Water4All CEO Gives Interview on Wastewater Reuse to Trend FM

András Érczfalvi: Good day, and welcome to *A Nap Vendége* (Guest of the Day) here on Trend FM. With me in the studio is Zsolt Eszes, CEO of Water4All. Efficient and innovative water and energy management – have I got that right?

Zsolt Eszes: You have. Our core business at Water4All is water reuse, together with all of its energy dimensions. Water reuse is fundamentally about the treated effluent produced by municipal wastewater treatment plants that are already built and operating – and reusing that water will, I believe, be one of the most important tasks ahead of us.

András Érczfalvi: We'll come to that in a moment – in less technical terms. In fact, let me offer my own take first. How long have you been in the field – four decades? And you're a water engineer, aren't you?

Zsolt Eszes: Yes, that's right.

András Érczfalvi: Two weeks ago, hydrogeologists from all over the world gathered here for the 53rd World Groundwater Congress, and I spoke with several of them. One thing became clear to me: we are in a very poor position when it comes to surface water – this summer was a case in point, though I'd like to hear your view. As for groundwater, the hydrogeologists said we shouldn't tamper with it too much, because it isn't limitless either. Which led me to conclude that what remains is the water we have already used once – wastewater, industrial water – and we have to squeeze every last drop of value out of it. That's why I'm glad you're here, since that is more or less what you do.

Zsolt Eszes: Absolutely. Let's start with the volumes – what surface water and groundwater actually look like. Take the Danube, which every year…

András Érczfalvi: There isn't much to look at right now.

Zsolt Eszes: Not much at the moment, admittedly – but even so, tens of billions of cubic metres flow through the country, and only a fraction of that surface water is ever used. Most of what is abstracted – two to two and a half billion cubic metres a year – serves energy generation as cooling water, and it is returned to the Danube. In other words, we use it purely for cooling.

András Érczfalvi: In Hungary, at least – because upstream and downstream, many countries also use the river to generate power.

Zsolt Eszes: Exactly. Here, hydropower from the river doesn't really feature. If we look at the Danube's annual discharge – which may well exceed 100 billion cubic metres, though let's simply say many tens of billions – that figure is expected to fall in the coming years, or at least to level off somewhere; we don't yet know where. The Tisza carries a quarter, a fifth, perhaps a sixth of that, but still 10 to 20 billion cubic metres a year. And we make very little use of either river; we hardly abstract from them at all.

Zsolt Eszes: As for groundwater, people often say there are several thousand billion cubic metres of water beneath the Carpathian Basin. But we shouldn't forget where that water is located, from what depth it must be abstracted and what its chemical composition will be – all long-term questions – and, of course, at what cost. I'd like to draw attention to the role of shallow, intermediate and deep wells. Water utilities supply drinking water from wells tapping confined aquifers, classified as shallow (down to 30 metres), intermediate (30 to 100 metres) and deep (100 to 300 metres). In Hungary, 45% of the drinking water supply comes from these confined aquifers, and another 35% largely from karst water and riverbank filtration wells. In total, water utilities currently abstract some 690 million cubic metres a year.

Zsolt Eszes: Set against those billions, 690 million cubic metres might suggest we are in an enviable position. We are not – because what are we planning for, and what does the future hold? Judging by precipitation trends, our rivers are likely to carry less water, and it will become harder to access. Even so, I would argue that groundwater is the water of the future – the water of our grandchildren and of the generations after them – which is why we must protect it so carefully. And given that around 95% of our public water supply currently relies on groundwater, it may be worth shifting the balance: on the one hand, by reusing the water we have already brought to the surface; on the other, by examining whether surface water could serve the same purpose – public water supply.

András Érczfalvi: And if we are reusing it, why not reuse it several times? Or use the same water in several different ways?

Zsolt Eszes: That's a good question – one I hadn't considered in quite those terms. What is certain is that Hungary is one of the least advanced countries when it comes to water reuse. Our reuse rate is below 5% – realistically, I'd say close to zero. Israel, by contrast, reuses 95%.

