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0 pointsmikeyouse2y ago0 comments

We just simply don't need that much brine for useful minerals -- it's a huge cost and you'll be left with massive piles of mostly useless salt.

On one of my hard drives, I've got an engineering / construction plan for a moderately sized intake + discharge for a small RO facility that would've passed muster in Australia, which has pretty reasonable environmental protections. Round numbers - the intake would have cost $25 million and the discharge more like $75 million. You need a massive structure to be able to emit that brine back into the environment in a way that doesn't just nuke the surrounding marine life. Huge pipes + check valves + cascading discharges, all either on the ocean floor if there aren't reefs and other sensitive areas or even worse from a cost perspective, tunneled out to a depth that can handle the amount of salt.

Seawater is ~35g/L of TDS - the author is talking about 5 million acre feet of desal - what's that, 20 million tons of salt annually?

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0xNotMyAccount2y ago

This is doable. Many coastal wastewater systems already have large pipes that extend miles to sea (1), and that's a rounding error compared to the many more miles of pipe routing sewage to the plant (2, pg A-3)

(1) https://www.wateronline.com/doc/new-10-mile-long-sewage-tunn...

(2) https://www.sandiego.gov/sites/default/files/ploovol4_15.pdf

Pipes tend to last a long time, in large part because it's relatively straightforward to manage the chemistry problem in the pipes.

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