What’s in a name? Understanding advanced water recycling

27 February 2026

On the Planet Possible podcast this month, host Niki Roach and guests explore the different ways in which the UK and US water sectors are embracing water reuse, essential technology for climate resilience

Regular readers will probably already be familiar with the challenges of the availability of clean water. And whilst it's often raining here in the UK, parts of Sussex, Cambridgeshire, Suffolk and Norfolk are already experiencing water shortages.

When we layer in population growth and increased demand from business –including water-hungry data centres – and the unpredictability of future rainfall due to climate change, the Department for the Environment, Farming and Rural Affairs (Defra) forecasts that England will need almost five billion more litres of water a day by 2050. There's lots we can do, individually and collectively, to tackle this challenge, and one option is advanced water recycling. The 12 February 2026 episode of CIWEM’s Planet Possible podcast explores exactly that.

Niki Roach and her guests explain what advanced water recycling is, how it's already being done internationally, and what this means for the UK where it's in its infancy. Joining Niki are Simon Langley, a business development director at MWH Treatment, and Heather Smith, senior lecturer in water governance at Cranfield University, who are both working on advanced water recycling in the UK. Then, to consider the US context, where this technology is much more familiar, she is joined by Dr Paul Pitt and Dr Gaya Ram Mohan from the water consultancy Hazen and Sawyer.

If you’d like to listen along, you can find the podcast episode here, on Spotify, Apple Podcasts or your favourite platform. Follow the podcast to stay updated on our monthly deep dives into pressing environmental challenges.

Now, over to Niki and her guests…

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Niki Roach: Welcome Simon and Heather. We're going to hear about some water recycling initiatives that you're both involved with in the UK. And I know it's quite a complicated regulatory landscape to get our heads around. It's very new. And I'm really keen to know what needs to be possible in order to make it happen. But before we do that, Simon, as somebody working with MWH Treatment, kind of at the sharp end of some of this, give us a bit of a view of what we mean by water recycling and where we're considering this in the UK.

Simon Langley: Thanks, Niki. I guess if we think about it as advanced water recycling. So at our usual wastewater treatment works, we take effluent from customers and clean it up and return that treated effluent to river. This is a step that takes that treated effluent and instead of sending it to a river or a discharge point, we're effectively going to upscale the treatment regime to that effluent to turn it into a water resource that could then be further treated or utilised in part of the water resources management plans, to perhaps relieve a little bit of pressure on things like groundwater sources and abstraction in the wider catchment areas. So it's about creating new water resources for potential treatment and use alongside other raw water sources.

NR: And where's that happening or is it happening at all in the UK? At the moment, Simon, is this completely new? Give us a bit of a sense of that.

SL: It's relatively new in its concept in the UK regulatory water market. It has been done for specific examples around things like industrial applications before: for power station cooling waters and things like that, where there's been a large demand, the water needs to be treated to a particular level and a raw water source is not available to do that or a treated water source couldn't sustain the levels. So, there's been some areas where it has been done in the past.

It's more regularly used in water stressed regions across the world though, in places like Australia, the west coast of the US, the Middle East. Quite frequently it's in places like Singapore, for example, where they've got a whole new water regime around public acceptance for advanced water recycling.

NR: Is it about taking that advanced treated wastewater and going directly into supply? What happens in practice, Simon?

SL: There are effectively two systems for advanced water recycling. There is what we call indirect and direct. In the UK, at this time, we're only really exploring the indirect route. And when we say indirect, that means we clean up the effluent to a very, very high standard. So there's effectively an equivalence to the raw water standard that it would be combined with and then gets again treated in a full water treatment plant. So that is the important thing. It's indirectly reusing that source, if you like, to generate a new raw water.

Direct, which has been used more readily across the globe, is when you literally take the final effluent, clean it up to a really high standard and directly inject it into the public water supply without it going through a natural environmental buffer, such as a raw water reservoir or a river or a natural source. It could also be an aquifer recharge, potentially. So that's the difference between direct and indirect, Niki.

NR: And I know that you were involved in some projects in the UK. Where are we talking at the moment?

