The Best Disaster Water Purification Methods

Contaminated water can carry waterborne pathogens that lead to debilitating illnesses. Because reliable purification methods were unknown in the Middle Ages, wine, ale and milk were consumed instead of water. Today, people in the U.S. take clean drinking water for granted, but when the supply becomes disrupted, knowledge of a few simple decontamination methods can be a life-saver.

Boiling

• The easiest way to purify water involves bringing it to a rolling boil for at least a minute, as advised by the Centers for Disease Control and Prevention (CDC). However, this is only effective against microorganisms. Other impurities may remain, such as chemical contaminants, and in a disaster situation, you may not have an energy source to heat the water.

Chemical Purification

• The CDC recommends adding non-scented, household bleach (sodium hypochlorite) to contaminated tap water--1/8 teaspoon per gallon for clear water and 1/4 teaspoon per gallon of cloudy water. Mix well and wait at least 30 minutes before drinking. Backpackers often use chlorine dioxide and iodine water treatment tablets, available at outdoor stores. Chemical treatment tablets cost more than bleach, but have the advantage of being small and portable. Iodine is reportedly more effective than chlorine against Giardia, a parasite commonly found in natural springs and creeks. As with bleach treatment, you should wait at least 30 minutes before drinking. To improve the taste, try pouring the treated water back and forth between clean containers, or add a pinch of salt or a vitamin C tablet.

Filtration

• Water filtration devices, also available at outdoor stores, usually have ceramic or carbon filters with pores of varying sizes that trap microorganisms. Larger pore sizes, 1 to 4 microns, work against parasites like Giardia and Cryptosporidium. Medium pore sizes--0.2 to 1 micron--filter out bacteria, such as E. coli and salmonella. The smallest pore sizes can trap viruses up to 0.004 micron.

  Activated carbon filters also remove chemical contaminants. While carbon filters offer the most effective purification method when both microbial and chemical contaminants exist, they treat only fairly small volumes of water at one time, and filter replacement is expensive.

Distillation

• For more extreme situations with scarce water sources, you can distill clean water from salt water or even urine by boiling the liquid and drawing off the steam. Heat a covered pot containing the contaminated water, and cool a nearby collection pot with ice or cold water, to facilitate condensation. Pass a tube from the top of one pot through the top of the other, to carry water vapor from the "dirty" pot to the "clean" pot. Similar to boiling, this method eliminates microbial contaminants, but trace chemical contaminants will remain.