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Is there a place for third pipe recycled water in Australia?

Taking a closer look at the success or failure of recycled water projects holds the key to effective decision-making moving forward, according to one expert, especially when considering the next phase of investment in water security infrastructure. 

The debate surrounding various options for water security investment is large and sprawling, with everything from desalination, further damming, potable reuse and source separation on the table for analysis. But Hunter Water Sustainable Wastewater Team Leader Daniel Livingston warns against denouncing third pipe water just yet. 

Presenting on Australian experiences in third pipe water recycling at Ozwater’20 Online this week, Livingston said that despite the unpopularity of third pipe projects – which deliver recycled water to residential areas through a separate pipe for use in washing machines and toilet flushing – the method still has a place.

“Many people view some of the third pipe projects as failures. But what can we learn from this trend? Industry members say it’s costly, more costly than potable water,” he said. 

“In general, people are saying there are reverse planning drivers, but it has a place in some situations. The infrastructure and investment is not justified for flushing toilets.

“If potable reuse is accepted, that could change the debate. But until then, third pipe water will have a place in the future of distribution.”

Third pipe pros and cons

Livingston said the disadvantages involved in third pipe water are largely in relation to infrastructure expenditure, but that connection issues are also a consideration. 

“There’s significant increased costs, as you have essentially duplicated infrastructure. But you can’t typically charge more than potable water. Typically, there needs to be a subsidy from somewhere,” he said. 

“Purified recycled water for drinking has a major cost advantage in that it does not duplicate the network. Increased costs are a major consideration if arguing for dual routing. 

“There is an increased cross-connection risk. There’s also the issue of limited demand for the water. Often, it can be only for toilet flushing and limited outdoor use. Less water is used.”

Regulatory incentives were needed to make third pipe water feasible, Livingston said. 

“Planning regulations tend to incentivise rainwater tanks or dual routing. However, there are arguments that these regulations incentivise perverse outcomes that may not be best for the whole of society economics,” he said. 

“In some cases, dual routing may be the most economic way to avoid major source augmentation. There may be cases where there are customers willing to pay, or other value that gets the case across the line. 

“There is an increasing expectation where our stakeholders, customers and communities expect that we will recycle without much of an understanding of the cost-benefit equation.”

Pimpama Coomera, Gold Coast

Livingston said the Gold Coast’s Pimpama Coomera recycled water treatment plant was once considered state-of-the-art infrastructure, showing just how quickly values and priorities can shift. 

“Back in the early 2000s, [the plant] was considered to be the shining light of innovative water management. But it was decommissioned in 2014,” he said. 

“Economic assessment in the 2010s showed that there was a $100 million disbenefit with continuing the scheme, not including all costs. 

“The most significant learning from my point of view is the importance of alignment of values, rules and knowledge (VRK). This framework has been used by a few organisations in the water sector already.”

Livingston said the VRK framework has been used in the decision-making context for quite some time; it assesses the greatest potential for buyable options where knowledge, values and rules are aligned. 

“In the Coomera case, a lot of work was needed to get alignment of values, rules and knowledge to be able to get a dual route system set up. With the passage of time, alignment of values rules and knowledge was significantly eroded,” he said. 

“Widely perceived as expensive duplication of infrastructure, but they are still being pursued by some utilities right now.”

Livingston said that while all major categories of source augmentation have varying levels of VRK alignment, it will be interesting to see how VRK alignments shift over the next decade as efforts to ensure water security ramp up.