California's Water Crisis

[Timsup2nothin]

I suspect that your ships used thermal vacuum desalination (basically, boiling off water, albeit at lower temperatures than 100C, and collecting it) It has high energy consumption (likely not too problematic when you have a nuclear reator on hand), and relatively poor efficiencies but is very easy to set up and operate, making it great for things like ships, and places with energy to burn.

Reverse osmosis (using a semi-permeable membrane which allows water but not salt to pass though, but pressurising the system such that instead of water flowing from low-saline to high-saline, it is reversed) is much more efficient in terms of water, and takes less energy (though still a non-insignificant amount), but has much much higher set up and non-energy operational/maintenenance costs and is more complex to operate. I believe it requires much cleaner water as well, so the seawater must be treated before it can be desalinated.

All those things are true. We could make fresh water out of the sludge that passes for water in a busy port, sluicing out the sludge with the brine and not caring a whit.

We certainly had energy available sufficient to do whatever we wanted. Submarines survive on stealth, not speed, and at a flank bell we sounded like a freight train. If I had a dollar for every time I had the reactor above 75% of its capacity during routine operations I couldn't buy lunch.

And since that reactor required us to consistently provide it with makeup fresh water under the adverse conditions of tooling around in a submarine, reliability vastly outweighed efficiency for us.

Still (pardon the pun), I was thinking "they have to be more efficient, probably ten, maybe twenty percent". You have expanded my perceptions here. Thanks.

 

[El_Machinae]

As in all things, conservation tends to be cheapest. But, unless property rights are assigned properly, your cutting back merely allows someone else's consumption.

 

[Hygro]

Phrox, nice posts

 

[Farm Boy]

I was lernimafying things Phrox! Keep going!

 

[Sommerswerd]

I wan to hear more too

Reverse osmosis (using a semi-permeable membrane which allows water but not salt to pass though, but pressurising the system such that instead of water flowing from low-saline to high-saline, it is reversed) is much more efficient in terms of water, although achieving the kind of efficiencies we're getting in this plant requires a pretty high pressure, and takes less energy (though still a non-insignificant amount).

Can you explain how/why this takes energy? What form? Why can't you let the water flow into the membrane and let gravity do the rest? Or is the energy use occurring in the pumping process after the filtration takes place?

 

[Timsup2nothin]

I wan to hear more too Can you explain how/why this takes energy? What form? Why can't you let the water flow into the membrane and let gravity do the rest? Or is the energy use occurring in the pumping process after the filtration takes place?

My theory, subject to correction by PhroX, is that when he says 'pressure' he isn't talking about something that can be produced conveniently by gravity. Creating high pressures in a high flow rate system takes a lot of power.

 

[PhroX]

Thing is, if you've got a semi-permeable membrane (in this case, something that lets water molecules pass, but not salt ones) between two bodies of water, one with higher salinity, if you just leave it, you'd get water flowing from the low salinity side into the higher salinity side until both sides have the same concentration of salt (~halfway between the two initial concentrations). This is osmosis. If you know much about biology, its much the same as how stuff passes through cell membranes.

But that doesn't really help get rid of the salt. Instead, we want to do the reverse - start with both sides the same salinity, and end up with one side low salinity and the other high salinity.

And here's the clever part - for water to flow, there must be a pressure across the membrane. That's why water flows in any situation, a differential in pressure. Therefore, if you apply a higher pressure in the opposite direction the water would naturally flow across the membrane, the water will instead flow the other way, and you get what we want: reverse osmosis. Moving the water across the membrane, leaving the salt behind in an increasingly saline "starting" side.

Unfortunately, to overcome the "natural" pressure across the membrane and get a reasonable flow rate in the reverse direction takes a lot of applied pressure. In the case of the membranes used for desalination, you can be talking pressures of upwards of 50bar IIRC (for reverse osmosis treatment of dirty water, it's less). And while you could achieve this kind of pressure through gravity alone, you'd have to have your saltwater starting at a significantly higher elevation than your plant [a rough conversion is that you need the water to be 10m higher to achieve a bar of pressure]. Which doesn't really help given that we're getting the saltwater from the sea.

