Why Is Desalination So Difficult?

An overview of seawater desalination: removing salt to make drinkable water from the ocean.

Correction: The Carlsbad plant produces 50 MGD, which is roughly 190,000 cubic meters per day (not 23,000 as stated).

It might surprise you to learn that there are more than 18,000 desalination plants operating across the globe. But, those plants provide less than a percent of global water needs even though they consume a quarter of all the energy used by the water industry. The oceans are a nearly unlimited resource of water with this seemingly trivial caveat, which is that the water is just a little bit salty. It’s totally understandable to wonder why that little bit of salt is such an enormous obstacle.

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This is not engineering advice. Everything here is for informational and entertainment purposes only. Contact an engineer licensed to practice in your area if you need professional advice or services. All non-licensed clips used for fair use commentary, criticism, and educational purposes.

SPECIAL THANKS
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This video is sponsored by Brilliant.
Stock video and imagery provided by Getty Images, Shutterstock, and Videoblocks.
Tonic and Energy by Elexive is licensed under a Creative Commons Attribution License
Video by Grady Hillhouse
Edited by Wesley Crump
Written and Produced by Ralph Crewe
Production Assistance from Josh Lorenz
Graphics by Nebula Studios

[dundonrl]

I've drank literally thousands of gallons of desalinated water over 20 years while I was in the US Navy. First ship used 7 stage evaporators and the last two used reverse osmosis. You couldn't tell the difference between them since it was pure water that came out of them and the engineers added minerals back into them to make them drinkable.

[morganmedrano]

I'm a Navy veteran and I served on a Nuclear Aircraft Carrier. We had a desalination system built into the Reactor system using the excess heat from the steam powerd turbines. It was actually very efficient.

[Stroheim]

Nuclear powerplants are basically just "big waterboilers." Many of them are of obvious reasons situated near oceans. In them you get a lot of desalinated water steam in them, which easily can be collected and used as drinking water, and many nuclear power plants has that dual function: generate electricity and desalinate water. THIS is the easiest and cheapest way.

[BlitzAttacker]

I grow salicornia (sea asperagas) at home and it does surprisingly well turning salt water into usable water and a snack thats pretty dang salty and not bad tasting in my opinion. Not sure if its great for every purpose but here in florida it works pretty well.

[WKfpv]

Here in Uruguay we are facing a drought right now, and the government decided to mix treated salt water in the normal fresh water supply, so now we are getting water on our taps with a salt concentration about 10x of what it used to be. This video turned out to be very well timed for us.

[n]

It is SO extremely important how you put things in perspective in these videos. “It took X kilowatt-hours to do this process.” You could end there and compare numbers at the end, but then people wouldn’t understand what that actually means. It’s great.

[bobby]

I really love the information you put out here. The only point I disagree is the privatisation of water treatment. Companys and investors deciding prices for drinking water after contracts have run out. There have to be other ways for water desalination or use of water rights.

[gamerin]

Really great explanations and comparisons. Thank you for taking the effort to set up the bench top examples. I believe that desalination won't come into popular view until it is the only choice left for larger regions of the world outside of the middle east. As mentioned, water is plentiful but the amount of energy it takes to transport it and prepare it is key.

[TheDd]

Lived in Saudi Arabia for a while and dad worked at the desalination plant there. Interesting bit was steam generated by the boilers were split into two pressure points. High pressure steam was used to turn the turbines to produce electricity while low pressure steam was used to make fresh water. Interesting when I heard about it the first time.

[TwinSteel]

I think one reason people may have a hard time wrapping their head around how difficult it is to get the salt out of the water is that they can’t see what it does - it’s not just swirling around in there, it’s dissolved - it’s harder than getting the cream back out of your coffee

[edewindt]

Really good explanation of it all! I’m an operator at a large ultrafiltration membrane plant not far from the Carlsbad plant. Membrane technology is definitely our future and we are going to see more sea water RO plants popping up as our population grows in the U.S.

[DerekFletcher]

I work in water treatment in my county as an operator. We adopted membrane filters in the mid 2000's and there are very few treatment plants (at least in Canada) with this newer technology. Our membranes are made by PALL. It's such a new technology that the lifespan of the membranes is still unknown (outside of salt water). We have ordered a complete new set of membranes that will be replacing the old ones next year but this is only cautionary and not reactive. Our tmp's (trans membrane pressures) have held up with only minor, routine maintenance. Our effluent remains well within the 0.1 micron spec and our turbidity exceeds our provincial standard by multitudes.

[craigbabuchanan]

Spoken like a true engineer... "The instructions didn't say to not run salt water through the pump"

[JohnFox-XXXX]

Well thank you Grady! My late father was a widely-acclaimed reverse osmosis water chemist but I never understood exactly what was special about RO, and the difference it could make. He travelled extensively in the UK and the Middle East, solving RO problems encountered by water utilities at local and even national levels, eg Namibia in Southern Africa. This video has resolved for me what had been a fog of comprehension, so I can’t thank you enough for facilitating a new enlightenment for me!

🙌 High five to you Grady!

[adammills]

Don't be afraid of nuclear technology.

[patronwizard]

Thanks for covering the renewable energy part, I've been grumbling about using that for years. Now I have a clue of the continuing drawbacks.

[ImpendingJoker]

Here in Tampa they tried to build a RO desal plant near the Apollo Beach Power Plant. The biggest issue was not any of what you outlined here. The problem was zebra mussels. They are a non native invasive species that would collect on the intake pipes for the desal plant and they were spending 100's of thousands of dollars each month just to keep the pipes clean, and that is what killed the project in the long run.

[crawford]

On our 470' research vessel housed 130 people, we had two distillers plus a reverse osmosis. The distillery was pretty brilliant as we pulled a vacuum on the container and we used heat from our diesel electric engines. When the vacuum was applied the water would vaporize at 165°F rather than 212° F pretty clever. The units on our ship produced 1200 gallons per day. Some of that water was additional purified by R.O. So the waste heat from the engines was not an additional cost only the energy used by the pumps was energy negligible.

[mikeclarke]

@17:38 the problem with that is: How many corners are the private companies going to cut, w.r.t the environment and how much oversight and inspection is needed?

[motbus]

The problem with private sector in this case is that there are many incentives for cutting costs and leaving the impact to the future generations