András Érczfalvi: Of course, that is a severely water-stressed country – but let's not forget that we're not so very different. What's more, they have a coastline: they take seawater, desalinate it and pump it inland through large pipelines, much as Saudi Arabia does. You mentioned that the EU Water Framework Directive is very important – so let's bring this back home to Hungary.

Zsolt Eszes: Indeed. The EU Water Framework Directive has addressed water supply and water management for a long time, and it set out its principles thoroughly and well. Those principles are precisely about reuse, and about the need to treat wastewater further, because it matters how we return it to rivers, lakes and the wider environment. Which brings us to the most recent element of that framework – the recast Urban Wastewater Treatment Directive, adopted at the end of 2024 and in force since 1 January 2025. It has been on the agenda for a year and a half now, and, all being well, it will be transposed into Hungarian law by next summer.

András Érczfalvi: Which is about how to reuse water better and more efficiently – or rather, how to start reusing it at all, given that, as you say, we're currently at zero.

Zsolt Eszes: Precisely. Interestingly, the focus there, too, is on agricultural reuse. I'd like to come back to that later: I don't see the need for reuse exclusively in agriculture, though it is the obvious place to start.

András Érczfalvi: Industrial, residential – you'll have to sketch out these categories, or clusters, so that I can follow too.

Zsolt Eszes: One more thing I'd highlight is the water reuse plan – that is key. It is something that should be developed at both local and regional level. These plans need to answer the essential questions: groundwater or surface water, in what quantities, where the water goes, how it is treated, and which pipeline needs to be built from A to B.

András Érczfalvi: And this isn't only about water. Looking at your portfolio, this holistic approach will clearly matter as well – I've read that energy is part of the picture too. Not just the energy that goes in, but energy on the other side: both input and output, as an opportunity.

Zsolt Eszes: On the one hand, this is an extremely energy-intensive sector: lifting, treating, conveying and processing water all consume vast amounts of energy. Water utilities use more than 800 gigawatt-hours a year – a considerable figure. And every further intervention, plan or concept will inevitably add to that demand, and not modestly. I'm thinking, for example, of advanced treatment: the directive introduces quaternary treatment – a fourth treatment stage designed to remove micropollutants from treated wastewater before it is returned to the environment. But there is also an energy question here…

András Érczfalvi: Microplastics, for instance – I've discussed them with experts before, and I understand the next generation of washing machines will come with built-in filters.

Zsolt Eszes: Absolutely.

András Érczfalvi: But forgive me for jumping in…

Zsolt Eszes: Not at all – it's an important point, because there is a great deal of mystery, or rather imprecision, surrounding this subject. Micropollutants fall broadly into two, perhaps three, main groups. The first is microplastics, which we hear about every day and which are already being found in drinking water systems. The second is residues – not only pharmaceutical residues, but anything excreted by the human body, as well as compounds generated by industry. The third group would be per- and polyfluoroalkyl substances (PFAS), the so-called "forever chemicals". There are nearly two million different PFAS compounds. They have been present in wastewater practically since 1970, ever since Teflon has been manufactured, and they find their way into the environment. But what can be done about them, and what it would take to remove them, are questions that, sadly, remain unresolved.

András Érczfalvi: But that's already the fourth stage, isn't it?

Zsolt Eszes: It is one of the issues that fall under quaternary treatment. Current efforts, though, centre mainly on removing pharmaceutical residues. Switzerland has provided Hungary with substantial support: as a non-EU country, it funds a range of programmes here independently, and quaternary treatment is among them. The Swiss–Hungarian Cooperation Programme has been running for three or four years now; the project is well advanced, and two or three pilot plants will be built – hopefully with our involvement as well.

András Érczfalvi: And what will such a pilot plant achieve?

Zsolt Eszes: The aim is to retrofit an existing municipal wastewater treatment plant with this fourth treatment stage, specifically to remove pharmaceutical residues.

András Érczfalvi: So: wastewater goes in, stage one, two, three, four – and what is the water that comes out of the pipe at the end good for?

