why can’t we use dirt to process salt water

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If we pumped salt water onto land, would it filter the salt out while adding to our underground water source?

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Sea water isn’t just a little salty, it’s 3.5% salt by weight.

For every gallon of water you purify you have to remove a quarter pound of salt.

The average household uses 300 gallons a *day*, so we’re looking at *seventy five pounds a day* of salt per household.

Dirt or clay or activated charcoal or any other kind of substrate filtration can pick some salt out of water, but the volume of salt you’re dumping here is immense.

Soon you have more salt than soil, and the whole thing is a brackish bog.

Nope. Regular filters don’t work on dissolved salt.

You have to actively push the water through, in a process called “reverse osmosis”, which is frankly, incredibly expensive.

And that’s without the environmental disaster you get from pumping tons of salt into the ground. There’s a reason the Romans salted Carthage after they burned it, too much salt prevents things from growing.

Because that dirt would become toxic to life from the filtered out salt/brine if it worked. A tiny bit of salt isn’t that bad but when you start doing it on scales needed to support human consumption it is going to create a lot of brine that needs to be disposed of properly to not affect the local ecosystems.

No. Dirt doesn’t filter salt out of water. The salt is not microscopic particles, it’s dissolved in the water. You need specially manufactured membranes with the right pore size to hold back the singular ions. On top of that, in the dirt where we pour the salt water, nothing would grow anymore, because plants can’t survive such a high salt content, just like we can’t survive drinking much salt water.

Thank you. I understand now.