4 ms·

I believe the environmentalists aren’t fond of desalination because you have to dump the extra super salty sludge that’s extracted back into the ocean somewhere

by xienze 3y ago

I believe the environmentalists aren’t fond of desalination because you have to dump the extra super salty sludge that’s extracted back into the ocean somewhere, thus increasing salinity levels in a particular area.

deleted 3y ago
[deleted]
oatmeal1 3y ago
Are there too many pollutants not to just evaporate the sea salt sludge until it's sea salt for cooking and sell it?
- akiselev 3y ago
  Think about how much water a person uses per day compared to how much salt. The former is measured in liters, the latter in grams. Desalination produces far more brine than humans could ever need.
- Denvercoder9 3y ago
  Regardless of pollutants, agriculture uses way too much water for this to be practical. Average seawater salinity is 35 g/L, and the WHO recommends a salt intake of at most 5 g/day, so from one liter of water you get enough salt for seven people for a day. Approximating global population at 7 billion people, that means we could consume the salt from about 0.365 km^3 of water per year. Just the US alone uses about ~110 km^3 of water for irrigation per year.
  - prottog 3y ago
    The water used in irrigation eventually (and pretty quickly) makes its way into the ocean, so is it actually a big deal?
    - Tangurena2 3y ago
      The water used to irrigate crops has dissolved minerals in it. As the water is taken up by plants (or evaporated), it leaves those minerals behind. This then raises the salinity of the soil. Eventually, the soil becomes too salty/mineral encrusted to support crops. This happened in the Middle East. What is now Iraq used to be the main grain growing region of the Middle East several thousand years ago. Over time, the salt in the soil rose to the level that wheat could not grow, but barley could. Eventually, the soil became too salty for barley. Today, some of the Iraqi desert shines in sunlight because of the salt crystals. It has never recovered and will never recover. California is progressing faster. Selenium is one of the minerals that ends up in the runoff of Californian agriculture. In some coastal areas, the selenium content is so high that bird eggs laid by wildlife never harden. Or the birth defects are so high that the hatchlings don't live.
adolph 3y ago
Maybe it could be used for the fluid used in hydraulic fracturing operations? https://oilandgasinfo.ca/know-fracking/what-is-frac-fluid-made-of/ https://oilandgasinfo.ca/know-fracking/what-is-frac-fluid-ma...
- no_wizard 3y ago
  In theory I'd rather not give fossil fuels any "leg up" as it where, though scientifically I appreciate where you are at with this, I certainly don't want it to have the knock off affect of encouraging more fracking
sologoub 3y ago
Are there any credible studies in the net effects of the added salinity vs how much water is dumped back in from rain run off, reclaimed sewage and other land based sources?
- stonemetal12 3y ago
  The dead sea is 10x normal ocean water salinity. If you remove most of the water from Pacific ocean water and pump the brine back in to the ocean, you are basically pumping water from the dead sea in to the Pacific creating a huge dead zone until it dilutes back to normal concentrations. It isn't the overall salinity that is impacted but local conditions.
  - sologoub 3y ago
    Even though the comparison is hard to take seriously, there is probably nothing we can do at our current societal scale to make the Pacific Ocean into the Dead Sea equivalent. Ocean acidification from all the GHG pollution, now that seems to be possible. DeSal scale is just not there and we don’t actually need THAT much extra water for cities. Agriculture could be another matter, but economics are not there yet. This report from 2012(!) outlines how any effects from brine can be mitigated and even direct direct brine discharge when properly engineered impacts the area of only tens of meters: https://www.waterboards.ca.gov/water_issues/programs/ocean/desalination/docs/dpr051812.pdf https://www.waterboards.ca.gov/water_issues/programs/ocean/d... When improperly dumped, there can be localized effects, but that’s no different from any other construction.
skybrian 3y ago
Well, not just dumped. It's diluted first. Or should be. As I understand it, San Diego's plant dilutes the effluent by mixing it with additional ocean water, but I don't have a good handle on how well that works.
bsder 3y ago
You simply can't desalinate water at a rate sufficient for agriculture. The only solution is to let the water price rise so that the agribusinesses quit growing crap like alfalfa.
stonemetal12 3y ago
They could repair the Bonneville Salt Flats. They have lost quite a bit of salt, more than 50 million tons. Edit: I bet that only covers a few years of farming use though.
cyberax 3y ago
This is just BS. The amount of desalinated water is completely dwarfed by normal evaporation. If we replace _all_ the water used in agriculture by desalinated water, we won't even make a dent in the global saltwater balance. Some local effects are certainly possible, but they can be mitigated by pre-diluting the brine.
- deleted 3y ago
  [deleted]
- thehappypm 3y ago
  Local effects are indeed the concern. If you dump the brine in something like a harbor (typically where cities are built) you can have extreme growth in salinity which also makes desalination harder. It’s a problem for Middle Eastern countries reliant on it
  - cyberax 3y ago
    It won't be a problem for CA, though. There's a strong current that goes right by the shore, it'll help to quickly mix the brine.
    - thehappypm 3y ago
      Along every inch of the entire coastline?
      - cyberax 3y ago
        Pretty much, once you're a hundred meters or so off the coast. Of course, not inside the coastal bays. You have to take it into account if you want to kayak to Channel Islands.

