he treatment process begins with aeration, which causes the metals to begin oxidizing (rusting) naturally. Aeration also removes most of the hydrogen sulfide in the water. After some detention time, an oxidizing chemical is added to ensure that oxidation is complete before filtering. Any metals not fully oxidized will simply pass through the filters. The filters also remove any remaining hydrogen sulfide.
I don't like the "oxidizing chemical" that is not named. And most assuredly the salt. I understand these may or may not be relatively harmless but that depends upon the quantity.
The first stage of theproces is to remove metals like iron manganese, uranium. these metals may be soluble if they are bonded to sulfide or chloride. But the oxide form is not soluble. So to remove these metals you put carbonate or hydroxide in the water like sodium hydroxide or sodium bicarbonate. The sodium reacts with the metals converting them to oxides which typically settle at the bottom of the tank.It is commonly done at many utilities with hard water sources.
Then they soften the water....
As to the impact of this water on human health, well size maters. because of our size we need a lot of sodium and potassium and the amount in the drinking water is likely not enough to satisfy daily needs. So food is still the primary source of sodium and potassium for people. but for a small fish in many gallons of water it would have a greater effect. But given that this is a utility they are probably aware of the risks of sodium and potassium and could easily be using a mix of sodium and photassium in the softening process. Meaning the fisk to you and your fish might not be as bad as I ordiinally said. Can you provide a link to your utility ? I would like to see the water qualityreport.
however all that said your water as it is right now is still a risk and if you want plants most fertilizes on the market will not work.
Thebest think you can do iso to get yourself a RO system. You can then start off with very clean water and just add a GH booster to the water to get the GH up to a level appropriate for your fish. If you want plants then we would have to come up with a fertilizer plan.