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Scientists cook up new recipes for taking salt out of seawater

phys.org

11–20 of 52 posts

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

#11
post #8
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…

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 don’t live at sea level, so you need to pump that sea water up before you can use it.

PS: Not to mention most distribution systems leak significantly, that 3$ assumes 100% efficiency at 50% it’s more like 6$.

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

#13
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?

Is it maybe easier to capture the rain that falls from the sky instead? The rain that falls from the sky is salt-free, right? It then becomes salty when it touches the ocean?

Here in the Virgin Islands, much of our personal water consumption comes via rainfall we capture from our roofs into our cisterns (big underground swimming pools). Even with that I still need to truck in water a few times a year when the rain hasn’t been sufficient.

My roof surface area to consumption ratio is such that this system works pretty well for me (big roof, small human). However with a farm the roof surface area to consumption ratio is flipped - big fields needing water and little to no roof (maybe a tool shed or garage). And you can’t increase roof surface area since that would block sun from the plants. Industrial uses also have a poor ratio. Dense usage of water in a limited size building.

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

#16
post #11
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…

My municipality loses about 60% of its water supply due to leaks.

They buy the water from the neighboring municipality for $3/1,000 gallons, and sell it to the users of the system for $23/1,000 for the first 1,000 gallons.

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

#17

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.

It looks like we have a few solutions already, like power generation and storage. I don't know how cost effective these are, but it's certainly a interesting area of research.

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

#18
post #14

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.

Sell it? Put it back into the ocean?

http://www.jqdsalt.com/our-salt/

100s of millions of years old sea salt for cooking from the Iapetus Ocean.

https://en.m.wikipedia.org/wiki/Iapetus_Ocean

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

#19
post #6
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.

Also transportation costs wherein desalinated water will mostly have to be pumped upstream to places where crops are grown

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

#20
post #14

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.

Sell it? Put it back into the ocean?

Nobody wants to buy the sludge.

Putting it back would kill ocean life in the area.

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