SL: There's a range of our UK regulatory water clients, the likes of Southern, Anglian, Thames, we've done quite a bit of this indirect reuse for. Taking their sort of final effluent, cleaning it up, and then popping it through the natural buffers. A lot of it is very much design and development stage, and testing and demonstration. It is a growing demand across the UK, and there's been an awful lot in the water resource management plans made of water reuse to hit the scarcity issue that's facing us.

NR: We visited Havant Thicket in the middle of last year – it was great to go on site and see it – and they're considering looking at some advanced water recycling there. It was just amazing to realise the scale of possibility, actually, going from a relatively modest reservoir to something that could really help Southern. It's quite interesting as well that it's Southern and Portsmouth water. So I'm a little bit aware, but it's really helpful just for you clarify what we really mean by it.

Heather, I'd love to bring you in. You've spent some time working with RAPID. If you can explain what RAPID is, that would be brilliant. Give us a bit of a sense on what the regulatory view is of advanced water recycling.

Heather Smith: RAPID is a coordinating body between the three water sector regulators. It sits between Ofwat, the Environment Agency and the Drinking Water Inspectorate (DWI) and it's meant to facilitate big water resource investments, smooth their transition through the regulatory processes, to bring the perspective of all three regulators to bear and help them move through that regulatory process a bit more smoothly. It's been in place for a while and they're dealing with something like 12 water recycling schemes at the moment that are kind of working their way through the different stages of their consideration.

So the work I did with RAPID was looking at how they're dealing with the water recycling schemes and how they're communicating about water recycling schemes. And one of their biggest perspectives at the minute is actually on some of the terminology. You heard Simon say at the beginning that we're talking about advanced water recycling – and you would not believe the amount of debate that has happened about that one particular word. Because the terminology about this is not consistent around the world. You hear about water recycling, water reuse, water reclamation, all of these different terms are thrown about and there's no consistency. But obviously from a regulatory perspective, you need to know exactly what you're talking about and what it is that you're regulating. So the terminology actually becomes quite important, even though to others it can feel quite pedantic. So there's been quite a bit of a debate about what are we actually talking about with water recycling and is ‘advanced water recycling’ the right term? Partly because some of the companies, particularly Anglian Water, have started to refer to their more standard wastewater treatment processes as water recycling. So we needed something else to go on top of that.

So a lot of what I did at the beginning with RAPID was just try to sort through the different terminologies and figure out, okay, if we're going to put this in regulatory language, what kind of language are we going to be doing it in and how is that going to be then communicated outwardly into the public? So we've sort of landed on this term, ‘advanced water recycling’ as a way of doing that. As Simon said, it's not strictly a new process. This has been done around the world for quite some time and there's nothing inherently in our regulations that prevent it. There's nothing massive that needs to change in our regulation to enable this to happen. It's just a question of how the different regulatory processes that are already in place manage the process and manage the risks involved, like we do with existing drinking water sources. Are there any extra risks that are being created by using water recycling and how do we then manage those risks within the current quite robust drinking water protection regulation that we already have?

NR: And are there any more risks? Because I guess when we think about treating sewage and putting that treated effluent back into the river, we have standards around that. And rivers have got all sorts of things in them, as well, as we know; there’s lots of debate in the media about highway runoff, agricultural runoff. So where does this advanced element of treatment sit? What are the extra risks that people are thinking about, given we're talking about indirect here? We're not talking about piping this straight into a water distribution network, we're talking about putting this back into the environment. It sounds to the uneducated ear like me that this is just better wastewater treatment. Am I being too naïve there? Help me understand the differences and the semantics of that.

HS: The reality is there's not much extra risk. And whenever you're talking about risk, you always have to put it in context. You know, risk relative to what, and relative to our current sources and relative to some of the other risks that we face in day-to-day life. The concerns that exist are not unique to water recycling. There are growing concerns around things like some of the more emerging contaminants, you know, your forever chemicals, your PFAS and things like that. There was some concern about microplastics. There's been concern about other contaminants that we know are in wastewater. And we know that we need to use more advanced technologies potentially to treat those. Those are the extra risks that exist just with wastewater treatment. If we then use the final effluent and use more advanced treatment to put that eventually into the drinking water supply, does that create any added risks in our drinking water? Possibly, but not a great deal. That's my impression anyway. Perhaps Simon has a different view on it. But relative to the risks that we already face with drinking water, there's not a significant added risk, is my view anyway.

