12 ms·
> In the meantime, the leftover salt continues to circulate through and out of the device, rather than accumulating and clogging the system. I don't want to de
by davideg 3y ago
> In the meantime, the leftover salt continues to circulate through and out of the device, rather than accumulating and clogging the system.
I don't want to detract from the innovation of this, however my understanding is that one of the largest unsolved problems with desalination is what to do with the waste product: usually incredibly salty brackish water. Dumping it back into the ocean can be disruptive to the local ecosystem.
A quick search turned up this Scientific American article about the issue: https://www.scientificamerican.com/article/slaking-the-worlds-thirst-with-seawater-dumps-toxic-brine-in-oceans https://www.scientificamerican.com/article/slaking-the-world...
"The excess salt decreases dissolved oxygen in the water, suffocating animals on the seafloor"
"In addition to harming sea life, extreme salinity also makes desalinating the water more difficult and expensive."
- BurningFrog 3y agoMy controversial take is that the best solution will be to accept that solving the drinking water problem for people is worth worsening the environment for some local sea life.
- SonicScrub 3y agoThat local sea life also provides humans with food. So even with the human-centric viewpoint, we have a strong incentive to solve this problem.
- missedthecue 3y agoA poorly implemented runoff would nuke a square km or five of ocean floor with high salinity waste. It would not impact food supply in any discernable way. The ocean is simply too big.
- mikeymz 3y agoWhich ocean? People used to think this about raw sewage discharge. Check the state of UK beaches
- onion2k 3y agoThat's impacting people who want to swim or surf in the sea. It's not impacting food supplies. Fishing boats operate much farther out.
- concordDance 3y agoDid so in person a couple of weekends ago. Looked fine, don't know what you're talking about.
- raducu 3y ago> poorly implemented runoff would nuke a square km or five of ocean floor with high salinity waste. So what is the problem then? We only need to lay pipes to ocean floors that are already not that lively?
- nonethewiser 3y agoWell no, that does not describe the local sea life everywhere.
- MBCook 3y agoWhy does that have to be the solution? Why not further concentrate it through evaporation? Then take that and pour it into old salt mines or spent oil wells? Or natural gas wells?
- Magiccupcake 3y agoFurther concentrated salt solutions deposit in the device, clogging it causing it to not work. You could harvest the salt, but then it is no longer passive.
- ranguna 3y agoThen don't concentrate it on the devices. Dump the water on a drying pool and extract the salt afterwards.
- djtango 3y agoIronically we'd probably need some amount of water to then purify the salt from the other random stuff
- 6510 3y agoNeed distilled water, luckily we were just making that.
- j16sdiz 3y agoYou are underestimating the volume. In that volume, you need a large drying pool.. which is no better than a parking lot.
- nielsbot 3y agocan we just pile it up into a huge salt mountain? and maybe eat some of it?
- imgabe 3y agoOr just sell it as salt? We use, I don’t know, billions of pounds of salt per year in food production?
- comboy 3y agoI don't think humanity is ever really considering environmental impact unless it impacts it somehow. We care about disappearing species which amuse us, which we can see at our scale level, not much below. Some rare lion? Tragedy! Thousands species of fungi living underground which don't impact us directly? Irrelevant. Same goes for climate change and others. We only care if it impacts us in any way, even if only our entertainment. So long story short we probably care about sea life.
- cf141q5325 3y agoIs turning it into a solid too energy consuming? The main problem seems to have been it clogging up the multi stage system. If you can dump it you should be able to turn it into a solid in a separate setup.
- 20after4 3y agoSalt is very hydrophilic, I believe this means that it's very difficult to get the last bit of water out. Further, if you leave dry salt out in a humid environment and it naturally pulls humidity out of the air.
- cf141q5325 3y agoIt collects on top though. Fleur de sel is made that way i believe. You arguably dont need to get all the water out of there as long as you have a steady stream of water with high salt content coming in. Much of the price of that is coming from not breaking the formed patterns during harvest.
- thomasahle 3y agoPour it out in the desert?
- zdragnar 3y agoMost deserts are inhabited by endangered or threatened species. There aren't actually a lot of deserts so lifeless that you could avoid environmental activists getting in the way, at least not in the US.
- midoridensha 3y agoUS deserts are full of life; they're very far from lifeless. They're nothing like the endless sand dunes we envision when we think of the Sahara desert, Saudi Arabia, or the planet Arrakis.
- willis936 3y ago
- scythe 3y agoOne possibility I have been thinking about is to locate desalination in an area with extreme tidal variation, particularly the northern Gulf of California (which coincidentally happens to be in a very thirsty region), where natural flows might be sufficient to disperse the brine. I have seen various studies talking about tidal currents dispersing brine but I haven't heard of any evidence that you can take advantage of highly tidal bays.
