
Desalination Is Booming. But What About All That Toxic Brine? - georgecmu
https://www.wired.com/story/desalination-is-booming-but-what-about-all-that-toxic-brine/
======
newyankee
Does anyone working in the field know if a 100-1000x reduction in energy
consumption of desalination is theoretically possible - using so called
promised supermaterials based on graphene/nanotubes etc. or some kind of
economies of scale ? Or are we limited by the law of physics here ?

I am really skeptical of promise of materials like graphene because although i
have heard about magical properties for so many years now i have never heard
of practical mass manufacturing completely upending an old school method for
something. May be i am not knowledgeable enough.

This is one of the technologies that is increasingly important for the future
of the earth especially in water poor countries with heavy population.

In the large scheme of things it might turn out cheaper to move population
closer to the coasts, have desalination plants instead of other solutions to
water scarcity assuming renewable energy costs reduce significantly as well
along with a lot of surplus.

~~~
brrt
The current state of the art (reverse osmosis) is already fairly good. The
first link I found [1] demonstrates the increase in efficiency - we're talking
about roughly 3 kWh/m3. I don't recall exactly, but I think that is in an
order of 5 of the theoretic maximum.

At an average, rather immodest level of water consumption per capita (~1580
m3/annum), then this is about ~4740kWh per year, or 13 kWh per day. I'd say
this is significant, but then:

For comparison, current energy use per capita in the USA is 7000kg-oil-
equivalent [2] (or 81000 kWh [3]), so an additional 4740 kWh is about 5%.

The real problem is that people use absolutely indecent amounts of energy and
water and other resources, usually for no good reason at all...

[1]
[https://s3.amazonaws.com/academia.edu.documents/45145253/The...](https://s3.amazonaws.com/academia.edu.documents/45145253/The_Future_of_Seawater_Desalination_Ener20160427-32244-1lwtahi.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1547574667&Signature=weT9blJw2YOThFa7WK1uTsgwZyw%3D&response-
content-
disposition=inline%3B%20filename%3DThe_future_of_seawater_desalination_Ener.pdf)
[2]
[https://data.worldbank.org/indicator/EG.USE.PCAP.KG.OE?locat...](https://data.worldbank.org/indicator/EG.USE.PCAP.KG.OE?locations=US)
[3]
[https://en.wikipedia.org/wiki/Tonne_of_oil_equivalent](https://en.wikipedia.org/wiki/Tonne_of_oil_equivalent)

~~~
buzzdenver
Are those numbers right? 1580 m3/year is 4.3 m3 or 1100 gallons per day.
[http://www.theworldcounts.com/stories/average-daily-water-
us...](http://www.theworldcounts.com/stories/average-daily-water-usage) says
100 to 175 gallons per day per person.

~~~
aqme28
Seems plausible within an order of magnitude. 1 pound of beef takes ~1,800
gallons of water.

~~~
Knufen
Please do not spread this twisted truth.

1\. Those numbers are from all the rain hitting the pasture divided by by the
cows mass (that is eatable)

1.a including whatever it eats

2\. The way it's told makes it seem that none of the water is reused which is
not true Though beef is a water intensive 'crop' it is not as bad as certain
people makes it out to be.

Edit: formatting

------
Simulacra
I think the problem of salt is a much bigger problem than we realize it. It's
toxic, you can't burn it for fuel, and you can't really do anything with it
except store it. Are there other ways of disposing of salt without
repercussions?

~~~
shagmin
I wonder given enough cheap salt, is there a possibility of it being useful
for something? Like at least a cheap building material for desalination plants
in areas where the deserts meet the coast, and the lack of rain would make it
last longer or something.

Or (this might seem crazy) considering Antarctic sea ice is melting at
increasingly faster rates, which isn't good in itself - is that causing the
water at the far south latitudes to be lacking in salinity? Would additional
salt there provide for keeping the ecosystems stable for longer at least?
Granted shipping would be another issue.

The former may require some free market ingenuity, the latter may require some
ingenuity and some sort of goodwill on the part of some governments.

~~~
elialbert
there's a fun kim stanley robinson book gaming out climate change (called 50
degrees below, or in that series anyway) where they dump a ton of extra salt
in the ocean near there for that exact reason. In the book, iirc, it sorta
stalls some bad stuff from happening but doesn't end up being that helpful
long term.

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dbatten
This article talks about newer technologies being "more efficient" in terms of
the brine they produce, by which they seem to mean that you get more fresh
water with less brine production.

