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Water Purification

Today, it is virtually impossible to find pristine water resources anywhere on the planet. For backcountry travellers and trekkers to foreign lands it is imperative that they use some method to ensure the water consumed is safe for drinking. There are two types of water contamination: Biological and Toxic. Biologic contaminations include a host of microorganism such as Giardia, Crytosporidium, Escherichia coli (E. coli), Salmonella, Hepatitis, Rotavirus, and Norwalk virus. Toxic contamination is chemical contamination from pesticides, mine tailings, and diesel spills etc. Boiling, filtering, or chemically treating water can remove or kill microorganisms, but it will not remove chemical toxins.


This method is the good old standby. Water after boiling does kill bacteria, and virus, etc. but has a tendency to taste rather sterile. Having to carry enough fuel to provide adequate water for your trip is a big disadvantage to some.


Unfortunately, there is no such thing as the perfect water filter. They cannot filter out viruses, and not all of them remove bacteria. A water filter pumps water through a microscopic filter that is rated for a certain-size organism. The micron is the standard size rating for filters. For reference purposes, the period at the end of this sentence is 600 microns. When selecting a filter you should have an idea of what potential organisms you need to treat against. Using a filter designed for Giardia will not help when travelling to areas where Hepatitis A virus is in the water.

The table below lists Common microorganisms and the filter size needed to ensure removal:

Organism Examples General Size Filter Type Particle Size Rating
Protozoa Giardia, Cryptosporidium 5 microns or larger  Water filter 1.0–4.0 microns
Bacteria Cholera, E. coli, Salmonella  0.2–0.5 microns  Micro filter  0.2–1.0 microns
Viruses Hepatitis A, rotavirus, Norwalk virus 0.004 microns Water purifier to 0.004 microns

Curtis Rick. 1998. Backpacker's Field Manual. Random House.

There are two basic types of filters:

  1. Membrane Filters use thin sheets with precisely sized pores that prevent objects larger than the pore size from passing through. They are relatively easy to clean; however, they clog more quickly than ceramic/carbon filters.



Examples: Katadyn Hiker PRO Water Microfilter , Katadyn Vario Multi Flow Water Microfilter






 2. Depth Filters use thick porous materials such as carbon or ceramic to trap particles as water flows through the material. Activated carbon filters also remove a range of organic chemicals and heavy metals. Rough treatment or freezing can crack the filter, leaving it useless. 

Example: MSR sweetwater.

Please note that there is a disparity between a filter and a water purifier. Filters do not remove viruses. Water purifiers, which pass the water through both a filter and an iodine compound kills any smaller organisms down to 0.004 microns. Purifiers should not be used by people who are allergic to iodine.

Chemical Treatments:

The main chemical treatments of water use Iodine or chlorine. Some of the most popular and effective brands are Potable Aqua Tablets, Polar Pure Water Disinfectant , and Aqua Mira . Please be aware that cryptosporidium is becoming very resistant to iodine and chlorine, so it is questionable how much longer this will be effective. One of the main issues with using iodine or chlorine is the taste they give the water. If using iodine, one effective method for reducing its taste is to add vitamin C to neutralize it only after the treatment has been completed.

Ultraviolet (UV) Light:

Compared to the other treatments, this is a relatively new process for treating water in the backcountry. Innovations in design have minimized the size and weight of these water treatment devices, making them an excellent choice for the backcountry. The SteriPen Adventurer has some excellent features geared specifically for those of us who need something durable, lightweight and effective. Weighing only 3.6 ounces with batteries included it will purify .5 liter/16oz of water in 48 seconds, or 1 liter/32oz in 90 seconds. It effectively destroys viruses, bacteria and protozoa. It is less effective in murky water. When treating water with suspended solids it is important you filter water through fabric or cheesecloth before applying the pen.

Check out Joe’s Sport & Surplus for all your water purification needs. We stock Katadyn and MSR filters and Aquatabs but can order in any system you require.