- jules 3y agoEverything we do affects the environment. Locally making the ocean a little bit saltier by removing water and not removing salt sounds like a very minor problem.
- cplusplusfellow 3y agoSeems like we could also just add it to the other places where water is flowing into the ocean. Do we not disrupt the ocean ecosystem with our fresh water runoff?
- steve_adams_86 3y agoFreshwater runoff is normal. The continents and the sky dump freshwater into the oceans constantly at very high volumes.
- toast0 3y agoIf you had a lot of fresh water runoff, you might use that fresh water for drinking rather than desalinating seawater though. But... If you are using this water for drinking, it's going to come back through the sewage system, and maybe you can dilute the brine with outflows from local sewage treatment plants. Depending on details, the combined outflow could be more or less salty than the seawater input to the desal plant.
- CydeWeys 3y agoOnly some of it comes back through the sewage system. A lot of it just ends up lost to evaporation, or being incorporated into products. Think about your typical use of water to irrigate farmland (which is the majority use of water in many places); you don't really get any of that back as freshwater discharge at all. If you did, that means they're irrigating too much to the point that they're flooding their fields and causing runoff.
- toast0 3y agoSure, but do people really pay desal prices to irrigate fields? Also, a lot of places are using desal to augment other supplies. If you've got 15% of your municipal water supply coming from desal, sewage treatment outflows should be significant compared to brine.
- iamthemonster 3y agoThe salinity is normally only increased by a factor of four (assuming a 25% reject ratio) so just be aware that brine discharge is a very highly localised environmental issue, it doesn't spread too far. I wouldn't call it an unsolved problem necessarily. We probably disrupt the ecosystem more when we build a parking lot.
- local_crmdgeon 3y agoThat's not a great example - surface parking lots and their runoff are fucking horrible for the environment
- SamBam 3y agoSo, it's probably a good example then, since we currently accept the building of parking lots. The point is, people are always writing letters to the editor and what-not when some green tech has some environmental impact, far more than they do over their city making another parking lot or any of a million other things. I assume it's because it triggers some notion of hypocrisy. c.f. wind turbines and dead birds. How about we put our energy into fighting cars and parking lots first, before we worry about solar-powered desalination that could potentially save the Western states from the over-extraction of water that's turning them into dust bowls?
- NavinF 3y agoI'm not going to lose any sleep over that. Permeable concrete exists, but it's just not worth the maintenance cost in most places https://en.m.wikipedia.org/wiki/Pervious_concrete https://en.m.wikipedia.org/wiki/Pervious_concrete
- winter_blue 3y agoThat's pretty cool. Personally, I'd prefer small roads and outdoor parking lots to be au naturel unpaved. Zero construction cost, and I imagine the maintenance cost is just trimming grass.
- iamthemonster 3y agoCheck out the pictures of the brine discharge diffuser at this desal plant in Western Australia: https://www.watercorporation.com.au/Our-water/Desalination/Perth-Seawater-Desalination-Plant https://www.watercorporation.com.au/Our-water/Desalination/P...
- mattclarkdotnet 3y agoThis plant helps Perth (a city of 2m people) get over half of its fresh water from desalination. We used to get most of our fresh water from the local aquifer and from dams, but this was totally unsustainable. The water table has been recovering over the past 10 years, and is on track to recover to pre-invasion levels in the next decade. By which time we should be at over 90% renewables for power too! Quite proud to be a West Australian really.
- midnitewarrior 3y ago> Dumping it back into the ocean can be disruptive to the local ecosystem. I question this as being a problem. The ocean is saturated with the salts that are exposed on the sea floor. When there is too much salt in a solution, the excess will precipitate as solids. As the ocean is already exposed to more salt than it can put into solution, I don't think this would cause a serious issue.
- willis936 3y agoThis is not true. https://en.wikipedia.org/wiki/List_of_bodies_of_water_by_salinity https://en.wikipedia.org/wiki/List_of_bodies_of_water_by_sal...
- justinclift 3y ago> As the ocean is already exposed to more salt than it can put into solution ... Haven't heard of that before. Wouldn't it mean there are underwater areas carpeted in salt crystals?
- ericjmorey 3y agoIt's been demonstrated as an actual problem with currently functioning desalinization operations.
- dclowd9901 3y agoWhy can’t we just eat it?
- kvdveer 3y agoFor the same reason we can't drink seawater: there is too much salt in it. The recommended water intake for a human is ~2kg, the recommended salt intake is ~2g. That's 0.2%, seawater has 1.5%. After you'd have eaten your share of salt, there is some leftover. You can't have someone else eat it, because then you'd also need more water. You could try to export it, but that requires quite a bit of extra processing, and the global demand for salt isn't high enough to pay for the transport costs.
