One of the joys of visiting places far off the beaten path is that you never know what you’ll find. Unfortunately, the same can be said for things you’d rather not find, such as unsafe drinking water. Avoiding water-borne illnesses caused by such organisms as E. coli, rotavirus, norovirus, and protozoa like Giardia and Cryptosporidiumis a challenge even for experienced travelers. As you probably know, in developing countries you should drink only bottled water or water you’ve boiled yourself. That’s still the best advice, but it’s often not practical, especially in wilderness areas.
Luckily, there are many portable disinfectant products you can buy on the Internet or at stores that sell travel and camping gear. Choosing one depends on how much convenience you desire, how much you want to spend, how much you want to carry, and how much you are willing to sacrifice in terms of taste. No water purification or filtration device is perfect; each has its strengths and weaknesses. In fact, some experts recommend combining systems to kill as many microorganisms as possible. Here are the pros and cons of the three main types of purifiers.
UV purifiers: a light idea
Pros: Ultraviolet (UV) light is the easiest purification method for removing or deactivating at least 99.9 percent of bacteria, viruses, and protozoa. You simply immerse a miniature UV lamp in 16 ounces of water for less than a minute, or use a device that has the lamp mounted on the underside of the water bottle cap, then follow the manufacturer’s instructions to agitate the water.). One popular brand, Steripen, is available for less than $100. UV purifiers generally run on batteries, but many are easily rechargeable, sometimes from a portable solar panel or even via a computer.
Cons: Portable UV purifiers require clear, sediment-free water to do their job—though certain models come with a small filtration unit to accomplish this. You have to shake the water during the purification process.
Tip: Be sure to bring extra batteries if your unit is not rechargeable.
Chemicals: a mixed bag
Pros: Chemical disinfectants—namely iodine, chlorine, or chlorine dioxide—are effective, lightweight, and inexpensive, and they’re good for treating large quantities of water.
Cons: Iodine and chlorine can impart an off taste, and they aren’t as effective against Giardia or Cryptosporidium compared with filters and UV purifiers. Iodine is not recommended for long-term use or for pregnant women or people with thyroid conditions.
Tip: Chlorine dioxide is more potent than iodine or chlorine, has no significant aftertaste, and will eradicate Giardia as well as Cryptosporidium—but Cryptosporidium requires a four-hour wait time.
Filters: good for sediment
Pros: Filters, depending on the specifics of the unit, can quickly remove sediment in addition to most bacteria and parasites. This makes them especially useful for wilderness areas. Some brands, including Lifestraw, sell convenient individual water bottles with a built-in filter. Backpackers can now buy large units that call for hanging a water reservoir bag from a tree limb—some with a bucket adapter—and letting gravity and the filter do the work.
Cons: Unless they contain a chemical disinfectant or use UV light, filters may not be effective at removing viruses, such as rotavirus and norovirus. (An exception is the Sawyer Point Zero Two purifier, which has a very small pore size and does remove viruses, according to its website.) Many require you to pump the water; this can be tiring.
Tip: Filters can clog from debris, so keep them clean as per manufacturer's instructions.
Bottom line: For most travelers, a UV purifier is an excellent choice, since they’re small and remove the vast majority of contaminants. If the water you’ll be purifying has a lot of sediment in it, however, look for a method that combines filtration with UV, activated carbon, or a chemical disinfectant. One such product, Water to Go (about $28)—sold in Europe but also available on Amazon—is a water bottle that combines several processes in one, including activated carbon and mechanical filtration, which together reduce contaminants, including viruses, by over 99.9 percent.
Also see Choosing a Home Water Filter.