In terms of limiting the need for external inputs, it would be difficult to imagine a technique simpler and more sustainable than boiling water. Water is simply placed in a clean container and brought to a full boil for at least three minutes. This will eliminate all pathogenic activity, including giardia (Extension Bulletin, 2003) “If you are more than 5,000 feet above sea level, you must increase the boiling time to at least 5 minutes (plus about a minute for every additional 1,000 feet). Boiled water should be kept covered while cooling (Drinking Water Resources, 2003). Unfortunately, external inputs are not the only obstacle to boiling drinking water.
Many developing countries experience a rainy season. During these times, finding enough or any dry wood for boiling water may be difficult or impossible. However, the major obstacle in this case is the basic availability of fuel wood. Boiling drinking water requires the consumption of these valuable supplies (in addition to draining the energy of the people of the developing world, fuel wood burning and harvesting both contribute to deforestation and air pollution). Even if adequate fuel wood is available, the time and energy required for its collection make boiling drinking water less than appealing (Bourgoing, 1989). Indeed, wood gathering becomes a further drain on the overworked people of the developing world, especially for women, as they are predominately the household fuel collectors. As fuel wood resources become more and more scarce around a village, women must walk further and further to gather the wood. This limits the amount of time they have available for their many other household duties and child rearing.
Furthermore, if fuel wood were not available in adequate supply with in walking distance, it would have to be purchased in order to provide safely boiled water (Troy, 2003). Because of typically low incomes in the developing world, and the traditional unwillingness of individuals to spend a large fraction of their income on something viewed as a luxury, purchasing fuel wood for water disinfection is unsustainable. Because of the complications associated with boiling, it is really only ideal in emergency situations and other, more sustainable methods of small-scale drinking water treatment should be sought.
Additional Links and Resources:
Provides an in depth explanation on how to construct and operate a water boiling device.
Simple water boiling procedure