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A vision for the alleviation of water scarcity in the US Southwest

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Re: A vision for the alleviation of water scarcity in the US Southwest

#141

Post by mrguyorama »

bell-cot wrote: post #33
pfannkuchen wrote: post #32

Earlier quoted context omitted.

Can’t we pipe the seawater inland and then deposit the salt on land?

When it rains, what happens to the run-off from a huge pile of salt?

Surely the massive open air pools of salt used for sea salt production have figured out how this process works.

On the Californian coast, there is already at least https://en.wikipedia.org/wiki/South_Bay_Salt_Works , a sea salt production facility that uses salt pools. They produce 80k tons annually of salt, which means they process 2666k tons of seawater to get that. If that one salt production facility used brine as their source instead of seawater, they would have allowed the facility to produce 2580k tons of freshwater. The "urban" usage of water in California is 10 million acre-feet (ish), so that's not exactly a significant amount.

Re: A vision for the alleviation of water scarcity in the US Southwest

#142

Post by ed_balls »

hnmullany wrote: post #3

Apart from whether the economics make sense brine disposal from desalinization is a big issue. Waste with high salt concentrations can wipe out marine life - it would be nice if this piece took the issue a little more seriously. It's a continuing problem in the Canary Islands which are dependent on desalinization plants: "Rejected brine is a serious threat to marine ecosystems, causing negative effects on both flora…

you could use brine for construction (Isreal build a wall along Jordan). Also you can pump it into a ship and dump into Pacific, slowly.

Re: A vision for the alleviation of water scarcity in the US Southwest

#143

Post by hnmullany »

tuatoru wrote: post #133
JohnMakin wrote: post #40

Earlier quoted context omitted.

He addresses brine, but not the waste products that come from brine, and only addresses it in one sentence: > The resulting depleted brine is piped back to the ocean where it is thoroughly mixed with sea water and discharged. This is not nearly as easy as this sentence implies.

Yes it is. We do it with urban wastewater in thousands of locations around the world. This is not a hard problem, nor is it expensive.

Waste brine is substantially more dense than regular seawater, so it tends to form a coherent layer that doesn't mix easily: it's why waste brine sinks to the sea-bed and spreads out in a layer.

Re: A vision for the alleviation of water scarcity in the US Southwest

#144

Post by alexb_ »

justinator wrote: post #64
alexb_ wrote: post #49

Just charge people for the natural resources of the country via taxes. Resource and land taxes solve basically every single problem in the current American economy yet people do not want to even think about doing it.

You're right - air's also getting a little too polluted for my taste. Maybe if I could get a hold of some taxed air, I could breath easy! We could put the pollutants back into the untaxed air too!

Why are you acting as if this is some fantasy thing? Pollution taxes absolutely are exactly what that is. You're "using up" all the good air!

Re: A vision for the alleviation of water scarcity in the US Southwest

#145

Post by gwern »

hnmullany wrote: post #3

Apart from whether the economics make sense brine disposal from desalinization is a big issue. Waste with high salt concentrations can wipe out marine life - it would be nice if this piece took the issue a little more seriously. It's a continuing problem in the Canary Islands which are dependent on desalinization plants: "Rejected brine is a serious threat to marine ecosystems, causing negative effects on both flora…

Your quote doesn't give any evidence it is a big problem. It simply asserts that it is a problem and includes some random factoid about the cost.

Re: A vision for the alleviation of water scarcity in the US Southwest

#146

Post by hnu123 »

sixstringtheory wrote: post #131
hnu123 wrote: post #97

Earlier quoted context omitted.

[flagged]

This is some negging bs. Current front page items include a paper on vector databases, an example of AI garbage that showed Amazon in a bad light, a quite in-depth treatment of “Trilinear Point Splatting for Real-Time Radiance Field Rendering” hosted on a PhD’s own github page, you know github, a huge gathering place for hackers to share their code with each other? An article criticizing Unity about banning an open s…

[flagged]

Re: A vision for the alleviation of water scarcity in the US Southwest

#147

Post by adhesive_wombat »

thehappypm wrote: post #14
nickparker wrote: post #6

Earlier quoted context omitted.

