To purify water, low-tech methods can be highly effective

If you’re headed to a developing country or bound for adventures where bubbling streams beckon, use common sense and consider the latest in water disinfection.

Contaminated drinking water can be a trip’s undoing, causing traveler’s diarrhea, an intestinal infection or other nasty problems. Beyond the United States, Canada and Western Europe, travelers often need to choose their drinking water carefully — and decontaminate it if they have any doubts.

New solutions are available. Among the most promising: portable water purifiers that use ultraviolet light to destroy waterborne organisms.

“Ultraviolet has been a revolution for the water industry,” says Zia Bukhari, a senior molecular biologist at American Water, a New Jersey-based company providing water services in 27 states. UV purification has long been used successfully in industrial settings, he says, and only recently has become widely available for personal use. “UV is especially useful to inactivate protozoan parasites such as Cryptosporidium and Giardia,” he says, referring to organisms that can cause diarrhea.

One UV device, the SteriPen, shoots ultraviolet light into water. It runs on four AA batteries, and depending on which kind (lithium, alkaline or nickel) are used, it can disinfect about 40 to 160 16-ounce glasses, says Miles Maiden, chief executive of manufacturer Hydro-Photon.

UV disinfection isn’t as foolproof as other methods, says Vern Schramm, chairman of biochemistry at the Albert Einstein College of Medicine in New York and past chairman of the American Chemical Society’s biological chemistry division.

“The concept is feasible, but it usually takes quite bright light,” Schramm says. Water that sits in shadows won’t be disinfected. In industrial applications, he adds, the water usually flows through a tube with UV light in the middle, minimizing shadows.

Schramm prefers filtration, boiling or chlorine drops. These solutions may be low tech, but they’re also low cost: The SteriPen retails for about $150; iodine and other sterilization treatments good for 25 quarts of water can cost as little as $5.

Boiling is still best, biologist Bukhari says. The Centers for Disease Control and Prevention recommends bringing water to a rolling boil for one minute and allowing it to cool to room temperature. Don’t add ice, which might be contaminated.

Recommendations change with altitude. At about 6,500 feet, for example, water should be boiled for three minutes or a chemical disinfectant added after one minute of boiling.

Disinfection products include tincture of iodine or tetraglycine hydroperiodide tablets (such as Coghlan’s or Potable Aqua), which are available at sporting goods stores. The CDC says you shouldn’t rely on iodine to kill Cryptosporidium unless the water can sit for 15 hours before being consumed.

Water filters are another option. To kill Cryptosporidium and Giardia, the CDC says, pick a filter whose label carries one of the following messages: “reverse osmosis,” “absolute pore size of 1 micron or smaller,” “tested and certified by NSF Standard 53 or NSF Standard 58 for cyst removal” or “tested and certified by NSF Standard 53 or NSF Standard 58 for cyst reduction.” (NSF International is a nonprofit organization that evaluates and certifies consumer products.)

Cancer patients on chemotherapy, people with AIDS, the elderly, the very young and others with compromised immune systems must be extra cautious about drinking clean water, Bukhari says. For these people, good old-fashioned boiling is best.