[ethbr0]

Depends on the initial use. Water treatment is a surprisingly interesting (to me at least) rabbit hole.

You don't really control the upstream: someone flushing their toilet, or a laundromat dumping solvents down the drain?

But it's a solved problem to continually test the incoming water supply for the basics (pH, TDS). Plus intermittent checks for full workup (heavy metals, etc).

After that, it's a question of working it through the appropriate steps to get it to the state you want. Sort of like a continuously operating manufacturing line, except you get to blend the product at the end and only have to QA the blended result.

As someone quipped, "Dilution is the solution." Given enough volume and time, you can dilute even an arbitrarily large amount of lead to safe levels.