Design & Innovation

Water security – what role can purified recycled water play?

Ryan Signor and Andrew Salveson | 12 June 2024 | 19:36

Podcast Transcript: Water security – what role can purified recycled water play?

Maria Rampa: Hi I’m Maria Rampa and welcome to this episode of Engineering Reimagined.

Water security is commonly cited as one of the world's most pressing challenges. Just 0.4% of the world's water exists in fresh and accessible ways for critical uses, including drinking.

Water supply is now being increasingly threatened by the impacts of a changing climate which is resulting in more frequent, severe and longer climatic events. This is prompting a rethink about how we use and source water, including water recycling schemes.

Purified Recycled Water, or PRW, is the process of taking water that has been used in households and industries, and repurposing it for applications like irrigation, power generation and other major demands. But there's one large and critical need for which Purified Recycled Water is being increasingly considered, and that's for human consumption.

In today’s episode of Engineering Reimagined Andrew Salveson, Vice President, Water Reuse Chief Technologist and Fellow at Carollo Engineers speaks with Aurecon’s Industry Director Water Ryan Signor. Together they discuss the challenges faced in establishing Purified Recycled Water schemes, how machine learning can play a part in PRW and why communities should act now to stay ahead of a potential water crisis.

Ryan Signor: To discuss how we can reimagine our water cycle and what it can take to have PRW as an integral, accepted part of it. I'm joined by Andrew Salveson. Welcome, Andy.

Andrew Salveson: Hey, Ryan. Nice to be here.

Ryan Signor: For our listeners who may not have heard of purified recycled water, what is it? How does it differ from other types of water recycling?

Andrew Salveson: So what is purified recycled water. And how does that compare to other types of recycled water that you may be more familiar with? So, all our recycled water, on a municipal scale, that comes from the discharges from our industries in our community. The wastewater discharges, it comes from our homes. It's your showers. It's your toilets. It's your washing machines. And that combination of municipal waste from the homeowner and industrial waste from different businesses, all find their way to your local wastewater treatment plant. And so we're not at recycled water yet. We have to go through the process of removing solids and biological treatment, and often there's removal of nutrients. Sometimes there's other levels of treatment, filtration and there's disinfection. So at that point, we take that water that's gone through this municipal treatment, which is pretty robust, and we can then use it with a little extra treatment for non-potable applications. We can go water a golf course, send it back to industry for some uses. And we'll put in filtration, disinfection, etc. to levels that are protective for the need. But purified recycled water is not just one other level. It is multiple other levels of safety and quality beyond that. Purified recycled water are additional barriers for chemicals, additional barriers for pathogens, and all the monitoring systems that need to go into that to result in a water that not only meets all regulatory criteria, whether you're in Australia or the United States or Europe, it exceeds those to a much higher quality. And that then, is your purified recycled water, which can then go to a municipal supply. It can go to a drinking water reservoir to be stored and later pulled out and used. It can go to a groundwater basin to be stored and later used, or it can go directly to the distribution system as a new supply. Whether we are in Windhoek, Namibia, Big Spring, Texas, Orange County, California, Water Corporation of Western Australia, these purified recycled water projects are all providing a high quality water.

Ryan Signor: Can you debunk some common misconceptions or myths? Some of those things that people think about it is that it's potentially not safe, can be expensive, it can be hard to implement. Are these things true?

Andrew Salveson: There are myths out there. Is it safe? The answer to that is absolutely. There's dozens of successfully operating PRW schemes globally. The majority of those are in the United States. In California, we have more than a dozen schemes running, that are now approaching 800 megalitres per day. And in the next ten years, that will double. And that is all based upon very stringent regulatory requirements, for chemical barriers, pathogen barriers. Every one of these schemes is protective of public health, highest quality water we're going to find. So is it safe? Yes. Back when I was a young engineer, WaterVal was up and running in and out of Australia, and we started pulling that into California. And so now when we're implementing PRW projects in California, there's a WaterVal reference, documentation or use of that research in our projects. We stole your name, CalVal. And so, CalVal and WaterVal are working together across the Pacific to elevate both programs, so that when we're talking about water quality, when we're going to the regulators or the engineers or even to the public, we have these standard procedures that we use and replicate on project after projects, so that we know that the safety is maintained. Purified recycled water with the advanced treatment barriers, whether we're dealing with reverse osmosis or other technologies that use less energy, they are all still expensive to implement. But what we see repeatedly is that they are the lowest cost, reliable alternative supply.