> RO desal splits the incoming ~3% salinity stream into two halves, one fresh and one ~6% salinity. This concentrated brine is fed to adjacent brine processing facilities (ideally in both countries) that exploit the region’s abundant solar and geothermal energy to extract potentially millions of tonnes of lithium, sodium, magnesium, chloride, and other metals found in sea water. The resulting depleted brine is piped…

Basically, I think you could take the Brine and just put it somewhere else. Like, into mine shafts, or into evaporation pools for mining purposes.

Considering that the brine output of a single large-ish plant might be 150,000m³ per day[1], that's a hell of a mine shaft to take it continuously. The rock with the same volume as a day's brine would weigh a million tons. The entire Aberfan spoil tips were only 2 weeks worth of that much volume (2 million cubic metres).

The gigantic Hambach open-pit mine grows by 0.3km³ a year, so that could take it (but it can't take the Saudi million m³/day plant). By the time the mine is depleted, the resulting 18km³ pit would not be filled by our single hypothetical plant for over 300 years, assuming it won't evaporate. Which leads to:

The evaporation pools might work: they'd "only" have to be 3000 acres (12 km²) to gather the 4GW of solar power at 1kW/m² for 8 hours a day to continuously evaporate that much water daily[2]. Which is certainly large, but not completely impossible. But then there's 2 million tonnes of salt per year which will accumulate continuously over time.

[1] the largest is over a million

[2] not including water not bring a perfect absorber of solar energy or differing insolation

Re: A vision for the alleviation of water scarcity in the US Southwest

#148

Post by anon84873628 »

konschubert wrote: post #86
BytesAndGears wrote: post #85

Earlier quoted context omitted.

Yeah, but if you’re pulling in water and disposing it from a specific region, eventually the water that you’re pulling in is progressively saltier, and you’re compounding the saltiness of that area. I’m sure that ocean currents will eventually equalize the salt, but if you’re continuously dumping salt into a specific area, it’s going to make that region of the ocean saltier.

You need pipes to spread it out. And I think you may be underestimating the scale and force of ocean currents. Every tide probably moves more water than California uses in a year.

Crucially but overlooked so far in these threads, is that the proposal does not have brine exiting on the California coast; it has it flowing into the Sea of Cortez.

That should be an obvious non-starter for anyone remotely familiar with the unique geography and ecology of the area.

Re: A vision for the alleviation of water scarcity in the US Southwest

#149

Post by anon84873628 »

nradov wrote: post #102
hnmullany wrote: post #3

Apart from whether the economics make sense brine disposal from desalinization is a big issue. Waste with high salt concentrations can wipe out marine life - it would be nice if this piece took the issue a little more seriously. It's a continuing problem in the Canary Islands which are dependent on desalinization plants: "Rejected brine is a serious threat to marine ecosystems, causing negative effects on both flora…

Brine discharge is an issue, but the geography of the North American West Coast is favorable for that. In most places the seafloor drops down fairly deep just a short distance offshore. Past about 400 ft / 120 m there is no flora at all, and most fauna is clustered around rock structures. So, the impact of brine discharge can be minimized with careful pipeline siting.

Careful pipeline siting indeed. The author needs to update the proposal to have the brine exiting on the Pacific coast, rather than annihilating the the Sea of Cortez.

Re: A vision for the alleviation of water scarcity in the US Southwest

#150

Post by warcher »

adrianmonk wrote: post #132
warcher wrote: post #126

Earlier quoted context omitted.

What I'm saying is that the freshwater reservoir is a totally free grid scale battery for a desal plant. No need to save it, just make fresh water while the sun shines and drink it whenever.

Energy storage would serve two purposes: (1) Ensure you always have fresh water available since you're continuously producing it. (2) Reduce the size of desalination plant you must build by allowing you to run it 24x7. You're right that you can just store the fresh water, so batteries aren't needed for #1. But the article is talking about how to achieve #2.

Yeah, I'm just saying-- a big desalination plant is a solved problem. Grid scale energy storage has been ten years off for almost as long as nuclear fusion. The original author just hand waves their way through what would be the biggest energy breakthrough in a hundred years to save a couple bucks running a desalination plant.
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