Saudi Thirst for Water Is Creating a Toxic Brine Problem | Hacker News Reader

Saudi Thirst for Water Is Creating a Toxic Brine Problem

bloomberg.com

57 pointssystemfreund53 comments

Saudi Arabia had water before their stint as a wheat exporter. You can literally see them drain their country's aquifier into agribusiness:

https://www.indexmundi.com/agriculture/?country=sa&commodity...

Man that ground water took thousands of years to build up and they are draining it in decades. Kinda like oil lol.

From what I understand the the same could be said of the Californian aquifers

> Saudi Arabia’s desalination plants produce about 31.5 million cubic meters of contaminated water each day. That volume of liquid, most of which is pumped back into the ocean, is equivalent to about 20 million barrels of oil a day, or, double the amount of crude it currently produces

I don't understand the math.

31.5e6 cubic meters * 1e3 liters/cubic meter = 31.5e9 liters

31.5e9 liters / 3.78 liters/gallon = 8333333333 gallons

8333333333 gallons / 42 gallons/barrel = 198412698 barrels

So it looks like this calculation is off by a factor of 10. Did I miss something?

I don't understand the equivalence to oil at all -- are they saying that one barrel of this contaminated water has the same environmental impact of dumping a barrel of oil in the water?

I don't really understand the relevance of equating water waste to exports, if it were a nation known for pork exports, would they put the water volume in terms of hogs?

It's an analogy. The average person knows Saudi Arabia exports a LOT of oil. This is 2x a LOT. So a WHOLE LOT.

I dunno if that's a good analogy if the desire is to make it sound huge. If it's a small enough quantity that it can be shipped by tankers (even huge super tankers), that doesn't sound like a lot compared to the size of the ocean.

The average person doesn't know how much a tanker holds.

They know Saudi Arabia = Oil.

  bash$ units
  You have: m^3
  You want: barrels
        * 6.2898108
        / 0.15898729

It seems you're right, yes, should be 200. (Gee, so a cubic metre is ~6 barrels? A 'barrel' is tiny, if that's right, 160 litres or so, much smaller than I imagined.)

The article isn't clear where the metals are coming from. It could be that the desalination process simply concentrates what's already in the seawater.

They add copper as part of the purification process

What's the source? The article says nothing about it, and seawater contains copper and other metal ions all by itself:

https://web.stanford.edu/group/Urchin/mineral.html

Why would they chlorinate the water before desalination? And where does the copper come from?

Apparently it's for prevention of fouling:

> Combined low concentrations of copper (5 μg/l and chlorine (50,μg/l have been effective in preventing both micro and macro-fouling in over 120 seawater installations since 1987.

https://www.researchgate.net/publication/242186534_FOULING_P...

It's also done in freshwater (great lakes) to prevent zebra mussels from clogging the intake pipes. Things like to grow where other things bring food by for free, and are sheltered from predators.

IMO the right direction is not conventional treatment, but as Swebs said, either create new salt flats, or use it as feedstock for algae or other single cell organisms that can be converted to feed, or biofuel.

I'm under the impression that this is just concentrated seawater?

With added copper

That impression is wrong.

Imagine what the extraterrestrial anthropologists will say about humans someday...

Like, what a nice overlords they ended up to be?

Less about that we graduated from savagery, but more how long it took.

"They took a garden and turned it into a parking lot."

"If this is paradise I wish I had a lawnmower"

"It appears plastic-based life forms co-evolved alongside carbon-based life on this body, how interesting, we thought only carbon-based life was possible but there is just so much microplastic with large concentrations in these ancient civilization centers! It also appears they dug up, refined, and relocated the bulk of the uranium and plutonium to this cave system, they must have worshiped it. How bizarre, they could have used this in Snarlsfarogogogog reactors with almost 100% efficiency and only had transmuted metals left as a byproduct. And what is with all of these 'AOL' squares and circles?! This must have been their servant class but there's no discernible means of locomotion"

Unless they are adding chemicals to the water before desalination (which I don't see mentioned anywhere), that sounds like the 'brine' is just ~1.5x concentrated seawater, which will get diluted back again? What am I missing?

