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Why is desalination so difficult?

practical.engineering

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Re: Why is desalination so difficult?

#291

Post by mcpackieh »

ramesh31 wrote: post #273
mcpackieh wrote: post #236

Earlier quoted context omitted.

Well if they can't afford to even subsidize fresh water, their choices are move or die. What's your point then?

> Well if they can't afford to even subsidize fresh water, their choices are move or die. Would you tell that to the Israelis if they couldn't afford it? The point is that yes, the original article is correct. Current desalination tech is woefully inadequate to replace fresh water surface reserves without putting a massive burden on the society using it.

> Would you tell that to the Israelis if they couldn't afford it?

Yes? What else would I tell them, to pray for a miracle? If they don't have enough water, can't get water profitably and cannot even afford to subsidize water, what else is there to do besides find somewhere new to live? What would you tell them?

> without putting a massive burden on the society using it.

Yeah, in some places it will be necessary to subsidize water, placing a burden on society. But considering we're talking about water, that's obviously a burden that needs to be borne. Acquisition of water comes before literally anything else a population might want to spend money on. And if there isn't enough money around to acquire sufficient quantities of water, there isn't enough money to live there at all.

Israel has a strong enough economy, they can afford to make desalination work for them. You objected that they have to subsidize the desalination, but I don't see any sense in that objection. If that's what they need to do, that's what they'll do.

Re: Why is desalination so difficult?

#292

Post by yhgxfvx »

gamegoblin wrote: post #77

I was surprised how cheap it is. Desalinated water costs ~50 cents per 1000 liters [1]. That's about the same amount of water as a typical American household uses per day. 50 cents per day for a fully desalinated water supply is... incredibly cheap. If you're interested in water policy and water management / engineering, I cannot recommend enough reading the book "Let There Be Water: Israel's Solution for a Water-Sta…

[flagged]

Re: Why is desalination so difficult?

#293

Post by fsckboy »

mschuster91 wrote: post #252
suddenclarity wrote: post #145

Earlier quoted context omitted.

No reason to keep the 1:1 ratio. Use the salt to replace our current salt mines/outtakes and then use the water as an addition to our current freshwater usage.

The problem is that salt brine from seawater contains a lot of side stuff - you still need purification at a scale you don't need mining rock salt.

is this true? I can understand why it would be true, but "sea salt" is a real thing that's been traditionally made in seaside communities through to today, and I find it hard to believe they're cleaning it at anything finer than a gross scale.

https://en.wikipedia.org/wiki/Fleur_de_sel

Re: Why is desalination so difficult?

#294

Post by bhandziuk »

lexicality wrote: post #258
timerol wrote: post #237

Earlier quoted context omitted.

No, 1000L/day is about right for a typical American household. [1] claims "The average American family uses more than 300 gallons of water per day at home." 300 gal is 1136 L. https://www.epa.gov/watersense/how-we-use-water

I know American toilets are comically big but 250L a day on flushing them seems insane to me. A cursory google suggests the average UK household uses 350L a day in total!

That's like 20 flushes. It's a lot more than I'd expect for "typical". Maybe a family of 5 does 20 flushes. Or maybe it's 2 people with strict anti-if-it's-yellow policy.

Re: Why is desalination so difficult?

#295

Post by r3trohack3r »

bsder wrote: post #165
gamegoblin wrote: post #77

I was surprised how cheap it is. Desalinated water costs ~50 cents per 1000 liters [1]. That's about the same amount of water as a typical American household uses per day. 50 cents per day for a fully desalinated water supply is... incredibly cheap. If you're interested in water policy and water management / engineering, I cannot recommend enough reading the book "Let There Be Water: Israel's Solution for a Water-Sta…

Agreed. Desalinization is cheap. It works just fine for providing water for coastal people . As California is proving. What it does not do is provide freshwater for argibusinesses. As California is also proving in the Central Valley. :(

From my (limited) understanding of agribusiness, particularly in California, it will be hard to be cost competitive with current water sources moving forward as they are heavily subsidized (read: near-zero costs).

The upfront cost from my understanding is in drilling a deep well. Those wells keep getting deeper and costing more. But, past that, it's just the cost of running the pumps to drain the underground aquifers. IIUC the cost of water is free plus the cost of harvesting it from the commons.

