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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

#111

Post by pdpi »

tim333 wrote: post #94
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. >…

The dictionary definition of brine is "water strongly impregnated with salt." ie salty water.

When in technical contexts, the technical definition matters more than the dictionary definition. Clearly the plant isn’t discharging the stuff I season my chicken with!

Re: The Dirty Truth About Turning Seawater into Drinking Water

#112

Post by eitland »

kiriakasis wrote: post #50
sunstone wrote: post #38

Earlier quoted context omitted.

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.

Actual question, how many time can air be breathed? I think you can live on second-hand breath.

Can't answer the question, but I can say that when I did HUET we'd breathe into a bag in the suit and back again. This worked surprisingly well for the time we needed to stay underwater before we could escape. I'd still warn against implementing ones own version of this without studying the topic well, there's a number of pitfalls that one might not be obvious of up front.

I've briefly considered if there might be something to remove CO2 inside the bag, but decided against it since this was training equipment so not sealed and probably reused multiple times.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#113

Post by Dirlewanger »

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…

It's Gizmodo. These "news" outlets are largely staffed by comms majors who couldn't find jobs elsewhere. You know that kid at the back of the class that never paid attention or missed half the semester, but somehow barely managed to graduate? Those are Gizmodo/Buzzfeed/etc. writers.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#114

Post by tda »

D_Alex wrote: post #86
tda wrote: post #53

Earlier quoted context omitted.

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...

Simple math will tell you that this increase cannot be due to desalination. Look: Volume of the Persian Gulf = Area (251,000 sq km) * average depth (50 m) = 12,000 cubic km approx. Total amount of desalinated water produced in the world, per annum = 86 million cu. m = 0.086 cu. km, So if all of the world's desalinated water was taken from the Persian Gulf, for 150 years, the salinity would only increase by 0.08*150/1…

Always good to do some math. I double checked your input figure, and that should be per day, not per year. So 365 times as high. Other assumptions being the same that would give 0.2% rise per year, or 4% in twenty years. Not 50%, but not insignificant.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#115

Post by tda »

rjmunro wrote: post #83

> In fact, the study concluded that for every liter of freshwater a plant produces, 0.4 gallons (1.5 liters) of brine are produced on average. I hate that they mix the units here. Why not "for every liter of freshwater a plant produces, 1.5 liters of brine are produced" or "for every gallon of freshwater a plant produces, 1.5 gallon of brine are produced" or even "for every unit of freshwater a plant produces, 1.5 un…

I believe at least some desalination plants add copper and or chlorine to the input water to prevent biofouling. In that case running more water through the plant to produce less concentrated brine would require more chemicals

Re: The Dirty Truth About Turning Seawater into Drinking Water

#117

Post by ryanmercer »

scotty79 wrote: post #71
nickles wrote: post #32

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. "The primary concern with human health in regards to microplastics is more directed towards the different toxic and carcinogenic chemicals used to make these plastics and what…

Still we are talking about ingesting few microscopic particles per day. If they were cyanide it might have been harmful but they are mostly inert undigestible polymer with possibly traces of some additive if they surivived all previous stages of plastics life. Like floating in saltwater for few years or perhaps even already being in digestive systems of some aninals. I wouldn't bother with microplastics in salt. Not…

>Still we are talking about ingesting few microscopic particles per day.

Which is going to increase. Plastic plumbing, plastic containers, plastic clothes, plastic cooking surfaces, plastic in the water, plastic in the salt, plastic in the air, plastic toothbrush bristles, plastic microbeads in body scrubs etc.

Most plastics are effectively forever, they break down into smaller and smaller pieces creating the microplastics. A recent (very small) study found every single person out of the group of 8 had microplastics in their stool, on average about 20 particles for every 3.5 ounces of stool. The study had one test subject per country from Finland, the Netherlands, Poland, Austria, Italy, the United Kingdom, Russia and Japan.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#118

Post by hamilyon2 »

masklinn wrote: post #84
kiriakasis wrote: post #50

Earlier quoted context omitted.

Actual question, how many time can air be breathed? I think you can live on second-hand breath.

I'd be quite dangerous and very uncomfortable: exhaled air contains ~4% CO₂, 16% O₂ and is at roughly 100% humidity. * at 4% CO₂ you'll be suffering from moderate CO₂ toxicity (narcosis, dizzy spells, increased heart rate & blood pressure, mild shortness of breath, exaggerated response to effort) * at only 16% O₂ (but assuming atmospheric pressure), you're well into chronic hypoxia land, not quite sure lethal but not…

Can you please provide sources? I am very interested

Re: The Dirty Truth About Turning Seawater into Drinking Water

#119

Post by alistairSH »

dahfizz wrote: post #101
mcv wrote: post #59

Earlier quoted context omitted.

> 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.

Yup, desalination doesn't require adding "chemicals" to the water. It works using heat, electricity, and osmosis membranes[1]. I'm not sure why the article took the tone that it did. [1] http://large.stanford.edu/courses/2011/ph240/parise2/

Don't they add copper and other chemicals to prevent fouling of the pipes? Not strictly required for desalination, but required to keep the desalination plant running with minimum manual cleaning.

Re: The Dirty Truth About Turning Seawater into Drinking Water

#120

Post by ryanmercer »

yummybear wrote: post #49

Can't this brine be mixed with cleaned sewage water to produce something similar to the original seawater wrt salinity and copper/chloride concentration?

> with cleaned sewage water

You're better off treating the 'cleaned' sewage water for reuse as drinking water, which is being done in many locations.

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