The Dirty Truth About Turning Seawater into Drinking Water

https://earther.gizmodo.com/the-dirty-truth-about-turning-seawater-into-drinking-wa-1831768754

by aceperry • 8 years ago

98 127 8 years ago

earther.gizmodo.com

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• 8 years ago

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?

bryanlarsen4• 8 years ago

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

damon_c• 8 years ago

Put it in big leaky boats that drive around in 1000km radius circles?

wlll2• 8 years ago

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.

simonh2• 8 years ago

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• 8 years ago

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.

twic2• 8 years ago

The estuary from which Maldon sea salt is harvested was also used for cooling nuclear reactors from the '60s until 2002 [1], so microplastics probably aren't even its most interesting feature.

[1] https://en.wikipedia.org/wiki/Bradwell_nuclear_power_station

kaybe• 8 years ago

Well you could probably run an osmosis power station off it. I'm not sure about the efficiency, but it's a viable way to store energy.

https://en.wikipedia.org/wiki/Osmotic_power

w1nt3rmu4e• 8 years ago

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?

pssst• 8 years ago

"While most studies focus on salinity as the primary cause of biological effects, many chemicals are used in the desalination process (e.g. antiscalants, biocides, etc.), some of which can be toxic."[1]

[1] https://www.waterboards.ca.gov/water_issues/programs/ocean/d...

arkades3• 8 years ago

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• 8 years ago

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

geofft3• 8 years ago

This isn't absurd at all. Sea water contains lots of components, not just salt. Many are non-toxic at their current concentration; if you remove the water and pump in the rest into the ocean, you're potentially increasing the concentration enough to make it toxic. It is quite literally toxic waste. And the journalist did you the favor of linking to scientific research that says the same thing.

bryanlarsen4• 8 years ago

"at their current concentration"

So the solution is obvious. Mix 1 part brine with X parts seawater before releasing. Oceans are big, so X can be a very large number, if that is necessary.

Dirlewanger• 8 years ago

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.

arkades3• 8 years ago

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."

nickthemagicman• 8 years ago

Is there any use for it at all?

jpfed• 8 years ago

It's possible to use salt water and limestone to capture CO2; I wonder whether brine could be used for this purpose.

otikik• 8 years ago

I guess you could use it to extract salt - one could place evaporation pools next to the water extraction plant. It would evaporate faster than regular seawater.

endorphone2• 8 years ago

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• 8 years ago

Diluting it with ... fresh water?

mcv5• 8 years ago

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.

mirimir• 8 years ago

True. Basically, the brine is just sea water with some of the water removed. Based on the numbers in TFA, 2.5L of sea water becomes 1.0L of fresh water and 1.5L of brine. And so the brine is just 67% more salty than the sea water was.

And it doesn't seem like diluting the brine with sea water before discharge would increase cost very much. From a 2010 presentation by Carlos Campos ("The Economics of Desalination for Various Uses") I get that seawater pumping and screening accounts for just 2-6% of the energy used in reverse osmosis.[0]

0) http://www.rac.es/ficheros/doc/00731.pdf at p 24

sunstone• 8 years ago

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.

kiriakasis• 8 years ago

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

dredmorbius2• 8 years ago

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

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

frobozz• 8 years ago

Yet somehow, we don't typically do Sylvester Brosch or Holger Nielsen any more. Instead, we favour the direct transmission of exhaled air as a method of artificial respiration.

tim333• 8 years ago

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

pdpi• 8 years ago

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!

manicdee2• 8 years ago

No. You can’t take the dictionary definition, ignore the important word, then claim two things are equal.

Salty water is not water strongly impregnated with salt.

To simplify, the difference between salty water and brine is that brine is very salty water. The concentration of salt completely changes the environmental impact. Dumping post-desalination brine back into the ocean is an environmental disaster.

yetihehe• 8 years ago

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?

arkades3• 8 years ago

2.5 L of water go in.

1 L freshwater comes out of pipe A.

1.5 L wastewater comes out of pipe B.

samatman• 8 years ago

For every 2.5 liters seawater, the products are 1 liter fresh water and 1.5 liters of brine.

falcor84• 8 years ago

That's a good point, but I assume what they meant is that to output 1 liter of fresh water, the plant needs to process ~2.5 liters.

xg152• 8 years ago

I guess, it's more "X gallons of sea water result in Y gallons of drinkable water and Z gallons of brine", where Y=1.0, Z=1.5 and X >= Y + Z.

senectus1• 8 years ago

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

xg152• 8 years ago

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.

simonh2• 8 years ago

If you're wanting to make fresh water there, it's probably because people do actually live there and want to do other stuff there, so any method of polluting the environment is going to have negative consequences.

