TechStuff Classic: TechStuff Gets Salty

originally published on October one, two thousand twelve. And you know, I'm being all ki and everything, but yes, this is an episode. It's about desalination, the process of removing salt from water and the technology behind it. I hope you

enjoy this classic episode. So, Chris, one of the big issues facing the world today is access to clean, drinkable water, and so we wanted to talk to someone who's an expert in a particular form of processing water to make something that isn't drinkable into drinkable water, and we have with us from ge Eric Hansen. Eric, welcome to the

to the podcast very much. We're excited to have you here, and we're going to talk a bit about desalination, which is a process where we're removing things like salt and other minerals from water so that you have clean drinking water as an as a byproduct, really the other one being the the salt the salute. So we want to talk a little bit about the process that you guys use over at g the things that you're looking into,

and um, how that has changed over the years. So to really start off, what what are the greatest benefits of desalination. Um, it's a great question. Uh. You know, the world today uh bases you know, ever increasing challenges and stresses on water supplies. But the good news behind that is the Earth's surfaces sent water. So even though less than one percent of that is accessible as fresh water today, the rest of it is is seawater, and we do have the technologies today to turn that into

usable water. So in fact, those technologies have been around for a really long time. Uh. You know, even hundreds of years ago, people would boil water, capture the steam from that water, and use the condensation from that that steam as purified water. So the concepts of of desalinating water using heat or thermal technologies, those aren't new concepts.

They've been around for a while. Desalination has been going on for a long time and even up through the most of the nineties, UH, thermal technologies were still very prevalent, albeit a little bit more advanced than just simply boiling water. But the concepts were still the same. Up the water, capturing the steam, and condensing it. Sure, in the in the nineties, different technologies started being applied. UH. Instead of heating up the water and boiling it, what we started

doing was applying membranes, special kinds of very advanced filters. UH. These membranes are able to remove the salts from the water, UH with much less energy. Takes a lot of energy to boil water. So using membrane technologies, we've been able to reduce the amount of energy it takes to remove the salt from water. And over the last twenty years there have been just a lot of advances in that in that field, which I'm sure we'll go into a

little bit more in our conversation. Sure, making the cost of desalinating water come down, UH, you know every year, right, And so you're talking about these these semi permeable membranes. Essentially we're looking at a process of reverse auso osis really um forcing the using pressure essentially to force water that has various minerals and salt in it. Through this membrane, the membrane separates out the minerals the salts, and the

water passes through. Normally, when you have a membrane between a solute and a solvent, the solvent is going to pass through the membrane until there's a an equilibrium there and osmosis pressure is osmotic pressure is built up. So in this case, we're actually applying energy on one side so that we get water on one end of the membrane and everything else is on the other. Is that that sort of a bird's eye view of what that technology is all about. Yeah, you described it very well.

You know. One of the biggest difference between membrane filtration and the types of filtration that most people are familiar with. It's when most people think of a filter, they imagine a barrier of some kind with one stream of water flowing into it, things being removed by that barrier, and then one stream of water flowing out the other side, and then after a while you have to do something to get all this stuff you've removed off that barrier.

So membrane technology doesn't exactly work that way. You still have a barrier and it's the membrane. But in membrane technology, the feed stream is actually flowing across the membrane, so you have one stream in, but then you're applying pressure, so some waters making it through the membrane. That's the purified water without much salt in it, and all the salt, all the salt is staying on the other side of

the membrane. So in membrane technology, instead of one stream in and one stream out, you actually have one stream in but two streams out, the saltier stream, so that saltier stream the brine. I know that that has caused some problems in the past simply because Brian, you know, what do you do with that after you've gone through the desalination process Now, Brian, because it has this concentrated amount of salts and minerals in an it's actually denser

than seawater. So if you were too simply dump that brine into the sea, then it would it would sink to the bottom of the sea floor where it could potentially cause damage depending upon the environment that you're in. Uh, can you talk a little bit about some of the approaches to to take care of that problem. I know there's some about mixing the brine in with other water that's going to be running into the sea, so it

it dilutes it. So I mean, if you step back and look at the desalination process, you know, from from thirty feet, uh, it can simply be considered really part of the normal water cycle, the hydrological cycle. So yes, there's water with more salt going back into the ocean, but the water that's purified and it's then used, uh, ultimately that goes back into the ocean as well, whether it comes through municipal wastewater and sanitary supers and it's

treated you know, in many other ways. You know that water all does essentially return to the hydrological cycle at some point. So you know, from a high level, the mass balance is fine. The oceans aren't going to get saltier because of this, because we are returning the purified water back to the oceans at some point as well.

