You'd think the most expensive part would be the quark-gluon plasma chamber, but it's actually usually the tube to the top of the atmosphere to carry the cosmic rays down.
The joke about adding well water back in again at the end is "correct". Reverse osmosis removes 100% of the solids from the water, but drinking water usually contains small quantities of solids - you can see a breakdown on the label of some bottled water. Completely pure water would leach all of the solids that have built up on the insides of water pipes over the decades, and leaches away the protective oxide layer from metal pipework, causing it to corrode surprisingly rapidly. It also tastes pretty shitty - kind of "dead". So a small amount of high-solids water is mixed back in after RO to bring the water back to normal levels.
All that other shit in the diagram? No. Purification and treatment takes place after the mixing step, it would be crazy not to.
But also yes. Pure water tastes awful. I'm one of those "super" tasters and I used to work for a water filtration company. Lemme say... what people think they want and what they actually want are often two different things.
Yeah, I'm with you there - worked for twenty years in water treatment myself. Water before it's been chlorinated / chloraminated for supply? Makes the best cups of tea and coffee ever - you need to boil it, of course. RO water? Vile.
This is why we have remineralization filters I love my highly insane filtered water. Goes through 10 stages before finally hitting reverse osmosis just to extend the reverse osmosis filter life. But it has a alkaline remineralization as the last step so it tastes amazing
Water taste is subjective. I absolutely hate the taste of high-mineral water and love pure water. RO or distilled water tastes absolutely amazing to me.
Here’s an idea. Once you’ve already split the water molecules with electrolysis, you should throw those streams into separate mass spectrometers, but without the detector obviously. The idea is, that with ions flying in a magnetic field, their mass would determine where they land. Anything that isn’t the right kind of isotope, let alone right kind of atom, would be separated into the waste stream.