Zsolt Eszes: First and foremost, it protects receiving waters. We want as few micropollutants as possible to reach the environment – that is crucial. Given its composition and quality, it could already be suitable for agricultural irrigation, for example. Until now, effluent has been discharged into rivers after three treatment stages, out of necessity, with tertiary treatment focused on removing nitrogen and phosphorus to reduce eutrophication. Further treatment is now needed to protect our waters, to prevent harmful changes in the environment, and to stop these forever chemicals from leaching into the ground. This is where the importance of protecting groundwater comes in – there is no way around it. And the way to protect it is to treat our wastewater further. That is the challenge.

András Érczfalvi: What does Water4All do?

Zsolt Eszes: Water4All's parent company – or, more accurately, its sister company – is Inwatech, which has been in the market for 25 years. We decided to divide our activities: Inwatech focuses on municipal wastewater treatment and conventional treatment processes, while Water4All concentrates on water reuse – which includes quaternary treatment – and on projects that meet a range of water demands. There are already one or two examples of this. On the energy side, wastewater treatment generates by-products – organic by-products.

András Érczfalvi: Right – I only talked about the energy-hungry side of the industry and cut you off before you got to the other side. So it can generate energy as well.

Zsolt Eszes: Exactly. If we separate out this organic matter, we can produce energy from it – essentially biogas. But we have taken the energy goal further, because the directive I mentioned also requires wastewater treatment plants to become energy-neutral. I'll stress that again: they are *expected* to become energy-neutral. In other words, whatever energy a plant consumes, it should also generate. A plant…

András Érczfalvi: …should break even.

Zsolt Eszes: Yes, that's the idea. Let me give an example. A medium-sized municipal wastewater treatment plant has a power demand of 300–400 kW. Over a 20-hour operating day, that comes to around 8,000 kWh. Supplying 8,000 kWh every single day to a single treatment plant is a very significant undertaking. These plants have the advantage of separating organic matter, from which energy can be recovered – but that alone is not enough.

András Érczfalvi: Biogas?

Zsolt Eszes: Biogas, yes. But biogas production alone may not suffice. Plants can also install solar panels or, where there is sufficient hydraulic head, water turbines – and a mix of these sources can cover the plant's entire energy demand.

András Érczfalvi: Which is why you said it is so enormously energy-intensive.

Zsolt Eszes: And this is where the holistic view comes in. So far, we have only talked about tertiary treatment; once quaternary treatment is added, its energy demand will be far from negligible. The same applies to any water management objective that determines what the further-treated water will be used for – that, too, requires energy, no question. That energy has to be provided on top, and the question is whether it can also be generated on site. These are major challenges.

András Érczfalvi: And if that energy is clean energy, the final balance… Let's step back a little – we have three or four minutes left in this segment, and despite my best efforts I've lost the thread. Where are we truly wasteful? We still waste drinking water, even though it is becoming ever more expensive and we can see ever more clearly how scarce it is. Where are the points at which we will have to intervene – and soon – to stop this wasteful run-off?

Zsolt Eszes: It may sound strange, but when I get up in the morning and follow how I use water throughout the day, that is where the waste is most evident – when we wash dishes under running water…

András Érczfalvi: Or leave the tap running while brushing our teeth, yes.

Zsolt Eszes: We can't ignore that. Average consumption is 105 litres per person per day – and in cities it is higher still, 120–130 litres or even more. We simply need to be more conscious of how we use water. On the other side, industry is also a major water user…

András Érczfalvi: Not to mention the industrial companies that have moved here in recent years – we all know about them. So volumes are going to grow even further. I understand – and I didn't want to labour the point about brushing teeth and washing up; we all know it, we just don't act on it. But once the water has been used, that's where I would look for the weak points.

Zsolt Eszes: Used water is wasted in the sense I mentioned at the start: nobody is reusing it. I would add some nuance, though: Government Decree 50/2001 (IV. 3.) on the rules for the agricultural use and treatment of wastewater and sewage sludge already sets out how they can be used. Let's not forget that the Hungarian water sector – both its regulatory framework and its expertise – is recognised and respected internationally.

