In today's backcountry environment, it is a fact that any source of water, no matter how high or remote, is susceptible to contamination by the creatures that visit it – birds, deer, goats, humans. Experienced backcountry travelers recognize the need to play it safe and treat water before drinking.Filters
Water-borne microorganisms cannot survive a rolling-boil. A few minutes (3 or 4) should
suffice. Boiling water is a reliable method of destroying Giardia. The problem here is twofold, (1) dirty water stays dirty--albeit safe, and (2) it takes a lot of heavy fuel to boil all your drinking water--particularly a problem on longer trips.
This is truly an inexpensive, ultralight water treatment. It is important to read the label to see if the manufacturer guarantees the tablet's effectiveness against Giardia, and follow their directions for use.
The downside of Iodine, (1) dirty water stays dirty--albeit safe, (2) it requires a lengthy wait while the iodine works its magic, before the water is safe--like 1/2 hour or more for cold water (3) its effectiveness is lessened in cold or murky water (4) it tastes terrible (although you can somewhat mitigate the iodine taste with flavored drinks) and (5) Iodine can have adversely affect health, especially in people with thyroid disease and pregnant women. An alternative to iodine treatment is Aqua Mira.
Household bleach can be used to disinfect water. The recommended treatment: Add four drops of bleach (sodium hypochlorite) per quart and let stand for 30 minutes before drinking. Chemical treatment can impart an unpleasant taste to water. An alternative to chlorine treatment is Aqua Mira.
Chlorine dioxide - sold as Aqua Mira in the U.S., or Pristine in Canada. It comes in two bottles. You mix drops of each together and chlorine dioxide is formed after five minutes. You then put that mixture into a liter of water, and it is purified in about a half hour, depending on the water temperature and clarity.
It's fairly quick, fairly easy, and works well. And it costs about $14 for 30 gallons of water. That comes out to about 12 cents per liter or quart.
The big advantage of Aqua Mira for many hikers and backpackers is that it has practically no taste. No iodine taste. And even less chlorine taste than chlorinated city water.
Aqua Mira also kills cryptosporidium, if you are in an area where this critter infests water. That's an advantage over iodine, which does not kill cryptosporidium.
These use a combination of filtration and chemical (iodine), enabling them to deactivate viruses and other microorganisms that are too small to be trapped by filtration alone. These are good choices for foreign travel. On the downside, purifiers are relatively costly (US $50 to $200) and heavy (1/2 to 2 lbs).
This method uses a hand pump to force water through a complex matrix of micropores that let water pass but trap harmful bacteria and protozoans. Filters eliminate bacteria, protozoa, as well as clarify the water. On the downside, they are relatively costly (US $50 to $250), and heavy (1/2 to 2 lbs).
The following is a list of preventative measures recommended by the Centers for Disease Control and Prevention to avoid infection with Giardia, Cryptosporidium, and other waterborne pathogens: