3 ms·

> diffusing accumulated salt back to the sea water. A big issue of desalinisation is the increase in salt in water: brine streams coming out of osmosis plants

by bertil 4y ago

> diffusing accumulated salt back to the sea water. A big issue of desalinisation is the increase in salt in water: brine streams coming out of osmosis plants are dead zones in the sea. I'm not sure this is a good idea for the shore.

ncmncm 4y ago
As I noted, there is no need to concentrate the brine to such a degree that discharging it could be a problem. But even if you did, discharging the brine through a long, leaky pipe or hose would avoid creating any dead zones.
- cma 4y ago
  How do you create a long leaky pipe without bio-fouling clogging it up? I guess the high salinity itself could prevent fouling.
  - ncmncm 4y ago
    With positive pressure and small holes, it would be hard for bio to get in and foul it. Generally you are more worried about biofouling on water intakes, with good reason.
labrador 4y ago
It's only seems like a big issue to people who don't know a lot about the ocean. I grew up surfing in a town at "sewer peak". The effluent from a sewage treatment plant was nearby. It was too close to shore, so they moved the discharge further out into deeper water. Discharging water with a higher salt content than the ocean wouldn't cause any harm at the discharge point, so this concern always seemed like a canard or unfounded theory to me. Some people don't want desal plants near them, so they throw this out there for NIMBY reasons.
- ncmncm 4y ago
  I gather San Diego discharged sewage into the sea forever. When they finally got to cleaning it up, maybe to appease surfers, they were forbidden because an ecosystem had grown up dependent on it the way it was.
  - labrador 4y ago
    Santa Cruz didn't clean it up because of surfers, who didn't care because it wasn't very noticeable, although you knew you were taking a chance of getting mildly sick. It's really difficult to resist going out when the waves are good. It was because the fecal bacteria count was over the new environmental standards that came to be in the last two decades of the 1900's. Many people don't realize there's an acceptable amount of mouse dung and insect carcasses in the food they buy, so it may sound gross to surf in gray water, but it really wasn't. It may be a bigger problem in San Diego because the water is much warmer than the cold currents the come down the coast from Alaska to Santa Cruz (along with some good waves)
- hamlsandwich 4y ago
  > Discharging water with a higher salt content than the ocean wouldn't cause any harm at the discharge point Sewage and hot, concentrated brine are not the same. Plenty of studies show that there is harm to ecosystems, that's often not properly addressed. - https://www.ccc.tas.gov.au/wp-content/uploads/2018/11/Apx-22-Desalination-Plants-Uni-Sydney-Brine-Discharge-Marine-Env-Impact.pdf https://www.ccc.tas.gov.au/wp-content/uploads/2018/11/Apx-22... - https://phys.org/news/2019-01-brine-discharge-desalination-good-news.html https://phys.org/news/2019-01-brine-discharge-desalination-g...
  - ncmncm 4y ago
    Again, this is a problem only if you just drain concentrated brine straight into the sea. But there are cheap, easy alternatives. Easiest is a long, leaky pipe leasing way out offshore. Or you could exhaust it into freshwater right before that enters the sea. Or you could dilute the brine with lots of seawater before draining it.
  - labrador 4y ago
    Yes, but out past the kelp beds and sea otters it's all flat sand until it hits the Monterey Bay canyon. The Bay is a marine sanctuary so we'd probably put the desal plant up the Coast on open ocean to serve mostly San Francisco, which now gets it's water from the Sierras. That may not last. Also interesting to me is that they turned the local fossil fuel electric plant that I grew up with into a giant battery: Moss Landing Battery Storage Project https://www.nsenergybusiness.com/projects/moss-landing/ https://www.nsenergybusiness.com/projects/moss-landing/ A few decades ago we lost power for a few days when the ELF (Earth Liberation Front) cut a main power line from Moss Landing to Santa Cruz. edit: I can't find the story and it wasn't the ELF so it must have been a sister group https://en.wikipedia.org/wiki/Timeline_of_Earth_Liberation_Front_actions https://en.wikipedia.org/wiki/Timeline_of_Earth_Liberation_F... Edit: The first link you shared says it's historically been a concern but seems to dismiss the concern by saying it's all in where you put the plant and how you do the discharge, which is obvious: Environmental impacts associated with concentrated discharge have historically been considered as a major environmental concern to marine life with desalination plants. The environmental impact of desalination plants will vary depending on several factors: i. The location of desalination plant. ii. The location of the inlet and outlet. iii. The method used in the desalination facility and the outlet (water channel and pipeline). The second link says nothing was harmed but regulation limits were exceeded, so they need to be considerate of that concern: The bad news in the study is that the salinity level in the discharge zone exceeded the permitted level, and the salinity plume extended much farther offshore than permitted under the California Ocean Plan. Senior author Adina Paytan, a research professor in the Institute of Marine Sciences at UC Santa Cruz, said the study provides valuable information for planners considering where to locate future desalination plants and what discharge technologies to use.
- bertil 4y ago
  My dad is a Marine biologist and was the Chief Science Officer of the largest sea research institute in the world.
  - ncmncm 4y ago
    So he probably knows all about how to mitigate problems with brine outflows.
    - bertil 4y ago
      He knows that people like to say it's possible, promise mitigation, and he knows what it feels like to come back later and see the devastation left by not implementing it to save costs.

by bertil 4y ago

ncmncm 4y ago

As I noted, there is no need to concentrate the brine to such a degree that discharging it could be a problem. But even if you did, discharging the brine through a long, leaky pipe or hose would avoid creating any dead zones.

cma 4y ago
How do you create a long leaky pipe without bio-fouling clogging it up? I guess the high salinity itself could prevent fouling.
- ncmncm 4y ago
  With positive pressure and small holes, it would be hard for bio to get in and foul it. Generally you are more worried about biofouling on water intakes, with good reason.

labrador 4y ago

It's only seems like a big issue to people who don't know a lot about the ocean. I grew up surfing in a town at "sewer peak". The effluent from a sewage treatment plant was nearby. It was too close to shore, so they moved the discharge further out into deeper water. Discharging water with a higher salt content than the ocean wouldn't cause any harm at the discharge point, so this concern always seemed like a canard or unfounded theory to me. Some people don't want desal plants near them, so they throw this out there for NIMBY reasons.

ncmncm 4y ago
I gather San Diego discharged sewage into the sea forever. When they finally got to cleaning it up, maybe to appease surfers, they were forbidden because an ecosystem had grown up dependent on it the way it was.
- labrador 4y ago
  Santa Cruz didn't clean it up because of surfers, who didn't care because it wasn't very noticeable, although you knew you were taking a chance of getting mildly sick. It's really difficult to resist going out when the waves are good. It was because the fecal bacteria count was over the new environmental standards that came to be in the last two decades of the 1900's. Many people don't realize there's an acceptable amount of mouse dung and insect carcasses in the food they buy, so it may sound gross to surf in gray water, but it really wasn't. It may be a bigger problem in San Diego because the water is much warmer than the cold currents the come down the coast from Alaska to Santa Cruz (along with some good waves)
hamlsandwich 4y ago
> Discharging water with a higher salt content than the ocean wouldn't cause any harm at the discharge point Sewage and hot, concentrated brine are not the same. Plenty of studies show that there is harm to ecosystems, that's often not properly addressed. - https://www.ccc.tas.gov.au/wp-content/uploads/2018/11/Apx-22-Desalination-Plants-Uni-Sydney-Brine-Discharge-Marine-Env-Impact.pdf https://www.ccc.tas.gov.au/wp-content/uploads/2018/11/Apx-22... - https://phys.org/news/2019-01-brine-discharge-desalination-good-news.html https://phys.org/news/2019-01-brine-discharge-desalination-g...
- ncmncm 4y ago
  Again, this is a problem only if you just drain concentrated brine straight into the sea. But there are cheap, easy alternatives. Easiest is a long, leaky pipe leasing way out offshore. Or you could exhaust it into freshwater right before that enters the sea. Or you could dilute the brine with lots of seawater before draining it.
- labrador 4y ago
  Yes, but out past the kelp beds and sea otters it's all flat sand until it hits the Monterey Bay canyon. The Bay is a marine sanctuary so we'd probably put the desal plant up the Coast on open ocean to serve mostly San Francisco, which now gets it's water from the Sierras. That may not last. Also interesting to me is that they turned the local fossil fuel electric plant that I grew up with into a giant battery: Moss Landing Battery Storage Project https://www.nsenergybusiness.com/projects/moss-landing/ https://www.nsenergybusiness.com/projects/moss-landing/ A few decades ago we lost power for a few days when the ELF (Earth Liberation Front) cut a main power line from Moss Landing to Santa Cruz. edit: I can't find the story and it wasn't the ELF so it must have been a sister group https://en.wikipedia.org/wiki/Timeline_of_Earth_Liberation_Front_actions https://en.wikipedia.org/wiki/Timeline_of_Earth_Liberation_F... Edit: The first link you shared says it's historically been a concern but seems to dismiss the concern by saying it's all in where you put the plant and how you do the discharge, which is obvious: Environmental impacts associated with concentrated discharge have historically been considered as a major environmental concern to marine life with desalination plants. The environmental impact of desalination plants will vary depending on several factors: i. The location of desalination plant. ii. The location of the inlet and outlet. iii. The method used in the desalination facility and the outlet (water channel and pipeline). The second link says nothing was harmed but regulation limits were exceeded, so they need to be considerate of that concern: The bad news in the study is that the salinity level in the discharge zone exceeded the permitted level, and the salinity plume extended much farther offshore than permitted under the California Ocean Plan. Senior author Adina Paytan, a research professor in the Institute of Marine Sciences at UC Santa Cruz, said the study provides valuable information for planners considering where to locate future desalination plants and what discharge technologies to use.
bertil 4y ago
My dad is a Marine biologist and was the Chief Science Officer of the largest sea research institute in the world.
- ncmncm 4y ago
  So he probably knows all about how to mitigate problems with brine outflows.
  - bertil 4y ago
    He knows that people like to say it's possible, promise mitigation, and he knows what it feels like to come back later and see the devastation left by not implementing it to save costs.