SL: The toxicology and microbial aspects are things that we are tracking and making sure that we've got good levels of confidence in treatment technologies to provide the standards that are required. So the product that's produced from this advanced water recycling is on a no deterioration basis. And that means it's no worse than the raw water that's already been treated through the existing controls and regime of Drinking Water Inspectorate regimes and auditing and sampling and analysis that goes on every day. It's an expanded list of parameters that we're looking at: somewhere in the region of around 400 is typically not uncommon for advanced water recycling.

We are always making sure that we're learning from the international experience as well and data that's out there. But it's really interesting: you have to apply that to a UK regulatory landscape and regime of audit and compliance. Regulations such as the Reg 31 Drinking Water Inspectorate, regimes for materials and contact and all of those good things that you've got to consider when you're looking at these advanced technologies to make sure that, not just in the treatment but also in the technologies that you deploy, that you're not imparting something that could get transferred to the raw water source. This has been a lot of the work that we've been doing about building stakeholder confidence and communicating that onwards.

NR: Are the regulations in the UK very different to what we see internationally?

HS: I think the regulations in the UK, they're extremely good for managing the risks with drinking water. We have really robust protections in place for drinking water already and really strong risk management practices, you know, through water safety planning and the like, that are already inbuilt into the regulatory process for drinking water. And that's why we're in actually a really good position to introduce some of these new sources or alternative sources, because we were already really good at managing the risks to make sure that drinking water is safe. And compared to some other countries, our risk management is probably a bit more robust. But in terms of the drinking water quality standards or things like that, we're probably not significantly different than a lot of the other advanced drinking water sector countries, but we just have those really, really hefty risk management measures that sit behind that.

NR: Simon, I'm wondering, given that you're involved in projects with companies, you know, this is starting to feel quite real, has there been much engagement with the public around this? And if so, I guess, what's their response been?

SL: It's a really great point. As much as it is the technical challenge of treating the stuff, it’s the stakeholder acceptance and confidence and communication to give them that reassurance that this could be accepted. Even what you call it is important because you're trying to make it really clear that this is about creating a water resource that can be used in the normal water treatment process and cycle, to bring drinking water to a same standard across the UK.

It's been great to get involved in these projects and it is a real collaborative effort to do that. Things like demonstration centres are really important to get that data to prove to people that the nuances of the UK can be catered to with what is a relatively known combination of treatment technologies; to get those standards consistently, robustly and over a period of time, to give confidence that any changes in temperature and different seasons don't cause an issue. The answer to your question, Niki, is yes, there's a lot of work gone on about engaging with the customer.

The first thing is the awareness that there's a need. Second thing is then what you're doing about it and programming that through things like the water resource management plans and introducing it into your plans and having those consultations about how are you going about it, the protection measures you're making to give them that reassurance. Again, I think most people would accept that there's a need for it and it's an option that should be looked at, particularly when you've got emerging demands coming through from various areas for additional sources, for things like data centres, hydrogen production, the things that are going to give us some renewable energy or additional computing power to make the world a better place. A lot of these things are really important, so advanced water recycling has got a massive part to play in helping plug that supply-demand balance deficit that we're currently facing in some of the more water stressed areas.

NR: Something that has just occurred to me, hearing you talk about AI and data centres – which feels like it is coming up increasingly as we record these episodes – is huge water demand for cooling. You talked about direct and indirect – for things that don't need drinking water quality standard water, potable water, is there an opportunity there? And are we starting to think about that for that direct treated final effluent?

