this post was submitted on 03 Oct 2023
63 points (95.7% liked)
Science
13182 readers
24 users here now
Subscribe to see new publications and popular science coverage of current research on your homepage
founded 5 years ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
Would it really create a dead sea zone? I mean to desalinate, you're pulling the water out, extracting salt. So effectively taking water from the ocean without the salt. Surely putting it back isn't going to be massive issue as currents will push out more salty water to less salty areas until it is back to where it was.
I guess the art of it would be the rate of returning it to the sea, and the surface area over where it is put back. Longed pipes to deeper water will probably make a less horrific situation, as more water = less salt concentration.
Though, we shouldn't rule out make a deal with social media, the share level of salt involved probably needs replenishing.
it seems that the sheer amount of salt we accumulate when desalinating for scale consumption is so large that there's no easy way to spread it. yeah, the ocean will take care of it eventually, but we aren't gonna ferry salt across a large body of water to dump it gently into the ocean. we'll pipe it somewhere, and wherever it is it will create a pocket of dead ocean water. it's a matter of choice and water regulation, really.
Yeah just looked this up. So the numbers ay not be perfect.
But at 3.5% salt in sea water. 6l of water will produce 210g of salt.
6g is the max recommended per day intake. So let's round down to 200g a day. X 365
76kg of salt per person per year. A small sea side village (1000) would be a dead-sea side village in a few years.
Also worth noting. While the dead sea is about 33% salt so 10x most living seas.
It would take well under 2x the salt level for fish to start dying in large numbers. So making the sea dead. Just as a fresh water fish would dehydrate due to excess salt drawing water from its cells in sea water. It would only take a small increase in the salt water vs cell salt content for sea fish to die.
PS 2l worth or 70g of salt will kill most humans without drastic care.
Just found looking that up interesting so thought id share.
Salt is highly corrosive, especially when concentrated into a slurry. If you dump it directly from shore you kill any local wildlife and destroy the local area before it dilutes. If you pipe it further out into the ocean the pipe will continually need maintenance due to corrosion and makes it more expensive
Isn't that assuming you pipe it out using metal. Would plastic or carbon fibre be viable for this? Or at least coating a metal pipe?
There are a number of alloys that are used when working with desalinization plants, but the effective ones are cost prohibitive.
Even if they had a way of pumping it out cheaper, it still comes with issues that are costly. There are chemicals used during the process which pollute the brine and cost money to remove. It also comes out much warmer than surrounding water which disrupts the ecosystem. The brine eats up oxygen levels and suffocates animal life in the area.
They are trying to dilute the brine before releasing it back to the ocean but this is either not effective enough since you're using salt water from the same source you're pumping into, especially if the area doesn't have strong currents to carry it away. Or you're using water which doesn't have high salt levels and can dilute it to healthy levels, which you might as well just treat and use in the first place instead of using saltwater.
It's not an easy problem to solve at the moment
Fair points. I appreciate the response.
UK water companies are starting to explore this option and are hitting huge regulatory barriers as the by-product is considered industrial effluent. It will require regulatory shift. I'm wondering if anyone has done the maths properly though. How much salt do we mine each year? And how does it compare to the salt produced by desalination? If the average consumption of water in the UK is 125 l, then we can compare the salt produced to the salt consumed per capita every day in the country (e.g. industrial use, salt spreading on roads, etc.).
The truth is that you'll never be producing 125 l for 69M people all from desalination. Only a very small fraction of the 125 l will come from desalination.
The challenge is being driven by climate change and stringent environmental legislation in the UK water industry. These challenges are creating large gaps in their water resource planning for their future water supply. Hence desalination and effluent reuse now being considered as options. Its all in the water company water resource plans that have been published on their websites.
And BTW, I don't fully understand why 3 people have down voted this post. Its an incredibly interesting topic.