. Water undergoes the world’s most rigorous purification processes, including real-time water quality monitoring, and testing for more than 260 parameters.

The Western Corridor Recycled Water scheme’s plants contribute three essential barriers of the advanced water treatment process; microfiltration, reverse osmosis and advanced oxidation.

• Microfiltration forces treated water under pressure through tiny straw-like filters which remove suspended material and micro-organisms including bacteria and some viruses.

• Reverse osmosis pushes water under high pressure through a semi-permeable membrane, removing viruses, organic compounds and inorganic compounds such as salt.

• Advanced oxidation is the final step of the advanced water treatment process. It uses hydrogen peroxide and ultraviolet light to destroy any remaining compounds. The outcome is a pure, safe and secure source of water.

WaterSecure CEO Keith Davies says the scheme’s advanced water treatment processes are second to none.

“International delegations from all over the world have praised the scheme and the environmental considerations we have made, as well as our best practice examples in design, construction and water treatment technologies. By using global experts throughout all stages of design and construction, we’ve ensured the best outcomes for the scheme. We’ve already provided more than 36 billion litres of water to Swanbank and Tarong power stations. This water is safe and satisfies stringent requirements of the Public Health Regulation.”

Mr Davies says the quality of water is further guaranteed by the Water Supply (Safety and Reliability) Act 2008.

“All water produced by the scheme must meet strict water quality and health standards outlined within this new regulatory framework,” he says. “This Act exists to protect public health and ensure the scheme can continue to operate and protect public water supplies. Under the Act, we are required to produce a recycled water management plan that identifies risks and details actions to minimise these risks.

“The Queensland Water Commission has also established a panel of international experts to provide the highest quality, independent technical advice. This panel includes world leaders in ecotoxicology, environmental science, public health, environmental microbiology, limnology and advanced water treatment. The expert panel has publicly reported that the Bundamba plant has consistently produced water that met Public Health Regulation standards throughout the testing period”.

Improving outcomes for Moreton Bay

According to Mr Davies, the Western Corridor Recycled Water scheme will leave a positive environmental legacy that will last for generations.

“Firstly, the amount of water supplied by the scheme is equivalent to a large scale dam. By providing this water from another source, we are preventing the need for at least one extra dam to be built in the future,” he says. “In the immediate term, the scheme is improving water quality in the Brisbane and Bremer rivers, which flow to Moreton Bay, an environmentally sensitive and internationally recognised wetland. Nutrients that would otherwise be released to these rivers are removed in the treatment process.”

“For example, treated wastewater is no longer released to the Bremer River at Bundamba. This reduces levels of phosphorus and nitrogen in the river, meaning we can expect an improvement in aquatic ecosystems including plant life, fish stocks and invertebrates. Where reverse osmosis concentrate is released to the Brisbane River, nutrient levels have been greatly reduced, in the case of phosphorus by around 90%.”

Innovative construction procedures allowed the scheme to provide positive environmental outcomes. To minimize the construction of more than 200 kms of pipeline through sensitive creek and estuarine habitats, WaterSecure undertook a comprehensive environmental and social impact assessment. The company used horizontal directional drilling to minimize the environmental impact, and replaced traditional trench crossings at a number of locations including the Brisbane River, Aquarium Passage and the lower reaches of Bulimba Creek.

2.5 years of construction – a phased approach

Because of its size and complexity, the Western Corridor Recycled Water Scheme was delivered in stages known as 1A, 1B, 2A and 2B. All construction deadlines for the four stages were met.

Stage 1A was designed to take immediate pressure off the Wivenhoe Dam by supplying Swanbank power station with up to 20 ML of water a day. It comprised construction of the first stage of the Bundamba Advanced Water Treatment Plant and associated pipelines, and was completed after just ten months of construction.

Stage 1B upgraded the capacity of the Bundamba plant to 66 ML of water per day and began supplying water to Tarong and Tarong North power stations. It included construction of almost 100 kms of pipeline and was completed in June 2008, just nine months after water first flowed to Swanbank.

Stage 2A entailed construction of the Luggage Point (66 ML per day capacity) and Gibson Island (50 ML per day capacity) advanced water treatment plants, and more than 80 kms of underground pipeline. This pipeline was constructed through some of South East Queensland’s most developed regions and posed considerable challenges. Stage 2A was completed on October 31, 2008 and marked the first time the entire 200 km system was linked together as a completed whole.

Stage 2B, completed in December 2008, was an upgrade of the Gibson Island advanced water treatment plant which increased its capacity to 100 ML per day.

In addition to the construction of core scheme elements, further drought contingency works were required to upgrade the system’s yield and ensure the pipeline could efficiently transport increased volumes of water. Keith Davies says the scheme has set industry benchmarks and will remain a key element of South East Queensland’s water supply strategy for generations.

Starting at the Bundamba advanced water treatment plant, the pipeline travels north-west for 32 kms to a five ML balance tank and pump station at Lowood. The pipeline then splits into two, with one pipeline heading 48.5 kms north to Caboonbah, via the Esk balance tank, where it links with pipelines supplying water to the Tarong power stations. The second pipeline heads 16.4 kms to Coominya, where water will be released into Wivenhoe Dam once combined dam levels fall below 40%.

Mr Davies says WaterSecure will provide the water required to ensure a positive future for South East Queensland.

“Water is the fundamental resource that we simply can’t do without. And in a region increasingly affected by climate change, drought and substantial population growth, security of our water supply is more important than ever. We now have two climate-independent water sources to produce a pure source of water that will directly assist South East Queensland’s population growth, economic growth and water supply certainty for generations to come.”