SL: Absolutely. I mean, I know in some of the work we've been doing with one of the UK regulated clients, they've almost got a matrix that they're developing of the different needs and what standard of advanced water recycling they would require for the different applications of how they could meet needs for industrial users rather than for drinking water. Equally, it's also about making sure that it's at the most affordable level as well. You don't want to over treat. There are other nuances around whether a catchment, maybe coastal, could introduce salinity because that changes the treatment needs as well. So the answer to your question, Niki, there's a variety of technologies and applications. They largely follow two fairly established trains of treatment technology elements. But as much as anything, this is going to be an exercise in collaboration nationally between the water companies and the regulators to establish standards, to establish data, to establish performance, to really push this across the UK.

HS: If I could just add to that, Niki, this is partly where some of the terminology comes back in, because when you're talking about producing non-drinking water or water that is not intended for drinking, regardless of its quality, that still tends to be called water reuse. The boundaries are never entirely clear, because if we look at some of the global examples, Singapore, for instance, they switch back and forth between providing that highly treated recycled water; sometimes they provide it for drinking when needed, but because that water is so pure, it's so highly treated, actually their biggest and best use for it is in the high tech computer chip manufacturing industry, which requires ultra pure water. So economically that's more advantageous. So it's incredibly high standard water, but it's provided for an industrial purpose. So you can get these kind of mixing and matching of different applications. But yes, it does bring in that question of terminology again because we get slightly confused between whether we're talking about providing drinking water or providing not drinking water.

NR: It sounds like we need a menu. Water is not just water or water unfit for human consumption, it's like a list of products, isn't it, which is absolutely extraordinary. What a time to be in the water sector! I tell you what, it's blooming interesting. We are painfully short of time, so you know what's coming and I'm going to ask you my final question.

But before I do, Marcus Rink, who's the chief inspector of the Drinking Water Inspectorate, who regulate drinking water quality in England and Wales, recently spoke at a meeting of the government’s Environment, Food and Rural Affairs Committee meeting, and he said the following – I'm hoping he was slightly influenced by our podcast – he said, “If I had my wish list and my magic wand, I would just say, we need an update of our drinking water quality regulations. I would argue that we need to put regulations in for sufficiency, and I would argue that we need to have grey water regulations for safe delivery of grey water within domestic and industrial premises.”

So that's Marcus's magic wand answer. I'm going to pass you both the Planet Possible magic wand. Give it a wave. Simon, I'll send it in your direction first. You could make anything possible in this space. What do you want?

SL: What I'd really love to see is collaboration with the water companies and the regulators on this to try and get an aligned set of national standards and accepted treatment technologies. Sharing of data of performance results from demonstration centres initially, to inform full-scale plans and to gain that public confidence that this is really a safe, sustainable technology to use as a water resource as we go forward and think about how we're going to meet them supply-demand imbalances.

NR: National standards – sounds very sensible. Heather, what about you?

HS: Well, if I had my way, we would be able to create a beautiful and publicly attractive demonstration centre for this kind of process. Those demonstration centres have been so key in different parts of the world in building that public confidence, in building those relationships between stakeholders, in building the confidence in the technologies and being able to trial different technologies. They've just had such a key role to play and so far, despite the wonderful efforts by the water companies of doing a lot of testing, we've not managed to establish an actual permanent demonstration centre. If you look at some of the ones in the US, they're just gorgeous. They've got these beautiful, designed landscapes and all these public information centres, and they use it for school trips and things like that. There's a huge amount of investment that has gone into these lovely centres, and I would love to see something like that here, both as a public engagement tool, as something for the regulators to learn what's going on, and as a technical resource to be able to understand all these different technologies and how they work in combination and how they work for some of these emerging contaminants that we've been talking about.

NR: I love that. Maybe MWH Treatment need to get on with building one, Simon. I mean, I think actually there's something about the power of telling stories and making it feel accessible and attractive and exciting. Two great answers. Thank you both very much. And thank you for joining me.

So you've heard the UK context and it's clear to me that there's some great progress, but much more still to be done. But this isn't a new technology. And so I wanted to hear from two professionals working in the US where advanced water recycling is a much more familiar approach, so I spoke with Dr Paul Pitt and Dr Gaya Ram Mohan from Hazen and Sawyer. Gaya, Paul, a very warm welcome to Planet Possible.

