Hulda Clark.... I skimmed some of her books. She was big back in the day. She also used some electrical devices that can be bought on eBay.
I remember her use of black walnut tincture which is/was a biggie in herbal medicine before she came along. This tincture used as anti-Parasite and dewormer too.
Water purification products do the trick also. Chlorine dioxide and “pool shock” (calcium hypochlorite)