On the subject of water, If you have arsenates in your water and you have iron in your water you can use the iron to remove the aresenates.
We have 25ppm iron and .5ppm arsenate.
I set up a system that pushes water through a Mazzei injector into a vessel. This causes air to be mixed well with the incoming raw water. The dissolved iron is oxidized to iron oxide. The arsenate is oxidized to a state that makes it easier to remove. The iron oxide adsorbs the arsenates. The resulting precipitate falls to the bottom of the tank. After a day or so the supernatant water above the precipitated floc can be pumped off through a common 20 micron houshold household filter. I follow this with a carbon filter. Most of the minerals remain, but the iron and the arsenate are removed. Detectable arsenate goes from 500 parts per billion to under 5 parts per billion and the only reagents used are your own water and air.
We are pretty lucky on that: Arsenates and iron tested as pretty low when I bought this place. That said, the testing was NOT right after a heavy rain, but, we don’t try to drink the well water after a heavy rain anyway, even 2-stage filtered (2nd stage being the activated carbon filtering for drinking water).
Still, it’s really fascinating how “simple” air can purify water of a number of things! Great post!