Let's just start by understanding a little bit about the context of what we would call in the UK, ‘advanced water recycling’, but I am reliably informed that it goes by a range of names. So maybe Gaya, if I come to you first, in a US context, what do you call it and how mature is it as an approach?

Gaya Ram Mohan: We tend to rely on the terminology ‘potable reuse’, intending to stress on the fact that it is planned and purposefully going to be used for drinking water. Within the context of potable reuse, there are multiple ways that indirect and direct potable reuse can be further defined. So I would say potable reuse is an accepted terminology in the United States.

NR: And how widespread is potable reuse across the US, Gaya? You're in Georgia, and then Paul is over on the west coast. Is this technology and approach widespread or quite localised?

GRM: Beyond potable reuse, if we zoom out a little bit, actually, and talk about advanced water treatment, or advanced water purification, as they call it out West, those are the means to achieving the end goal of potable reuse. There are some distinct geographical drivers that vary depending on which part of the United States you are looking at. For example, where I come from, on the east coast of the United States, there are a lot of really nutrient driven discharge limits that led utilities to realise: look, we have to implement advanced treatment that is not inexpensive by any means, so why do we not look at what benefits on a holistic level could we be achieving? Versus if you go to where Paul is on the west coast, a lot of drought prone areas that are arid regions that are heavily dependent on limited ground water supply. So in order for utilities to have access to alternate water supplies, advanced treatment is being embraced more than ever in the past.

Paul Pitt: There are the states that always had this, the obvious ones where they had drought conditions – California, where I am, Florida. What's really interesting is that we're seeing now, whether it's water security, water scarcity, climate change, all these different drivers, in many states in the US that you wouldn't think of – Virginia, the Midwest – to look at this advanced treatment for what we would call the IPR [indirect potable reuse], DPR [direct potable reuse]. Because of the states and because we have federal, state and local regulations, it's very interesting how different states are adopting different regulations, which we'll get into. But I'd say that over the last five, six years, we're involved in more of these projects than ever before. There's a huge increase because of these drivers.

NR: “So IPR, indirect potable reuse and DPR, direct potable. And Heather and Simon talked a little bit about the differences between those, which is really helpful. I am keen to hear about the regulatory context because that's definitely something that in the UK we are sort of chewing over a little bit at the moment. But before we do that, because it sounds like your approach is more mature and more developed than we are at in the UK at the moment, what do consumers think about this? Is it something they're even aware of, particularly for direct potable reuse? And I'd be really interested to hear any lessons or insights you can share around that, because I think there's a risk here, isn't there, with this around the yuk factor as to how people might perceive what's going on?

GRM: That's a very key question that our industry has been intentionally paying attention to now that potable reuse is front and centre. It's no longer considered a luxury, rather a requirement at this point. So there have been efforts, several case studies, particularly dedicated to public outreach, demonstration facilities. There are pilots running at different utilities in all parts of the United States, that we have been a critical part of; everything from planning to implementation of those pilot demonstrations. And we don't only look at that opportunity to assess alternate technologies, we also use that opportunity to provide public tours where possible. We bring in several key stakeholder groups and use that as an opportunity for the meeting of the minds, whether it's the utility leadership, whether it's the regulators that need a better understanding of these alternatives that we're proposing, or it's the public that ends up paying for these indirectly and are the end users of it. We try to use these demonstration facilities as an opportunity to engage our key stakeholders and promote public outreach. And I would say, Niki, that public acceptance was seen as a barrier maybe a couple of decades ago, but our industry has done a proactive job in engaging such key stakeholder groups that, with transparent data and a comprehensive communication plan, it no longer appears to be a critical barrier.

NR: That's fantastic to hear. You want an educated audience, don't you, who can then see the science and the evidence.

