If you’re heading out to do some backpacking, some form of water filtration should be in your emergency kit, even if you don’t plan to be far from treated water. The reason is simple: injuries, wrong turns, or severe weather could leave you out on the trail with no access to clean water and your own water supply running low. With a water purifying system, you can use natural water sources with a minimum of risk.
Natural Water Threats
Drinking untreated natural water exposes you to a wide range of potential pathogens, including bacteria, protozoans, and viruses. Some may take weeks to cause symptoms, while others can sideline you quickly. Most cause gastrointestinal issues, including diarrhea, which can quickly cause dangerous dehydration.
All these tiny threats are invisible to the naked eye and you cannot judge the quality of water by its clarity. And not all pathogens respond to the same type of water treatment. Viruses, for instance, can slip past even the most powerful filtration system, while protozoa can survive chlorine treatments.
Your water treatment system needs to be able to remove these invisible threats while also filtering out particulates: silt, decaying plant material, dead bugs, and similar debris that can cloud the water and leave it tasting horrible.
Chemical Water Treatments
Water purification tablets such as iodine and chlorine dioxide are easily transported in your backpack. Each has its own advantages and disadvantages.
Iodine will kill bacteria, viruses, and most protozoa, although it will not kill the common Cryptosporidium which causes severe diarrhea. Iodine also has a strong taste and odor which makes drinking treated water unpleasant. In addition, iodine water treatments should not be used if you are pregnant, have an iodine hypersensitivity, or suffer from thyroid problems.
Chlorine Dioxide will kill almost all infectious microorganisms and viruses, and works in a wider range of water pH than chlorine. Chlorine Dioxide also purifies cloudier water better than chlorine, which is a serious consideration when out in the wilderness, where water clarity may be an issue.
Filters: Size Matters
A water filter’s ability to remove pathogens depends on the size of the gaps in the filter medium. Filters with gaps 0.5 microns and smaller will strain out particulates, most protozoa, and larger strains of bacteria. Filters sizes of 0.2 microns will remove most smaller bacteria as well.
Unfortunately, filtering alone will not remove viruses, so it best used in combination with another treatment type.
Water purifiers combine filters with chemical treatments to kill viruses while filtering out larger pathogens. While most use iodine or chlorine dioxide, some need no chemicals, such as the Katadyn Expedition Water Filter, which kills pathogens using silver particles embedded in ceramic. Capable of treating large amounts of water quickly, water purifiers are ideal for the frequent hiker who travels in larger groups.
Ultraviolet Light Treatment
Small, portable ultraviolet light filters are an excellent choice for backpackers who want to maximize packing space and would only need to treat water for drinking. Designed like thick straws, such filters allow you to drink straight out of natural water sources.
Ultraviolet light treatment works by using UV light to damage the DNA of bacteria, protozoa, and viruses, all of which need to reproduce and build up in the human body to cause illness. By damaging the pathogens’ DNA, the water treatment ensures this cannot happen.
While certainly lightweight and eminently portable, ultraviolet backpacking treatment systems have a limitation. They work best with clear water. Using them to treat cloudy, silty water may allow pathogens to escape UV damage, so consider water quality carefully before using them.