The Dirty Truth About Turning Seawater into Drinking Water
earther.gizmodo.com
earther.gizmodo.com
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.
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.
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.
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.
No water added just less removed from input - which means more but less potent.
> 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."
Though I assume you then still have a waste product you need to do something with, and how fast are we going to run out of limestone if we start doing this on a large scale?
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.
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.
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.
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
* 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 far, the hyperventilation from CO₂ poisoning will make this slightly better but nowhere near good
* the combination of hypoxia and CO₂ poisoning will make effort (let alone exercise) possibly to probably lethal
* the extreme levels of humidity will make the entire thing even worse as you'll have a hard time cooling down
You can probably live in this situation for a few days, but the CO₂ levels alone would make it lethal past a few weeks, the combination of all factors means likely no more than a pair thereof, at best.
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.
https://sciencing.com/chemical-composition-exhaled-air-human...
But if you're not breathing on your own, it can save your life. That's what rescue breathing (what used to be called "artificial respiration") is.
There is more than enough oxygen in exhaled air to support life. At least until medical care arrives.
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.
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.
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.
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.
To take truly economically fantastic extremes for current technology if desalination was fiscally cheaper than drilling wells we would see them doing that far more.
Sound like really obvious places to use solar.
Desalination is good for drinking water but its not going to save California's farming though.
[0] https://www.watercorporation.com.au/water-supply/our-water-s...
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.
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.
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.
In that context, it would be shortsighted and naive to pretend it couldn't have any impact at all even on bigger and longer scales.
The two competing theories seem to be 1. desalination and 2. climate change causing excessive evaporation.
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.
My mother used to love sea salt, but recently switched to rock salt.
"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.
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.
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.
[1] https://www.sciencedirect.com/science/article/pii/S026974911...
[1] https://en.wikipedia.org/wiki/Bradwell_nuclear_power_station
I am intrigued to hear how the author plans to take water from sea level then use it to generate hydroelectric energy.
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.
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?
[1] https://www.waterboards.ca.gov/water_issues/programs/ocean/d...
Maybe let's not attack the journalist.
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.
As the article points out, desalinization produces "37.5 billion gallons (142 billion liters) of this salty-ass junk every day." What's your plan for pumping in X times that from the oceans, diluting it, and then pumping it out?
They're already pumping in 37.5B + 37.5*2.5/1.5B gallons of it, so pumping in a multiple of that is just a problem requiring money.
But getting the money to do so requires scaring the public into giving it to them, thus the scare articles like this one in the press.
Also, why do you think that paper does not address the option of pumping in more ocean water and diluting it? (It's paywalled - if you'd like a PDF I can get you one.)
Any problem of providing fresh water for human civilization is "just a problem requiring money." It's not like there is a lack of water on the Earth. So it's kind of silly to pick one single particular aspect (diluting brine) to try to hand-wave away as just a money problem.
In general, money is a significant constraint on engineering and can't be hand-waved away.
For example if they are extracting fresh water from seawater, they are probably also already using groundwater as well which your proposal would pollute.
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.
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.
Probably the sensible answer is to dry it and bury the powder salt.
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...
I don't think salt is something that is in particularly short supply.
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.
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.
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.
https://www.radiotimes.com/news/tv/2018-02-09/blue-planet-vi...
You're better off treating the 'cleaned' sewage water for reuse as drinking water, which is being done in many locations.
Why is this ratio so bad? What would it take to recover more water and produce more concentrated waste that could be managed differently?
/depressed sarcasm/
How does removing water from solution makes more of that solution?
1 L freshwater comes out of pipe A.
1.5 L wastewater comes out of pipe B.
What do you suggest using instead?
can we not harvest those?