I think the article author is completely confused and doesn’t understand what’s happening. There are hints of what’s happening in this paragraph.
Fresh water—or treated wastewater—is placed on one side of a membrane. On the other side is seawater, made even saltier by concentrating leftover brine from a desalination process. The difference in saltiness pulls the fresh water across the membrane, increasing the pressure on the saltwater side. That pressure is then used to drive a turbine, generating electricity.
I don’t think any fresh water is being used. I think what’s actually happening is…
Very salty wastewater (from the desalinization plant) is placed on one side of a membrane. On the other side is seawater. The difference in saltiness pulls the wastewater across the membrane, increasing the pressure on the saltwater side (or maybe the other way around). That pressure is then used to drive a turbine, generating electricity. The waste then is just water that’s saltier than sea water, but less salty than what came from the desalinization plant.
According to Japanese sources Mainichi, it is indeed treated waste water one one side and desalination brine on the other. Both the waste water and brine are meant to be dumped anyway, and it’s also harmful to sea life to dump brine directly. Treated waste water isn’t saline, so is perfect for diluting the brine. Might as well get some free power out of it.
Lots of places treat their wastewater and then discharge it. For example, where I live, wastewater, that is to say, sewage which has had solids filtered out, is still rather pooey and pissy but not salty, gets treated (I don’t know how) and is then injected into natural underground aquifers where it eventually percolates out to bores or springs where it’s collected and used for irrigation, contributes to natural springs, or possibly even winds up in a drinking water catchment.
All wastewater, regardless what happens to it, has to be treated before release. If it’s still 99.9% fresh, then why not use it to create osmotic pressure before dumping it.
I think the article author is completely confused and doesn’t understand what’s happening. There are hints of what’s happening in this paragraph.
I don’t think any fresh water is being used. I think what’s actually happening is…
Very salty wastewater (from the desalinization plant) is placed on one side of a membrane. On the other side is seawater. The difference in saltiness pulls the wastewater across the membrane, increasing the pressure on the saltwater side (or maybe the other way around). That pressure is then used to drive a turbine, generating electricity. The waste then is just water that’s saltier than sea water, but less salty than what came from the desalinization plant.
According to Japanese sources Mainichi, it is indeed treated waste water one one side and desalination brine on the other. Both the waste water and brine are meant to be dumped anyway, and it’s also harmful to sea life to dump brine directly. Treated waste water isn’t saline, so is perfect for diluting the brine. Might as well get some free power out of it.
That makes a lot more sense than sea water and fresh water.
Yeah, it’s just recovering a little of the energy spent in desalination, making it slightly less energy consuming.
So it’s a turbo engine.
Why isn’t it fresh (non-salty) wastewater?
Lots of places treat their wastewater and then discharge it. For example, where I live, wastewater, that is to say, sewage which has had solids filtered out, is still rather pooey and pissy but not salty, gets treated (I don’t know how) and is then injected into natural underground aquifers where it eventually percolates out to bores or springs where it’s collected and used for irrigation, contributes to natural springs, or possibly even winds up in a drinking water catchment.
All wastewater, regardless what happens to it, has to be treated before release. If it’s still 99.9% fresh, then why not use it to create osmotic pressure before dumping it.
There*
Friggin hell. Thanks.