PP: Gaya mentioned the pilot. They're often at the heart of these programmes. Take, for example, we're involved with two very large projects in Los Angeles. In the case of Los Angeles, you have a wastewater entity teamed up with a water utility. For example, Los Angeles County Sanitation Districts, a very large wastewater treatment facility in Los Angeles, is teamed with Metropolitan, which is the largest water purveyor in the US. They have a joint venture where you have a pilot programme that sits at the heart of this facility. It's really well done. We're engineers, so we always concentrate on the technological solutions, but you need a very effective PR programme. We bring in everybody – the politicians, school children, the public - and at the heart of this is a pilot programme. At the end of it, there will often be the ability to drink some of the water, with a little tap that comes off there, and we have a very significant effort to explain very sophisticated technology simply, and how that wastewater ends up being a very pure water supply. And so that these programmes and these pilots are really a very effective tool, as Gaya mentioned, for public education.

NR: That's wonderful to hear. That's really positive. It gives me hope, I think.

One of the things that we're certainly grappling with in the UK are microplastics, PFAS, you know, forever chemicals. Sometimes those get concentrated in wastewater for obvious reasons and then if you're thinking about particularly direct potable reuse, you're taking a concentrated stream of those and then putting them back into the drinking water supply. Is that something you've been grappling with as well in the US? And how have you handled that, if so?

GRM: I would zoom out from the focused pieces of your question and say, at the basics of potable reuse, we are asking the public to trust us because there is an involuntary risk piece associated with potable reuse assets. So we, as engineers and scientists, are putting on multiple hats with the ultimate goal of ensuring that there is the highest level of public health protection and environmental protection. That is kept at the centre, the primary objective of anything and everything we do in direct potable reuse.

Your question essentially goes back to water quality. There is a need to think holistically when it comes to potable reuse, because if you think about it, here is wastewater treatment and here is drinking water treatment, that in the past were operated in silos. One did not talk to the other necessarily until potable reuse became front and centre. And now potable reuse sits in the middle connecting the dots. It is absolutely required and there are plans associated with enhanced source control even before it gets to the wastewater treatment plant. What enters your collection system, to what happens at your wastewater treatment plant and then that ends up being a feed to your advanced treatment facility or your advanced purification facility, which is your recycling centre or your reuse treatment. This in turn impacts what happens downstream at your drinking water treatment plant. Because we live in this ‘one water’ nexus, we can no longer look at how do I address PFAS or how do I address microplastics in any one particular piece of this entire circle. It needs to be addressed and mitigated in all of these along the way.

So I would say in potable reuse, one of the key reasons we adopt and implement multibarrier schemes is particularly to address the question that you have in mind: which is that from wastewater, there's a lot more diversity in the type of contaminants that could end up in an advanced treatment facility versus what we may be used to seeing in a raw source water to a drinking water treatment plan. Therefore, there needs to be a robust treatment train with multiple barriers that are able to tackle multiple types of contaminants. You hear about things like a reverse osmosis-based advanced treatment process or a carbon-based advanced treatment process. They have anywhere between four to five different unit processes that are working in a sequence. And if you take, for example, California, they have a hybrid that is a combination of a carbon-based and reverse osmosis-based treatment process that gives them an additional level of treatment and protection. So all of this again goes down to, how do we reduce risk? How do we ensure that the public only gets to consume the highest level of treatment for the water that they are going to be provided? Potable reuse with the inclusion of those multi-barrier schemes absolutely addresses water quality concerns.

PP: We take a holistic view. Let's take that step back. We have to look at the whole programme for the contaminants you mentioned, PFAS, contaminants of concern. Going down to California once again, which requires this very specific technology required for California programmes – I go back to these pilot demonstration. There's a huge effort in that sampling. So we have that step back, we do the holistic look at the programme, look at critical control points, and then when we've got a pilot running there, we do intensive sampling, for example, on the contaminants you mentioned. So we actually have that information, we have that data to share both with the regulators and the public. And that goes back to that public education. We have a very significant spotlight on these contaminants of concern, and this is how we're dealing with them. And that's part of the education. It's also part of the regulations that are set up in the United States.

NR: So let's touch on regulation for a minute. It can often feel a bit dry, but it's a really key enabler to all of this, isn't it really? Water quality regulation, where does that sit? And how much control is there federally and then through those tiers?