- RetroTechie 3y ago2g/2kg = 0.1% not 0.2% And seawater has ~3.5% salt content by weight, not 1.5%
- mlyle 3y agoThis device is small-scale for individual families and small off-grid communities. It's solar powered and passive. There's limitation on the salinity of the brine because you don't want to accumulate in the device. My impression is that this is not going to be a very big problem.
- mostertoaster 3y agoThere are always trade offs. As someone who has essentially unlimited access to clean drinking water, I might not feel the trade off is worth it. But if I was someone who didn’t have a superabundant supply of clean drinkable water, I’d probably say to hell with the sea life.
- tfourb 3y agoUntil you notice that in some indirect way your life livelihood (or that of others in your community or some other actor with influence) does depend on that sea life. People are really quick to argue for the seemingly simple fix when interacting with complex systems. It rarely works out in the long term.
- robertlagrant 3y ago> It rarely works out in the long term. How've you determined this?
- tfourb 3y agoSource: climate change. It was really nice to emit a lot of carbon for a few decades, now it begins to cause real problems, conflicts and costs. Technical innovations should not simply assume that negative externalities are „fine“. Innovators should have to assume the burden of identifying and resolving the externalities before widespread distribution of the innovation.
- robertlagrant 3y ago> Innovators should have to assume the burden of identifying and resolving the externalities before widespread distribution of the innovation. Based on what timescale, though? We can only work with what we know about. E.g. until Radium was deemed highly unsafe, it was deemed safe. No one paints Radium onto watch hands any more because we discovered that that's a terrible idea. Or, it might turn out in 30 years that CO2 has a large positive effect on re-greening the Earth, and all those low CO2 innovations were harmful. In other words: I don't understand how your statement makes sense without hindsight, and I don't understand how any innovation can happen if hindsight (that is based on that innovation happening) is its prerequisite.
- tw04 3y agoWhy not sell the brine for lithium extraction?
- kvdveer 3y agoAfter lithium extraction, there's still a brine with roughly the same salt concentration, but likely with more other pollutants. You'd just be kicking the problem down the road.
- tw04 3y agoBut the issue is dumping the brine into the ocean as the only economical way to deal with it. If someone can make a significant profit off the brine, it may be feasible to truck it to a lithium facility then deal with disposal in a way that isn't just "dump it in the ocean and pretend it's not a problem".
- doikor 3y agoCan’t you just dilute it with more sea water? Basically before releasing it back mix it with sea water at 1:10 or 1:100 ratio and it should not make that much of a difference. And make the outlet pipe quite far away from the inlet directly into a current if possible so it will mix with the rest of the sea.
- umvi 3y agoDump it in the great salt lake in Utah
- deleted 3y ago[deleted]
- somecommit 3y agoThere is a plan made by Israel and Jordan to bring water from the red sea to a desalination plant, and dump the leftover in the dead sea, it's like the perfect solution
- wolverine876 3y agoThanks for posting a substantive examination of the issue. The first engineering question always is, I wonder how the tradeoffs can be reduced? Let's try that before jumping to popular political positions of ridicule and dismissal.
- shaky-carrousel 3y agoEasy, evaporate it in a salt lake and use or store the resulting salt.
- gigatexal 3y agoYeah this is one of my concerns, too: what impact on on the oceans will this have? Maybe the salt can be used in electric car batteries somehow? What impact if any would desalination have on oncean water levels? If the process makes for water cheaper than at the tap what’s to stop industrial users?
- quickthrower2 3y agoThe water ends up in the ocean again one way or another.
- WithinReason 3y agoAs water with different salinity levels mixes entropy increases, so you can gain energy. You could build a power plant around the water mixing: https://www.bbc.com/future/article/20150610-blue-energy-how-mixing-water-can-create-electricity https://www.bbc.com/future/article/20150610-blue-energy-how-...
- aqme28 3y agoYou're using solar energy to separate the saltwater from freshwater. You're not going to gain any more energy than that from mixing them back again, so this idea is just solar with extra steps.
- WithinReason 3y agoThe extra step being the gain of freshwater
- thom 3y agoMake bricks! https://nocamels.com/2022/11/bricks-made-of-salt-the-building-material-of-the-future/ https://nocamels.com/2022/11/bricks-made-of-salt-the-buildin...
- bandie91 3y agopresentation on the screen is in comic sans. serious?
- BurningPenguin 3y agoI grew up in a city that was once an important part of the salt trade routes to Bohemia. These routes were called "Goldener Steig" (golden path), and salt was considered "white gold". Entire wars were fought for salt. And now it's so abundant, that we're sitting on mountains of it, not knowing what to do with it. Thinking about that feels kinda unreal.
- h1fra 3y agoLooking at the comments, I'm baffled by the number of people that still think it's "minor issue" while doing absolutely no research. It's not just a little bit of salt, it's enough to kill fishes and whole ecosystem at scale, and it's all in the quoted article that people have definitely not read.
