6 ms·
Scientists cook up new recipes for taking salt out of seawater
- amelius 7y agoHow efficient and robust is the use of a membrane in these kinds of solution? It would seem to me that the membrane is the weakest link, and also expensive.
- sayusyz 7y ago"The current state-of-the-art in RO desalination works very well, but the cost of RO desalination driven by electricity is prohibitive," Why is taking salt out of sea water such a challenge?
- MuffinFlavored 7y agoIs it maybe easier to capture the rain that falls from the sky instead? The rain that falls from the sky is salt-free, right? It then becomes salty when it touches the ocean?
- phpnode 7y agoYes indeed, much easier. The problem is that the places where you need desalination tend to be the places without much rain.
- JacobDotVI 7y agoHere in the Virgin Islands, much of our personal water consumption comes via rainfall we capture from our roofs into our cisterns (big underground swimming pools). Even with that I still need to truck in water a few times a year when the rain hasn’t been sufficient. My roof surface area to consumption ratio is such that this system works pretty well for me (big roof, small human). However with a farm the roof surface area to consumption ratio is flipped - big fields needing water and little to no roof (maybe a tool shed or garage). And you can’t increase roof surface area since that would block sun from the plants. Industrial uses also have a poor ratio. Dense usage of water in a limited size building.
- justinator 7y agoThere's actually water rights/legal issues to this. For example until recently it was illegal for me to do this in Colorado; the law has changed to allow ~114 gallons/year.
- Retric 7y agoDesalination is cheap in day to day terms, it’s the scale of water we use that’s the issue. Sure, we can get ~1,000 gallons of drinking water for 3$ via desalination. That works out to a monthly water bill increase of ~45$ for a family of 5. Unfortunately, crops need incredible amounts of water. So, growing corn etc with desalination would case food prices to ~quadruple.
- riffraff 7y agoIs drip-based watering used at scale?
- BubRoss 7y agoAt what scale?
- riffraff 7y agoLarge commercial monocultures, rather than personal vegetable gardens
- JosephHatfield 7y agoDrip irrigation is heavily relied on by commercial farms in Israel
- mythrwy 7y agoIt is. t-tape for instance is widely used commercially for irrigation of high value horticultural crops like strawberries, tomatoes, peppers etc. also drip systems (with individual emitters, not t-tape) are used commercially in many tree crops (citrus etc). https://rivulis.com/product/drip-tapes-drip-lines/t-tape-drip-tape/ https://rivulis.com/product/drip-tapes-drip-lines/t-tape-dri... However for agronomic crops (like corn, wheat, soybeans, alfalfa etc), which occur in mass plantings I'm not aware of any drip applications. Certainly at minimum if drip is used for these crops, it is extremely rare and probably not practical.
- 7y ago
- comicjk 7y agoSeparating mixed things always means putting in work because it reduces entropy. Around 3% of US energy goes just to distilling oil, for instance.
- Overtonwindow 7y agoI don’t think the problem we should be focusing on is how to remove salt from water, but what to do with the salt after it has been removed.
- RandomTisk 7y agoMake a great big pile of it out in the desert? These[0] guys are doing it in the forest. [0] https://en.wikipedia.org/wiki/Monte_Kali_(Heringen) https://en.wikipedia.org/wiki/Monte_Kali_(Heringen)
- heymijo 7y agoDoesn't look like doing it in the forest is the best idea. From your link... > Ecological impact The amount of salt that goes to the region's soil and rivers is enormous. The Werra river has become so salty (up to 2.5 g/L chloride ions, which is saltier than parts of the Baltic Sea) that few freshwater organisms can survive in it. The groundwater has become salty as well.[4] K+S are licensed to keep dumping salt at the facility until 2030.[3]
- umvi 7y agoSell it? Put it back into the ocean?
- dillonmckay 7y agohttp://www.jqdsalt.com/our-salt/ http://www.jqdsalt.com/our-salt/ 100s of millions of years old sea salt for cooking from the Iapetus Ocean. https://en.m.wikipedia.org/wiki/Iapetus_Ocean https://en.m.wikipedia.org/wiki/Iapetus_Ocean
- brokensegue 7y agoNobody wants to buy the sludge. Putting it back would kill ocean life in the area.
- umvi 7y ago
- abdullahkhalids 7y agoThe paper https://www.nature.com/articles/s42004-019-0151-2 https://www.nature.com/articles/s42004-019-0151-2
- fghorow 7y agoHaving fancy chemistry as in the article is great, but there already exist thermal desalination solutions that require heat (e.g. geothermal, industrial waste heat) rather than work (e.g. electricity for R.O.). For example MED: <https://en.wikipedia.org/wiki/Multiple-effect_distillation> https://en.wikipedia.org/wiki/Multiple-effect_distillation> or MSF: <https://en.wikipedia.org/wiki/Multi-stage_flash_distillation> https://en.wikipedia.org/wiki/Multi-stage_flash_distillation.... Steam is not required for MED. Hot water < 100C is adequate. Many ocean-going vessels already use the waste heat from their engines and MED to make freshwater from seawater. ORC driving RO seems to be most efficient in some situations <https://www.mdpi.com/1099-4300/17/11/7530> https://www.mdpi.com/1099-4300/17/11/7530>, but MED is a simple, no-moving-parts solution that is also efficient.
- ChuckMcM 7y agoThis is a great paper, the really cool bit is that it seems fairly straight forward to convert this to a larger process. Basically add saltwater, warm it, take the settled part of the solution (which is now desalinated) out of the bottom, and the salt dense water out of the top, cool it and precipitate out the salt. Nothing has to evaporate everything runs at a normal vapor pressure so you aren't struggling with high pressure and low pressure domains. I'd love to see if you could use spent nuclear fuel (which is an excellent heat source) to just run one of these things continuously for a couple of decades :-).