Boiling water kills bacteria and parasites like giardia and cryptosporidium. Cool and do not contaminate it with dirty utensils, hands or containers after boiling. Boiling water concentrates nitrate levels. Therefore, don't boil if there's nitrate in the water. Water can also be disinfected with chlorine, bromine, iodine, or ozone.
Chlorine oxidizes iron and manganese so they can be filtered out.
Yet, high concentrations of chlorine give water a bad taste. They may combine with other components to form cancer-causing compounds. Ozone may be used to disinfect public water supplies, but is rarely used for private supplies. Chlorine is used most often to disinfect private wells. A well may be contaminated when flooded or when the watertight casing is no longer intact.