16-29 Segment 1: Making water safe to drink

boy drinking water from a faucet

 

Much of the world is without clean, potable water on a consistent basis, and even in developed countries where water is available, cleaning it for drinking and bathing and treating the wastewater is expensive and uses a lot of energy. We talk to a scientist who is working on new technology that will make filtering and sanitizing water more efficient, use less resources and provide clean drinking water to countries where water-borne diseases negatively affect the population at alarming rates.

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Guests:

Seth Darling, scientist from Argonne National Laboratory outside Chicago, Fellow at the Institute for Molecular Engineering at the University of Chicago

Links for more info:

 

The End of Water As We Know It

Gary Price: The English poet W. H. Auden said that “Thousands have lived without love, not one without water.” We’d hate to have to live without either, but he’s right that water is a necessity for biological life as we know it. Sadly, in many parts of the world plants, trees, animals and people are dying because of a lack of usable water, and in underdeveloped countries it’s reached the crisis stage…

Seth Darling: Every 90 seconds a child dies from a water-related disease. So, you know, in the length of this conversation we’re having there will be a number of children who have died.

Price: That’s Seth Darling, a scientist at Argonne National Laboratory outside Chicago, and a fellow at the Institute for Molecular Engineering at the University of Chicago…

Darling: What they’re dying from are pathogens in the water, you know, viruses and bacteria leading to diseases like cholera and so on. And, you know, we can do better.

Price: Darling is working on ways to filter water to clean out the pathogens – viruses and bacteria – from water in developing countries as well as find more efficient ways to clean out the filtration systems we to treat wastewater.  When it comes to killing the nasty bugs in water now, he says developed countries turn to chemicals, for the most part…

Darling: The way that we disinfect our water here in the developed world is typically one of two approaches. We either put chlorine in the water – the same reason the chlorine is in a swimming pool, it kills that stuff – and there are problems with that. First of all you have to be very careful, of course, because chlorine itself can be very hazardous when it’s in the wrong concentration, but also it’s just damaging to certain types of membranes and things like that so it just causes headaches in processing. Another way that we disinfect water is with ultra-violet light. Here in Chicago, actually, at the O’Brien plant — they’re now the Metropolitan Water Reclamation District here — is reducing the pathogens being sent back into the Chicago River by using ultra-violet disinfection in a huge treatment plant.

Price: The ultraviolet lights work fine, but they use a lot of energy and that’s expensive. It’s also expensive to use filters that clog up from dirt and human waste and have to keep being cleaned or changed…

Darling: A big challenge in water treatment, especially when you use membranes to clean up the water, is that they get dirty. They grow films on them called “biofilms,” they get fouled, essentially, and that plugs up the holes so protein and bacteria and other stuff just start depositing and growing on the membrane and it plugs up the holes and you can no longer get water through them and they have to be either cleaned or replaced. And that is a massive cost and lack of efficiency in the system. And people haven’t really come up with a good solution to that problem other than just replacing or cleaning the membranes to date.

Price: Darling says that at Argonne, they’re working on materials that will solve the problem of clogged membranes and make cleaning wastewater more efficient and less expensive…

Darling: What we’re trying to develop here is a membrane that will clean itself as long as you’re shining light on it. And the light that we’d imagine using here would be sunlight so you don’t have to invest any energy in the process. You’re just using a natural source of energy – sunlight. And we’ve developed a way to coat a material on the surface of, essentially, any membrane that can give it this property that when you’re shining light on it like sunlight it will cause reactions to happen which will chew up all that stuff that would be trying to grow on the surface and just keep it cleaner for a much longer period of time.

Price: Pathogens such as viruses and bacteria are also a big problem and, as we said, chlorine is the chemical of choice for dealing with these disease-causing bugs despite the dangers of over-infusing it into drinking water. Darling says that to filter all the pathogens out of water is a tricky thing to do because the pathogens are so tiny, they can slip through most of the materials we have today…

Darling: The size of those pores that you need to capture some of those little viruses is just a few tens of nanometers. And a nanometer is a billionth of a meter, so we’re talking about really tiny holes. And you want them all to be just that right size. You can’t have big holes and little holes because the big holes would allow those viruses to get through. So it turned out that the membranes that we have today that have holes around that size range have a big mixture of little holes and big holes so they’re not very effective at filtering out all the pathogens.

Price: Darling says that they’re working on a material that not only has pores small enough to trap the pathogens, but that can create consistently-sized holes – all by itself!

