A Salty Podcast


What is desalination? What are the two main desalination techniques? Why is desalination not an idea solution for water shortages? Learn more about desalination with Jonathan, Joe and Lauren.

Narrator: Brought to you by Toyota, Let' go places. Welcome to Forward Thinking.

Jonathan: Welcome everyone to Forward Thinking. My name is Jonathan Strickland; I am your host extraordinaire, joined by my co-hosts extraordinaire...

Joe: Joe McCormick.

Lauren: Lauren Vogelbaum.

Jonathan: And today we wanted to talk a little bit about H2O, and how we get salt out of salt water. Well, why are we even talking about this Joe?

Joe: Well around the world, water scarcity is actually a big problem. Now, there's lots of water on planet earth, I mean -

Lauren: Well, what we're 70 percent water or something like that?

Joe: It's 70 percent of the surface of the earth, yeah is covered in water but about more than 97 percent of that water is salt water. We can't use it. We can't drink it, we can't use it for agriculture, and we can't use it in cooking. I mean it's just not very useful to us. In fact, in 2007 the World Health Organization estimated that 40 percent of the people on earth are affected by the water scarcity.

Jonathan: Right, and so if there were some way to use that salt water, that could go a long way to alleviating some of that water scarcity issue

Joe: Right, and the water scarcity manifests in a lot of ways. I mean in some ways, it's just that people can't get clean drinking water and that's obviously one of the biggest things, and it's useful for sanitation and all these things too. But, it's also crucial in getting the food we need. I mean I think the figure is that, yeah according to the Food and Agriculture Organization of the United Nations, 70 percent of the water worldwide is used in agriculture as a consumptive water use.

Jonathan: So, not only are we having a water scarcity issue, but this could also be a food scarcity issue. I mean when you got so much of your water tied up in the production of food sources, then it makes it doubly important to get that access to fresh water. Joe: Right

Jonathan: And then on top of that, water scarcity is not just regionalized, but it also can be dictated by circumstance. For example, after a natural disaster, like a massive hurricane hits an area, that could mean that there is a, at least temporary, shortage of access to clean water. So, this is one of those problems that are persistent in some areas, and sort of an acute problem in other areas, in the after math of some sort of natural disaster or catastrophe. And as a result, it is a good idea to try and find ways of addressing this including desalination.

Lauren: Right, which people are working on. The industry has grown about 15 percent a year recently. There are currently 16,000 plants operating today and that's - the entire thing has expanded something like 276 percent since 2001.

Jonathan: That's an encouraging number. I mean the problem is that desalination is, well I guess to use a terrible metaphor, and it's a drop in the bucket. I mean the water scarcity issues can be offset somewhat by desalination, but it's hard to really address the problem head on completely with it.

However, before we get into the drawbacks or the enormity of the problem, maybe it's a good time to actually talk about how we go about removing salt from salt water. This is a practice that is centuries old.

Joe: Well, yeah I mean the simplest one, the one you've already thought of is to boil it, the simple distillation process, or actually, you don't even have to boil it. You can just leave it out in the sun and reproduce the natural process of evaporation that creates the water cycle on earth.

Lauren: Just as long as you have something to catch it, yeah you just let it evaporate and then it will drip down in to a fresh reservoir.

Jonathan: Yeah, here's a fun science experiment for you to try at home. You get a bowl of salt water and you get an empty glass. You put the empty glass into the boil of salt water. You cover the whole thing up with some plastic wrap. Maybe you poke a hole in there. Put it out in the sun for several hours. You are going to have the water evaporate from the bowl of salt water and it will end up condensing on the plastic wrap and dripping down into the glass so the water you get in the glass is drinkable. Lauren: Super simple, everyone should do it.

Jonathan: By the way, you should not drink the salt water because your cells in an effort to dilute the massive amount of minerals that are coming into your system will start to push water out of the cells and this is a bad thing. In fact, it can eventually result in kidney failure and then you can have something called death, which is what we generally like to avoid.

