How can we better store our water supply?

Do circular water systems hold the key to increasing supply during times of drought?
30 August 2022

Interview with 

Jan Hofman, University of Bath


a wastewater treatment plant


With more extreme weather predicted to happen more often owing to climate change, what can we do to be better prepared for dry summers? Perhaps the most simple strategy is to collect and store more of the water that falls in winter, and find better ways to use our so-called “grey” waste water which, at the moment, goes straight down the drain. This is the concept known as “circular water storage” and some countries are already well ahead on the curve. Jan Hofman is at the University of Bath where he looks at the circular water economy across Europe.

Jan - Yeah, a circle economy in practical terms means that you are actually storing water and reusing it. And as you say, there are countries in Europe where this is already common practice or done in a structural way. For instance, in Flanders, new homes have to install rainwater tanks with a volume of 5,000 liters, which can be used for toilet flushing, washing machines, and watering the garden. But we're also working on a large European project where we are running demonstration projects at full scale. In the Netherlands, in Germany, in Sweden, but also in Spain and Greece, where we can really demonstrate these circular water technologies in practice.

Chris - I suppose one of the big challenges though, is that new builds are all very well. And it's important that something is happening, but that's not where most of the housing stock is, is it? Most of the housing stock already exists. And so it's really a question of what we can do to retrofit this for millions of people, millions of consumers, all with a big water footprint, rather than just worry about the few million new houses we're building every year.

Jan - Yes, indeed. When you build a new house, you can make use of the technologies and just build them in there. But if you have the existing housing stock, you have to do different measures. Nevertheless, you can do things, we all know that there is quite an old sewer system in the UK and when you renew sewer systems, you can create a separated sewer system for file water and rainwater. And if you connect or disconnect the roofs from houses, from the file sewer to a new rainwater sewer, you can actually collect rainwater again and reuse it in the houses.

Chris - Is it then that the plan that basically you just collect water en masse like that, or is it envisioned that people would do more kind of micro collection, their own house, a slightly bigger version of a water butt in the sense that you could, you could get your bath water and your shower water, and use it to water the garden? Or is it a more communal thing?

Jan - You can do both? As I said in Flanders it's an individual system with the 5,000 liter tank, a big rain barrel so to say. But I think for larger situations, I think the communal or collective systems are much more in favor because it's easier to maintain, it's better to keep the water quality good, and it's better regulated if you do it in a communal way.

Chris - If you are thinking of retrofitting, and that has to ultimately be part of the equation, doesn't it? Because of the huge demand that we've got in existing housing stock in terms of their water consumption, is that economical, is that feasible? And what sort of price tag are we looking at to try and get people with existing housing stock on this grid?

Jan - Yeah, I think it depends on how you look at things. Of course, if you just look at investing in the technology at your home, it will cost you money. In contrast with, for instance, solar cells, they earn you money in the end, but here you have to invest in technology and you have a double system, which costs money. But on the other hand, there are also societal benefits. You were speaking on the show about combined sewer overflows. If you can collect rain water then you can prevent sewers from overflowing because the water is taken out of the sewer before the overflow occurs. It also can prevent damage from flooding damage of property and things around. So there are more benefits for society. And if you compare that with the costs in the broader context, then it also might be reasonable to give subsidies for these rainwater collection systems. And in that case, you create an incentive for investing in it.

Chris - Why is it not happening more already? That's the big question though, because some countries are very good at this and they're countries that have faced water stress or acute water shortages in the past. Australia is well ahead of the curve on this, but then they've had to be, whereas here, you know, is it just because in a country like the UK, historically, we've been so blessed with this beautiful weather and plenty of water that we haven't had to worry about it? And now with the effects of climate change and these departures from what we've regarded as normal, it's focusing people's minds.

Jan - Yes, indeed. I think if you look at doing innovation in the water sector, it's a slow process. And if you see how quickly, in recent years, changes in climate are happening, we are actually a bit surprised by all these things. And yeah, it takes time to adapt. And the change in the climate is going more rapidly than the pace of adaptation and I think that's where we have to accelerate.

Chris - And just thinking about the home situation to finish here in the UK, I'm tearing my hair out because I'm watching new properties going up. And then, the bill to put solar into them is pushed onto the homeowner. If they decide they want it, why are we not doing something whereby new developers are told you must put renewable sources of energy onto all your houses and the architects design them in so they're aesthetic and you must also include a water solution. Why is that not happening?

Jan - Yeah, that's a good question. I think it's a matter of time. It's also a matter of having a very open market economy, and market mechanism. I think going into a situation where you can incentivize through minimum requirements for new build homes would be a way forward. I think, as you said, you can use subsidies to enforce things or to stimulate things, but also put regulations in place for minimum requirements. But it takes courage. It takes political courage to do that. And yeah, I think maybe the pressure needs to be even more higher than it is now, even more higher than we have now to go that way.


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