András Érczfalvi: The whole water sector, over recent decades…

Zsolt Eszes: Of course – just think of the water engineering exports Hungary achieved in the 1970s and 1980s. And although our numbers are dwindling, there are still plenty of professionals in this field who are well regarded, well known and able to work internationally. We ourselves don't operate only in Hungary, either. But coming back to waste: yes, reuse is the real question.

András Érczfalvi: We're where we were with bottles and plastics over the past 10, 20, 30 years – go on – now we know, we collect them; for glass, I believe the recycling rate is now 60–70%. And at some point you wake up and say: we can't let this go on…

Zsolt Eszes: I think circumstances forced it upon us: drought – the rain simply didn't come.

András Érczfalvi: And suddenly: good heavens, give us water, now!

Zsolt Eszes: That is a problem from every angle, because the profession has been worn down – over the past 16 years it has aged considerably. It wasn't just out of focus; nobody really paid attention to it. Now, as I mentioned, this government decision is a well-crafted document with sound content for the period ahead.

András Érczfalvi: And that means – let's continue with this in a moment – that municipalities, industry, farms and residential communities in Hungary now need to focus on this.

Zsolt Eszes: Collectively.

András Érczfalvi: Collectively, yes.

Zsolt Eszes: Say I have a hundred units of water at a given location – reusable, treated wastewater. What should those hundred units be used for? Consider the stakeholders: there is a city with an urban heat island problem – it is well documented how much temperatures in cities have risen during heatwaves…

András Érczfalvi: Which also takes water, I assume.

Zsolt Eszes: Indeed – water is the most effective way to cool, no doubt about it, and the cheapest. Then there is a farmer who has been working a thousand hectares and urgently needs irrigation. They, too, need water – or at least it may make sense to supply it – if they can't get enough from the surrounding ditches and channels. So that is an obvious solution. But I'd go further still – and I want to stress this – all the way to drinking water. Let's not forget that any water can be turned into any other kind of water. Even wastewater can be made into good drinking water. I know the very idea turns people's stomachs, but I'd point out that Windhoek, in Namibia, has been producing drinking water from treated wastewater since 1968 – not its entire supply, but a substantial share. Why? Because the nearest large-volume water source was 500 kilometres away, which made this economical – or, rather, a necessity and a strategic asset. South Africa, Africa…

András Érczfalvi: The Maltese have also done a project like this, as I recall – we discussed it at length.

Zsolt Eszes: Indeed. These are questions we must not ignore, and the water-use plans I mentioned should address exactly this: coordination within a given region or area. If I can't lay a DN1000 pipeline from Szigetköz – where I have bank-filtered water reserves – then I should consider producing the water I need locally from treated wastewater, rather than building 800 kilometres of pipeline. Those are the kinds of questions involved.

András Érczfalvi: Let's pick up from there – drinking water could be a good starting point. Zsolt Eszes, CEO of Water4All, is our guest of the day here on Trend FM. We'll be back in a few minutes.

András Érczfalvi: …this is *A Nap Vendége* on Trend FM, and sitting opposite me in the studio is Zsolt Eszes, CEO of Water4All. Efficient and innovative water and energy management was our starting point today, but we've covered a great deal of ground – for the past twenty minutes we've been circling around water and the water cycle. We talked about an EU framework that is forward-looking on efficient water reuse – I'm choosing my words carefully, so do nod if I'm not talking nonsense. And you mentioned a Hungarian measure numbered 1265 – I'm not a fan of these numbers, but here it matters.

Zsolt Eszes: It is Government Decision 1265/2026 on the Sustainable Water Management Action Plan, published on 25 August. It is very recent, and some outlets have described it as historic. Without exaggeration, I would call it a necessary step.

András Érczfalvi: Well, you said we had been giving this issue zero attention – a line that will keep coming back to you – so it was high time.

