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Drinking Water Safety

What is water disinfection?

Water disinfection means destroying microbes or removing them from water. Two common microbes in water are parasites Giardia and Cryptosporydium [1].

Disinfection of Water for Personal Use for Travelers

Boiling water for one minute is very highly effective in killing all microbes [2]. At altitudes higher than 6,500 feet (2,000 meters) water should be boiled for 3 minutes [2].

Reverse osmosis pumps are highly effective in removing all types of microbes [3].

Other water purifying methods:

Filtering through a dense cloth can remove gross impurities, but not microbes [3].

Coagulation-flocculation tablets can make cloudy water clear but do not remove microbes [3].

Disinfection with iodine tincture or tablets is highly effective in destroying bacteria and viruses, but does not reliably destroy parasites [1,2].

Disinfection with chlorine in the form of sodium hypochlorite (household bleach) or calcium hypochlorite (tablets) is highly effective in destroying bacteria and viruses, but not parasites [2]. Water should sit for 30 minutes before use [1]. Tablets that release chlorine dioxide are highly effective in destroying all microbes [3].

Water filters with absolute 0.3 micron or smaller pore size are highly effective in removing parasites, such as Cryptosporidium and Giardia, and moderately effective in removing bacteria but not viruses [2].

Water purifiers that use filters with absolute pore size 0.3 micron or smaller pore size, combined with iodine or chlorine are very highly effective in removing parasites and bacteria but not viruses [2,4].

Portable MIOX (Mixed Oxidation) devices destroy most microbes within four hours [5].

Portable UV lamps may kill most microbes in clear water by ultraviolet light, but more testing is warranted [3].

Note that freezing does not kill all microbes, so, when traveling, you better avoid using ice cubs.

Disinfection of Municipal Water and Well Water

Chlorination of municipal or well water destroys most bacteria and viruses, but not parasites, such as Cryptosporidium and Giardia, and helps to remove iron, manganese and hydrogen sulfide [207]. Several studies have shown that a long-term drinking of chlorinated tap water is associated with increased risk of the bladder and rectal cancer [6,7,8]. Residual chlorine can be removed from the water by using activated carbon or charcoal filters [207].

Ozonation, that is adding ozone (O3) to water, destroys most bacteria and viruses and is more effective in destroying Cryptosporidium than chlorination [9]. Theoretically, ozonated water represents smaller cancer risk than chlorinated water [10].

Mixed Oxidation (MIOX) uses electricity and salt solution (brine) to produce antioxidants (chlorine, chlorine dioxide, ozone, hydrogen peroxide) to kill most microbes, including Cryptosporidium and other parasites [11].

Microfiltration is very highly effective in removing parasites, such as Cryptosporidium and Giardia, but only moderately effective in removing bacteria, and does not remove viruses and chemicals [12].

Ultrafiltration is very highly effective in removing parasites and bacteria and moderately effective in removing viruses [12].

Nanofiltration, reverse osmosis and distillation are very highly effective in removing all microbes [12].

Ultraviolet water purification (UV-C lamps) are very highly effective in removing parasites and bacteria, and highly effective in removing viruses from clear water [12].

In the U.S., the National Sanitation Foundation (NSF) provides reliable information and certificates for home water systems in the United States [13].

Disinfection of Water in Rural Areas

Ceramic filters can significantly reduce bacteria and parasites, but not viruses, in drinking water [14] and lower the occurrence of waterborne diarrhea [15].

Biosand filters can effectively remove parasites, most bacteria, and some viruses and toxins from water [17].

Solar disinfection (SODIS) is disinfection of small amounts of water with the help of the sun. The ultraviolet (UV) light from the sun in tropic and subtropic areas can kill all microbes in clear (but not cloudy) water placed in a translucent plastic or glass bottle in six hours on a sunny day or in two days during cloudy weather [16]. Be aware that SODIS does not remove or destroy eventual toxins in water.

Contaminants in the Drinking Water

The United States Environmental Protection Agency (EPA) has determined allowable levels of water contaminants that may affect health–Maximum Contaminant Levels (MCL)–and levels of contaminants that may have cosmetic or technical effects–Secondary Maximum Contaminant Levels (SMCL).

Does water allergy exist?

In rare cases, contact with water can cause a skin reaction with red wheals, known as aquagenic urticaria, which is a form of physical urticaria [18]. Allergic reaction does not occur after drinking water.

  1. Curtis R, 1998, OA Guide to Water Purification  Princeton University
  2. A Guide to Drinking Water Treatment and Sanitation for Backcountry & Travel Use  Centers of Disease Prevention and Control
  3. Water Disinfection for Travelers  Centers of Disease Prevention and Control
  4. Schlosser O et al, 2001, Bacterial removal from inexpensive portable water treatment systems for travelers  PubMed
  5. Wilson S, 1999, Disinfection Efficacy Studies With Electrochemically Generated Mixed Oxidants in the Development of CT Values for Drinking Water Pathogens  United States Environmental Protection Agency
  6. King WD et al, 1996, Case-control study of bladder cancer and chlorination by-products in treated water (Ontario, Canada)  Springer Link
  7. Villanueva CM et al, 2003, Meta-analysis of studies on individual consumption of chlorinated drinking water and bladder cancer  Journal of Epidemiology & Community Health
  8. Morris RD et al, 1992, Chlorination, chlorination by-products, and cancer: a meta-analysis  PubMed Central
  9. Rennecker JL et al, 2001, Inactivation of Cryptosporidium parvum oocysts with sequential application of ozone and combined chlorine  PubMed
  10. Chevrier C et al, 2004, Does ozonation of drinking water reduce the risk of bladder cancer?  PubMed
  11. Venczel LV et al, 1997, Inactivation of Cryptosporidium parvum Oocysts and Clostridium perfringens Spores by a Mixed-Oxidant Disinfectant and by Free Chlorine   PubMed Central
  12. A Guide to Drinking Water Treatment Technologies for Household Use  Centers of Disease Prevention and Control
  13. Home Drinking Water – Quality and Treatment  National Sanitation Foundation
  14. 2008, Household water treatment options in developing countries: ceramic filtration  Centers of Disease Prevention and Control
  16. 2008, Household water treatment options in developing countries: solar disinfection (SODIS)  Centers of Disease Prevention and Control
  17. Slow Sand Filtration  Centers for Disease Control and Prevention
  18. Park H et al, 2011, Aquagenic Urticaria: A Report of Two Cases  PubMed Central

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