What, again?
New method turns ocean water into drinking water, without waste
211–220 of 230 posts
Re: New method turns ocean water into drinking water, without waste
#212[flagged]
Re: New method turns ocean water into drinking water, without waste
#213Earlier quoted context omitted.
>Persian Gulf has 20% more salt in water because of the humans I would like to read more about this from an authoritative source.
Through the magic of Googling "Persian Gulf salinity" it seems like it's more that it's a shallow Gulf in a dry area so it has significant evaporation. Desalination does effect it but it's only a few percent of the total evaporation (which is still surprisingly big) and doesn't sound like the main driving factor or an imminent ecological concern. https://www.frontiersin.org/journals/marine-science/articles... https:/…
Look at a map. The Persian Gulf is a dead end, and all ocean water flow has to come through the Strait of Hormuz. There's some fresh water coming in from the Tigris and Euphrates rivers, but less each year as that fresh water is captured and used, and as global warming increases evaporation.
The San Francisco bay has to be actively managed for similar reasons. It's a large body of water with a narrow outlet, fed by a river system from which much water is captured. If too little water comes in from the Sacramento River, the delta will turn to salt water. Managing that is what the Bay Model, mentioned recently, is for.
Re: New method turns ocean water into drinking water, without waste
#214Earlier quoted context omitted.
I think your sense of scale is off. 90% of sea life is on the surface. 0.029% of ocean water is replenished from rainfall annually. Desalination concentrates are absolutely toxic to life. The current daily volume of brine discharge would require more than half the tankers in the world to be filled and discharged every single day. They would of course not last long with such a routine.
Is that a total for all of the oceans? I understand that as a whole, rainfall is literally but a drop in the ocean. However, confined just to the local area where the rain is falling, the area’s salinity has to change. Just like adding the the desalinated brine is a minuscule amount compared to the whole ocean, it has large effect locally. Regardless, it is totally possible to reintroduce the brine back to the ocean…
In my opinion you are hand-waving away a difficult engineering problem and proposing a naive solution as if it would solve a problem that has already been partially solved, by rejecting all the work that has already been done on it. Don't dump on the surface, don't burn millions of tons of fuel a year to do it, study what has been done and improve on it instead.
Re: New method turns ocean water into drinking water, without waste
#215Earlier quoted context omitted.
If you use fat pipes that go a decent distance from shore, diluting your brine with ocean water, you’ll have a negligible impact on the ocean. The problem is if you dump lots of brine in shallow waters. Old designs did have that flaw, but it’s not that difficult to design around this constraint now that we know about it. IMO this is an issue where NIMBYs are using environmental concerns as a smokescreen to block new…
The city of Corpus Christi, TX is currently considering options for desalination plants—all of which pump their brine into the shallow water inside the bay or the ship channel.
Sounds on brand for Texas.
Re: New method turns ocean water into drinking water, without waste
#216I believe the most efficient method to turn "ocean water into drinking water" is called "rain". We just need to better collect and transport the output of what is effectively the world's biggest solar-powered desalinator.
Geography and prevailing winds have conspired to make certain regions devoid of rain, even many that are right next to the ocean. Competition over resources like water are behind a lot of human misery. The more potential solutions for obtaining fresh water, the better.
Re: New method turns ocean water into drinking water, without waste
#217Earlier quoted context omitted.
That’s what daring means. You try things that do not guarantee success. I remember a decade of people shitting on Dubai for all of the crazy projects it was building. It really paid off for them (pre Iran war). They made something out of nothing and still are. What’s stupid about a kilometer high tower? It’s fucking awesome.
Speaking of shitting on Dubai have they built any plumbing yet or are they still trucking their sewage out of town?
Still trucking but that’s another attempt at diminishing some pretty great achievements. Turning a sterile, hot piece of sand into a “destination” isn’t easy but they managed to do it. Do you bring up lead pipes and police violence every time someone talks about the US?
Re: New method turns ocean water into drinking water, without waste
#218Earlier quoted context omitted.
ScholarlyArticle: "Extreme salt-resisting multistage solar distillation with thermohaline convection " (2023) https://www.cell.com/joule/fulltext/S2542-4351(23)00360-4 .. https://scholar.google.com/scholar?cites=7551078272963689346... "Desalination system could produce freshwater that is cheaper than tap water" (2023) https://www.eurekalert.org/news-releases/1002811 ScholarlyArticle: "Highly efficient and salt reject…
I remember the MIT press release. I wonder if they've found any commercial success.
MIT had a spin-out company some years ago doing HDH (Humidification-Dehumidification) desalination.
In thermal cycles, the problem has been in the condensation step. If there is a carrier gas present this inhibits heat/mass transfer at the condenser surfaces. The usual way of getting around this has been to operate the system with no carrier gas, but that requires pressures below atmospheric pressure, requiring strong walls to withstand external atmospheric pressure.
The MIT invention was a bubble tray contactor, where air is bubbled up through trays of progressively cooler water. The water/air bubble interface provides a large surface area at low cost. One of the markets for this was cleaning up brine from fracked wells.
The company, Gradiant, is still around but has evolved to involve a wider range of water treatment technologies (which is very sensible from a business viewpoint, as customers buy complete solutions, not individual technologies). https://www.gradiant.com/
Re: New method turns ocean water into drinking water, without waste
#219There is a fundamental minimum amount of energy needed to desalinate: you can't take less energy to do it,than you could gain back (from osmotic pressure) if you allowed the desalinated water to expand a cylinder containing the residual brine. This is large. This paper is a thermal method, so it doesn't have an electricity input, but to justify their efficiency claim, they should really compare against what you could…
I always thought that if separating water and salt were easy, our bodies would have evolved to do it so that we'd be able to drink sea water and be fine. It must have been so expensive that searching for fresh water was worth it or there were plenty of fresh water that it was never a evolutionary pressure. Evolving kidneys capable of concentrating urine beyond 3 something percent concentration (sea water) perhaps req…
>I always thought that if separating water and salt were easy, our bodies would have evolved to do it so that we'd be able to drink sea water and be fine.
Unfortunately for terrestrial animals, it's just not that simple. Seawater contains a lot of microbial life, some of which can be infectious or toxic. Going to the coastline to drink is potentially hazardous, because it usually means descending a hill on a predictable route which will be attractive to predators. And you need to get pretty far into the water, usually, because of nasty stagnant runoff, which can come from decaying matter that washes ashore, and sand in the surf. That means you risk drowning. Plus, you don't just need the energy for desalination, but the infrastructure (similar problem to real life!), which means more and larger juxtamedullary nephrons in the kidney, which is already a major weak point on the back due to the high blood flow in the kidney. Meanwhile, most of your food contains a lot of water, especially if you're one of the 99.99999% of animal species that doesn't cook it.
Re: New method turns ocean water into drinking water, without waste
#220Earlier quoted context omitted.
except for the pharmaceuticals anyway
That’s been a solved problem, engineering-wise, for a while. The advanced treatment stages take care of it. Between UV, ozone, and nanofiltration, etc. we can remove the pharmaceuticals. Actually the problem is the water comes out too pure out of a well designed water reuse system, to the point where the mineral content can be too low and you need to add some back in.
Cite for it being solved? All the articles I can find have it as ‘active and growing problem with some potential mitigations which are not universally applied’.
All the recycled water systems I’m aware of still have PCC issues and excess ion contamination problems too still.