- olalonde 3y agoA "whole ecosystem" could mean a 2 square meter area or a 500 square km area. The article doesn't really specify how big of an issue it really is.
- jillesvangurp 3y agoIt's actually only a challenge in shallow water that doesn't move, which if you think about it isn't that surprising. If you pump it out a bit further, you quite literally have a whole ocean to dilute the salt in. Off the coast of California, for example, which is a state that should have no water shortage as it has abundant access to clean solar and wind energy and the entire pacific to desalinate, ocean depths drop quickly even just a few miles out. You would not be able to affect salinity levels of ocean waters there in any measurable way even if you wanted to. So, the solution is pipes and pumps. Those add cost of course but it's a completely solvable problem otherwise. Exhausting natural sources of ground water and aquifers also has an impact. Desalination done right might give some of those stressed ecosystems a chance to recover.
- bmitc 3y ago> It's actually only a challenge in shallow water that doesn't move, which if you think about it isn't that surprising. If you pump it out a bit further, you quite literally have a whole ocean to dilute the salt in. What do the studies say what the effects of stripping water from the oceans and increasig the concentration of salt and other things are?
- dflock 3y agoAll the water we take out of the ocean ends up back there after a while, as part of the water cycle, we just borrow it for a bit.
- bmitc 3y agoYea, but it's different. For example, we have harmed ecosystems by our flood, erosion, etc. control of rivers. They're supposed to move, but we don't let them, and that has detrimental downstream, figuratively and literally, effects. And it's because we view rivers as just a vessel or tract of water rather than as part of a system. Analogously, the ocean is not just a bucket of water. Coastal ecosystems are particularly sensitive and are already at a tipping point. Are they meant to have bits of it pumped out, filtered, and everything but the water dumped back in? I have been downvoted here, but is it really a bad thing to attempt to understand things a bit better? Before we solve one problem by creating another problem, something humans are really good at?
- k3liutZu 3y agoI wonder, wouldn't we be able to dump it into some flat spaces, allow the water to evaporate and then harvest the salt that remains?
- Liquix 3y agoThe brine more often than not contains traces of pretreatment chemicals, heavy metals, and other byproducts. It's frequently treated before being disposed of. Methods include pumping it down to the ocean floor or mixing with a source of less salty (wastewater/hydro) runoff. Removing the trace chemicals to make salt out of the brine would be prohibitively expensive.
- deleted 3y ago[deleted]
- amelius 3y agoJust dump it into an active volcano.
- kome 3y agoSorry for the extremely ignorant comment: but can't salt be solidified and stored somewhere as waste? and then maybe sold as food or for industrial uses? Surely it would be more efficient than salt pans or mining salt as we do today...
- danmaz74 3y agoMy understanding is that this system is meant to be used at a small and distributed scale, not at an industrial scale like city-level desalination plants. In that case, it shouldn't be a big issue.
- erie 3y agoSo could it be behind this dead zone? ''The largest such dead zone in the world is in the Gulf of Oman, a strait bordered by Iran, Pakistan, Oman, and the UAE. It occupies a whopping 165,000 square kilometres of the water body, an area bigger than even the state of Tamil Nadu (130,060 square kilometres). https://nyuad.nyu.edu/en/news/latest-news/science-and-technology/2019/june/arabian-sea-dead-zone-expansion.html https://nyuad.nyu.edu/en/news/latest-news/science-and-techno...
- IvanMilatForPM 3y ago[dead]
- 1-6 3y agoBrine can be pumped into ponds and evaporated for salt. People holding water rights are usually lobbying and spreading disinformation.
- cassepipe 3y agoI don't know anything but how about putting it in a hole ? What would be the consequences of that ? (Sure there are plenty but I am too dumb to think of any)
- webmobdev 3y agoThe flush tank of my toilet was leaking. I called a plumber, and the first thing he did was to scoop up more than 2 handful of salt solids from the flush tank and clean it well - I wasn't aware that our community uses untreated hard water for toilets. And I was shocked, as I wasn't aware this happened, at the amount of left over salt that had accumulated! Salt is a by-product of desalination and, as I understand, not easy to dispose without affecting the ecology of the area where it is disposed (let's not forget that salting of fields was done as an act of warfare against the enemy to make their lands barren, and then there's the natural Dead Sea - https://en.wikipedia.org/wiki/Dead_Sea https://en.wikipedia.org/wiki/Dead_Sea - that exists and highlights what happens to marine life when water has too much salt content in it). Unless salt waste disposal is solved, desalination isn't going to become popular.
- bryan_w 3y agoPut it in a box and use it as a heat battery for solar/wind
- sambeau 3y agoWouldn’t the rising sea levels more than counter any salt being returned to the sea, as long as it’s dumped far out enough? Won’t climate change cause the concentration of salt in seawater to go down?
- mistermo 3y agoUse it for food consumption.