How do you purify water over a fire?
After filtering as many of the particulates as possible. Fill your container with water, place over the fire, bring to a rapid boil, then allow to cool (drinking hot water can induce vomiting). Boiling will kill the harmful bacteria in the water, as they cannot withstand the temperature.
Is boiling river water safe to drink?
Treat natural water before you drink it
Bring the water to a rolling boil, cool it and then use it for drinking. Boiling is effective against most microbial contaminants such as bacteria, viruses and protozoa. If boiling the water is not practical other treatment methods can be used.