3 ms·

The volume of the Pacific Ocean is 1.583x10^8 cubic miles. (https://www.wolframalpha.com/input?i=volume+of+pacific+ocean+in+cubic+miles&lang=ja https://www.wolf

The volume of the Pacific Ocean is 1.583x10^8 cubic miles. (https://www.wolframalpha.com/input?i=volume+of+pacific+ocean+in+cubic+miles&lang=ja https://www.wolframalpha.com/input?i=volume+of+pacific+ocean...) The world's freshwater need is about 950 cubic miles a year. (https://www.wolframalpha.com/input?i=worldwide+water+use+in+cubic+miles&lang=ja https://www.wolframalpha.com/input?i=worldwide+water+use+in+...) You can just put the leftovers back without worrying much about it.

ninkendo 3y ago
> You can just put the leftovers back without worrying much about it. Yes, just not all in one place/time. Separating seawater into pure water in one place and pure brine in another, you don’t want to let that brine out all at once in one spot, it’ll kill a lot of ocean life. Most desal plants that are attempting to do this right, will pump the brine into pipes that diffuse it over a wide area to avoid oversalinating. And it still kills a lot of ocean life.
- fiddlerwoaroof 3y ago
  It might be better just to sacrifice specific spots rather than to try to spread it evenly.
  - SargeDebian 3y ago
    It will still need to spread from that spot.
    - fiddlerwoaroof 3y ago
      Yeah, but depending on the details and design of the sacrificed area, it might be less environmental impact overall.
  - chongli 3y ago
    Or another solution would be just to take a hit on efficiency and not produce highly concentrated brine as a water product. If instead we extract just a bit of fresh water out and return saltwater with slightly elevated salt concentration then it wouldn’t be so lethal to marine life. Or we could have a premix station where we pump in sea water and mix it with brine at a certain ratio and then return that to the sea.
    - Cthulhu_ 3y ago
      Well yeah but the net result is just less fresh water; it's a fairly predictable process like that. And with your second process, you still end up with a higher concentration of salt / brine around where it's returned to the sea, still killing animals. I'm thinking of pumping the brine onto large evaporation lakes and harvest the salt or whatever - which also already happens to produce sea salt. And if there's too much salt for the market, just stockpile it. Like underground salt mines.
- theonething 3y ago
  Why not sell the leftover salt?
  - ianburrell 3y ago
    The brine isn't that salty, it is twice as salty as sea water. The Dead Sea is 10x saltier than seawater. They make Dead Sea salt, but the concentration is only slight advantage. The big problem with making salt from sea water is evaporating the water. It either takes a lot of energy, or a lot of time and area.
libraryofbabel 3y ago
For some reason this topic of desalinization waste keeps coming up on hacker news! The dilution principle here is correct but it’s not as easy as you think to dispose of the waste in the ocean, because if you just pipe it out to sea you’ll create a nasty big marine dead zone around the outlet of your pipe.
rocqua 3y ago
On ocean scale, the waste won't do anything horrible. But on local scales, near the waste dump location, the waste will damage local ecosystems and water quality. It takes a lot of time for the salt to just diffuse out over the ocean.

ninkendo 3y ago

> You can just put the leftovers back without worrying much about it. Yes, just not all in one place/time. Separating seawater into pure water in one place and pure brine in another, you don’t want to let that brine out all at once in one spot, it’ll kill a lot of ocean life. Most desal plants that are attempting to do this right, will pump the brine into pipes that diffuse it over a wide area to avoid oversalinating. And it still kills a lot of ocean life.

fiddlerwoaroof 3y ago
It might be better just to sacrifice specific spots rather than to try to spread it evenly.
- SargeDebian 3y ago
  It will still need to spread from that spot.
  - fiddlerwoaroof 3y ago
    Yeah, but depending on the details and design of the sacrificed area, it might be less environmental impact overall.
- chongli 3y ago
  Or another solution would be just to take a hit on efficiency and not produce highly concentrated brine as a water product. If instead we extract just a bit of fresh water out and return saltwater with slightly elevated salt concentration then it wouldn’t be so lethal to marine life. Or we could have a premix station where we pump in sea water and mix it with brine at a certain ratio and then return that to the sea.
  - Cthulhu_ 3y ago
    Well yeah but the net result is just less fresh water; it's a fairly predictable process like that. And with your second process, you still end up with a higher concentration of salt / brine around where it's returned to the sea, still killing animals. I'm thinking of pumping the brine onto large evaporation lakes and harvest the salt or whatever - which also already happens to produce sea salt. And if there's too much salt for the market, just stockpile it. Like underground salt mines.
theonething 3y ago
Why not sell the leftover salt?
- ianburrell 3y ago
  The brine isn't that salty, it is twice as salty as sea water. The Dead Sea is 10x saltier than seawater. They make Dead Sea salt, but the concentration is only slight advantage. The big problem with making salt from sea water is evaporating the water. It either takes a lot of energy, or a lot of time and area.

libraryofbabel 3y ago

For some reason this topic of desalinization waste keeps coming up on hacker news! The dilution principle here is correct but it’s not as easy as you think to dispose of the waste in the ocean, because if you just pipe it out to sea you’ll create a nasty big marine dead zone around the outlet of your pipe.

rocqua 3y ago

On ocean scale, the waste won't do anything horrible. But on local scales, near the waste dump location, the waste will damage local ecosystems and water quality. It takes a lot of time for the salt to just diffuse out over the ocean.