I am really skeptical of promise of materials like graphene because although i have heard about magical properties for so many years now i have never heard of practical mass manufacturing completely upending an old school method for something. May be i am not knowledgeable enough.
This is one of the technologies that is increasingly important for the future of the earth especially in water poor countries with heavy population.
In the large scheme of things it might turn out cheaper to move population closer to the coasts, have desalination plants instead of other solutions to water scarcity assuming renewable energy costs reduce significantly as well along with a lot of surplus.
At an average, rather immodest level of water consumption per capita (~1580 m3/annum), then this is about ~4740kWh per year, or 13 kWh per day. I'd say this is significant, but then:
For comparison, current energy use per capita in the USA is 7000kg-oil-equivalent  (or 81000 kWh ), so an additional 4740 kWh is about 5%.
The real problem is that people use absolutely indecent amounts of energy and water and other resources, usually for no good reason at all...
Note that those numbers when I last looked into it typically include industrial and agricultural water use - residential water consumption is usually approximately 15% of total water use, so that fits reasonably.
One problem is that in many countries, water consumers (e.g. farmers) are able to withdraw water from their own soil, and so nobody really knows how much water that is, although it's possible to make educated guesses.
1. Those numbers are from all the rain hitting the pasture divided by by the cows mass (that is eatable)
1.a including whatever it eats
2. The way it's told makes it seem that none of the water is reused which is not true
Though beef is a water intensive 'crop' it is not as bad as certain people makes it out to be.
Also, the main thing to focus on is cost of water produced. If you design a new filter that is much more energy efficient but costs 100x more than the standard plastic filter, it may not provide much advantage.
Or (this might seem crazy) considering Antarctic sea ice is melting at increasingly faster rates, which isn't good in itself - is that causing the water at the far south latitudes to be lacking in salinity? Would additional salt there provide for keeping the ecosystems stable for longer at least? Granted shipping would be another issue.
The former may require some free market ingenuity, the latter may require some ingenuity and some sort of goodwill on the part of some governments.
The challenge is how to understand and work with natural ecosystems well enough to not burden them with salt concentrations that harm them, and perhaps even to fit and enrich them.
* Problem 2: If dumped into the ocean, it increases the salt concentration (see: Middle East).
Disclaimer: Worked on some related projects on how to find a positive use for Brine.
The scale is the problem. At the end, you still end up with lots and lots of inorganic material, which is toxic for the environment.
But there's also industry that extracts the salt from the Great Salt Lake, via evaporation. This shows that, if you've got salt to dump somewhere, there's actually a market for that. (That is, if it's pure. Others pointed out the problem of chemicals added to the salt water to make it easier to process.)
Or dilute it. The solution to pollution is dilution.
For a while. The scale of human population and our increased per capita resource usage starts to make that less often viable.
The salt comes from the ocean in the first place, and the water returns to the ocean relativly quickly. Unless something changes and we start to notably change the volume of water in the ocean, dilution is the only way to maintain the ocean chemistry. If we don't, then we would be reducing the salinity as the water returns without the salt.
The problem is that it isn't perfectly diluting, it's concentrating the salt in areas near the desalination plants, changing ecosystems and causing problems locally.
There's also the semi-related problem of salt that isn't from the ocean making it's way there, increasing the overall salt concentrations over time.
If we could find a way to use the salt from desalination (at least partially) somewhere else, then maybe we could help offset the "saltification" of the ocean and can more easily avoid destroying ecosystems around desalination plants. (it doesn't need to be an all-or-nothing solution, we could still dump some salt back into the ocean while keeping some out and used in other areas)
> But a less chattered-about problem is the effect on the local environment: The primary byproduct of desal is brine, which facilities pump back out to sea. The stuff sinks to the seafloor and wreaks havoc on ecosystems, cratering oxygen levels and spiking salt content.
> The primary byproduct of desal is brine, which facilities pump back out to sea. The stuff sinks to the seafloor and wreaks havoc on ecosystems, cratering oxygen levels and spiking salt content.
The issue is the dissolution process is slow enough that the salt has time to wreck havoc on the environment. And if you're taking river water or aquifer water to dilute the brine to a point near the local salinity why go through the whole desalination process to start with instead of using the water to dilute this byproduct?
It's easy to forget that at large scales the ocean doesn't really disperse things evenly. Surface salinity for example ranges from 30-40 g/kg across the surface of the ocean.
How is this possible? Your input has a certain amount of salt and water in it, right? How do you take out the same amount of water, but leave less salt behind? Am I missing something?
This is a very bad article - pure FUD.
It's chief disadvantages are low power density and low power to weight ratio, neither of which matter for grid storage.
It just seems to have all the hallmarks of traditional industrial solutions. But, of course, lithium ion has the same advantage ubiquitous silicon semiconductors have- massive, massive economies of scale and endless R&D dollars.
With sea levels rising there's not going to be a global shortage of water.
>The stuff sinks to the seafloor and wreaks havoc on ecosystems, cratering oxygen levels and spiking salt content.
>Because this stuff is denser than typical seawater, it sinks to the seafloor and disrupts vibrant communities of life, which find themselves wanting far less salt and far more oxygen.
>But brine is more than just hypersaline water—it can be loaded with heavy metals and chemicals that keep the feedwater from gunking up the complicated and expensive facility. “The antifoulants used in the process, particularly in the pretreatment process of the source water, accumulate and discharge to the environment in concentrations that can potentially have damaging effects on the ecosystems,” says Jones.
Bad journalism. Bad science. A desal plant is essentially a brine production facility. A more efficient plant won't output less salt. It may be less by water volume but that water will just be all the more salty. This cannot be avoided short of piling the salt up on the land. Brine is bad, but when mixed in with the vast volumes of the oceans is a non-issue. All the brine produced by desal plants is nothing compared to the brine produced by sunlight on the ocean surface.
>> "But herein lies opportunity: The discharge can also contain precious elements like uranium."
Ya. Um, that is an entirely different story. Uranium from seawater is a thing today even without the brine.
Some put the amount of natural uranium in seawater in the billions of tons. Every country in the world suddenly having ready access to a limitless supply of uranium? Desal might be the least thing to worry about.