So we have to use pumps. And pumps that can achieve this pressure for the kind of volumes of water we're talking about (several cubic meters per second) aren't that cheap to buy, run or maintain.


And that's only for the RO itself. On top of this, you have to get the water out of the sea and up to the plant - which takes further pumping, albeit not at such a high pressure (and you can't just use one set for both parts, as you have to treat the water before the RO as the kind of stuff you find in seawater can damage the membranes - and the treatment itself can also be energy hungry depending on what methods you use. Most "low energy" types of treatment take up a fair bit of space, something you don't always have). That's actually the bit I'm mostly knowledgeable on - the designing of the intake pumping station - as I'm a hydraulics modeller rather than a process engineer, but it's hard not to pick up at least a general overview of how the main plant works when you're working on a project for a year and a half (albeit not full time).

 

[Timsup2nothin]

Well, I didn't get corrected, but that was far more thorough!

 

[PhroX]

Hehe

I suppose if there's one thing to take from this in a non-technical sense, it's that desalination is not a particularly good way to get water at the present (technology is improving pretty quickly though, so who can say what things will be like in the future). It's expensive and even the more efficient methods like RO are still energy hungry. It's just that, of course, in many places, it's the only way to get sufficient water. When the consequences of not getting water - whether its a matter of supplying people's houses, or keeping the world's largest copper mine operational - are large enough to outweigh the costs, then there is little other choice.

 

[Timsup2nothin]

I know this is harping on a point, but once again even if it is a very expensive way to make up the current shortfall of supply it is certainly doable. Even as an expensive source it is a small enough contributor to the total supply that average unit cost is barely affected.

The problem remains that we have demonstrated that every increase in supply will be met by increased demand such that the shortfall is maintained. If nothing is done to stabilize demand bringing supply up to meet it is pretty much pointless.

 

[Wolfbeckett]

Maybe you're approaching the demand aspect from the wrong angle Tim. Maybe the solution isn't to make California less attractive, maybe we need to convince other places to stop sucking so much.

 

[Timsup2nothin]

Maybe you're approaching the demand aspect from the wrong angle Tim. Maybe the solution isn't to make California less attractive, maybe we need to convince other places to stop sucking so much.

My sister had a brilliant idea that fits that perfectly. We could plow snow into C-5s on the east coast and drop it on the Sierra Nevadas. Take the C-5 to altitude the snow doesn't even melt in transit.

 

[Farm Boy]

Maybe you're approaching the demand aspect from the wrong angle Tim. Maybe the solution isn't to make California less attractive, maybe we need to convince other places to stop sucking so much.

My thought was that people need to stop liking stupid things, but I think we're all on the same page. People are dumb, therefore, the more people you have, the dumber you get.

 

[FriendlyFire]

My thought was that people need to stop liking stupid things, but I think we're all on the same page. People are dumb, therefore, the more people you have, the dumber you get.

Have you seen the Middle East lately ? With the drought in Syria and Yemen cause of the civil war which is spiraling out of control.

California can reduce it water consumption by a 5th to Australia levels and stop wasting water like Americans if it cannot do this then it can just buy expensive bottled water while complaining a lot.
And stop planting water intensive crops, those farmers that have done so are going to learn the hard way when there expensive nut trees, grapes and almonds are wiped out by the drought.

That or vote Republican into power and proclaim no climate change
Problem SOLVED !

 

[GoodSarmatian]

Unfortunately, to overcome the "natural" pressure across the membrane and get a reasonable flow rate in the reverse direction takes a lot of applied pressure. In the case of the membranes used for desalination, you can be talking pressures of upwards of 50bar IIRC (for reverse osmosis treatment of dirty water, it's less). And while you could achieve this kind of pressure through gravity alone, you'd have to have your saltwater starting at a significantly higher elevation than your plant [a rough conversion is that you need the water to be 10m higher to achieve a bar of pressure]. Which doesn't really help given that we're getting the saltwater from the sea.