The article said the brine has chlorine and copper (added, and remaining).

It says 'about 1.5 liters of liquid polluted with chlorine and copper are created', but doesn't explain if these are additives or some kind of byproduct.

Even if it's just extra salty it's still a local problem. You can't just dump it all in the ocean because it would still kill everything. You'd need to dump it out slowly or over a much wider area for the concentration not to be harmful. It's like a polluted river killing everything where it dumps out even if the amount of pollution is inconsequential overall.

Someone correct me if I'm wrong (not the best at math), but the ocean is massive. The entire amount of brine they mention (31.5 million cubic meters) fits in one 300m square cube. Even if you drop it in an enclosed 1km-wide area of seawater, it will barely increase concentration by 0.01%. It would take millenia for us to increase sea salinity by this method, and all that treated water is eventually coming back.

Even if you took the total daily water consumption of the entire human race - 150l per person * 7 billion, or 1^12 liters, and made it extra salty, it is dwarfed by the total of 1.26^21 [mostly sea]water on earth.

This would be harmless assuming we are not adding anything to the byproduct, which unfortunately seems to be the case according to the other comments.

The concern is not ocean-level damage through the salt directly but in localized ecological system destruction. The mangrove forest encompases a tiny portion of the ocean overall but removing this forest affects a large portion of sealife. The creation of 'deadzones' through salinity will have knockoff effects elsewhere that cannot necessarily be predicted.

At worst these dead zones would be tiny. They could dilute the waste stream by dumping it into the local sewage system, but I don’t think that’s going to change much.

It’s on the order of building a mall parking lot. Sure bad for the local ecosystem, but we have vastly larger issues.

It's going to be dumped near the shoreline, where sea life is very different from what is supported in the open ocean. If the shoreline is made uninhabitable, the marine life there might not have anywhere else to go.

Near in this case would need to basicly be directly into. Actual desalination plants don’t do this.

Further by parking lot I mean an actual parking lot. Dump it even 1000 feet from the shoreline and you would have trouble detecting the extra salt in the surf.

There are over 7500km of shoreline in Saudi Arabia, so marine life can move along the coast away from the salt water outlets.

Shoreline is also highly variable and localized, and effects to the shoreline have staggering effects even if the region affected is small. I'd recommend looking at mangrove forests, coral reefs, and the mouths of rivers.

The local sewage systems can't deal with volumes this large. The sewage systems of the entire UK, population 66 million, deal with about 11 billion liters per day:

https://assets.publishing.service.gov.uk/government/uploads/...

Saudi Arabia, with a population of only 33 million, isn't going to have sewage systems sized to accommodate 31.5 billion liters of waste brine.

You would mix after the sewage treatment, simply placing the pipes next to each other would work.

As to impact the quality of brine is less important than the amount of surplus salt. Sea water is ~3.5% salt. You need 1:1 fresh water produced to get back to the default at discharge. While a significant fraction of the water produced would be lost as evaporation etc, desalination is not their only source of water.

Edit: Digging into the numbers it looks like Saudi Arabia is not limiting things to cities which have a closer relationship between water and sewage production.

Dissolution takes time. If we’re to dump the extra salty water off the coast, it would be hard to create an area of higher salinity.

Of course over time it would dissipate and barely change the salinity is the ocean.

How about dumping it into a shallow pit and letting the water evaporate, creating new salt flats.

>Saudi Arabia emits 31.5 million cubic meters of liquid effluent a day

You'd need some massive pits and you'd have to displace way more than 31.5 million cubic meters of soil as it isn't all going to evaporate in a day. Ideally you'd want really shallow pools so you'd eat up an insane surface area.

For some reference an Olympic sized swimming pool is about 2,500 cubic meters so you'd need 12,600 (pools) just to hold one day worth of the contaminated water.