RGM: One of the unique things in the United States about potable reuse is that potable reuse is not regulated at the federal level as, in contrast, are wastewater and drinking water. For both wastewater and drinking water, there are pages and pages of federal regulations and additionally state regulations that require an operating entity or a utility or water company to meet those strict limits. On the other hand, the United States Environmental Protection Agency recognises that the states have primacy when it comes to potable reuse regulations. Well, while this could have some pros, as we saw with regards to PFAS. Until PFAS went under the national primary drinking water standard that was developed and released not too long ago, every state was coming up with a new limit. Those discrepancies were causing more concern and chaos than [the rule change] helped. The public was looking to us to see, who do I trust? Is there a difference if I live in Georgia versus if I lived in Florida? Because these two have different limits now. I would say that states such as California and Arizona, Florida, Colorado, among the ones that have gone through a rigorous process in order to develop and publish potable reuse applications, absolutely we have got to commend them. The level of effort that went in and having those independent advisory panels and the scientific panels, and doing the research, all of this, so again, the public will be able to trust us with making the right judgment on their behalf – that needs to be recognised. But I do want to add that not all states in the United States have published potable reuse regulations. It still appears to be an evolving area where states are looking up to others that do have published regulations – which was a handful – in order to draw inspiration and publish their own.

NR: In the UK context, water companies talk to each other all the time. In the absence of regulation, they will still have those conversations and they will come together and try and find a practical way through and they'll share best practice. But the US is a little bit bigger than the UK. Does that happen? I mean, is there conversation and kind of sharing best practice between states? And because obviously water's managed and owned differently as well. But so where there are states with gaps in regulation, are they just not doing it? How is that all connected? I'd love to get a bit of a sense of that landscape, really.

RGM: To me, that's where us as consultants come in. We have that knowledge base that's essentially transferable. And we've been requested to be a part of these task forces for the different states. We've led a lot of this effort and really been instrumental in providing support for states like Arizona, Colorado, California, Tennessee, which is one of the states that doesn't yet have published regulations, but we are supporting them with everything that we discussed previously, pilot demonstrations where we've led them. What are we seeing? What sort of robust control is required? What are the different aspects beyond the treatment technologies? What are the different aspects that need to be kept in mind? So I would say in those ways, our industry is doing a really good job in ensuring lessons learned from one get transferred to the other. We're not waiting to the last minute for a gap to be filled.

PP: There's a lot of exchange of information that's really picked up in intensity over the last five to 10 years, back to the drivers, everything we've talked about, climate change, water security, drought. So you have these joint ventures now, and this is where we look at things when it comes to win-win. You just take the wastewater treatment plants, take the LA examples: these are large plants discharging to the ocean. What's coming is nutrient regulations in the ocean. So there's acidification going on in the Pacific Ocean, we’ve got to get the total nitrogen removed, so we're looking at that. And if we just take that individually, you know, we can go in as engineers and we can design these plants, and we can remove the total nitrogen from the effluent. And then we say, well, we've got these other drivers, and we've got the water purveyors saying that we need to do something about them. And this is where the win-win scenario comes in, when we link these wastewater agencies with the water purveyors and say, well, we need to remove nitrogen from here, we need to remove phosphorus. They're looking for these programmes with IPR, DPR, where we have to do that. We link that together, and it's a natural win-win scenario where we can solve some of these drivers that we went through on the reuse perspective on the advanced treatment, and at the same time, we're removing that nitrogen from the environment where we would have had regulations. These multiple drivers now are bringing together all these different players. You know, as engineers, that's our job to look at this and look for that synergy and link these programmes together for the win-win scenarios.

NR: And are you finding sort of circular economic benefits of that, as in you're taking nitrogen and phosphorus out and there's a value to that as a by-product, isn't there? And we use those things: we'll use phosphorus in drinking water treatment. They're both fertilisers. So is there a connection there as well? Are you finding that there's beneficial reuse of some of those products that you're starting to take out in order to facilitate water reuse?