Zsolt Eszes: Indeed. Monitoring, in my view, starts with data. Water utilities operate wells – and here we are talking about confined aquifers and drinking water supply, since confined groundwater accounts for the vast majority of our drinking water. These wells need to be monitored dynamically: utilities measure pumping and static water levels. The frequency of these measurements is critical, and it should be determined on the basis of hydrogeological conditions. At first glance, my view is that pumping and static levels should be read monthly – so that we can see, sense and measure what we still have, and what we might still have. That's one aspect. The other is how surface precipitation affects shallow, intermediate and deep wells, and with what time lag. We need to understand these dynamics. Since everything is interconnected – surface water with groundwater – understanding them matters, because they will determine how groundwater resources can be protected and how far they can be used.

András Érczfalvi: Do I draw on one, or spare it and draw on the other…

Zsolt Eszes: How much I abstract, for instance. And here comes the point I also mentioned: protecting groundwater is a very weighty issue. But if I don't abstract from groundwater, where do I take it from? From surface water? Yes – then we can turn to surface water and draw that volume from the tens of billions of cubic metres I mentioned. But that entails huge investment: long-distance transmission pipelines, distribution challenges. Budgets are not unlimited.

András Érczfalvi: Nor are the quantities.

Zsolt Eszes: Nor are the quantities, exactly. In terms of volumes, treated wastewater amounts to 550 million cubic metres a year. So, to recap: we abstract 690 million cubic metres for drinking water production and return 550 million cubic metres as treated wastewater. Compared with 690 million, those 550 million cubic metres are a considerable amount. To what extent, and for which purposes, we will be able to reuse it will always be a question – locally and nationally. Decisions have to be made about objectives and how each will be achieved. This is where the government's intention comes in: to review, assess and monitor the state of our groundwater and surface water, and to determine how supply can be secured from a combination of the two. Water management, water use and water reuse objectives, however, differ widely, as I mentioned earlier. Water reuse can mean agricultural irrigation – both the EU framework and the government decision lean somewhat towards that use as a priority.

András Érczfalvi: Yes, but people come first, then animals, and then crops.

Zsolt Eszes: Exactly – and I agree that drinking water must absolutely come first.

András Érczfalvi: Because in times of drought, this decision or legislation comes into effect…

Zsolt Eszes: Looking at the monitoring task – the deadline for preparing the related rules is 31 October 2026 – it really needs to be put into effect very quickly: we must start measuring and observing, and begin the work that will produce findings on groundwater use and on how surface conditions affect the quantity and quality of groundwater. Measures must then be defined on that basis. But yes, drinking water always comes first, and everything else after it.

András Érczfalvi: The layman in me is speaking again – I'm not a water engineer like you. Here we have this enormous buffer, an enormous opportunity. It is hugely expensive to treat and hugely expensive to move, whether by electricity, diesel pumps or anything else – yet this water, which now simply flows away and could be used in far more valuable, efficient and innovative ways, has to be captured at various points. Where are the biggest problems? I remember how pleased we were when Budapest's wastewater was finally treated – just yesterday I went for a swim; the river below Budapest is much cleaner now, and you can even swim at Százhalombatta. So we were delighted about that – but where do we need to intervene, and quickly? At the big industrial companies? The local authorities?

Zsolt Eszes: There too. Let me refer back to the decision again, because managed aquifer recharge (MAR) – replenishing aquifers with water – is one of its stated objectives. The idea is that if I divert water from the Danube onto an area of a certain number of hectares where aquifer recharge is feasible, we can then abstract that water as groundwater. Not to mention the welcome side effect that the ground acts as a natural filter – in effect, a biological treatment stage for raw Danube water, which obviously can't be drunk directly. Groundwater abstracted from a recharged aquifer, however, may need only minimal treatment before being fed into the network as drinking water. It is a very topical solution – and one already in operation along the west coast of the United States.

András Érczfalvi: They're struggling with the same problems: no water, nothing in the rivers; what there is gets diverted somewhere, recharged and then abstracted again. They're already fighting over it – livestock farmers, agriculture, everyone else, power plants.

Zsolt Eszes: And this is where the question of water use comes in. That "fighting over it" is a very important point – it is exactly what I keep trying to draw attention to. It's one thing that agricultural water use is now priority number one, the hot topic. I understand: we need to produce food. It is critical that so little of our land is irrigated…

András Érczfalvi: Four or five per cent.

