141–150 of 644 posts
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Couldn't they just replace fossil fuels with nuclear and solve the emissions issue?
Not sure that largish, easily targetable, nuclear facility on a tiny spot of land is a good idea.
Is it just me, or did this article dance around the question? I am not a physicist but let me give it a stab: except for a few specialized steps like UV or oxidizing heavy metals, most filtration is mechanical. A series of filters with smaller and smaller pores capture more and more of the mess in the water like bacteria and particulates while UV breaks down viruses, the oxidizer precipitates out metals, and so on. N…
You've pretty much nailed it except for one minor nit: > It takes less energy but produces a concentrated liquid waste stream that must be disposed of. This implies that creating a concentrated waste stream is a problem unique to reverse osmosis. It isn't. No matter what you do you're going to end up with a bunch of salt that you have to get rid of somehow.
I've often wondered why dont we have more pure water pumped through the water mains in various countries, and I think after reading about Super K the Japanese Neutrino detector [1] and how the water in the tank was so pure it had dissolved a spanner/wrench that was left in the bottom, years ago, I might have the answer.
Firstly there is health implications for drinking pure water, and whilst it probably wont dissolve your guts [2], it will drastically and quickly alter your chemistry [3] which in moderate doses may be a good way to calm down, I havent tried personally yet, but there is another problem.
The ultra pure water would probably dissolve the older ceramic and metal pipes used to deliver water around the countryside, from the inside out.
In fact I would even go so far to guess that water mains pipes last longer if its delivering hard water compared to soft water, and probably explains the pub culture as the water is standardised in various alcohol brands.
Either way I prefer soft water, its more relaxing and could well help to reduce a certain amount of anxiety in the population along with stress levels, that could be useful for built up cities, but watch the GDP levels of the region go down if that happened and the profile of crimes change [5], not to mention health conditions!
[1] https://www.businessinsider.com/super-kamiokande-neutrino-de...
[2] http://physicsandphysicists.blogspot.com/2018/06/super-kamio...
[3] https://chemistry.stackexchange.com/questions/30754/effect-o...
[4] https://nuscimagazine.com/water-so-pure-it-will-kill-you-261...
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7576670/#:~:tex....
"Turning sea water into clean, drinkable water costs $2 to $5 for 1000 gallons. Less than half a penny per gallon is obviously absurdly cheap." - Elon Musk, 2023-05-07 https://twitter.com/elonmusk/status/1655262008898383872?ref_...
It's very easy to forget that we use orders of magnitude more water than comes out of our tap. A pound of beef is about 2,000 gallons, so that would be a nontrivial price increase.
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It takes less energy but produces a concentrated liquid waste stream that must be disposed of. I've heard that this brine is toxic. Does this make disposal an issue? Is the toxicity true or hyperbole? I mean, do we know how bad it is, and if we can do anything safely with it? It seems like "salt" is useful in a lot of contexts, including industrial, so can we do something with the brine besides disposing it somewhere…
It’s toxic only because of concentration. AKAIK, there aren’t any compounds in the brine that weren’t present in the seawater to begin with. The solution is dilution, but I’m sure it’s easier for me to type that than it is to achieve in a desalination plant. But, why not really-long-pipe-with-small-holes-along-the-length? That seems to me like a simple mechanism to send the brine back into the ocean without causing a…
The OP mentions that this is common in practice, although it's easier to tell in the video that this is what is being described.
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good thing people need salt!
If people needed as much salt as was contained in the water to begin with, we wouldn’t need to remove it in the first place.
Can I shower in salt water? Then all I need to do is desalinate drinking water. “Distributed” home desalination for drinking water seems like the best approach in my mind, then people can pay as much or as little they need, but I have no real data to back this up.
It's not difficult. It's just energetically uphill. Undoing entropy costs energy. Second Law of Thermodynamics.
The thing is, it doesn't have to be. The energy released by mixing salt into water is small, around 3.9kJ/mol. Molar mass of salt is 58g/mol, and the average sea water salinity is around 3.6% So a cubic meter of sea water will have 1000*0.036/0.058=620 moles of salt, and it'll require 2.4MJ of energy to remove the salt in a perfect desalinator. In more common units, 2.4MJ is about 0.75 kWh. Around here electricity is…
For 90% salt removal with 50% waste-water, they say the limit is 1.09kWh per cubic meter (3.924 MJ)
NB: It is not 100% clear to me if the result is independent of the type of technology, but they do claim:
> We first derive the general expression of the thermodynamic minimum energy of separation determined by the Gibbs free energy, which is independent of the method of desalination
"Turning sea water into clean, drinkable water costs $2 to $5 for 1000 gallons. Less than half a penny per gallon is obviously absurdly cheap." - Elon Musk, 2023-05-07 https://twitter.com/elonmusk/status/1655262008898383872?ref_...
I'm looking at this and unclear what he's talking about. Essentially, citation needed Elon?
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But we're talking about increasing the per-gallon cost of everything. So the baked in cost would increase.
Or moving water intensive operations away from areas where water is expensive. No one is going to be doing desalination in Michigan.
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I believe I had read just dilute it until concentration is ok then release. But might be more tricky than that ^^ : https://www.sciencedirect.com/science/article/abs/pii/S00489...
dilute it with what? the clean water you just removed the salt from?