PP: That's the first driver. Once again, I go back to the programmes I'm dealing on the wastewater end: we know what's coming there that is necessary to remove nitrogen and phosphorus from the effluent. That's also required if we're going to get into these advanced treatment systems. So then we look at cost sharing between the two. And then we can look at other drivers there.

For example, can we mine and do resource recovery? That comes in as the secondary benefits. But the first benefit, as Gaya mentioned, is really we have a set of regulations going on in the wastewater for effluent, particularly for nitrogen right now in California, all the way down the coast, all the way down from San Francisco down to Los Angeles. So we know we're going to have to spend significant dollars on infrastructure to remove that from the effluent. If we can team that then with an advanced treatment system and solve more than one problem, that's the win-win scenario. And that's where we're seeing a lot of activity. And we sit in the middle of this as consultants, as engineers, trying to get these win-win scenarios, the scenarios that give the best value solutions.

NR: So you have heard a little bit about where we're up to in the UK, and I know you know the UK landscape as well. What kind of lessons would you both share with listeners that are working in the UK context, given that you are certainly ahead of where we are here in the UK in many ways?

GRM: I would say, from the few examples that we've talked about thus far, the California example, it's a drought-prone geography. You know, reuse projects are looking at diversification because of climate stress, things that are similar in the UK's landscape, right? Lesson learned would be to embed reuse into your regional supply plants. Don't wait for when it becomes a necessity that you have to start building something. Start early. Look at those investment frameworks early, paired with multi-year community engagement. We talked about how it is critical to engage with the public and win their trust over before you even embark on this journey of portable reuse. It's a multi-year journey, and you certainly want all stakeholder groups to support you.

From the east coast, where you have inland utilities, for example, that don't necessarily have access to ocean discharge. In Georgia there are advanced utilities here that don't have access to an ocean discharge. We look at alternate treatment processes and technologies that are comparably robust, can give you highly treated water and meet those stringent water quality objectives using maybe a carbon-based advanced treatment process. So keeping in mind all the alternatives that suit your site-specific conditions, while meeting those stringent potable reuse standards, are some things that we have really got a pretty good grasp of, having spent several years in the United States working all these different case studies. So I would say both of those would be critical to take with us to the UK's landscape and apply it there.

PP: It's never too early to start. Look at the drivers and then try and match these drivers along with the potential for benefits. The wastewater utilities have got a set of requirements, the water purveyors have a set of requirements and we look for that synergy. The second thing is having pilot programmes can really be beneficial, not just for the technology but back to that public education – we can't take our eye off the public education piece. So these programmes in the US have done a very good job of hiring communication personnel. That's a key element of these successful programmes – education of the public and even education within our industry. So I think it's never too early to start; get a very diverse team; take that step back. And I know it's different – obviously it’s privatisation, so it's a different situation – but looking for those win-win scenarios. You do find out that once you get those innovative groups together to look for these solutions that the win-win scenarios can become apparent.

NR: I think the landscape in the UK is changing. We're having a review of water at the moment that you're probably aware of, and so part of the outcome of that will be regional water bodies and I think they will play a pivotal role in water resource planning moving forward.

Okay, final question for you both. I'm going to pass you the Planet Possible magic wand. Give it a wave, Gaya, I'll come to you first. What would you like to make possible?

GRM: Given my own life experiences, having lived through the tsunami when I was back in India, having seen some of the worst droughts and floods, I would say a lot of people take basic amenity like water for granted. So given that I have the magic wand, I want everyone in the world to have access to high quality water.

PP: Damn, that's a difficult one to beat, Niki. So I should have gone first. I think I go back to the fact that the public, they turn the tap on or they flush the toilet and that's the end of the situation for water. I think we're coming a long way in education, but an understanding of how important water is, is at the centre of everything. Both the clean water and protecting the environment and public health and our ability as a community to look for these holistic solutions for the environment that could be win-win. And so, breaking down some of the regulations, breaking down some of the barriers where people are in their own little silo and get these more holistic solutions. And I think we can really go forward in the future with a much better situation as regards water, clean water, sanitation and protecting the environment.

NR: Thank you both so much for joining me. It was an absolute joy to speak to you both.

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