So really, the the more immediate concern is just that very point at which you're introducing the brine back into the ocean, and depending on the characteristics of the seabed and what's living in that area. Uh, sometimes there are special considerations that are taken. Uh. And you know, there are many different ways you can return the brine back into the ocean. You can just have a pipe that puts it right into the ocean. You can create an elaborate grid of pipes underneath the seabed to uh, to

blend it a little bit better. There's a number of different methods. And even though desalination may seem like a niche to some people, there are actually quite a few specialties within it. And uh, you know, really thinking through how the brine is going back into the ocean and how it's going to affect marine life is uh is quite a science in itself. But you know, there's been a ton of progress on that really in just the

last ten years. And you know, I think in nearly all cases we're now able to come up with with special schemes and and the right technology to blend up without harming marine life. Fantastic. Hey there it's Jathan from two thousand nineteen. We're gonna take a break from this salt extravaganza and here from our sponsor. Well, moving on to another question. What what's the greatest barrier to adoption

of desalination? I mean, why, uh, what's keeping this technology from being more widespread and used in more areas of the world. You know, I think there are you know, you could probably classify it into two different barriers. One of one of them is, uh is more perception. Uh. You know, there are some areas where the public still isn't really that on board with it yet, just for you know, things they've read in the news and their

own ideas about it. Other parts of the world are doing this uh often uh you know, in the Middle East or in Southeast Asia. You find de cell plants all over the place. They have largely solved all the environmental issues that people should be worried about. Um. You know, but some people are slower to adapt than others, and it takes a while to to come to terms with with some of that mentally. UM. So that you know,

that's a harder problem to solve. The easier problems to solve really are are the energy problems, because when you do desalination, it isn't the cheapest way to get water. If there's other uh supplies of water of alable to you uh that don't have so much salt in them, they're most likely going to be less expensive than desalination.

So today people are doing desalination really only in areas where they don't have a lot of other alternatives, where they're in a water scarce area and they simply need to do it. So driving down the energy cost is really the primary goal and desalination it has been for the last twenty years, and there have been a lot of different improvements over the last really fifteen years that have really made progress in driving that down UH, and

they're in a number of different areas. Obviously, the amount of energy that you need to drive the salt out of the water is a big deal, and you can lower that through advances in the membrane chemistry, so actually improving the membranes. You can do it through advances in the efficiencies of pumps UH, and you can also do it through advances in energy recovery devices. So there's a you know, a number of different area is that that

people are working on. And then in addition to that, you know, simply the operation of these plants, you know, it requires a the amount of of manpower just to keep these things running. So we've also been making a lot of improvements and innovations and the pre treatment to these plants. So as as the pre treatment to the water gets better, they're lower operating costs as well. So lots of different levers to pull in order to lower the operating costs. You know, I was wondering a little

bit about the equipment itself. I mean, the process itself seems pretty uh, pretty straightforward, but um, you know, is the is the equipment itself large? Does it take up a lot of space or or does it require a lot of high pressure to to make it work? Yeah, the two different things. In terms of size. It doesn't take up really any more space than a traditional water treatment plant for the same capacity would. But the big

difference is pressure. The more salt that you have dissolved in any in any given amount of water, the higher the osmotic pressure of that water, something Jonathan referred to in his earlier explanation. So the more salt, higher the osmotic pressure, the more pressure you need to apply to the water to drive the salt out of it. So take for example, the Middle East in the Gulf, in the Middle East, that's really some of the saltiest water

