[Here is information on water treatment for metals from the Berkely Pit mine.](https://pitwatch.org/learn/water-treatment/) Same issue, manganese, I believe. Raise PH and allow metals to precipitate and settle. You may be able to do this with baking soda, but more likely you will need lime. It is still not good for drinking, but has less metal. I think you ride this out with alternative water source for drinking, cooking, and washing hair if your hair is blond or light grey.