by xienze 3y ago

deleted 3y ago

[deleted]

oatmeal1 3y ago

Are there too many pollutants not to just evaporate the sea salt sludge until it's sea salt for cooking and sell it?

akiselev 3y ago
Think about how much water a person uses per day compared to how much salt. The former is measured in liters, the latter in grams. Desalination produces far more brine than humans could ever need.
Denvercoder9 3y ago
Regardless of pollutants, agriculture uses way too much water for this to be practical. Average seawater salinity is 35 g/L, and the WHO recommends a salt intake of at most 5 g/day, so from one liter of water you get enough salt for seven people for a day. Approximating global population at 7 billion people, that means we could consume the salt from about 0.365 km^3 of water per year. Just the US alone uses about ~110 km^3 of water for irrigation per year.
- prottog 3y ago
  The water used in irrigation eventually (and pretty quickly) makes its way into the ocean, so is it actually a big deal?
  - Tangurena2 3y ago
    The water used to irrigate crops has dissolved minerals in it. As the water is taken up by plants (or evaporated), it leaves those minerals behind. This then raises the salinity of the soil. Eventually, the soil becomes too salty/mineral encrusted to support crops. This happened in the Middle East. What is now Iraq used to be the main grain growing region of the Middle East several thousand years ago. Over time, the salt in the soil rose to the level that wheat could not grow, but barley could. Eventually, the soil became too salty for barley. Today, some of the Iraqi desert shines in sunlight because of the salt crystals. It has never recovered and will never recover. California is progressing faster. Selenium is one of the minerals that ends up in the runoff of Californian agriculture. In some coastal areas, the selenium content is so high that bird eggs laid by wildlife never harden. Or the birth defects are so high that the hatchlings don't live.

adolph 3y ago

Maybe it could be used for the fluid used in hydraulic fracturing operations? https://oilandgasinfo.ca/know-fracking/what-is-frac-fluid-made-of/ https://oilandgasinfo.ca/know-fracking/what-is-frac-fluid-ma...

no_wizard 3y ago
In theory I'd rather not give fossil fuels any "leg up" as it where, though scientifically I appreciate where you are at with this, I certainly don't want it to have the knock off affect of encouraging more fracking

sologoub 3y ago

Are there any credible studies in the net effects of the added salinity vs how much water is dumped back in from rain run off, reclaimed sewage and other land based sources?

stonemetal12 3y ago
The dead sea is 10x normal ocean water salinity. If you remove most of the water from Pacific ocean water and pump the brine back in to the ocean, you are basically pumping water from the dead sea in to the Pacific creating a huge dead zone until it dilutes back to normal concentrations. It isn't the overall salinity that is impacted but local conditions.
- sologoub 3y ago
  Even though the comparison is hard to take seriously, there is probably nothing we can do at our current societal scale to make the Pacific Ocean into the Dead Sea equivalent. Ocean acidification from all the GHG pollution, now that seems to be possible. DeSal scale is just not there and we don’t actually need THAT much extra water for cities. Agriculture could be another matter, but economics are not there yet. This report from 2012(!) outlines how any effects from brine can be mitigated and even direct direct brine discharge when properly engineered impacts the area of only tens of meters: https://www.waterboards.ca.gov/water_issues/programs/ocean/desalination/docs/dpr051812.pdf https://www.waterboards.ca.gov/water_issues/programs/ocean/d... When improperly dumped, there can be localized effects, but that’s no different from any other construction.

skybrian 3y ago

Well, not just dumped. It's diluted first. Or should be. As I understand it, San Diego's plant dilutes the effluent by mixing it with additional ocean water, but I don't have a good handle on how well that works.

bsder 3y ago

You simply can't desalinate water at a rate sufficient for agriculture. The only solution is to let the water price rise so that the agribusinesses quit growing crap like alfalfa.

stonemetal12 3y ago

They could repair the Bonneville Salt Flats. They have lost quite a bit of salt, more than 50 million tons. Edit: I bet that only covers a few years of farming use though.

cyberax 3y ago

This is just BS. The amount of desalinated water is completely dwarfed by normal evaporation. If we replace _all_ the water used in agriculture by desalinated water, we won't even make a dent in the global saltwater balance. Some local effects are certainly possible, but they can be mitigated by pre-diluting the brine.

deleted 3y ago
[deleted]
thehappypm 3y ago
Local effects are indeed the concern. If you dump the brine in something like a harbor (typically where cities are built) you can have extreme growth in salinity which also makes desalination harder. It’s a problem for Middle Eastern countries reliant on it
- cyberax 3y ago
  It won't be a problem for CA, though. There's a strong current that goes right by the shore, it'll help to quickly mix the brine.
  - thehappypm 3y ago
    Along every inch of the entire coastline?
    - cyberax 3y ago
      Pretty much, once you're a hundred meters or so off the coast. Of course, not inside the coastal bays. You have to take it into account if you want to kayak to Channel Islands.