What can hikers and back packers do to treat stream water to make it safe to drink?
Any water that looks good enough to drink can be made microbiologically safe by boiling. Vigorous boiling for 20 minutes will kill bacteria, viruses, and protozoan cysts (pathogens). Water purification tablets, available at drugstores and camping supply outlets, can be put into a glass of clear water. They take about 5 minutes to dissolve and release a disinfectant .These tablets will not protect against Giardia (the primary concern in most areas) or parasitic worms. Portable water filters available in the market can provide effective treatment.
