In many regions of the world, I see large scale indirect or even direct potable water reuse projects popping up. Except in Europe. My big hypothesis is that it is not a lack of reuse needs, nor a lack of technical solutions. I think the number one cause is a lack of leadership. In Europe, you are not allowed to talk about 'potable reuse'. Initiatives will likely have to start bottom up, just like anywhere else. So, I am waiting for the leading country, region, or utility to emerge and set the standard. I hope to get some input from people that are with their feet in the field or with their hands on the data.

Large-scale potable reuse initiatives of today

I seriously started thinking about this question ('why not Europe?') when our company started working on one of world’s largest indirect potable reuse (IPR) projects in the US: SWIFT (The Sustainable Water Initiative for Tomorrow - swiftva.com) (Virginia, US). The water stress in Eastern Virginia was not as severe as in Southern California. But still they decided to go build this 100 MGD reuse capacity in a matter of one decade, with a 1 MGD demonstration facility up and running. Just to compare, Eastern Virginia (1.119 mm) has significantly more annual rainfall compared to my 'rainy country' Belgium (858 mm).

Figure 1: Drinking reused water at the SWIFT research centre (left to right: Samantha Hogard (HRSD), Mack Pearce (HRSD), Wim Audenaert (AM-TEAM), Germano Salazar-Benites (HRSD)

The benefits of SWIFT, and likely (I)PR in general are:

• To help restoring the environment (i.e., treatment to potable reuse standards compared to secondary effluent discharge)
• Replenish groundwater reservoirs
• Counteract land subsidence, potentially getting a larger threat with rising sea levels
• Prevent saltwater intrusion in groundwater tables
• Support the local economy (increased water availability)

So, to come back to Europe: are none of these factors of relevance to us? I think not too many people deny the needs. There are other drivers for this lack of action.

The drivers of water reuse in Europe

I got really interested and subscribed for a webinar on water reuse organized by the European Water Association (EWA) on Sep 16th, 2020. Europe recently came with new reuse regulation, and I had high hopes. My assumption that the reuse needs are also recognized in Europe was validated (Figure 2 was presented during the webinar). The drivers for reuse don't differ too much from the bullets presented earlier. I don't see land subsidence and saltwater intrusion on that slide, but I know European countries facing these risks.

Figure 2: surprise surprise - the drivers in Europe - Presentation Jiri Wanner during EWA webinar water reuse

We can of course support it with lots of data at European, national, and regional levels. I am just showing you two graphs: one at microscale (Flanders), and one at macroscale (Europe). Figure 3 shows that the last couple of years the groundwater in Flanders has difficulties getting 'back to normal'. No surprise if we are 'water stressed' for many years already (Figure 4).

Figure 3: shallow groundwater is getting more scarce in rainy Flanders (Picture adopted from a tweet by @MarijkeHuysmans - professor groundwater hydrology)

Figure 4: no denial of water stress in Europe - Presentation Jiri Wanner during EWA webinar water reuse

The (lack of) actions in Europe - and the taboo around 'potable'

Figure 5 shows that IPR is almost non-existent in Europe. Worth mentioning however is that a true pioneering IPR project was established in Belgium in 2002. The local utility IWVA treats the secondary effluent from the WRRF Wulpen (operated by Aquafin) based on membranes and dune infiltration. It was a true IPR pioneering project at the global scale...

So, what is the reason that this was the first and only potable reuse project in Europe in 20 years???

Figure 5: the non-existence of IPR in Europe - Presentation Jiri Wanner during EWA webinar water reuse

A lack of regulation can be part of the answer:

• Some regions/utilities are followers of regulation: they are driven by regulatory compliance
• Some regions/utilities are leaders: they act beyond compliance and impact regulation through their pioneering projects

it's very simple: if regulation is lacking, you need to count on leaders to evoke change. In Europe, potable regulation is lacking. And leaders are not emerging.