For a fun little compassion (that amuses me and might someone else) it is estimated that all of the silver ever mined adds up to about 166,375 cubic meters Source: https://www.usgs.gov/faqs/how-much-silver-has-been-found-wor...

And only about 8000 cubic meters of gold has been mined. Source: https://www.jmbullion.com/investing-guide/james/gold-supply/

Edit: derpity-derp-derp fix

Couldn't they just run a big pipe out into the middle of the desert and pump it there? Maybe they could create giant salt flats and extract rare earth elements from them, even...

Wait. Do you mean a cube of silver|gold that's 55|20 meters on one side, as in the width of the cube and not its volume? As in 55^3 = 166,375 m^3 of silver, and 20^3 = 8000 m^3 of gold? That 5.36m diameter cube illustration representing a single year's gold production in the source is already 154 cubic meters.

A cube 55 meters on a side, not 55 cubic meters. That's a huge difference: 166K+ cubic meters

the copper will be an issue.

So call it a copper mine instead of a salt flat?

it's not a copper mine except in the sense that it has contaminated, zero-value output as a side effect.

At 35 degrees Celsius (308 K, 95 F), it takes about 44 kilojoules to evaporate 1 mole of water [1]; at 55.6 moles/liter, that's 2.4 megajoules per liter.

Averaged over a year, the energy available to evaporate water over a given area is roughly equal to insolation from the sun. Saudi Arabia has excellent solar resources averaging 2200 kWh/m^2/year [2], e.g. 6 kWh/m^2/day, e.g. 21.7 MJ/m^2/day. With perfect sunlight absorption you could evaporate 9 liters per m^2 of evaporation-pit per day.

They're currently discharging 31.5 billion liters of liquid per day, per the article. That translates to about 3,500,000,000 m^2 (3500 square kilometers) of pit area. So that's probably one reason why nobody deals with desalination brine this way. It would require very large evaporation pits even if you have excellent sun levels to evaporate the waste. It seems like it would be technically possible in SA, as they have a low population density and lots of unused land, but it sounds expensive. Some countries that rely on desalination, like Israel, don't have the spare land area even in theory.

[1] https://en.wikipedia.org/wiki/Enthalpy_of_vaporization#/medi...

[2] https://www.sciencedirect.com/science/article/pii/S101836391...

Nice analysis! Three things to consider:

I don’t think you can just look at insolation over a given area. Wind and even the cooling itself will cause the air over the area to redistribute with warmer dryer air that can continue picking up water.

Besides that it’s more important to consider how saturated the air in the region is. If it can hold more water it will.

Other things to consider

Some of the water would seep into the ground instead of waiting around to evaporate. Maybe there are ways to speed that up too.

Finally Another option is the spay the water into the air to speed up evaporation a bit.

I considered mentioning wind from warmer neighboring regions but at this scale you are basically remaking geography, so I wouldn't count too much on said winds reaching the middle of your evaporation ponds. ("Manmade shallow hypersaline lakes", rather than ponds, at this scale.)

Seepage into the ground -- good point. If there is existing groundwater, seepage would taint it. If there is no existing groundwater, but ground is permeable, that helps.

Spray water into air? That costs more energy. Just waiting for natural evaporation is nice because it doesn't require any more human-added energy.

Of course you'd want to analyze more than the One Big Factor if you were pondering implementing this in practice. But I think that the one-factor approach illustrates why this hasn't been an "obvious" disposal solution for waste brine.

See the nice photos here:

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

It's from anti-fouling and general corrosion. Not sure what makes these plants special though since a population's regular water supply infrastructure would end up producing the same type of waste from pumps and what not.

> which will get diluted back again

Also raising the concentration of salts in the oceans, especially in the immediate area where they're dumping it back into the ocean in the gulf that has weak ocean currents (due to being a gulf). I can't imagine the wildlife will enjoy that much. It also makes it harder for future desalination, as it's having to desalinate an ever increasing percentage of salt since they just dump it back into the ocean.

https://www.scientificamerican.com/article/desalination-brea...

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