Darling: What we’re trying to design here is a membrane were all of the pores are exactly the same size and we can tune that size to be essentially anything we want with very high precision. We’re taking these materials that do what’s called “self-assemble.” They actually arrange themselves into a very highly-ordered structure where you can have pores that are all, say, 20 nanometers in diameter and every one of the pores is going to be 20 nanometers in diameter – not 10 or 50 – but 20. Thereby, if you can build such a membrane and you can do it cheaply, that’s why we want them to self assemble – you can effectively filter out virtually 100 percent of those disease-causing viruses from a water stream. Now you might say, “Why not just make the pores super tiny and then you’re sure nothing’s going to get through even if they vary from one nanometer to five nanometers then nothing that’s bigger than that will ever get through?” That’s true but you’re going to have to push really hard to get the water to go through those tiny little holes and that takes energy. So you want them just the right size and that’s a bit of a challenge. That’s what we’re working on.

Price: Not only does this material self-assemble itself into just the right sized pores, Darling says that, like the filters to clean out the sludge, it can even clean itself…

Darling: It’s titanium dioxide it’s the material, and that material has what’s called “photo catalytic” – photo meaning light, and catalytic meaning it’s driving chemical reactions — with very little energy input. So, it’s activated by the light and then it’ll break down films, like biofilms that we grow on the membrane. These self-assembling materials which are polymers, they’re organic materials, and we transform them into titanium dioxide which has this photo catalytic ability so that it can be self-cleaning and it can also even break down other pollutants that might be in the water. Organic type pollutants that are in the water could be chewed up and hopefully harmless species as long as, again, you’re eliminating with light.

Price: Taking salt water from the oceans or brackish water from underground and removing the salt from it – desalination – is another way to create more water that’s usable for drinking, manufacturing and agriculture. There’s research on doing that more efficiently and less expensively, but right now it’s not viable for removing the salt from the enormous amounts of water we need. Providing large amounts of safe water for human use is not just a modern problem. Darling says that it was a problem faced more than two thousand years ago by the Romans…

Darling: The Ancient Romans were special when it came to water. They were really impressive. Just master water engineers, way ahead of their time which enabled those living in Ancient Rome to have access to a massive amount of water per person for bathing and, you know, just other general daily use. They invented technologies that only showed up in most civilizations much later – water mining and things like that. So they really came up with very creative ways both to move water around but also to how to use it. And because of all of that technological ingenuity that they displayed, they’ve had per capita water use that was pretty similar to what we use today.

Price: One of the ways that the Romans devised for saving water was a method of separating it into various streams – potable and “gray” water. A strategy that many water conservationists around the world are supporting today…

Darling: What the Ancient Romans did is they had different streams of water that had different levels of purity intended for different purposes. So if you have just a fountain in the middle of, you know, Ancient Rome for decoration, that does not necessarily need to be potable water that you can drink. Whereas if you have water that you’re bathing (in) and drinking, that needs to be a different level of purity. And they actually did that. They had different streams of water. Somewhere along the line we went away from that and you know in your home or your business you have one water inlet pipe and that water is potable water because you’re going to use it for drinking but you’re also going to use it for everything else, including flushing your toilet or water the lawn or anything else. And there’s no reason to be using potable water for some of those other purposes.

Price: It’s often difficult to get a lot of movement on water issues in any but the most drought-ridden areas of our country. Darling says that we all need to realize that water is more than what we drink or wash in…

Darling: To me water is so central that people don’t even realize how central it is. It’s not just about having enough water to drink. Everything in and around you is water. To make the food that you eat, it takes massive amounts of water. To make the materials that are used to make the clothes you wear, the phone that you talk on, the car that you drive, all of those things take water to make. So water is actually everything, and when we start seeing that, when we start seeing the virtual water that is in everything around us I think that will help us recognize how important a resource it really is.

Price: Darling says that we have many big problems in our world today such as climate change, financial and political crises and the like, and they’re very important to resolve. However, he says that humans have a natural “affection” for water that we don’t for all of those other issues, and he hopes that this relationship will move us forward on water conservation…

Darling: Water is something that is so a piece of us. We are, in fact, literally mostly water. Our bodies are mostly water that as soon as we’re born we seem to have this natural affection for water. You know, little kids splash in the puddles when it rains. We’re drawn to water, it is part of who we are. And that feeling is something that gives me hope that this is a crisis that we’re going to be able to solve because that just natural human affection for water can be what drives us to address the crisis.

Price: You can learn more about Seth Darling’s work with water at the Argonne National Laboratory website at anl.gov, and at the University of Chicago’s Institute for Molecular Engineering at ime.uchicago.edu. You can also view his talk titled “The End of Water as We Know It” on YouTube. For more information about all of our guests, log onto our site at Viewpointsonline.net. You can find archives of past programs there and on iTunes and Stitcher. I’m Gary Price.

 

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