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Scientists cook up new recipes for taking salt out of seawater

phys.org

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Re: Scientists cook up new recipes for taking salt out of seawater

#21

Post by sologoub »

amluto wrote: post #8
Retric wrote: post #6

Earlier quoted context omitted.

Desalination 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.

Why do you think that the cost is an increase? I pay quite a bit more than $3/kgal, and a large fraction of that goes toward funding the SFPUC’s massive infrastructure for bringing Hetch Hetchy water to the Peninsula. A desalination plant would be located on the coast or on the bay and would not require this infrastructure. As far as I’m concerned, the problem is the capital cost of the plant and the plumbing to safe…

Seems like using our fog might be an easier idea short term: https://csumb.edu/fernandezlab/fog-collection-project

Re: Scientists cook up new recipes for taking salt out of seawater

#22

Post by amluto »

Retric wrote: post #11
amluto wrote: post #8

Earlier quoted context omitted.

Why do you think that the cost is an increase? I pay quite a bit more than $3/kgal, and a large fraction of that goes toward funding the SFPUC’s massive infrastructure for bringing Hetch Hetchy water to the Peninsula. A desalination plant would be located on the coast or on the bay and would not require this infrastructure. As far as I’m concerned, the problem is the capital cost of the plant and the plumbing to safe…

Sewage and distribution is not included in these costs. Current systems get water for almost nothing it’s mostly distribution and sewage systems that you’re currently paying for. As to why this is, a single pipe carrying 1,000x as much water costs no where near 1,000x much per foot. Each home might only need 1/10,000,000 the water, but it’s got to be built for peak demand not average useage. On top of this, people do…

None of this is at all relevant to my point. SFPUC charges over $4/ccf for wholesale water. This does not include distribution costs, and this is paid regardless of whether the water is sold, leaks, or is used for firefighting. If SFPUC’s wholesale customers purchased desalinated water and managed to escape their SFPUC contracts, they would eliminate this expense.

edit: http://bawsca.org/water/rates/wholesale

Re: Scientists cook up new recipes for taking salt out of seawater

#23

Post by RandomTisk »

Overtonwindow wrote: post #12

I 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.

Make 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)

Re: Scientists cook up new recipes for taking salt out of seawater

#24

Post by thinkcontext »

amluto wrote: post #8
Retric wrote: post #6

Earlier quoted context omitted.

Desalination 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.

Why do you think that the cost is an increase? I pay quite a bit more than $3/kgal, and a large fraction of that goes toward funding the SFPUC’s massive infrastructure for bringing Hetch Hetchy water to the Peninsula. A desalination plant would be located on the coast or on the bay and would not require this infrastructure. As far as I’m concerned, the problem is the capital cost of the plant and the plumbing to safe…

> As far as I’m concerned, the problem is the capital cost of the plant and the plumbing to safely suck in saltwater and discharge brine and has essentially nothing to do with electricity.

Nothing to do with electricity? What is this based on? Everything I've read indicates it's a very large cost. For example, this [1] paper puts electricity's share of costs at 44% vs 37 for fixed costs.

https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1936-704X....

Re: Scientists cook up new recipes for taking salt out of seawater

#25

Post by mythrwy »

riffraff wrote: post #7
Retric wrote: post #6

Earlier quoted context omitted.

Desalination 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.

Is drip-based watering used at scale?

It 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-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.

Re: Scientists cook up new recipes for taking salt out of seawater

#27

Post by heymijo »

RandomTisk wrote: post #23
Overtonwindow wrote: post #12

I 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.

Make 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)

Doesn'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]

Re: Scientists cook up new recipes for taking salt out of seawater

#28

Post by comicjk »

sayusyz wrote: post #3

"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?

Separating mixed things always means putting in work because it reduces entropy. Around 3% of US energy goes just to distilling oil, for instance.

Re: Scientists cook up new recipes for taking salt out of seawater

#29

Post by heymijo »

Overtonwindow wrote: post #12

I 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.

There was an article linked to here in 2016 about an inventor who developed a process that reduces the need for brine disposal by nearly 100 percent. [0]

Not sure what progress has been made since

[0] https://www.scientificamerican.com/article/desalination-brea... [1] https://news.ycombinator.com/item?id=12191089

Re: Scientists cook up new recipes for taking salt out of seawater

#30

Post by amelius »

Retric wrote: post #6
sayusyz wrote: post #3

"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?

Desalination 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.

Since seaweed can grow on salt water, can we perhaps engineer other crops to do the same?
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