Ryan Signor: Why though, is there a need to adopt PRW as part of our water supply? What's making it such a part of a future solution?

Andrew Salveson: This is really a challenge with the climate cycles that you see in parts of Australia, I see it in California, we’ll have flood cycles first for multiple years, and then we'll have drought cycles extend 5 to 7 years. What we see here in California is agencies diversifying their water supply portfolios, building PRW schemes, so that during those drought years, you're not having a significant impact on the available water supply, and the quality and standard of living within these different communities. So PRW is not looking to replace all of a community's water supply. It could be 10%. It could be 20%. Now there are cities that have pushed that boundary further. So in Southern California, there's several agencies, large cities that are targeting anywhere from 50 to over 70% of supplying their water locally with alternative supplies, instead of taking water that's come long distances in the western United States, that's from the Colorado River or the Sacramento River systems. Going back to how much can we or should we rely on PRW? It depends on how reliable your other water supplies are, and it depends how much you can recover from your system. But it is a valuable component of an overall reliable water scheme. Now I want to take a moment and highlight El Paso, Texas. So El Paso has implemented surface water supplies from their conventional surface water systems. They have implemented desalination systems. They've implemented what we call indirect potable reuse, where the purified water is going back into the groundwater basin to later be pumped up. And now, in their last stage of climate resilient water supply, they're implementing direct potable reuse, where the purified recycled water is going directly into the distribution system. We're talking about four supplies for one city so that it is able to confidently move forward and know that they have the water their community needs for drinking, for industry, and for overall well-being.

Ryan Signor: So let's return to that concept of cost. We talked about these schemes being expensive, but the economics can stack up, and that's why we're seeing them rolled out around the world. At Aurecon, we've explored this regarding two of our largest cities, Melbourne and Sydney. In Melbourne's case, we've done some work that can show that the levelised cost, that is, the cost efficiency of production for water can actually be lower than for the current systems in place there. And in Sydney PRW now sits in the Greater Sydney Metropolitan water strategy as an option that the water utility Sydney Water is really touting and stating that there are multi-billion dollar economic opportunities of moving to circular economy models and PRW being a part of that. So if we can accept the criticality of the issues we face, the changing climate, resource stress and the place of innovative water recycling, circular economy solutions at the heart of addressing these, then there seems to be a disconnect with our recorded pace of change. Are there times when PRW really stacks up?

Andrew Salveson: The primary drivers on implementing a PRW scheme is there is not nearly enough water, we're watching reservoirs drop, tens or hundreds of feet, and we're watching groundwater basins drop and we're watching seawater intrusion come in. There is a critical need, and we cannot see it resolving.

Ryan Signor: One thing I've been pondering a lot lately is time and progress of purified recycled water projects. Water can move quickly from one state to being ready for potable use. Yet it takes us such a long time to develop PRW projects resulting in a lot of projects scrutiny and escalating costs. How do you think we can overcome some of those challenges?

Andrew Salveson: Our industry is really good at implementing multi-year, two, three, four year projects. We do a study we assign a capital cost for that project. We vote on it in our city council meeting or our elected board meeting. And then we build the project and we're done. Purified recycled water takes a lot more time. If you are at the leading edge of these concepts of purified recycled water, you have to develop, support, and show confidently the safety of the water to all your different stakeholders. And so that stretches the timeline out. It could take seven at best, ten, fifteen years. And over that time frame you have all these cycles that are happening. You have the cycle of elected officials that's happening that oversee your project and approve your budgets. You have people coming in and out of the community. Say you might have project opponents emerge or project proponents leave. I want people to understand, it's a challenge to implement a PRW project, but it can be overcome. We have to build that internal infrastructure, just like we build a pump with a duty pump, a standby pump, and one on the shelf. We have to do that with our internal infrastructure of people that understand the project value and are ready to step forward and reassert that value, whether it's a regulator, whether it's an elected official, whether it's public stakeholders. You've got to build that bridge that intellectual, project stakeholder bridge to the future. And it never stops through project development, project construction and project operation.