So we have to use pumps. And pumps that can achieve this pressure for the kind of volumes of water we're talking about (several cubic meters per second) aren't that cheap to buy, run or maintain.

Potentially stupid question: Can't you build the desalination plant underground to get pressure from gravity and run the desalinated water into an aquafier?
Or would that be too inpractial and expensive ?

 

[PhroX]

Potentially stupid question: Can't you build the desalination plant underground to get pressure from gravity and run the desalinated water into an aquafier?
Or would that be too inpractial and expensive ?

Not even remotely practical. To eliminate the need to pressurise the membranes with pumps, you'd need to be something like half a kilometer below sea level.

 

[Godwynn]

Let the sea levels rise. Why should the Floridians and Californians get all the good weather? Come to the safe Midwest where we are surrounded by food and 20% of the world's fresh water.

 

[Farm Boy]

Have you seen the Middle East lately ? With the drought in Syria and Yemen cause of the civil war which is spiraling out of control.

California can reduce it water consumption by a 5th to Australia levels and stop wasting water like Americans if it cannot do this then it can just buy expensive bottled water while complaining a lot.
And stop planting water intensive crops, those farmers that have done so are going to learn the hard way when there expensive nut trees, grapes and almonds are wiped out by the drought.

That or vote Republican into power and proclaim no climate change
Problem SOLVED !

Well, yes, farmers aren't exactly strangers to getting donkey punched by the weather.

Look at it like a farmer does though. You own land, or you have access to land through renting it. Either way, through the purchase price and mortgage combined with property taxes, or the price of the rent, access to land that you "own" costs you a certain amount every year. The more valuable that land is, the more it costs you to maintain access to it every year, even if you own it. Now: if water is underpriced on the market such that the Chinese outbid Californians for it even while they're running short, water is pretty underpriced. If certain foods are highly valued, such as fresh grapes, almonds, and trees, ground that can produce them will increase in value to reflect the available profitable use of that land. Attempting to buy or retain land that the market will put a premium on as "prime irrigated almond ground" and then using that land to grow unirrigated cotton? That farmer is going to get eaten by the market if he can't pull an additional income stream from it, like hypothetically, selling the water either directly or through some permutation of a set-aside program. After (s)he gets eaten, somebody else will take it over. Farmers plant what they think the market will buy and what will pay their bills and hopefully make a profit. I know in the era of The Monsatan it's trendy to assume that they almond orchard wasting the water is not only doing something dumb(yes) but that it is also orchestrating the situation. It's not. People are doing that in the grocery stores.

 

[Sommerswerd]

I know in the era of The Monsatan it's trendy to assume that they almond orchard wasting the water is not only doing something dumb(yes) but that it is also orchestrating the situation. It's not. People are doing that in the grocery stores.

But this makes the situation seem utterly hopeless, because even if water became so scarce or expensive that Californians actually had some anti-waterhog-crop movement and started boycotting almonds... well then the price would go down and everyone else in the country would just say "woohoo! Cheap @$$ almonds! I luvs me sum almonds! Buy buy, buy!"...the crop would remain profitable and nothing would change for California. Or am I missing something?

 

[Farm Boy]

We're stumbling onto the why the boring-ass farmer supports several degrees of government intervention, pricing regulations, subsidies, and agricultural programs(such as set-asides). We're also stumbling onto some of the why I have a degree of visceral disgust for the people that buy premium/organic foods and then female-dog at all the dumdums that are buying the mass produced stuff. Premium/organic doesn't mean ethically/efficiently produced. It just means produced under a different set of guidelines.

Edit: You probably are right to an extent. The rest of the country, if not particularly invested in agricultural issues, may very well be more than happy to shuck and devour California's resources for their own benefit if they can get away without bearing the full costs themselves. Ironically, this would be Californians being outpulled by the gentle auspices of the will of the majority. Something that should be kept in mind when rubes support things like the Electoral College and the design of the Senate.