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The Dirty Truth About Turning Seawater into Drinking Water
- bryanlarsen 8y agoThe 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 8y agoWhat 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 8y agoSeawater (edit: and air, too. one of the problems is the brine has little dissolved oxygen).
- damon_c 8y agoPut it in big leaky boats that drive around in 1000km radius circles?
- wlll 8y 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.
- simonh 8y agoSea 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 8y agoI 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 8y 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. "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
- w1nt3rmu4e 8y 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 8y 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/desalination/docs/dpr051812.pdf https://www.waterboards.ca.gov/water_issues/programs/ocean/d...
- arkades 8y agoI 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 8y agoHe should not call something "salty-ass junk" if he wants his "work" to be respected.
- geofft 8y agoThis 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.
- 8y ago
- arkades 8y agoJust 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 8y agoIs there any use for it at all?
- jpfed 8y agoIt's possible to use salt water and limestone to capture CO2; I wonder whether brine could be used for this purpose.
- mcv 8y agoThat would be really interesting. Two birds with one stone: clean water and capture CO2. 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?
- otikik 8y agoI 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.
- endorphone 8y ago
- yetihehe 8y 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?
- arkades 8y ago2.5 L of water go in. 1 L freshwater comes out of pipe A. 1.5 L wastewater comes out of pipe B.
- samatman 8y agoFor every 2.5 liters seawater, the products are 1 liter fresh water and 1.5 liters of brine.
- falcor84 8y agoThat'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.
- xg15 8y agoI 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 8y agohuh I always wondered about what they did with it. especially now that plastics are showing up in a lot of table salts...
- xg15 8y agoStupid 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.
- simonh 8y agoIf 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 8y agoSaudi 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.
- loudmax 8y agoI 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.
- deleted 8y ago[deleted]
- abalone 8y agoIt’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?
- aphextron 8y agoI’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 8y agoCarbon 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 8y agoMost 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 8y agoI’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.
- csense 8y agoSure, 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 8y agoOr just mix it with more sea water before releasing it.
- tda 8y agoThat 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/43493/dispute-over-cause-of-persian-gulf-salinity https://financialtribune.com/articles/people-environment/434...
- D_Alex 8y agoSimple 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.
- freeflight 8y agoIt doesn't need to be responsible for all of the change, it might only be one among many contributing factors like climate change. 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.
- deleted 8y ago[deleted]
- Tepix 8y agoI 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.
- yummybear 8y agoCan't this brine be mixed with cleaned sewage water to produce something similar to the original seawater wrt salinity and copper/chloride concentration?
- ryanmercer 8y 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 8y agoI 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.
- mcv 8y agoI 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 8y agoYou 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 8y agoThis 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-energy-storage https://www.solarreserve.com/en/technology/molten-salt-energ...
- saagarjha 8y ago> 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 8y agoBut 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?
- salty_biscuits 8y agoEasy solution, use brakish water or sewage for desalination rather than sea water. Not difficult. And stop flushing drinking water down the toilet.
- tempestn 8y agoThat sounds like it might be part of a possible solution, but not an easy one.
- saagarjha 8y ago> And stop flushing drinking water down the toilet. What do you suggest using instead?
- salty_biscuits 8y agoGrey water
- jaddood 8y agoSewage 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 8y agoNo 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
- jcobber 8y agoI guess they didn't think of the byproduct when designing this. Question is, why didn't they add this on the lifecycle assessment, I'm sure they know from the start that there is a byproduct. How to handle this waste, ergo, toxic waste should've been treated as an important part of the process.
- nabla9 8y agoThis 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 8y agoIn Southern California I think the plans are to mix the brine discharge with the treated sewage outflow.
- jamisteven 8y agoSounds like they just need to find a good use case for brine, turn it into some kind of fuel or additive.
- mabbo 8y 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.
- peteretep 8y agohttps://en.wikipedia.org/wiki/Tidal_range https://en.wikipedia.org/wiki/Tidal_range
- rocqua 8y agoA 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 8y 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.
- freeflight 8y 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.
- twic 8y agoYou 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-extrinsic 8y agoYou can just dilute with seawater, as discussed elsewhere in this thread.
- kup0 8y agoDoes 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.
- lawlessone 8y ago> The high concentrations of salt, as well as chemicals like copper and chlorine, can we not harvest those?
- rajaravivarma_r 8y agoThe ever dreamed of space slingshot seems to be the only safest, everlasting option to dispose brine.
- deleted 8y ago[deleted]