Ryan Signor: Let’s return to one part of what you called social licence and having the buy in to do these things. We recently conducted a survey to understand everyday Australians attitudes toward PRW and found that communities are willing to consider alternative water supplies like this if the water utility has earnt their trust. We also found that water literacy needs to improve to increase community acceptance of PRW. What's been your experience in the US?

Andrew Salveson: The first step in this water literacy is the first step in a PRW program. Make sure the community understands the challenges. And those challenges have to be very clear. We can't hide from those. We've got to bring them forward. And once they understand the challenges and what the water situation is and what the wastewater situation is, then you can jump into explaining how we solve these problems, how we solve them with alternative water supply as a starting point. This isn't selling PRW or selling desal. This is selling the need for reliable alternative water supply. And then you can go through with your communities and explain here are the options. We're trying to make sure that our communities have this long-term resilient water supply and getting them to that point where they're comfortable with it is a challenge.

Ryan Signor: And others have been on this journey around the world. Over 35 cities have adopted PRW as part of their drinking water supply, including Singapore. What can we learn from Singapore and other cities about how to get communities on board with PRW? You've talked about the need to have the discussion about alternative water supplies and making sure the case stacks up. What else can we take from other places about how they’ve driven this process and delivered?

Andrew Salveson: Singapore have been pioneers in technology. We've watched them develop membrane bioreactors at large scale for PRW schemes. You see the Singapore bottled water is showing up all over the world at conferences. They have developed more innovative online monitoring systems to show the safety of it. But I'm a little parochial. I like to look at California. 800 megalitres per day of PRW is happening in California now. That is going to at least double, if not triple in the next 10 to 15 years. In the city of LA There is a 600 megalitres a day project that's being developed, and a thousand megalitres a day project is being developed and we can learn a lot from those projects, but also from the small ones. And I start with a reminder that PRW is hard and it's costly. But it is extremely reliable. What is the impact of not doing an alternative water supply project? What does that do to your business community? What does that do to your standard of living? Where I sit today before the drought broke, they were cutting back water supplies by more than 50% for every homeowner in this community. So what we can learn is, don't wait. Start diversifying now, because that drought will come back, and you need to be able to tap different resources. We can learn that transparency is critical. There have been three projects in the state of California that have failed because of the yuck factor fear, lack of transparency and, and frankly, I'll say some level of fear mongering. The last thing that I like to say, is that what we've learned is that you have to be courageous. So the first projects out of the gate in a region, an agency, a group of elected officials, the engineering leadership have to be courageous and say, we need this project. We've proven to ourself that it's safe. And this is the right economic decision for reliable water supplies, not the cheap decision, the right economic one. And then you have to stick to that. Now you got ten years of being battered with concerns and questions that will keep coming through that long period until you're making the water and you've now gotten people around the bend, and they can see that this was the best solution for your community.

Ryan Signor: You've got some really interesting ideas on what the opportunities are around digital technologies like machine learning and AI to overcome some of the challenges in this field, in PRW. Do you want to talk a little bit about those?

