This man has exhibited such gross blundering or worse in his management of great public works, it’s no exaggeration to say he has robbed the taxpayers of this state of many millions,” read The Sunday Times of Australia on February 9, 1902. The target of this diatribe was an Irish engineer overseeing one of the late 19th century’s most colossal engineering projects: the largest drinking water network in the world at the time. This was the Golden Pipeline, the brainchild of Charles Yelverton O’Connor, which today supplies water to 100,000 people in Australia through more than 9,000 kilometers of pipeline. In its current form, it’s known as the Goldfields & Agricultural Water Scheme (GAWS).

Time has disproven the furious attacks from the press and the skepticism of the early 20th-century political class. After all, few civil engineering works have been recognized as historical heritage or even inspired a novel. 

And there may be even fewer engineers who have been honored with two statues and a song. Yet, that is the legacy of a visionary like O’Connor.

Sustainable water management today also demands the courage and vision for long-term projects like the Mundaring drinking water treatment plant (DWTP). Designed, built, and operated by ACCIONA, it uses an updated version of O’Connor’s infrastructure to distribute the equivalent of sixty-six Olympic-size swimming pools of drinking water daily with zero waste discharge. Thus, the Mundaring DWTP has been providing water to industry, livestock, agriculture, and the local population for the past ten years in a country plagued by aridity and water restrictions. In this article, we explain how it achieves this and why it is leading the way in water management in Australia.

In May 2024, an article in Australian ABC News featured a farmer living near Bridgetown in southwestern Australia. She had to travel sixty kilometers to shower at a community center because her tanks were empty. It hadn’t rained since September of the previous year, complicating access to drinking water and increasing fire risk. Unfortunately, this trend isn’t recent; since the 1960s, rainfall in the region has decreased by 20%, according to the Australian Bureau of Meteorology.

In this context, marked by climate change, technologies like desalination plants, water purification plants, and water distribution systems such as O’Connor’s dream from over a century ago have become critical. Fortunately, there is hope near the town of Mundaring, where the GAWS network begins and where ACCIONA’s DWTP is located.

This water treatment plant processes water from three different sources, which is a challenge as water quality varies significantly. First, it draws water from the nearby Mundaring Reservoir, known as CY O’Connor Lake, fed by rainfall in the upper Helena River. The lower Helena River also supplies water to the Lower Helena Dam, the second source. The third source is the Perth Integrated Water Supply System (IWSS), whose water comes mainly from two desalination plants supplemented by wells, reservoirs, and an aquifer refill system.

The triple supply ensures water availability year-round for over 100,000 people. However, before it reaches the GAWS network, it must be treated and made drinkable, where ACCIONA’s DWTP comes into play.

Inaugurated in 2013 as a result of a public-private partnership between the Australian Water Corporation and a consortium formed by ACCIONA, TRILITY, and the former Royal Bank of Scotland (now abrdn), this DWTP has a minimum operating commitment of thirty-five years, ensuring the region’s water future until at least the mid-21st century. This plant integrates the latest technologies in sustainability and efficiency, making it a cornerstone of Australia’s water strategy.

Each day, the Mundaring DWTP can treat up to 165,000 m³ of water, with the potential to expand in the future to reach 240,000 m³. It exclusively supplies water to GAWS through a main pipeline 600 kilometers long and almost half a meter in diameter, branching into over 9,000 kilometers of pipes to reach all users. However, two main purification processes are applied to ensure optimal conditions for farmers, ranchers, consumers, and industries.

First, a pretreatment removes solid particles through coagulation, flotation, and filtration. The sludge from this phase is not wasted, as we’ll see later. On the other hand, once these impurities are removed, the organic content, as well as odors and tastes, are reduced thanks to the Activated Carbon BioFilters.

Finally, bacteria, viruses, and microorganisms are deactivated through chlorination and other chemical treatments, which also enhance the water's taste quality. This process includes the addition of fluoride and pH correctors.

Thanks to the employed technologies, the amount of chemicals used is minimized, preventing the excessive formation of chlorine byproducts in the long distribution network. This is accomplished by reducing organic matter without the use of chemicals, unlike other conventional DWTPs.

As mentioned earlier, all the sludge obtained during the water purification processes at the Mundaring DWTP is ultimately utilized. This is achieved by means of a drying process from which the dehydrated sludge is obtained. In the last “harvest” more than 1,300 tons of these clays were collected, the equivalent of the garbage generated by four hundred families during a year. These materials are then used in the construction industry or for landscaping and recreational areas as a water-retaining layer.

At the helm of the Mundaring DWTP is a team of just a dozen employees who manage all the processes. This team is composed of individuals from countries as diverse and distant as Australia, Scotland, Iran, Sri Lanka, India, Malaysia, Pakistan, and Spain. They ensure the plant’s daily operation through the use of advanced technologies, IoT, sensors, and a high degree of automation.

In fact, after regular working hours, the presence of an operator is unnecessary. Operators can monitor alerts from their cell phones, tablets, or laptops at home. The system usually intervenes automatically in the event of anomalies and sends messages when manual action is required. This setup ensures that there is no significant loss in the quality or quantity of water produced.

The use of these sensor technologies not only automates processes but also allows the Water Corporation to access real-time water quality information transparently, even though ACCIONA fully operates the plant.

This collaboration marks a significant step in managing the water cycle in Australia. With ACCIONA's construction, operation, and maintenance of the Adelaide desalination plant, which supplies water to two million inhabitants, and the recent award of the new Alkimos desalination plant, we are helping to increase the available volume of drinking water and reduce the overexploitation of aquifers in the country.

Sources: ABC News, Water Corporation