I lectured environmental regulation for 3 years at Ghent University. So I was excited to read EU's new regulation (2020/741) on 'minimum requirements of water reuse'. I was not expecting the level of sophistication of the Californian reuse standards, but I was hoping for some vision for the future. However, as expected, the words 'potable reuse' did not appear in the text. During the webinar I asked the following questions:

Question: "It seems like the majority of reuse projects are for non-potable purposes. What do you see the future of recycling for potable uses in Europe?"

Answer by EWA: "If you look at the structure of water usage in Europe, the water consumption for potable uses is just a small fraction of total water demands in all Europe regions. Most of water use is connected with industry/energy and agriculture."

Question: "I was wondering why up until now; indirect potable reuse has been largely neglected in regulation. This is in contrast eg to some regions in the US. What is the main driver causing these differences? Is it public perception, cultural, or climatological?"

Answer by EWA: "I think the answer will be similar like for the previous question. In addition, yes, the public perception of reclaimed water use for potable purposes, both indirect and direct, is very low. There are also some historical connotations because Europe suffered until the end of the 19th century from large cholera pandemics caused by poor quality of drinking water. Europe has also a very developed market of high-quality bottled water."

When I got these answers my first reaction was: OMG. Asking further revealed that 'potable' was a no go for multiple countries. Sensitive topic apparently.

Please reread the answers again. To me it became clear that if we think like this at European level, it is not only slowing down progress at the water reuse front, but it is also acting against it. Why? Because the followers will eat this and will hide behind it (i.e., justify inaction by it). I could only conclude that an integrated perspective was completely missing (with integrated I mean: connect it to environmental and climate benefits, economic benefits etc.), likely stimulated by conflict avoidance between individual countries.

What are the solutions and why is it urgent?

Just take a look at any major potable reuse initiative worldwide, call those people and ask what their biggest challenges were, i.e., what took most of the effort and the time. It's not the engineering and construction. It's the public perception.

I very much liked former WEF executive director Eileen O'Neil's contributions in the webinar: she was sharing the experience and hard lessons learned from the US. She demonstrated that even in rather 'reuse averse' regions in the US, success stories could be built. This says to me that there's no excuse: it's not the lack of regulation. It's not the lack of money. It's not the lack of specific circumstances. It's a lack of leadership. And leadership means getting the people on board. Here's her number one lesson from the US:

Figure 5: the non-existence of IPR in Europe - Presentation Jiri Wanner during EWA webinar water reuse

A lack of regulation can be part of the answer:

• Some regions/utilities are followers of regulation: they are driven by regulatory compliance
• Some regions/utilities are leaders: they act beyond compliance and impact regulation through their pioneering projects

 it's very simple: if regulation is lacking, you need to count on leaders to evoke change. In Europe, potable regulation is lacking. And leaders are not emerging.

I lectured environmental regulation for 3 years at Ghent University. So I was excited to read EU's new regulation (2020/741) on 'minimum requirements of water reuse'. I was not expecting the level of sophistication of the Californian reuse standards, but I was hoping for some vision for the future. However, as expected, the words 'potable reuse' did not appear in the text. During the webinar I asked the following questions:

Question: "It seems like the majority of reuse projects are for non-potable purposes. What do you see the future of recycling for potable uses in Europe?"

Answer by EWA: "If you look at the structure of water usage in Europe, the water consumption for potable uses is just a small fraction of total water demands in all Europe regions. Most of water use is connected with industry/energy and agriculture."

Question: "I was wondering why up until now; indirect potable reuse has been largely neglected in regulation. This is in contrast eg to some regions in the US. What is the main driver causing these differences? Is it public perception, cultural, or climatological?"

Answer by EWA: "I think the answer will be similar like for the previous question. In addition, yes, the public perception of reclaimed water use for potable purposes, both indirect and direct, is very low. There are also some historical connotations because Europe suffered until the end of the 19th century from large cholera pandemics caused by poor quality of drinking water. Europe has also a very developed market of high-quality bottled water."

When I got these answers my first reaction was: OMG. Asking further revealed that 'potable' was a no go for multiple countries. Sensitive topic apparently.