Zsolt Eszes: Extremely little – and food self-sufficiency is, of course, a matter of national strategy. That takes water, there is no way around it. At least periodically, irrigation has become almost a necessity. And if it is a necessity, it has to be designed properly. Now, if that is the priority, set against cooling urban heat islands in summer – where mortality has risen – the two can already come into conflict. And there's more: an industrial company whose operations require volumes of water that cannot be sourced elsewhere – this is where the battery plants come in. So priorities have to be set. The cooling-water demand of battery plants is well known – and in fact, it was in this very context that we were among those in Hungary who argued, in 2022–23, that cooling water should be supplied by further treating municipal wastewater.

András Érczfalvi: So that it doesn't come from drinking water. But for me the essential point, once again, is that whatever leaves the treatment plant is reused in the best possible way, at the highest possible level.

Zsolt Eszes: Absolutely. Systems of this kind have been designed in Nyíregyháza and Debrecen, and we are involved in these projects in one way or another. The aim is for municipal treated wastewater to be reused to the greatest possible extent. Nyíregyháza, for example, has two wastewater treatment plants, one of which is involved in supplying water to the battery plant.

András Érczfalvi: So they had to be upgraded to meet that demand…

Zsolt Eszes: That investment is under way now, and we hope to hand it over next year – we are very much looking forward to it ourselves.

András Érczfalvi: Then at least I can rest assured that the battery plant isn't squandering drinking water – using it for cooling, of all things.

Zsolt Eszes: Exactly. And remember what I said: any water can be turned into any other kind of water. If I supply reclaimed water – municipal treated wastewater given further treatment – to an industrial company, it can produce ultrapure process water from it, and drinking water too. So, taken to its logical conclusion, a plant could simply connect to a municipal treated-wastewater supply. Which raises the question again: who will compete for that quantity – for the reclaimed water that can be produced there?

András Érczfalvi: What will happen here over the next ten years? We see the frameworks, the legislation and the struggle for water. I know it well only because on the Nádor Canal I saw how livestock farmers, fish-pond operators, those desperate for irrigation water and everyone else either observed or ignored the rules that set out how much water could be abstracted, and how.

Zsolt Eszes: I believe what is needed is cooperation between the local communities I mentioned – self-organising stakeholders who are attuned to water needs.

András Érczfalvi: The municipality, an industrial park – they need to join forces…

Zsolt Eszes: On the one hand, work is under way at government level; in parallel, concrete demand for water has emerged. And again, there are examples – Nyíregyháza is a perfect case in point – where the further reuse of the city's treated wastewater is now being planned.

András Érczfalvi: All the way to drinking-water quality?

Zsolt Eszes: No.

András Érczfalvi: So not quite "crystal clear", as the Austrians like to say of their beer?

Zsolt Eszes: Not yet – but, as I put it earlier, I wouldn't rule it out in the long term. That obviously need not be the goal, since we are perhaps not in such a bad position. As I say, the monitoring data will tell us, and that will be the deciding factor.

András Érczfalvi: But the point is to get the best possible quality out of any water – industrial water, wastewater, municipal water, reclaimed water – to put it to use, and to let nothing go to waste, isn't it?

Zsolt Eszes: Yes. I would certainly set concrete targets. If you ask me about the next ten years: reuse 50% of treated wastewater within a decade. That is an entirely concrete goal.

András Érczfalvi: That's why I compared it to plastics and everything else.

Zsolt Eszes: You can then map out where that 50% could be used and which facilities need to be built – and we could probably calculate, almost instantly, the total investment required for that volume. It is a great deal of money, of course, so the economic questions and calculations will follow.

András Érczfalvi: Yet on the other side there is water scarcity, which has to be addressed somehow. Divert it from here, divert it from there – as I said when I sat down in the studio – from the Tisza, from the Danube, into Lake Velence… But there is no water in the Tisza, and none in the Danube either – so in the end we have to turn to what we already have: the water we have already used, and polluted.

