3 ms·
Even these numbers are too small if you're going to RO seawater. I suspect what you have in upstate NY isn't access to seawater but access to some kind of less
by msandford 5y ago
Even these numbers are too small if you're going to RO seawater. I suspect what you have in upstate NY isn't access to seawater but access to some kind of less than amazing mostly-not-saltwater.
The osmotic pressure you need to overcome to perform desal is directly proportional to the concentration. So 500-1000ppm water that you don't love is a lot less challenging than seawater which is about 3.5% or 35000ppm.
You can do "I want extra pure drinking water from 'normal' water RO" for a few hundred, sure because the pressures are in the range of 20-60 psi. Reasonably efficient seawater starts somewhere around 400-600psi and I've heard of plenty of systems that work at more like 800-1000psi. Different pumps, membranes, membrane housings, piping, all of it. It's a couple thousand dollars plus a fair amount of energy unless you buy even more expensive energy recycling pumps that use the pressure in the brine output to help on the input.
- kortex 5y agoExactly, there's a pressure/flow/salinity tradeoff triangle. Higher salinity needs higher pressure and/or waste bypass. This was running around 100-150 psi, was a few years back, don't quite remember. But a few hundred bucks will still get you from either "potable but not great" to fairly pure, or brackish to potable. If you have effectively infinite seawater and power, you can still pump at lower pressure and get pure permeate, it's just less efficient per unit pump and filter lifetime. If you had a super reliable pressure system (low friction ceramic pumps for example, not cheap but last forever) and cheap first-pass filters, you can run it for quite some time. But you're spot on in that you get to a point of engineering-give-a-mouse-a-cookie and it just makes sense to optimize the whole stack.