
The Dirty Truth About Turning Seawater into Drinking Water - aceperry
https://earther.gizmodo.com/the-dirty-truth-about-turning-seawater-into-drinking-wa-1831768754
======
rjmunro
> 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 units of brine are produced"

Also, producing more brine would make the brine less concentrated and less
harmful - it would be better not worse.

~~~
freeflight
> Also, producing more brine would make the brine less concentrated and less
> harmful - it would be better not worse.

Producing more brine, by diluting it, still would require something to dilute
it with.

The most obvious, non toxic, choice would probably be water, but the whole
exercise is about getting water in the first place.

~~~
semi-extrinsic
You can just dilute with seawater, as discussed elsewhere in this thread.

~~~
kup0
Does diluting it with seawater (after which I assume it is returned to the
sea?) result in an endlessly increasing salt level in the seawater, over a
long period of time, that will reach a dangerous level at some point?

Edit: I realize my naivety now. Other comments mentioned the desalinated water
(at least some of it) will end up back in the sea eventually, so that would
maybe counterbalance such a concern.

~~~
manicdee
The short term effects are increased salinity and reduced oxygenation for
water in the immediate vicinity of the desalination plant, which is enough to
drastically alter the biome (aka “kill all the sea life”).

------
arkades
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.

> “Brine underflows deplete dissolved oxygen in the receiving waters,” said
> lead author Edward Jones, who worked at the institute and is now at
> Wageningen University in the Netherlands, in a press release. “High salinity
> and reduced dissolved oxygen levels can have profound impacts on benthic
> organisms, which can translate into ecological effects observable throughout
> the food chain.”

It's an actual waste product that has to actually be responsibly handled. It's
not "just the salty water from the ocean that we can dump back in however we
want."

~~~
endorphone
_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 is simply
diluting it before discharge, ensuring that the salt content isn't high enough
that it sinks and forms a brine pool.

~~~
Jeff_Brown
Diluting it with ... fresh water?

~~~
endorphone
You churn it with a large volume of sea water and then discharge it when the
salinity is only acceptably above the natural amount. I believe France limits
it to 10% above the natural salinity.

e.g. take 3 gallons of sea water and extract 1 gallon of fresh water. You have
2 gallons of +50% salinity brine. Churn it with 8 gallons of seawater and
you're back to +10% salinity. Wash it out into the ocean.

------
aphextron
I’m surprised this article mentions nothing about energy. Practically all
desalination in existence is powered by fossil fuels, with Israel and Saudi
Arabia being the worst offenders. The only reason it’s even economically
viable is the externalized cost of carbon emission. It’s simply not a long
term tenable solution until this is addressed.

~~~
loudmax
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 to convert existing plants to non-fossil fuel sources is another matter.
But at least from an engineering perspective there is a way forward.

What I get out of the article is that disposing of brine is an ecological
hazard. This shouldn't really be a surprise since any engineering effort at
large scale is going to have some kind of environmental impact, but this is a
new consideration for those of us who don't work in the industry and hadn't
thought too deeply about the process.

~~~
beagle3
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 desalinated continuously -- and that's something which makes sense in
general, possibly grid scale as storage technology improves, regardless of the
specifics of water desalination.

~~~
adamcharnock
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.

------
nabla9
This is not a show stopper. If you discharge brine into the sea, you should
have to have a plan to dilute and mix brine.

High concentration brine does not automatically mix into the sea water. The
underflow goes into the bottom of the sea and forms a separate layer. But you
can use nozzle diffusers, mixer etc. and discharge into high currents.

~~~
Gibbon1
In Southern California I think the plans are to mix the brine discharge with
the treated sewage outflow.

------
csense
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 beaches, fisheries and reefs?

Maybe have an additional pump to send fresh seawater into the areas of highest
concentration, basically set up a countercurrent exchange gradient.

I'm sure there are trivial, low-cost engineering solutions to this problem.

~~~
tda
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...](https://financialtribune.com/articles/people-
environment/43493/dispute-over-cause-of-persian-gulf-salinity)

~~~
D_Alex
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*150/12000 = 0.1%,
roughly.

Edit: the entire article is bad, and the headline is sensationalist bullsh#t.

~~~
tda
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.

~~~
D_Alex
You are right, thanks for pointing this out. I hate making mistakes like that.

------
wlll
> At the very least, we should be treating the brine so it’s safe to discharge
> into the ocean.

This amused me as I pictured people mixing newly produced fresh water with the
brine and releasing this "new" seawater back.

Seriously though, I guess I assumed people were at least turning this stuff
into salt. I watched a documentary on salt production (Italy I think) and they
just got sea water and evaporated it in huge salt beds.

I kind of assumed the sea salt (Malden) I buy has been created using the same
process.

~~~
simonh
Sea salt has it's own problems due to it's microplastics content. Around 90%
of domestic sea salt contains microplastics and the average adult consumes
around 2,000 microplastic particles as a result every year. People who go out
of their way to buy sea salt presumably ingest significantly more on average.

My mother used to love sea salt, but recently switched to rock salt.

~~~
zaarn
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.

~~~
nickles
> 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 they carry. It has also been thought that
microplastics can act as a vector for pathogens as well as heavy metals. More
specifically, pregnant women in particular are in danger of causing birth
defects to male infants such as anogenital distance, penile width, and
testicular descent. This comes from phthalate exposure and DEHP metabolites
that interfere with the development of the male reproductive tract."

"Another dangerous ingredient is called Tetrabromobisphenol A (TBBPA) which is
a flame retardant in many different types of plastics such as those used in
microcircuits. This chemical has been linked to disruptions in thyroid
hormones balance, pituitary function, and infertility. The endocrine system is
affected by TBBPA through disruption of the natural T3 functions with the
nuclear suspension in pituitary and thyroid."