Zsolt Eszes: It is very important to repeat this: if we abstract water from underground, we should reuse it. We can't simply discard it. I wouldn't say there is no reuse at all today – when treated wastewater is discharged into rivers, everyone downstream draws on it from ditches, streams and watercourses for irrigation or other purposes. But this isn't systematic, planned or well defined. It needs a framework. We have to decide that these areas will be irrigated, for this purpose.

András Érczfalvi: But then everything has to be maintained – dredging, and a great deal more.

Zsolt Eszes: Indeed. That is how it all connects, and that's where the holistic approach comes in: everything is deeply interconnected. Whatever issue I take on, whatever task or plan I put forward, it is all interlinked.

András Érczfalvi: It's worth visiting Water4All's website. I looked at those marvels there – how dirty water becomes clean, and the journey water takes. I would show them to children in a good geography or biology lesson – not to promote the company, but to talk about the subject itself; I have something of a teacher's instinct, and a teaching qualification too. But you have been part of this cycle for four decades: do you see that something is genuinely starting to happen now?

Zsolt Eszes: Yes, absolutely. I think it is evident from several directions. Let's not forget that Hungary isn't facing this problem as an isolated island. It is fundamentally a European problem: the precipitation deficit across Europe is severe and affects a vast area.

András Érczfalvi: Which raises the question of whether water will still reach our rivers – and then there's the battle for water.

Zsolt Eszes: Clearly, if there is no water in these rivers' catchments, most of Europe is affected. And if it is affected, then, in my view, you need an action plan – and an action plan means allocated funding and defined tasks. But as I said, the framework directive has long been in place; it now needs to be implemented.

András Érczfalvi: Tell us about a project you're proud of, one you're fond of, where everything we've discussed can be seen in practice – proof that good solutions and small steps exist.

Zsolt Eszes: Nothing on quite that scale yet. The truth is that, across both companies, we design, build, service and maintain wastewater treatment plants on both the municipal and the industrial side. I can mention one very small step: at an industrial company, we have just installed an online analyser system that optimises chemical dosing and keeps the quality of the treated water within discharge limits. I mention it because there is no doubt that monitoring will require serious, continuous online instrumentation. On the one hand, plants have to be automated because there aren't enough skilled operators; on the other, automation allows a treatment plant to maintain water quality far more reliably and safely. So instrumentation and automation are absolutely key objectives.

András Érczfalvi: Then a different question to finish: where is the greatest waste when it comes to water that has already been used? We've covered where drinking water is wasted.

Zsolt Eszes: Where treated wastewater seeps away somewhere it serves no purpose – it simply soaks into the ground without even replenishing groundwater.

András Érczfalvi: Or evaporates somewhere.

Zsolt Eszes: Exactly – evaporation is perhaps the best example.

András Érczfalvi: Not to mention – since you brought up water utilities – that 10, 20, 30, even 40% is lost through leaks in the network.

Zsolt Eszes: Absolutely.

András Érczfalvi: In some regions.

Zsolt Eszes: The truth is that in many places the networks are a hundred years old.

András Érczfalvi: Here in the city too.

Zsolt Eszes: No doubt. Replacing those pipes, building new ones or relining them will cost an enormous amount of money – but it is a major and important task. Let anyone who disagrees cast the first stone, but I don't necessarily consider it rational to create water replenishment schemes where evaporation is very high and the water cannot be put to good use. There are many such proposals, with preparations and designs under way – they call for very careful thought.

András Érczfalvi: Even irrigation isn't done the way it was twenty years ago. People now say it's wasteful…

Zsolt Eszes: That's a very important point, because so-called sprinkler irrigation evaporates enormous quantities of water, and it carries risks too: that water does contain bacteria, and it isn't wise to disperse them into the air. So drip irrigation – again, look at Israel – is the kind of reuse we should be striving for.

András Érczfalvi: Do come back again – I really enjoyed this. Thank you very much. Zsolt Eszes, CEO of Water4All, was our guest of the day. Apologies that we didn't stick strictly to the technical side.

Zsolt Eszes: It was great – I really enjoyed it. Thank you very much.