Hi Coragyps,
The reason that water out of wells is typically reinjected deep into the earth is because it's too nasty to treat otherwise. The salt content, including table salt, calcium, magnesium, sometimes barium, and sometimes sulfates, make it largely impractical and uneconomical to purify. Even if you could distill it, all those salts would still need to be dealt with. You could take a lot of it to Smackover, Arkansas, and dump it on the ground like they did in 1915, but it would just make another big treeless patch there.
It seems to me that the issue is that the amount of such water slurry material has increased dramatically with the newer fracking wells, and that this has caused the increase in noticeable quakes, plus they are doing it closer to places where people live, again making it more noticeable.
Is it a problem in itself? probably not. Is it something to be ignored? probably not. It seems to me that a bigger concern is the possible contamination of potable water aquifers that would permanently render them unsuitable for consumption.
Personally I am looking at roof mounted solar panels and a small wind generator (as seen on sailboats) to decrease my dependency on fossil fuels (sorry).
Enjoy
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