Joe: Right, that's why you don't drink salt water. So, we've been boiling salt water to get the fresh water out of it for hundreds of years. But, recently we've gotten some much more advanced techniques of this, right. It's better than distillation. It's boiling 2.0. It's a procedure called, "Multistage Flash," where they have different chambers of very rapid heating that violently boils the water and then reapplies steam to the chambers of new water to create a rapid and efficient boiling process.

Jonathan: Right, right, you're boiling the water multiple times in order to get as much fresh water out of that salt water as possible. You are left with fresh water in one container and a very salty brine in the other.

Joe: Which is good for marinating pork chops.

Jonathan: Actually, it's not good for much of anything. That's one of the issues about desalination. But again, I guess we could wait till we get to the end of the whole discussion there.

So, yeah that's a very popular method of getting fresh water out of salt water. Then there's also the use of reverse osmosis.

Lauren: How does that work? Because I mean, you know osmosis is the basic thing which says that, when you've got a membrane between two liquid solutions, one with more stuff in it and the other with less stuff. The solutions want to even each other out, right.

Jonathan: Yeah, that's essentially what osmosis is. So, you get a semi-permeable membrane, meaning that it's going to allow some things to go through, but it's going to restrict other things. Upon one side of that membrane, you put salt water and then you use pressure to push the salt water through the membrane and then fresh water comes through the membrane the salt is restricted. It's essentially filtered out by this membrane. You have to use lots and lots of pumps to do this. It actually uses quite a bit of energy. Joe: It uses less than boiling the water does.

Jonathan: Yes.

Joe: But, yeah it's still energy hungry.

Jonathan: Yeah, so you are pumping water, essentially pushing the fresh water through this membrane and retaining the salt. Also, the water that you get on the other side of the membrane may not be perfectly salt free. You know some salt particles can get through depending on the type of membrane you are using, and also there are other issues with this. But, it's a way to process a lot of water in a relatively short amount of time.

There are a lot of Desalination Plants that use this approach to it. It does also mean that you have a lot of moving parts, so things like the pumps or even the membranes themselves have to be maintained and replaced on a regular basis. So, there is an ongoing cost of manufacturing and maintaining these pieces in order to keep the plant in working order. So, yeah that's another method.

There is a method that essentially uses gravity. Now, this is a very small-scale desalination technique. When you are talking about a desalination plant, you're talking about on the level of millions of gallons of water. But, for the gravity method, it's really more for something like a community. You know you think of a small community, not like a major city, and it is essentially a series of filters that are vertically stacked. You pour the salt water at the top, gravity pulls it downward, and as it passes through the filters, the filters filter out all the salt until you get fresh water at the bottom.

Joe: So, it's like using the potential energy of gravity in place of the pumps you would use in a reverse osmosis plant.

Jonathan: Right and again, it's a much smaller scale. We're not talking about something that is going to be producing millions of gallons of fresh water.

Joe: Right, well some of these plants are pretty impressive. I was reading about the Carlsbad Desalination Project and that's a plant that is under construction now in the San Diego area. San Diego is one of these places that is good for a desalination project because it's dry, but it's on the coast. So, it has access to the water, but not as much fresh water. What they are claiming is they will be able to supply fifty-million gallons per day. That's [inaudible]

[Crosstalk]

Jonathan: That's a lot of fresh water, yeah. That would be an enormous offset obviously that would be fantastic. And of course, there are other communities that have - even large cities that have even less access to fresh water than someplace like San Diego does.

Joe: They have a lot of places in the Middle East use desalination.

Jonathan: Sure

Lauren: Yeah, Saudi Arabia I think is currently the largest producer of Desalination Plants.

Jonathan: And also, what is interesting to me is that culturally in some of these areas especially in the Middle East, desalinated water is thought of as being inferior to water that was just fresh to begin with.

Joe: Really!

Jonathan: Yeah, there's actually a cultural perception that the water tastes differently and that it has an unhealthy affect on one. Tests have not born that out but the perception is there. And of course, if the perception is there, that can really shape people's behavior and adoption of these sort of technologies. So, some of the obstacles to desalination are culturally based not even technologically based.

Joe: So, we've looked at these couple techniques and so they can both be very effective for producing water in a dry area that borders the ocean but they're still pretty energy hungry, reverse osmosis is better, but can we do any better than this?

