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Comment by inglor_cz | Hacker News Reader

A lot of exceptions apply.

Sana'a, the capital of Yemen, is located at an altitude of 2,250 meters (approx. 7 thousand feet). It has almost three million people. Pumping required amounts of water from sea level to such heights is quite a challenge.

Tehran is at 1200 meters. Tabriz, 1350 meters. Mashhad, 1000 meters altitude and far from the sea.

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Tehran is quite close to the Caspian Sea, Tabriz is close to Lake Urmia which while it’s shrinking is a huge salt water lake.

Sana’a is indeed more problematic but if pumping water isn’t feasible the pumping people closer to coast is.

Lake Urmia is enormously salty. Over 20 % of its water is salt.

Can contemporary technology even desalinate such brine efficiently? It is, after all, tailored to normal seawater with its 4 per cent salt content.

I don't know anything about desalination but from what I've seen on YouTube, desalination does not result in clean water and powder table salt. It results in water and very salty water. What do we do with this very salty water? Apparently, it isn't safe to just dump it into the water source...

Use it for power generation, trials have been run using the osmotic pressure to run turbines.

Of course, the salty brine is still there.

One word: pickles.

I was a photographer on a cruise ship a couple of times this year and when we toured the engine rooms with the engineers, they said that the on-ship desalination plant was not able to operate anywhere near populated shore because they weren't allowed to dump the resulting brine.

i don't know what sort of quantities we're talking about here, but would it be feasible to use the brine for evaporative cooling, and then you've just got a solid to clean up afterwards.

As it gets more concentrated, the evaporation rate really drops (and boiling point goes up a lot), so less and less effective for cooling.

Most desalinization plants actually do just dump the waste brine back into the water source. If the outflow pipe goes deep enough it's not too bad.

I wonder why they don’t just dump it into some bit of land where it can evaporate. Obviously this approach doesn’t work everywhere, i.e., if there is risk of it seeping into groundwater or other parts of the environment, but a few sq km of middle eastern desert? Seems fine.

If managed correctly there is little point. However it seems that the plants in Israel also use evaporative pools on some of the brine and sell it off to some chemical plants but at the scale they desalinate it just not feasible to pool all of if and you still need to get rid of the salt eventually. https://www.sciencedirect.com/science/article/abs/pii/S00431...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6959559/

Disposing the salt is a problem however there has been some exploration of using the salt brine as a building material.

The Caspian Sea's altitude is 27m below sea level, so that actually doesn't help (https://en.wikipedia.org/wiki/Caspian_Sea).

Doesn’t help what? We pump oil and gas across entire continents we can somehow pump water up a hill.

Tehran is similarly situated to the Caspian as Reno is to the Pacific. Maybe closer but certainly at high altitude.

We have 5000km oil pipelines… the WestEast gas pipeline that China is finishing will be nearly 9000km… the Caspian Sea is like 120km off the outskirts of Tehran.

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