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The Dirty Truth About Turning Seawater into Drinking Water

earther.gizmodo.com

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Re: The Dirty Truth About Turning Seawater into Drinking Water

#51

Post by yzb »

arkades wrote: post #14
w1nt3rmu4e wrote: post #4

> this salty-ass junk Do you mean sea water? The amount of fresh water the human race will extract from the oceans will be what fraction of a percentage point of the total? Not accounting for, of course, the fact that most of it will make its way back to the oceans. If pumping it back in has a local effect, then by all means try to mitigate that. But the idea that we're producing 'toxic waste' by creating saltier sea…

I know it's not generally accepted on HN to say "please read the article before commenting on the article." But it's worth noting that the contents and effect of the "brine" as distinct from "sea water" get two full paragraphs devoted to them in the article. Maybe let's not attack the journalist.

He should not call something "salty-ass junk" if he wants his "work" to be respected.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#52

Post by sandworm101 »

snowwrestler wrote: post #36
zaarn wrote: post #29

Earlier quoted context omitted.

I don't think microplastic particles in the human digestive system are that big of a problem; most of it is fairly inert and will just pass through, the other stuff is in low enough quantities that our stomach should be able to deal with it.

Things can get weird at very small sizes because of the huge ratio of surface area to mass. An amount of plastic that is safe to place against your skin as one object, might have more significant chemical interactions as a collection of particles in your digestive system--which specializes in leaching complex chemicals out the materials that pass through it.

There can also be strange physical issues at small scales. A block of plastic cannot get lodged between cells or poke through into the bloodstream.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#53

Post by tda »

csense wrote: post #42

Sure, the high salt concentration kills sea life for a couple hundred meters around where the waste comes out, but compared to the total size of the ocean, I'd imagine the affected area would be TINY. Once you get to a larger area it'd be totally diluted by the normal salinity seawater. Why don't you just build a pipeline to put the dead spot a couple miles away from shore, far away from economically important beache…

That is what I intuitively thought, until I learnt that salinity in the Persian Gulf (a huge body of water connected to the ocean) is up significantly due to desalination. Salinity has risen 50% over the last two decades. See e.g. https://financialtribune.com/articles/people-environment/434...

Re: The Dirty Truth About Turning Seawater into Drinking Water

#54

Post by adamcharnock »

beagle3 wrote: post #37
loudmax wrote: post #34

Earlier quoted context omitted.

Carbon emissions is a grave problem with existing desalination infrastructure, but this seems something that can be solved. I'd expect desalination to be well suited for opportunistic use of solar or wind power. Build up reserves of clean water when it's sunny or windy, then deplete those reserves when cheap spare energy isn't available. Of course this goes for new desalination plants. Whether there's political will…

Most desalination plants around the world are operating at 100% capacity all of the time, because that's what needed to avoid depletion of the reservoirs. To be able to "build up reserves" means that you have to build much higher capacity, but only use as much of it as clean energy allows - in today's world, this is highly uneconomical. If anything, the reserves to be built are energy reserves that allow water to be…

I’ve heard on the grapevine that facilities are now being designed which work at under 100% capacity in order to soak up excess/cheap power.

I believe this is coming about because: 1) the high cost of power and presence of sporadically cheap power makes it economically viable, and 2) designing equipment with lower duty cycles can actually provide substantial cost savings. Ie a facility which only runs 50% of the time is much cheaper to build & run than once which runs 100% of the time.

Sorry I cannot cite sources right now.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#55

Post by ginko »

I assume the brine is heavier than regular sea water. Could leading it through a pipe directly into the deep ocean be a (slightly) better option? There's less marine life there and it can slowly mix with the ocean water. Deep ocean water also has a higher salinity and lower oxygen content already.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#56

Post by dredmorbius »

sunstone wrote: post #38
arkades wrote: post #6

Just to be clear, "brine" isn't "salty water." > This untreated salt water can’t just hang around in ponds—or, in worst-case scenarios, go into oceans or sewers. Disposal depends on geography, but typically the waste does go into oceans or sewers, if not injected into wells or kept in evaporation ponds. The high concentrations of salt, as well as chemicals like copper and chlorine, can make it toxic to marine life. >…

Yes, just like exhaled breath is a waste product full of C02 and containing very little oxygen. If other people had to breath that they would become very sick or even die.

Exhaled air consists of 78 percent nitrogen, 16 percent oxygen, 4 percent carbon dioxide.

https://sciencing.com/chemical-composition-exhaled-air-human...

Re: The Dirty Truth About Turning Seawater into Drinking Water

#57

Post by Gupie »

abalone wrote: post #19

It’s saying for every 2.5L of seawater only 1L of freshwater is recovered and the rest is brine, which also includes chemical byproducts. Why is this ratio so bad? What would it take to recover more water and produce more concentrated waste that could be managed differently?

Alternatively recover less water and have a waste that is only marginally more salty that seawater.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#58

Post by mcv »

I admit I had not expected this to be a problem. The salt water comes from the sea, I'd expected it to be fine to release the salt back into the sea.

But I understand that untreated, this extra-salty water would, in large amounts, become a current of its own that's significantly different from regular sea water. And apparently there are added chemicals in it that I suppose were necessary for the desalination process? Shows how little I know about desalination, I guess.

Still, cleaning and diluting it and releasing it back into the ocean seems like the only workable solution. It just needs to be cleaned better and with an eye on the consequences of how and where this enters the ocean.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#59

Post by mcv »

endorphone wrote: post #30
arkades wrote: post #6

Just to be clear, "brine" isn't "salty water." > This untreated salt water can’t just hang around in ponds—or, in worst-case scenarios, go into oceans or sewers. Disposal depends on geography, but typically the waste does go into oceans or sewers, if not injected into wells or kept in evaporation ponds. The high concentrations of salt, as well as chemicals like copper and chlorine, can make it toxic to marine life. >…

Just to be clear, "brine" isn't "salty water." It mostly is, and the additional chemicals they mention are already in the sea water, not that were added somehow in the process. It's just concentrated. That it's concentrated is a problem, obviously -- very high-saline water (e.g. brine) and concentrated toxins are a problem, and would cause environmental problems if just dumped. The most common way to deal with brine…

> the additional chemicals they mention are already in the sea water, not that were added somehow in the process.

Are you sure? The article made it sound like they were added. If they're natural to sea water, simply diluting it with more sea water or possibly sewage that's headed for the ocean anyway, sounds like the obvious solution.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#60

Post by JulianMorrison »

mcv wrote: post #58

I admit I had not expected this to be a problem. The salt water comes from the sea, I'd expected it to be fine to release the salt back into the sea. But I understand that untreated, this extra-salty water would, in large amounts, become a current of its own that's significantly different from regular sea water. And apparently there are added chemicals in it that I suppose were necessary for the desalination process?…

You can't dilute it; the entire point of the exercise is to obtain and not use up fresh water.

Probably the sensible answer is to dry it and bury the powder salt.

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