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Comment by SamBam | Hacker News Reader

What is being done to use the brine produced by desalination?

Whenever I look into this, it seems that all the brine questions revolve around how to dispose of it in a safe manner, or how to re-introduce it gradually to the sea.

Why can't we turn brine into table salt, or use it in some industrial process?

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World demand for salt is about 260 million tonnes:

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

Seawater contains ~3% sodium chloride by mass:

http://www.seafriends.org.nz/oceano/seawater.htm

2015 desalination rates of 86.8 million cubic meters per day would produce 950 million tonnes of sodium chloride per year (86.8 * 365 * 0.03):

http://idadesal.org/desalination-101/desalination-by-the-num...

Potential salt supplied from desal dwarfs demand. The excess, which is most of it, will be dumped.

Sea water is about 3.5% salt by weight [1]. The city of Los Angeles uses about 14 billion gallons of water in a month [2]. This works out to something like 2 million tons of salt being produced just by LA in a single month. So we can turn it into table salt... but it's something like six tons of table salt per year per person.

[1]: https://en.wikipedia.org/wiki/Seawater [2]: http://projects.scpr.org/applications/monthly-water-use/los-...

Where does all the waste water go? If 10 billion goes down the sewer and back to the ocean, you can "re-salt" that water on the way out..

Even better, you can build an osmosis power station and create a lot of electricity. The energy in the salinity difference between the water of a river and the water of the ocean is enormous.

(It basically works like this: You have two containers with water of different salinities, connected with a membrane that only lets the water pass, but not the salt. The water will move through the membrane to balance the salinity - osmosis - and one container will have a rising water level, which can be used to generate electricity with turbines.)

Wouldn't it be better to simply recycle the non-salty water instead?

Depends. You only need a difference in salinity, not non-salty water. If the brine is much more saline than the ocean, there's your energy potential. On the other hand, this kind of power plant also goes well at the mouth of a river. You don't need clean water at all.

I don't know about California, is all the fresh water fully recycled until the rivers are dry? That would be hard to imagine.

I don't think the rivers would run dry if we recycled waste water, as a majority of it is just dumped into the ocean.

Though, wouldn't there be a potential for more industrial based uses of the salt? http://eusalt.com/salt-uses

Also, see http://www.nbcnews.com/business/economy/road-salt-winters-2-...

I always thought we might be able to reuse empty strip mines and dump the salt in there but someone smarter than me can chime in on why that may not be environmentally sound.

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