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Why is desalination so difficult?
611–620 of 644 posts
Re: Why is desalination so difficult?
#612For a blog about "practical engineering", it doesn't address the fact that in practice, saltwater isn't just "water and salt" but also all kinds of particules, pollutants and impurities that will clog any membrane after a while.
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Re: Why is desalination so difficult?
#613Earlier quoted context omitted.
Part of the flavor of maple syrup is due to caramelization and the Maillard reaction of components of the sap. Just concentrating the sap would get you a syrupy substance sourced from a maple tree but it wouldn't be maple syrup .
I've never liked the flavour of maple syrup very much. At the same maple syrup place visit, we had some, on pancakes. WTF? This is plain table sugar! What kind of stunt are you pulling here? The guy supervising the boil said don't you know? The very best grade is like that, hardly maple-y at all! Turns out it really was about the sugar all along, with the initially undesirable maple flavour coming to be prized over t…
Fun fact, early abolitionists marketed maple sugar as a replacement for cane sugar, since cane sugar was made by slaves while maple sugar was made by northern farmers.
So the old grading system rated the lighter colored plainer sugars and syrups higher than the darker more flavourful varieties. Since less maple flavour made for a better all-purpose sweetener and a more direct competitor to cane sugar.
Nowadays we usually use maple syrup for the flavour, so the grading system is non-judgemental that way. And the darker grades are more likely what you want.
Re: Why is desalination so difficult?
#614Re: Why is desalination so difficult?
#615Earlier quoted context omitted.
Is not just a question of preferences, there are risks also. If the problem is that we need lots of energy to create pressure to separate salt from brine, well... I figure out that there is a lot of free "all that you can eat" pressure in the sea bottom. The problem would be to calculate if moving all this weight up and down the sea (and in open sea) would be economical or not. Or of would unavoidably lead to people…
> I figure out that there is a lot of free "all that you can eat" pressure in the sea bottom. > Things either float or sink without extra energy added. That seems intuitively wrong... where is the energy coming from in this scenario? It's like saying we could use the pressure at the bottom of the ocean to spin a turbine and get free electricity. I guess the obvious problem that sticks out in my mind is that once you'…
A corpse of freshwater immersed in saltwater would experience a force up because its lower density. The weight of the submarine itself cancels this but if we keep adding freshwater at some point we would cross a density threshold. Probably a big volume. Maybe too much to be practical. Dunno.
Even more, ice floats so in a case of live or death if we could freeze with liquid nitrogen or so a big enough volume of cold water while avoiding the effects of the increase in volume, in theory the submarine could emerge automatically. We can't do it in the main submarine (would explode and the non frozen parts would implode immediately), but maybe in an independent storage area attached and able to absorb the extra volume?... dunno
A way to lower the temperature just when the oxygen is about to end would add also some precious extra time. A corpse is dead only when is warm and dead. In any case I'm just digressing wildly about an extreme and hypothetical emergency case. I could be totally wrong or not practical. I prefer not to test it.
Re: Why is desalination so difficult?
#616Earlier quoted context omitted.
Residential water use is nothing. In California, where we have persistent water shortages, residential, commercial and industrial water use ( including all landscaping, golf courses, etc) all put together still only amount to 10-20% of overall water use, depending on rainfall
Is the only remaining use left agricultural?
Letting it flow through the rivers and delta to the ocean is half of it.
Re: Why is desalination so difficult?
#617Earlier quoted context omitted.
>In 2022, 85% of the country's drinkable water was produced through desalination of saltwater and brackish water. Israel does this by burning massive quantities of fossil fuels: https://en.wikipedia.org/wiki/Energy_in_Israel#/media/File:E... It's not even remotely economical without huge government subsidies. Completely untenable with current technology for poorer countries, or anyone that cares at all about carbon e…
A lot of public goods are that way. What you’ve stated is practically a tautology. “Government subsidy” just means the public is paying for it. Other things that fall into that category are universal education, the military, and police.
Fresh water isnt a "public good", technically or economically speaking. A "public good" is a commodity that is neither rival or excludable. This means that the quanity or quanity is not deminished by people using it, and that you cant prevent anyone from using it. A lighthouse or public radio are examples of public goods.
Fresh water, economically speaking, is a classic private good. It gets consumed as someone uses it, and can people can be easily restricted from acess if they dont pay.
https://en.wikipedia.org/wiki/Public_good_(economics)#Defini...
Re: Why is desalination so difficult?
#618Earlier quoted context omitted.
A lot of public goods are that way. What you’ve stated is practically a tautology. “Government subsidy” just means the public is paying for it. Other things that fall into that category are universal education, the military, and police.
Fresh water isnt a "public good", technically or economically speaking. A "public good" is a commodity that is neither rival or excludable . This means that the quanity or quanity is not deminished by people using it, and that you cant prevent anyone from using it. A lighthouse or public radio are examples of public goods. Fresh water, economically speaking, is a classic private good . It gets consumed as someone use…
*quantity or quality
Re: Why is desalination so difficult?
#619Earlier quoted context omitted.
Is the only remaining use left agricultural?
Looks like on average the data shows 42% agricultural. https://water.ca.gov/Programs/California-Water-Plan/Water-Po...
No, you are being misled by “environmental water,” which is a fancy way to say it’s water we don’t use because were not allowed to. This doesn’t make any sense, how can you include water you don’t use in your accounting for water use?
The reason this is there is to downplay the outsized use in agriculture, and also to shift some blame to folks that voted not to allow this water to be used in the first place.
But still, if you want to cut spending and are looking for where your money is spent, you don’t include money you choose not to earn in your list of spending.
Re: Why is desalination so difficult?
#620Earlier quoted context omitted.
Nuclear power in general would be the answer to a lot of energy problems. But the general public in most places doesn't like it.
Is not just a question of preferences, there are risks also. If the problem is that we need lots of energy to create pressure to separate salt from brine, well... I figure out that there is a lot of free "all that you can eat" pressure in the sea bottom. The problem would be to calculate if moving all this weight up and down the sea (and in open sea) would be economical or not. Or of would unavoidably lead to people…
> I figure out that there is a lot of free "all that you can eat" pressure in the sea bottom.
Have you heard of the second law of thermodynamics?
There's also lots of all-you-can-eat heat in any piece of matter, eg sea water or rock. But that doesn't mean you can get at it for anything useful, without a heat differential (or a pressure differential).