in the world. So on detail plants, they're running them as high as as eighty p s I, which is pretty high pressure. Uh. In other parts of the world, like say the Caribbean, the water is a little less salty, still absolutely seawater, but it's not quite as stalin as as the Middle East. So there you because it has slightly less salt, you can use slightly less less pressure. Now, are these plants often um sort of piggybacked onto other plants like pour generation. I was wondering if there was

a lot of cogeneration going on with desalination plants. Yeah, that's a great question. Uh. And this is actually one of the reasons that g is is uh, you know, so active in this market. Uh. You know, there's just an inex Uh. There's a there's a obvious tie between energy and water. So to produce energy, you know, power plants need water to produce energy. In fact, almost ten percent of all global water withdrawals go to the production

of water, so it's a pretty significant amount. Uh. And then the reverse of that is to desalinate water, you need energy to do it. So power plants and deesel plants are are are very linked. In the past, when the technologies were more thermal based, that was another advantage of tying the plants together because many power plants, especially power plants in the past, had a lot of waste heat, so they could use some of that heat uh for

the thermal desalination. Power Plants today are much more efficient, so there isn't so much waste heat coming from them. Uh. And the membrane technologies come to a point where really that's the propol and technology for desalination. So we're not seeing them tied together as much anymore because of waste heat from the power plant, but we are seeing them tied together simply because the power plant needs water, uh and the decail plant needs power. Excellent. Hi, it's Jonathan

two nineteen again. I decided that I needed to get a little salt, so I came back to visit this episode. While I'm doing that, let's take another quick break. So what is ge doing to make desalination more feasible to address water scarcity issues? So we're working in a number of different areas. We've worked a lot in the past on the membranes, and uh, you know, there are really some very high quality membranes now used in this salimation. Uh,

they're not at entitlement yet. There are still some games to be made there UM, but they're they're getting close. The membranes are very efficient today. UM pre treatment is very important. So when when we talk about membranes and how they take the salt out of water, they're great at taking the salt out of water, but they aren't great at taking suspended solids out of water. So you don't want to put salt or sticks or stones or anything like that into a membrane. That's bad for it.

So pretty much every membrane plant in the world has some kind of pre treatment in front of it to take the suspended solids out before it gets to the membranes. UH and G has been leading in this area as well.

We have some terrific advanced prefiltration another type of membrane called an ultrafiltration membrane, and it it provides really superior UH suspended solids removal, so that the water that gets to the the reverse us most of the membranes is as clean as it can be, still salty, but it's had everything else removed and that makes the life of those membranes last a lot longer, which in turn lowards

the overall cost of ownership. UM. Then the other pieces of the pumping side, there are a lot of different kinds of pumps in the marketplace. The most efficient types of pumps are positive displacement pumps. If you think of pumping water, you can imagine you have a fixed geogray fixed geometry of water. The most efficient way to raise the pressure of it is just to push on it um and that works today in in relatively small sizes, but as plants get larger and larger um there aren't

so many good positive displacement pumps. So instead what people use their centrifugal pumps. So that's more like spinning the water. The water that gets thrown to the outside has a higher pressure. So you know, we've been working developing a new pump which is a positive displacement style pump, but is much larger than other positive displacement style pumps on

the marketplace. That's a pretty new product for us, but we expect that within the next year we're gonna start seeing more of more of that pump out in de cel plan and that's going to knock as much as another ten percent of the energy off, so that when we get that fully commercialized, not in the marketplace, it's gonna lower the electrical costs by about ten percent more, which is really significant when you're talking about, you know,

the cost of desalination. Sure. So, so that's sort of leads into what do you see as the future of desalination? Where do you see us going in another few years, like another decade or two decades. Yeah, that's a great question and a hard question because there are many many technologies out there today. Uh. You know, I I think most people in the industry, myself included, really see reverse osmosis as continuing to be the most prevalent technology, uh

for at least the next five or seven or ten years. Um. It's certainly possible that some other technologies could could come along. And you know, honestly, if there are other technologies that will dramatically lower the cost of desalination, that would be great for the planet. Um. But I you know, I think over the next five or seven years, what we're going to see is people figuring out how to link