I might be wrong here, but all the billboards that say "is growing food wasting water?" along the interstates in California don't really matter over long time horizons. They're advocating for draining the water tables. You can't do that forever. Doesn't matter if it was a "waste" or not, it'll be gone soon and they'll have to pay to pull water from somewhere else or stop growing crops there (or the state will pay to give them water).

When "free" water runs out, other water sources will suddenly be cost effective. But it's hard to compete with free.

Re: Why is desalination so difficult?

#296

Post by hasmanean »

londons_explore wrote: post #235
singleshot_ wrote: post #228

Earlier quoted context omitted.

Surely the salt falling on the farmland would have some kind of deleterious effects, right? I imagine you’re not trying to grow sea cucumbers in this scenario, and I’m not sure most land plants would be crazy about a ton of salt. Just ask the Carthaginians… Guessing that you know something I don’t here, though.

I believe that when every spec of salt creates a far larger water droplet - and the overall concentration in rain ends up tiny. If anything, doing lots of this might reduce the salt concentration in soils, due to increased rainfall.

That’s probably what the antediluvian civilization said before they tried it in North Africa! ;)

Re: Why is desalination so difficult?

#297

Post by actionfromafar »

fsckboy wrote: post #293
mschuster91 wrote: post #252

Earlier quoted context omitted.

The problem is that salt brine from seawater contains a lot of side stuff - you still need purification at a scale you don't need mining rock salt.

is this true? I can understand why it would be true, but "sea salt" is a real thing that's been traditionally made in seaside communities through to today, and I find it hard to believe they're cleaning it at anything finer than a gross scale. https://en.wikipedia.org/wiki/Fleur_de_sel

It increasingly has plastic and other crap in it.

Re: Why is desalination so difficult?

#298

Post by actionfromafar »

pas wrote: post #231
eropple wrote: post #225

Earlier quoted context omitted.

Is that true when we take into account environmental externalities? I am not an expert in this field; I know that many forms of mining are capital-B Bad for the environment but I don't know how salt mines impact the area around them.

well, mines are bad on the short term. the long term damage is not of the actual digging, but of the separation processes. which all can be done as clean as we wish it just costs more.

Cost more energy

Re: Why is desalination so difficult?

#299

Post by function_seven »

rs999gti wrote: post #288
bsder wrote: post #165

Earlier quoted context omitted.

Agreed. Desalinization is cheap. It works just fine for providing water for coastal people . As California is proving. What it does not do is provide freshwater for argibusinesses. As California is also proving in the Central Valley. :(

There are no water pipes from the coast to the central valley? I wonder if NIMBYism blocked that? And if an agency wanted to transport water like the USA national oil pipeline system, would they be blocked similarly?

There are aqueducts between the CV and coastal areas. The water goes the other direction.

If desalination becomes widespread, I imagine the water not shipped to the coast could remain in the Central Valley. I don’t know one way or another if this would make political or economic sense.

EDIT: Wikipedia has a good overview: https://en.m.wikipedia.org/wiki/Water_in_California

Re: Why is desalination so difficult?

#300

Post by throw0101a »

johnwalkr wrote: post #285
ftxbro wrote: post #253

Earlier quoted context omitted.

Does this mean I can buy watery maple syrup that is 2x watery for less than half the normal cost like maybe a quarter of the cost? Or does the volume and weight for shipping and handling offset that savings or does no one want watery syrup so there is no market so they don't make it?

Not Canadian maple syrup, it's regulated. I am pretty sure the regulations started from the producers getting together, or at least has the full support of the producers to keep up quality/reputation.

> Not Canadian maple syrup, it's regulated.

Correct for things with that specific label, but other X syrup labels can be fair game:

> In the United States, table syrups can be sold under a name consisting of any word followed by the word syrup with the exception of maple, cane, and sorghum. Commonly used names are table syrup, pancake syrup, waffle syrup, and pancake and waffle syrup.[1]

* https://en.wikipedia.org/wiki/Table_syrup

* https://en.wikipedia.org/wiki/Maple_syrup

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