Travel: Water Treatment and Purification Options for Travelers (Part 2)
Filter, disinfect, boil, or radiate? You have a few choices when it comes to making water safe enough to drink. Some are better than others. Here are the options I considered.
- Boiling.
- UV Radiation.
- Filtering.
- Chemical Disinfection.
- Mechanical filtration followed by chemical treatment or UV radiation.
Boiling (heat disinfection)
The CDC and WHO recommends boiling as the sure fired means of killing pathogens in water. The recommendations are simple -- bring water to a full boil for 1 minute; add 1 minute to the boil time for every 1000 feet in elevation. At 100 degrees Celsius, most pathogens will be killed.
I have found that there is some disagreement to how long you need to boil the water. It is safest to follow the WHO and CDC recommendations.
For a backpacker, this means boiling over a camp stove, but as an international traveler, your options are limited to a bulky electric kettle or an immersion coil. Immersion coils must be submerged in water while plugged in, otherwise it will be permanently disabled if they get too hot (safety feature to keep from starting a fire).
For me, the electric kettles are too bulky, and the immersion coils require a source of electricity and possibly a travel adapter to be functional. Additionally, many online reviews point to the device's fragility -- the number 1 complaint is about units no longer functioning.
Chemical Disinfection / Purification
Following boiling, chemical disinfection is the advice most frequently given by municipalities and government agencies when faced with an emergency. However, the effectiveness of chemical treatment is related to the temperature, pH level, and clarity of the water.
They include:
- Halogens (chlorine and iodine), which are no longer thought to be 100% effective against Cryptosporidium.
- Iodine. Contact time 30 minutes. Ideal concentration 3-4 mg/L or 4 PPM. Water that has been disinfected with iodine is NOT recommended for pregnant women, people with thyroid problems, those with known hypersensitivity to iodine, or continuous use for more than a few weeks at a time. Also, it has an unpleasant taste. Furthermore, recent studies have shown that iodine is not as effective against Cryptosporidium as originally thought [1], [2].
- Chlorine. Contact time 60 minutes. Ideal concentration depends on water pH and temperature. Recommended dose: add 4 drops (0.2 mL) of household bleach to one liter produces a 10 PPM concentration.
- Chlorine Dioxide (Katadyn Micropur MP1, Portable Aqua, AquaMira, Pristine, KlearWater). Chlorine dioxide is a powerful oxidant with germicidal properties. It is unaffected by water pH and does not discolor water.
- Katadyn's Micropur is EPA approved as a "purifier," and is effective against Giardia and Cryptosporidium if the water is treated somewhere between 30 minutes (20 degrees Celsius and clear) and 4 hours (4 degrees Celsius and dirty).
- MIOX. Electricity is applied to a salt-water solution which produces a hypoclorite / mixed oxidant solution, which is mixed with the untreated water. The MSR MIOX system is an EPA approved purifier. Contact time: Viruses, bacteria --15 min; Giardia -- 30 minutes; Cryptosporidium -- 4 hours. These treatment times are conservative, like the chlorine dioxide times.
Mechanical Filtration
Filters do not work against viruses, but they can filter out bacteria and protozoa effectively (as long as the filter has a pore size of 0.2 microns). Since you are unlikely to find viruses in streams and lakes in North America and Europe, filters are often recommended for hikers. They can also filter out sediment, and things that can cloud or taint the water -- which are not handled by chemical or UV disinfection.
UV Treatment
UV light has been used for years on commercial water treatment, and works by damaging the DNA in the microorganisms. There are several manufacturers, but SteriPEN is the hands-down market leader and has a growing following.
However, the SteriPEN only ONLY treats water inside the bottle and ONLY the water under the waterline. Water droplets inside the bottom or on the threats of the bottle will not be treated.
Resources
- [1] "Inactivation of Coccidian Parasites by Water Purification Chemicals and Treatment Device for Campers and Hikers." Lee, M.B. and Lee, E.H.; Environmental Review. Winter 2005.
- [2] "Do Iodine Water Purification Tablets Provide An Effective Barrier Against Cryptosporidium Parvum?" Stark, Bowman, Labare, Fogarty, Lucio-Forester, Barbi, Jenkins, Pavlo, Butkus; Military Medicine. October 25, 2001.
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