How is this possible? Your input has a certain amount of salt and water in it,
right? How do you take out the same amount of water, but leave less salt
behind? Am I missing something?

~~~
mjevans
I believe they're ignoring the concentration of salt in the brine, instead
only counting the volume of 'highly salty water' that is output.

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nanomonkey
I'm curious what the mineral content is of the brine water. There are a few
cyanobacteria, like spirulina, which thrive in alkaline water that other algae
can't handle. One could likely use the run off to process high nitrogen
content sewage water and produce spirulina which could be used for food, oil
and ethanol production.

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StreamBright
What about [http://news.mit.edu/2015/shockwave-process-desalination-
wate...](http://news.mit.edu/2015/shockwave-process-desalination-water-1112)?

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powera
I'm disappointed this article talks so much about brine, and so little about
the even-more-dangerous Dihydrogen Monoxide that is a result of the process.

This is a very bad article - pure FUD.

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makerofspoons
Aquion Energy is making salt water batteries, that could be a good use for
this stuff: [http://aquionenergy.com](http://aquionenergy.com)

~~~
plainOldText
Sadly their FAQ states they’re in the process of rebuilding their business as
a consequence of filing for bankruptcy.

~~~
ip26
I'm still kind of shocked lead acid is faring so poorly when it comes to grid
storage. One of the oldest (the oldest?) battery chemistries, well understood,
really cheap, mostly safe, simple, durable, serviceable, recyclable.
(sidenote, submarine warfare was, for decades, powered by lead acid)

It's chief disadvantages are low power density and low power to weight ratio,
neither of which matter for grid storage.

It just seems to have all the hallmarks of traditional industrial solutions.
But, of course, lithium ion has the same advantage ubiquitous silicon
semiconductors have- massive, massive economies of scale and endless R&D
dollars.

~~~
dzhiurgis
Lead acid doesn't handle (input or output) current so well. Perhaps 5x or so
than lithium.

~~~
ip26
Sure, so you buy more capacity. And since it's like 5x cheaper than lithium...

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lawrenceyan
Use the waste byproduct for molten salt energy storage:
[https://www.maltainc.com](https://www.maltainc.com). Not only efficient, but
profitable even to do so.

~~~
partingshots
Is there any constraint on what types of salt or salt compounds are usable for
energy storage? Or does it not really matter for the most part?

~~~
lawrenceyan
Not really, though a commonly used thermal salt is the eutectic mixture of 60%
sodium nitrate and 40% potassium nitrate, which can be used as liquid between
260-550 °C. Table salt, or sodium chloride, has a melting point of around 800
°C. So it really depends on what attributes your looking for.

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solarkraft
TL;DR No inherent terrible problem, just issues as it scales.

With sea levels rising there's not going to be a global shortage of water.

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CyberDildonics
This article is terrible. It contains lots of exaggerations and conflates all
sorts of problems like the assumption that all energy usage means burning
fossil fuels.

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unchocked
It came from the ocean. Put it back in the ocean.

~~~
lightbyte
From TFA:

>The stuff sinks to the seafloor and wreaks havoc on ecosystems, cratering
oxygen levels and spiking salt content.

>Because this stuff is denser than typical seawater, it sinks to the seafloor
and disrupts vibrant communities of life, which find themselves wanting far
less salt and far more oxygen.

>But brine is more than just hypersaline water—it can be loaded with heavy
metals and chemicals that keep the feedwater from gunking up the complicated
and expensive facility. “The antifoulants used in the process, particularly in
the pretreatment process of the source water, accumulate and discharge to the
environment in concentrations that can potentially have damaging effects on
the ecosystems,” says Jones.

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sandworm101
>> totaling 141.5 million cubic meters a day, compared to 95 million cubic
meters of actual freshwater output from the facilities. Bad news for the
environment, to be sure, but things aren’t altogether dire: Desal tech is
rapidly evolving, so plants are getting far more efficient, both in the brine
they produce and the energy they use.

Bad journalism. Bad science. A desal plant is essentially a brine production
facility. A more efficient plant won't output less salt. It may be less by
water volume but that water will just be all the more salty. This cannot be
avoided short of piling the salt up on the land. Brine is bad, but when mixed
in with the vast volumes of the oceans is a non-issue. All the brine produced
by desal plants is nothing compared to the brine produced by sunlight on the
ocean surface.

>> "But herein lies opportunity: The discharge can also contain precious
elements like uranium."

Ya. Um, that is an entirely different story. Uranium from seawater is a thing
today even without the brine. Some put the amount of natural uranium in
seawater in the billions of tons. Every country in the world suddenly having
ready access to a limitless supply of uranium? Desal might be the least thing
to worry about.

~~~
flavius29663
it's indeed a bad article. Probably newer plants will have to dump their brine
further away from shore, where it's dissipated easier? What is the effect of
the brine on the local ecosystem? Is it on par with the warming of water by
thermal plants? The article raises more questions than it answers.