the cell plants more to other renewables. So already we're starting to see people thinking about how do you combine a de cell plant with wind turbines and a wind farm, or how do you combine a de cell plant with a solar farm. You know, it turns out that a lot of places in the world but neat desalination, places that are water scarce, are also places that have quite a bit of sun. So there there's some nice natural

links between, you know, combining solar with de cell. In some ways, there's also challenges because you know, in addition to having a sun, you know, some of these places also have a lot of sand and it's dusty and and dust and solar don't don't always hair so well. The dust coats the panels and they become less efficient. But you know, now we're talking about some pretty um discreet challenges. You know, people are doing this now, they're learning,

they're getting better at it. There's not a lot of solar plus D cell or wind plus D sell out there today, but I think in the next five to ten years we're probably gonna start to feel a lot more about Yeah, it's really exciting and to give our listeners an idea of the impact that these sort of technologies have made so far. Uh, it wasn't that long ago that the estimated population that could not get access to clean water was around twenty but according to the

World Health organization. They had a two thousand twelve report which took numbers from and took a look at that. They said that it's is still a massive problem. Still s million people lack access to safe drinking water, according to this report, and that's a you know, that's a

sobering number. But the silver lining here is that that's that's half of what it was before, so that the numbers of people who are getting access to safe drinking water, they're on the rise, which I mean, that's obviously the way we want to see this trend go. So it's exciting to see this sort of technology combined with the efforts of other organizations out there dedicated to making sure that that people across the world get access to this water. Yeah.

I couldn't agree more. You know, one of the statistics that that I often hear is that today it's one and every six people today doesn't have access to clean water, which is, as you said, really a sobering number. Um. You know, I I think there's an interesting combination here

where you read a lot about this today. You know, ten years ago you didn't generally see water articles in mainstream media, and today, you know, every week you're going to see an article in mainstream media talking about water scarcity, and you know, it is a serious problem and it is alarming. But the plus side of this publicity is that they're more entrepreneurs, more large companies like GE, just more people out there starting to think about what are

some possible solutions, uh, And there's lots of them. You know. Desalination is a great example of ways that we can solve water scarcity. Water reuse is another great example of ways that we can solve water scarcity. Water reuse is just taking water that's already been used for one purpose, uh, and treating it and cleaning it up and finding a

way to use it for another purpose. So, you know, I think all the current press that we hear about water scarcity is actually helping to feed a pipeline of new innovations and new ideas that will actually helps all the problems in the long run. Fantastic, Eric, Uh. That that's a great look at the desalination process and what g E is doing to to really push this technology forward. And we really appreciate you coming on the show and

talking with us. It's been a really educational experience for me and especially as as as liberal arts majors whose whose background and engineering is saying, Wow, that's cool. Uh, it's really great to get people like you on our show to talk about this and and give our listeners this uh this sort of Uh look, is there anything else you would like to say before we wrap up? Well, you know, Jonathan Chris, I'd just like to say thanks,

thanks for having me on the show. Um. You know, at ge we're doing a lot of really interesting and innovative things to solve the very problems that we were just talking about for the last half hour. Uh. You know, one of the great things about being in this kind of business is when you come up with innovations, you can actually see you that they're helping people. Uh. So you know, it's it's a rewarding business to be and

Geez very committed to it. We're investing a lot and solving problems today and in the future, and and uh, you know, I love talking about it and I'm really excited about where this can all go over the next couple of years. And that wraps up this classic episode

of tech Stuff where we learned all about desalination. There's been a lot more work on that over the last few years and maybe I'll do a follow up episode to talk about this and the challenges around desalination and how we need to really be cognizant of those challenges before we pursue desalination on a grand scale. It turns out it's a lot more complicated than just taking salt out of water. I hope you guys uh enjoyed the episode.

If you have suggestions for future topics for tech Stuff, feel free to reach out to me the email addresses tech stuff at how stuff works dot com, or pop on over to our website that's tech stuff podcast dot com. You will find links to all of our old episodes.

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