"Many people can expect to come in contact with various types of microplastics
on a daily basis in the aforementioned sources (see sources). However, the
average citizen is exposed to microplastics through their various types of
food included in a normal diet. For instance: Salt. Researchers in China
tested three types of table salt samples available in supermarkets and found
the presence of microplastics in all of them. Sea salt has the highest amounts
of microplastics compared to lake salt and rock/well salt."

Even if we ignore the environmental impact, there's ample evidence to indicate
we should not dismiss the dangers of microplastics to human health without
further research.

[0]
[https://en.wikipedia.org/wiki/Microplastics](https://en.wikipedia.org/wiki/Microplastics)

~~~
scotty79
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 when I'm exposing my blood
directly to mixture of hydrocarbons and soot with every breath I take.

~~~
ryanmercer
>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.

~~~
scotty79
I'm just saying there are bigger concerns right now. Such as air quality.

------
mabbo
> how about generating electricity with hydropower

I am intrigued to hear how the author plans to take water from sea level then
use it to generate hydroelectric energy.

~~~
rocqua
A while back in the Netherlands, there was a plan to use the saline gradient
between salt and fresh water as a battery. It was briefly in the news, and
then I never heard anything, but perhaps that is the idea?

The energy from desalination goes into creating a fresh-salt gradient. It
stands to reason that some of that energy could be recovered from the gradient
between the brine and the sea water.

------
w1nt3rmu4e
> 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
water is absurd.

What is with journalism today?

~~~
arkades
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.

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

------
xg15
Stupid question: Being that a large fraction of the problematic plants seem to
exist close to or within desert countries, couldn't you simply pump it into
the desert? I figure, if you find an appropriate area, you'll have not much of
an ecosystem to destroy anyway and the area could eventually function as an
enormous evaporation pond.

~~~
loudmax
I think the issue is the scale of the operation. It's not that the desert
doesn't have the capacity to absorb brine, it's that pumping all that brine
into one spot creates a local ecological catastrophe. To avoid a concentration
of toxins you need to spread it around, which is expensive.

My expectation is that the brine will have to go back into the ocean. The
deserts a big, but the ocean is bigger. What the paper mentioned in the
article points out is that you can't dump this all in one place.

------
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.

~~~
JulianMorrison
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.

~~~
jamesholden
This is what I thought too. Why not dump them out into long shallow 'trays'
which can then dry out in the sun, leaving behind just the salt, which can
then be stored/used/disposed of.

Also, I am not an expert.. but, couldn't we use the leftover salt for energy
storage?

[https://www.solarreserve.com/en/technology/molten-salt-
energ...](https://www.solarreserve.com/en/technology/molten-salt-energy-
storage)

~~~
saagarjha
> Also, I am not an expert.. but, couldn't we use the leftover salt for energy
> storage?

I don't think salt is something that is in particularly short supply.

~~~
lifeformed
But wouldn't having it in a stable form as a mountain of salt be a decent
storage solution? Or would the volumes produced be quickly untenable?

~~~
kijin
The mountain of salt will have a mass of at least 3.5% of the total amount of
water you produce. It will be a lot more than that if you only use some of the
water and let the rest evaporate.

For example, Israel produces more than 1 million tonnes of fresh water per
day. That's 35,000 tonnes of salt, or 16,000 cubic meters -- enough to cover a
football field to a depth of 3 meters -- every single day.

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

~~~
ryanmercer
> 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.

------
abalone
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?

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

------
bryanlarsen
The desalinated water will end up back in the oceans eventually, so should the
brine. Of course you can't just dump it back in directly, but if diluted and
released responsibly, the ocean is the right place for the brine.

~~~
CamTin
What do you dilute it with? You just spent a bunch of time and energy
seperating water from it. I guess we should ship/pipe the brine to wastewater
treatment facilities, and mix it with the treated waste before discharging it
back into the ocean/river?

~~~
bryanlarsen
Seawater (edit: and air, too. one of the problems is the brine has little
dissolved oxygen).

------
Tepix
I see this as an opportunity. Before you dilute the brine with sea water and
pump it back into the ocean, ideally you remove the microplastics and perhaps
some other problematic substances and thus clean up the ocean.

~~~
Arn_Thor
where's the money in that?

/depressed sarcasm/

------
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.

------
yetihehe
> 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.

How does removing water from solution makes more of that solution?

~~~
arkades
2.5 L of water go in.

1 L freshwater comes out of pipe A.

1.5 L wastewater comes out of pipe B.

------
salty_biscuits
Easy solution, use brakish water or sewage for desalination rather than sea
water. Not difficult. And stop flushing drinking water down the toilet.

~~~
jaddood
Sewage contains other volatile products that would evaporate and condense
along with water. Cleaning sewage water for use in drinking is probably much,
much harder than doing it with just sea water.

~~~
salty_biscuits
No it really isn't. Most people just think it is disgusting. It is less energy
intensive than sea water.

[https://en.wikipedia.org/wiki/NEWater](https://en.wikipedia.org/wiki/NEWater)

------
senectus1
huh I always wondered about what they did with it. especially now that
plastics are showing up in a lot of table salts...

------
jamisteven
Sounds like they just need to find a good use case for brine, turn it into
some kind of fuel or additive.

------
rajaravivarma_r
The ever dreamed of space slingshot seems to be the only safest, everlasting
option to dispose brine.

------
lawlessone
> The high concentrations of salt, as well as chemicals like copper and
> chlorine,

can we not harvest those?

