I know that generally speaking, disposing of waste in the ocean and expecting it to disperse enough to be harmless is foolish and wrong. But in the case of salt, It would seem to me that the ocean can handle that amount of salt. Course, I haven't done the math. But it would seem to me that the back in == salt taken out. We'd only be changing the net salinity by the amount of water subtracted. Without having done the math, my gut reaction is to think that's something the ocean can handle.

The problem, as I see it, is localized concentrations. While the ocean at large might be able to absorb it, the localized concentrations can be very problematic.

There are potentially some good reasons to just spray the brine into the air.

Seawater sprayed into the air becomes tiny salt crystals, which in turn help clouds to form, and cause increased rainfall. The rain produced has negligible levels of salt.

In places with dry climates, this often can turn desert land into farmland across an area hundreds of kilometers wide.

Surely the salt falling on the farmland would have some kind of deleterious effects, right? I imagine you’re not trying to grow sea cucumbers in this scenario, and I’m not sure most land plants would be crazy about a ton of salt.

Just ask the Carthaginians…

I believe that when every spec of salt creates a far larger water droplet - and the overall concentration in rain ends up tiny.

If anything, doing lots of this might reduce the salt concentration in soils, due to increased rainfall.

That’s probably what the antediluvian civilization said before they tried it in North Africa! ;)

I guess what I’m forgetting is that the water has a chance to wash salt away back to the ocean. But how much salt does one drip of water absorb? What if the spec of salt that starts in the water droplet is as much as the droplet can wash away?

I suppose it must be slowly becoming clear that I have no idea what I’m talking about (save for a nickel worth of Roman history).

This is what happened with Aral Sea.

It might just cause earlier rainfall, not more of it. There's x amount of water in the atmosphere, and you can't add more by spraying salt crystals.

You can though. The amount of precipitation (averaged over a long enough period of time) is inversely proportional to the amount of evaporation and other water entering the atmosphere (averaged over a long enough period of time). Note that the two things being compared are _rates_ not _masses_. If all you do is cause water to fall sooner then:

1. The humidity in the air drops, increasing evaporation rates because of the lower partial pressure of water vapor in the air.

2. The humidity on the surface increases (dusty areas becoming moist, plant leaves uncurling to expose more surface area for other processes but incidentally increasing evaporation rates, reservoirs having more surface area, ...), increasing the evaporation rate.

There are limits of course, and that back-of-the-napkin analysis ignores 2nd-order changes in temperature and all of the other hairier bits of climate modeling, but it illustrates that things are more complicated than they appear anwyway.

Edit: "inverse" here just meaning a multiplication by -1

Ah yes, that actually makes sense. Making the air drier speeds up the entire water cycle, thus more rainfall.

It would be interesting to have a water cycle simulation with sliders.

Would this be worth doing straight from seawater? I.e. place enormous solar/wind powered rigs in the ocean to spray massive volumes of seawater into the air? What would be the effect (beneficial and otherwise) of that?

The problem with brine from desalination is that it kind of behaves like a heavier liquid, sinking to the bottom. That causes it to stay together, taking longer to mix with the regular ocean; and the coastal seafloor there is a lot of life that doesn't appreciate water with double the salinity of regular ocean.

To solve that you can just dilute it more, either mixing with some other waste water stream or by releasing it over a larger area rather than a single outlet.

Double the salinity? Other comments suggest it’s only slightly more salty than sea water.

Only a very small fraction of water is isolated from a very amount of sea water.

The article states

> Modern desalination plants generally recover about half of the intake flow, which means their brine stream is about twice the concentration of normal seawater.

I imagine this heavily depends on the actual plant design though. Also because of the above mentioned issues you generally don't discharge it like that but blend it with other water.