Please reread the answers again. To me it became clear that if we think like this at European level, it is not only slowing down progress at the water reuse front, but it is also acting against it. Why? Because the followers will eat this and will hide behind it (i.e., justify inaction by it). I could only conclude that an integrated perspective was completely missing (with integrated I mean: connect it to environmental and climate benefits, economic benefits etc.), likely stimulated by conflict avoidance between individual countries.

What are the solutions and why is it urgent?

Just take a look at any major potable reuse initiative worldwide, call those people and ask what their biggest challenges were, i.e., what took most of the effort and the time. It's not the engineering and construction. It's the public perception.

I very much liked former WEF executive director Eileen O'Neil's contributions in the webinar: she was sharing the experience and hard lessons learned from the US. She demonstrated that even in rather 'reuse averse' regions in the US, success stories could be built. This says to me that there's no excuse: it's not the lack of regulation. It's not the lack of money. It's not the lack of specific circumstances. It's a lack of leadership. And leadership means getting the people on board. Here's her number one lesson from the US:

Figure 6: the number one lesson from the many potable reuse projects in the US - getting the people on board (i.e., reuse = psychology) Slide by Eileen O'Neil

I hereby conclude the following:

Successful potable reuse is psychology first, technology second

The key to get it going is demonstration

There is only one way to get this going: the launch of major pilot and demonstration facilities that provide the confidence and can be used as showcases. Take into account that if you have the public on board, you have the politicians on board (i.e. politicians are more followers than leaders as nicely stated by Simon Sinek). So this is what worries me most: it's not the fact that potable reuse is lagging behind in Europe - it's the lack of real demonstration cases that are the key enablers. Is anyone planning to launch it soon? Just bear in mind that it takes years to over a decade to get even started...

So how to get to demonstration?

I can't summarise it better than Eileen did. These are the four factors that drive a successful potable reuse project:

Figure 7: the four drivers of a successful reuse project, based on US experience - Slide by Eileen O'Neil

Please correct me if I'm wrong, but at this very moment I don't see any major potable reuse initiative in Europe that meets these requirements. And where should it start? Likely with leadership at the utility level, gradually supported by the local community.

Conclusion and opportunities

In Europe, much thinking is spent on digitalization, micropollutants, energy neutrality climate change impacts and resource recovery. All are importan

topics by the way, with very motivated people behind them and good results.

Figure 8: the main focus points in the water industry in Europe, and how potable reuse connects to it

The three main reasons I think why potable reuse is more challenging than the others are the following:

• Potable reuse is on the intersection between the wastewater and drinking water fields. Going there inevitably means leaving your safe niche and talking to the other side. It's also overcoming politics in a sometimes scattered utility landscape. That's leadership challenge #1.
• Potable reuse is multidisciplinary and multifaceted in terms of technology. Look at the figure how it connects different sub-areas. For example: human consumption means smart monitoring, but also advanced treatment and an integrated view (e.g., how can a water reuse initiative be seen in the broader whole of environmental impact). It means bringing together top experts in a well-functioning team. That's leadership challenge #2.
• Potable reuse is about public perception. We as engineers like technology and 'wonder why they don't get it'. Leadership challenge #3 is likely the most important one: mastering the psychology of water reuse and acting accordingly.

The opportunities are abundant

• Europe has world class research institutes and experts, and strong activities in the focus areas mentioned (i.e., digital, resource recovery, ...)
• Many countries are investing hundreds of millions of EUR in micropollutant removal. Isn't that advanced treatment an excellent starting point? So, looking at it from reuse perspective instead of discharge perspective? The millions of EUR ozonation plant suddenly becomes more valuable.
• Europe has many densely populated hotspots that can serve as demonstration sites
• Europe has a couple of leading utilities that would be willing to take up this challenge
• We can learn from the many cases out there. Let's not discuss for hours before having visited those projects and having talked to those people....
• ...

I have identified this leadership gap in the potable reuse domain. Which utility, city or region is willing to take it up?