4th stage purification is cheaper and far less damaging to the environment.
I posted that somewhere. It is well over a gallon for one single almond.
Salt blocks are probably fairly similar to cinder blocks and softer red bricks. You would need to coat them with some sort of varnish, to water protect them, but they might be a fairly cheap alternative that has some nice translucency aspects for certain applications…
Do you need to desalinate water that’s used for purposes other than drinking?
Could you pipe saltwater into the city for showers, toilets and the like, and then install a small unit like this in every house to produce drinking water on demand at the site it’s needed?
You don’t want to use saltwater for showers (there’s a reason there are showers at beaches).
You can use it for toilets, but you’ll need a parallel water system, i.e. re-work existing plumbing. Sea water is generally corrosive and our plumbing isn’t designed for it. And you’ll still need a treatment plant for it.
Onsite treatment of it to produce potable water is also not trivial. It’s not as simple as filtering the salt out. Seawater has all kinds of stuff in it. If you want to treat it, it’s going to be better to have a centralized plant.
Just as an aside… “acre feet per acre” is one of the more interesting units I have encountered. I guess the easiest way to understand it is that 1 acre foot per acre is exactly equal to 1 acre ampere sievert foot per acre per ampere per sievert.
Some people here seem to think the waste output of desalination is big mounds of salt. It’s not; the waste is brine. And this isn’t a trivial amount: the ratio of drinking water to brine is around 2:3, although newer plants are getting closer to 1:1. Still, it’s a massive volume and you can’t easily extract the salt out of it.
Good to know.
So perhaps build a desalination plant right next to a pickle factory?
Thanks for that tidbit. LA uses 524 million gallons of water a day. If they extracted it all from seawater super efficiently (let’s posit 1:1 ratio, even tho we’re not there yet), every year they’d have to figure out what to do with brine that would cover 584 billion acres of land 1 foot deep. That’s over 2500 square miles. Or a square 50 miles on a side. Just for LA.
Interesting problem.
What happens if you pump it a couple hundred miles off the coast, and then disperse it over a few hundred square miles?
Will that be enough to keep it from causing environmental damage?
There is still the additional cost/risk of pumping/moving waste brine from “here” to “over there”, which makes the overall cost of the operation even less attractive. Cheaper to use the fresh water we do have more judiciously.
according to this source hypersaline brine fucks up plankton and phytoplankton the most, and it’s already under stress. I’d guess piping it out hundreds of miles wouldn’t reduce its effect on the ecosystem as a whole. Never mind the cost of piping things out into the ocean.
I strongly suspect there is no feasible way to deal with such waste brine that isn’t horrendously destructive. The question would simply be, “which ecosystem are we going to destroy? Land or sea?”
I’m glad the question is academic as there is no way such a scheme would ever get green-lit.
To be clear, the question is not academic - there are many desalination plants in use today. The most common method of disposal by far is returning it to the ocean, although not 100 miles out. If it is dumped unmixed, it settles to the bottom (being heavier than sea water) and suffocates everything there. The linked article discusses other methods of dilution, such as using multiple outlets, releasing it under pressure, or diluting with other wastewater streams. None of these are great options.
In my part of the world, we built a desalination plant and it’s been in use for several years now.
I drink tap water every day, so it is certain that I’ve been drinking desalinated water for years now.
Pulling the numbers from that, where it can produce 150 gigalitres a year, means it can water approx 30,000 acres. California has 43 million acres in use, so they’d need around 1400 of these plants.
At an idle cost of $608 million a year each, another $132 million if they are in use, puts the annual cost of watering $50 billion worth of agricultural products comfortably over a trillion dollars.
I’m sure the numbers I used can be finessed a bit, but we are talking about costs of 20 times that of the value, just for the water. That’s not gonna work.
(and that’s not counting the environmental costs)
I wasn’t suggesting it’s the answer everyone’s looking for, just saying that desalination isn’t some science-fiction concept, it’s daily reality for millions of people. And just because it’s not happening in the USA does not mean there’s any real reason for it to be somehow impossible to do in the USA.
Personally I think the best answer is moving the industries that need fresh water to, you know, places that have plenty of fresh water. That would help. And, of course, making some actual real progress towards dealing with climate change.
No one has said that it’s a science fiction concept, just expensive.
It is done in the USA. Just not on the scale that would be necessary to replace the water that has been taken for granted for decades.
I would agree, but the industries in question are agricultural, and it’s easier said than done to move an almond grove to the Ohio River watershed.
Yes, the industries that use a very large fraction of that water are agricultural, and they need appropriate soil, sun, and temperatures as well as enough water.
Also, there are actually huge advantages to growing crops in a desert: there aren’t a lot of local pests, because there aren’t a lot of local wild plants that are closely related to those crops. That means less cost to fight fungal infections, insects, weeds, and critters that would prey on your crops in other parts of the country.
Yep. And it is bad for the environment when you suck it in, and when you put it back, not to mention using huge amount of energy. Wastewater treatment is far better over all.
Besides, drinking water is not the issue. Residential water is not the issue, either.
You can’t. That is simply impossible.
And again desalinization is not the solution. Not for the West Coast anyway.
If you have a small demand and a nuke power plant, it can work.
It isn’t industry either. It is water wasting water thirsty farming, of which almonds are the words.
If CA curtailed almond growing by 10%, that would save more than every house stopping their lawn watering.