Andrew Salveson: I think it's really important to first define what machine learning and artificial intelligence is. Because there are valid concerns about turning over water security to an evil robot. machine learning is taking complex data, with very poor correlations to each other and bringing that data set together and allowing one of many different software programs to find correlations that tell us something useful and that could be telling us about a chemical contaminant, a microbiological contaminant. It can be telling us about ways to reduce energy use, reduce chemical use, or just help operations. You make decisions. My personal vision is one where machine learning gives us information and hands that to an operator and the operator will then make an educated decision on what to do with it. Machine learning and artificial intelligence should never be controlling, at least today. So what we've shown now over the last four years, the United States Bureau of Reclamation, the United States Department of Energy. They have both been funding millions of dollars into PRW research on machine learning, and I've been privileged to lead that work. And we are able to show that there is anywhere from 20 to 30% savings that can be had from the best PRW schemes on planet Earth. Another critical item is that machine learning is able to tell us things that we can't see with our own eyes. So it is able to provide us advance warning of a water quality difference coming into our advanced treatment and advanced warning. So I'm very excited about this future. This future is a good robot. It's not an evil robot. And the end decisions are all falling into the hands of certified operators and is not being controlled by the machine itself.

Ryan Signor: My last question for you, Andy. Does PRW taste better?

So when we produce this high quality, purified recycled water, we can add minerals back into it. So let's add in a little extra calcium and magnesium here, a little less there. And you can make it match the beautiful Sierra Nevada California spring water. PRW is a blank canvas that you can match your local supplies if that's the direction you want to go.

Ryan Signor: Andy, thanks for sharing your insights, experiences, sage words with us today. I've really enjoyed the discussion. What I'm taking away is that we really need to keep the momentum up. We need to keep investing in these things, even when times don't feel like we need to be focusing on our water issues. That's actually the right time to be investing in it and making things happen. Thanks again very much for sharing your experience in California and around the world.

Andrew Salveson: My pleasure Ryan. I'm glad to contribute.

Maria Rampa: We hope you enjoyed this episode of Engineering Reimagined.

It’s fascinating to hear the potential that Purified Recycled Water can provide for a community; especially in areas where clean drinking water isn’t readily available or becomes threatened due to a changing climate.

If you enjoyed this episode, hit subscribe on Apple or Spotify and don’t forget to follow Aurecon on your favourite social media platform to stay up to date and join the conversation.

Until next time, thanks for listening.

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Water security through purified recycled water

Water security is commonly cited as one of the world's most pressing challenges. Just 0.4% of the world's water exists in fresh and accessible ways for critical uses, including drinking.

Water supply is now being increasingly threatened by the impacts of a changing climate which is resulting in more frequent, severe and longer climatic events. This is prompting a rethink about how we use and source water, including water recycling schemes.

Purified Recycled Water (PRW) is the process of taking water that has been used in households and industries, and repurposing it for applications like irrigation, power generation and other major demands. But there's one large and critical need for which PRW is being increasingly considered, and that's for human consumption.

“There are myths out there, is it safe? The answer to that is, absolutely,” says Andrew Salveson, Vice President, Water Reuse Chief Technologist and Fellow at Carollo Engineers.

“Purified recycled water with the advanced treatment barriers, whether we're dealing with reverse osmosis or other technologies that use less energy, they are all still expensive to implement. But what we see repeatedly is that they are the lowest cost, reliable alternative supply,” he continues.

For this episode of Engineering Reimagined, Andrew Salveson speaks with Aurecon’s Industry Director for Water, Ryan Signor.

Together they discuss the challenges faced in establishing PRW schemes, how machine learning can play a part in PRW and why communities should act now to stay ahead of a potential water crisis.

Andrew and Ryan also touch on how PRW has been used within drought affected communities and how vital water literacy and education is in successfully launching a PRW scheme.

Meet our guests

Learn more about Ryan Signor and Andrew Salveson.
Ryan Signor- Industry Director, Water, Aurecon 

Ryan Signor

Industry Director, Water – Australia, Aurecon

Dr. Ryan Signor leads Aurecon’s water community, driving the positive impact we seek to have within the industry and the communities we support. He connects clients and organisations that have roles to play in water stewardship.

Andrew Salveson- Vice President, Water Reuse Chief Technologist and Fellow, Carollo Engineers

Andrew Salveson

Vice President, Water Reuse Chief Technologist and Fellow, Carollo Engineers

Andrew Salveson is a is an internationally recognised expert in water reuse treatment and regulations and provides guidance and expertise on potable reuse and reclaimed water purification. He has been honoured with numerous awards including WateReuse Person of the Year.

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