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It's a Jungle Out There
In times of yore, filtering was pretty much a matter of straining obvious cooties like pine needles and particulates with a scrap of cheesecloth. Now, this is simply considered the prefilter phase, though still an important step—visible, larger waterborne debris only clogs the business end of modern filters. Most prefilters are little more than a wad of foam or a coarse screen. (If you lose yours, you can cobble one quickly with a square of cotton or silk bandanna and a bit of duct tape.)
In depth filters—the kind you pump water through—the real action takes place in the element, or cartridge.
Carbon , an age-old filtering material, is still present in some elements—primarily to eliminate bad taste, since the EPA's protocol for microbiological water purifiers is rigid, and carbon alone won't cut the proverbial mustard.
Ceramic , another porous material, has been proven to work consistently to trap the little buggers, and the element can be cleaned many times before replacement. Check out MSR's MiniWorks EX Microfilter for durable performance as reliable as its cookstoves.
Molded fiberglass is also found in many filter cartridges, though it is not as long-lived as more costly ceramic elements.
Microfiber technology has its place in most depth filters; there is often a sheer screen built into the contraption that will stop protozoa smaller than a micron—and no, you can't see monsters that small.Many units combine the virus protection of a chemical treatment with cyst-stopping filters—some even in a water bottle that you simply fill and drink from, like the Katadyn Exstream XR Purifier. These are most suited for solo travelers.
Large groups might consider a gravity-feed filter, which works like it sounds. This eliminates the inevitable clogging of a small pump and the unsafe guesswork of treating water on a big scale. Consider the Katadyn Base Camp filter for your camp workhorse. This updated model filters at a much faster rate than its predecessor.
Newest Development in Purification
"Going beyond chemicals is what's state-of-the-art," says Miles Maiden, a solar engineer who developed the SteriPEN, which is not a filter, but a compact ultraviolet light that devastates microbes without changing the taste or mineral content of water. You dip the battery-operated (four AA's) pen in 16 ounces of water and stir until the light goes off. Painless operation (until you need to dispose of the batteries) and relatively economical, the SteriPEN reduces bacterial, viral, and protozoan cyst pathogens by 99.9 percent."Ultraviolet detoxification/disinfection has been used for nearly 75 years in water treatment," explains Maiden. "Your favorite bottled water is likely purified this way." You might also want to check out MSR's MIOX Purifier, which releases a powerful dose of mixed oxidants using just common camera batteries and salt.
Filter Care and Maintenance
Whatever you choose, make sure you use it, a lot, so that you're drinking plenty of fluid out there. Dehydration is often the root cause of bumbling accidents and trail maladies.
Read the instructions. Always.
Use a prefilter.
Learn recommended cleaning procedures and your filter will last longer.
Pump water completely through filter and allow it to air dry between uses. Carry it in an outer pack pocket or in a mesh stuff sack.
Manufacturer Websites
SteriPEN: www.hydro-photon.com
AquaMira: www.mcnett.com
MSR: www.msrcorp.com
Katadyn: www.katadyn.com
Potable Aqua: www.potableaqua.com
Details mentioned in this article were accurate at the time of publication
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