Jonathan: Well, that's a good question.

Lauren: That is the question of the day I think.

Jonathan: Yeah, I mean if you've got these methods of removing salt from salt water to get fresh water, but they require huge amounts of energy, really you're talking about an energy problem not just a water problem. I mean, where does this energy come from? That's a big question to ask. I mean, it seems simple on the face of it, but when you really start to think about it; if you have to burn fossil fuels in order to generate fresh water, really your problems are kind of shifting. Even if you get enough fresh water, you are still having the problem of having to depend upon fossil fuels. You also have the problem of pollution. So how do you get around that?

One method might be to try and harness solar power to generate the energy needed to run these Desalination Plants. That would be a very clean way relatively speaking. I mean you have to take into account what it takes to build a solar panel.

Joe: It takes a lot of overhead.

Jonathan: Yeah, and there are rare earth minerals and things of that nature that you have to think - everything is a big picture when you ultimately look at it. But, the generation of the power itself would be clean using solar energy. The only issue there really, is being able to generate enough solar energy to provide what is necessary for running a plant. Luckily, I guess you can say, for a lot of these areas where a desalination plant is most needed, they also tend to get a lot of sunlight.

So, you could, if you were able to build an efficient enough solar panel and then build arrays of these solar panels, an entire solar farm, you can generate the energy needed to run a desalination plant, which in turn would generate the fresh water you need.

You still would have to find a way to dispose of the brine in a way that is responsible, because the brine itself is very dense. It has a lot of salt content. Remember that's where all that salt was before, you know when you got all the salt water all that salt is there.

Lauren: Yeah, concentrated down, yeah.

Jonathan: Exactly

Lauren: Yeah, most of the time it ends up as run off in a fresh water river, which of course is not good for the natural wildlife.

Jonathan: Yeah, and you're talking about -

Joe: Even if you just dump millions of gallons back in to the ocean, that can't be good for the local wildlife.

Jonathan: No, because this stuff sinks down and then it immediately starts to really impact the oxygen producing elements in the ocean. So, you start to really make a severe impact on the local area and of course, that ends up being kind of a domino effect and you get this whole Ian Malcolm Chaos Theory problem that ultimately results in dinosaurs eating somebody.

Joe: But of course, he would say that life finds a way.

Jonathan: Finds a way, yes he would.

Joe: But -

Jonathan: Sorry, go ahead.

Joe: Well, I wanted to ask another question.

Jonathan: Sure

Joe: Why can't we just manufacture water? Now think about it here.

Jonathan: Okay

Joe: Water is two parts hydrogen, one part oxygen. We know exactly what's in it and how to make it.

Jonathan: Yes, we do.

Joe: And these are some of the most abundant elements in the Universe. So, why is it that we can't just make water?

Lauren: Well, we could, I mean we would need a lot of energy.

Jonathan: Yeah, well also Joe, we need to get that hydrogen. That's the problem. You see hydrogen yes, extremely plentiful. In fact, the most plentiful element in all of the Universe. However, or at least our Galaxy, however hydrogen on earth does not really - it doesn't really occur un-bonded very much.

Joe: Right, it's not free

Jonathan: Yeah, there's a little bit of free hydrogen on earth, but really percentage wise it's a very small amount. Most of hydrogen on earth is bonded to something else and in order to get to that hydrogen, you have to expend energy to free the hydrogen from whatever it is that it's bonded too. For example, salt water, I mean ocean water. There you got lots of hydrogen; you have all that hydrogen right there in the ocean. That's really the biggest and most accessible source of hydrogen that I can think of. So, I guess if you ran electricity through ocean water -

Lauren: So, we just need to process this ocean water somehow to desalinate the hydrogen out of it.

Jonathan: Right, if only there were a way to process ocean water so that you pull the hydrogen out and the oxygen out, and then combine it to make fresh water. I mean you could just boil the stuff. That's what you could do, but why not run electricity through it so that you could use electrolysis to free that bond. Yeah no, that's the problem. You go right back to that energy issue, which is, without that source of hydrogen, you really can't manufacture water in any way that makes sense. Especially, when there are other ways of getting at the water, that are less energy intensive then you are playing a losing game, so that's why.