For example if they are extracting fresh water from seawater, they are probably also already using groundwater as well which your proposal would pollute.

growlist• 8 years ago

Saudi is enormous - no doubt there are vast expanses completely away from civilisation, and I'm guessing there are plenty of remote oil field areas that are already degraded to some extent. However: firstly as you hint at the desert does have an ecosystem, and secondly salt is not the only contaminant in the sea. I could imagine an Aral Sea type scenario where heavy metals, for example, were evaporated out in significant concentrations over time. Then with a little wind blowing the dust towards populated areas, you are in trouble.

loudmax2• 8 years ago

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.

swish_bob• 8 years ago

I think you're underestimating how much of an ecosystem there is in a desert. It's often a fairly fragile one as well.

abalone• 8 years ago

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?

cagenut• 8 years ago

energy

Gupie• 8 years ago

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

aphextron• 8 years ago

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.

loudmax2• 8 years ago

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• 8 years ago

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.

mcv5• 8 years ago

Practically all desalination in existence is powered by fossil fuels, with Israel and Saudi Arabia being the worst offenders.

Sound like really obvious places to use solar.

rocqua3• 8 years ago

Perhaps the issue is that solar farms are more susceptible to sabotage, simply by taking up a much larger area?

Tsubasachan• 8 years ago

Well the US is currently a net producer of oil and gas. The fracking boom is huge- America has more fossil fuels they know what to do with.

Desalination is good for drinking water but its not going to save California's farming though.

foxrob92• 8 years ago

In Western Australia, a desal plant was built a few years ago [0]. At the same time, a wind farm [1] that offset the power use of the desal plant was built.

[0] https://www.watercorporation.com.au/water-supply/our-water-s...

[1] https://en.wikipedia.org/wiki/Emu_Downs_Wind_Farm

csense• 8 years ago

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.

ndnxhs• 8 years ago

Or just mix it with more sea water before releasing it.

tda3• 8 years ago

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...

D_Alex3• 8 years ago

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.

pwagland• 8 years ago

Except that the article you link to explicitly states two opposing theories as to why the salinity is so high, and has risen so much.

The two competing theories seem to be 1. desalination and 2. climate change causing excessive evaporation.

Tepix• 8 years ago

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• 8 years ago

where's the money in that?

/depressed sarcasm/

D_Alex3• 8 years ago

Unfortunately the volumes of "cleaned" brine are just not significant. See my comment elsewhere in the thread.

yummybear• 8 years ago

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

ryanmercer2• 8 years ago

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.

ginko• 8 years ago

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.

mcv5• 8 years ago

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• 8 years ago

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• 8 years ago

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...

nabla92• 8 years ago

Of course you can dilute brine into sea water.

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

pvaldes• 8 years ago

Is a bigger problem in shallow water. At open sea, salt will sink to the next deep water layer with the same density. (Marine organisms are relatively customed to deal with reasonable amounts of salt, the deeper the more customed).

Could be pre-diluted offshore with an unlimited amount of surface sea water available. But if there is more things than salt in the mix, or if we want to just dump it at the sea for saving some dollars, then we are creating a problem.

On the other thing, humanity needs salt, specially in badlands and deserts or in very cold areas. We could just refine, clean and then eat it.

peteretep2• 8 years ago

Different process, but interesting:

https://www.radiotimes.com/news/tv/2018-02-09/blue-planet-vi...

kbutler• 8 years ago

There are no extra chemicals - the brine is just concentrated sea water. The chemicals are present in sea water, they've just been concentrated by removal of 40% of the water.

salty_biscuits3• 8 years ago

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

tempestn• 8 years ago

That sounds like it might be part of a possible solution, but not an easy one.

saagarjha2• 8 years ago

And stop flushing drinking water down the toilet.

What do you suggest using instead?

salty_biscuits3• 8 years ago

Grey water

jaddood• 8 years ago

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_biscuits3• 8 years ago

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

nabla92• 8 years ago

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• 8 years ago

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

jamisteven• 8 years ago

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

mabbo• 8 years ago

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.

peteretep2• 8 years ago

https://en.wikipedia.org/wiki/Tidal_range

rocqua3• 8 years ago

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.

rjmunro• 8 years ago

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.

freeflight2• 8 years ago

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.

twic2• 8 years ago

You could produce a larger volume of more dilute brine by extracting less water per unit of input seawater.

You would need to spend more energy on pumping seawater and brine, but less energy on moving water up a concentration gradient. I have no idea which cost would dominate.

semi-extrinsic2• 8 years ago

You can just dilute with seawater, as discussed elsewhere in this thread.

Nasrudith2• 8 years ago

There is also the concentrate it less option - don't wring out all of the water just what is easy and move onto the next batch vs "supersaturated brine".

No water added just less removed from input - which means more but less potent.

tda3• 8 years ago

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

lawlessone• 8 years ago

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

can we not harvest those?

rajaravivarma_r• 8 years ago

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

The Dirty Truth About Turning Seawater into Drinking Water

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