Lauren: There are, there are new processes that are coming out. One of the newer ones is called "Ion Concentration Polarization." This basically just runs an ion current through a non-porous membrane. Salt and larger particles like bacteria and viruses, stuff that you really don't want in your water anyway, are pushed away from the membrane and clean water flows through it.

Jonathan: Wow. That sounds so like Star Warsy.

Joe: So wait, you say the membrane repels it.

Lauren: Yes, any kind of charged anything is going to deflect right away from the membrane and so the brine kind of goes up away and the fresh water flows directly through it. And this (A) keeps the membrane clean so you don't have to get it all dirty and gunky and clean it or replace it all the time.

Joe: I bet those in the other plants get pretty grimy.

Lauren: Yeah, oh yeah, I'm sure. Unfortunately, it only works on a very small scale. Again, this is a personal community kind of thing. They are using it in a lot of rescue operations. I think during Katrina, they had some ground units for that sort of thing.

Jonathan: Yeah, and this sort of stuff is great for those acute problems we were talking about. For a persistent issue where you have to deliver a significant amount of fresh water to a large population on a continual basis obviously, that would not be the ideal solution.

The good news is, there are a lot of companies working on this. As you said Lauren, I mean this is an industry that has grown considerably over the last several years. I have personally spoken with an engineer over at General Electric that was all about designing Desalination Plants and finding new ways to make them more efficient, so that it is less of an energy investment to create fresh water from salt water. This is a problem that is not going to go away anytime soon. I mean obviously this is something that we are going to have to really concentrate on in order to support our communities.

Some of us are very fortunate that we live in places where access to fresh water isn't such an issue, but for other people, I mean this is a fact of life. This is just an ongoing thing that they have to solve.

So, I'm really optimistic about the future in general. I think technology is going to play a large role in helping us get access to fresh water. But, Joe I think you would agree with me that technology is only going to play one part and that a significantly large part of this is going to have to require some behavioral changes.

Joe: Oh right, I mean you cannot, as far as we know, there is no quick easy technological solution to this. As we said, we have this energy barrier. There is always a huge amount of energy that you would need in order to get fresh clean water to the people who need it. And so, one of the easiest solutions, one of the most viable solutions is just to use less, conserve better, and manage more efficiently.

Lauren: Right, it's a little bit outrageous that we here in America use fresh water, fresh drinking water in our toilets, and that kind of thing is just incredibly wasteful. There is no really good infrastructure way to get around that right now but -

Jonathan: Yeah, it is one of those things where during the whole design process for it, I don't think anyone was thinking, hey maybe we should find some way of using gray water in these systems in order to conserve the fresh water, because why worry about it. You've got plenty of access to fresh water all the time.

Lauren: It's everywhere.

Jonathan: Yeah, but it's definitely one of those things that we have to think about. And Joe, you know in the video episode of Forward Thinking, I think you really nailed it. You said, "Changes are coming" and they have to, because without them we're going to really - especially depending on where in the world we live, we're going to be facing some really tough, tough problems in the foreseeable future. So, we have to take responsibility and accountability and make these changes so that the future generations don't suffer for it.

Joe: Absolutely.

Jonathan: Thank you for agreeing with the point that you made on the video series, I appreciate that Joe. I was afraid you were going to leave me out there. I was like -

Lauren: Nope changed my mind.

Joe: Turn on all the faucets please.

Jonathan: Okay, well I'm glad that we got that out of the way. All right, guys, remember Forward Thinking is a video series. We got it launched and going and it's fantastic. I could not be happier with it. The website is fwthinking.com. We are on Facebook, we are on Twitter, and we are on Google Plus. Go check us out, let us know what you are excited about in the future. What future topics get you really jazzed and what you want to see us tackle, because we want to hear from you. We want to take those topic suggestions from you and turn them into amazing episodes. So, let us know what you think and we will talk to you again really soon.

Narrator: For more on this topic and the future of technology visit ForwardThinking.com

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Duration: 21 minutes

Topics in this Podcast: energy resources, desalination, water