Most Common Treatments to Make Water Drinkable

Water found in lakes and streams while camping and hiking or water supplies contaminated by floods or other natural disasters should not be used for drinking, food preparation or brushing your teeth without being treated. There are several ways to effectively treat water to make it safe to drink, depending on available time and resources.

Settling and Filtering

• Water that is cloudy or contains visible debris should be settled and filtered. Place the water in a clean container and let stand for at least 24 hours if possible. Large debris may settle in one to two hours (See reference 2, Chapter 6, section 2). The debris should have formed a sediment at the bottom, allowing you to pour or draw clear water from the top of the container.

  If the water is not completely clear after 24 hours, filter through a fine, clean cloth, paper filter or a clay filter if one is available. Very fine particles in the water may require coagulation (See reference 1, Page 26).

  Water that has been settled and filtered should still be boiled or chemically treated.

Boiling

• Boiling is an effective way to destroy water-borne bacteria, viruses and parasites of all kinds (See reference 2, Chapter 5 , Section 1).

  Bring water to a rolling boil for one to five minutes. The World Health Organization recommends adding an additional minute of boiling time for every 500m above sea level (See reference 1, Page 30). Water should be stored in the container in which it was boiled and ideally used shortly after it has cooled.

Chemical Treatment

• Chemical disinfection is the most effective way to make water safe for drinking (see reference 2, Chapter 7, section 4.1).

  Chlorine is one common method of water treatment. Add 10 drops of a 1 percent solution of chlorine or one to two drops of unscented household bleach per liter of clear water and let sit for 30 minutes (see reference 1, Pages 28-29; reference 3).

  Iodine is another common method of making safe drinking water for short term use. Several different preparations of iodine are commercially available.

  Other, less common, chemical treatments are also used for treating water on the community level.

Solar Treatment

• Solar treatment works by heating water and exposing it to UV radiation. This method is easy and inexpensive, but takes several hours.

  Fill a clear water bottle three-quarters full of clear water and shake to aerate. Add water to fill the bottle completely. Place the bottle in the sun, ideally on a piece of metal roofing, on your roof or in a solar box. A solar box can be made by lining a box or crate with aluminum foil.

  Leave the bottle in place for six hours in full sun, or for up to two days in partial sun (See reference 2, chapter 5, section 3).

  This method is more effective if the side of the bottle facing away from the sun is painted black to absorb and radiate heat. Heavily scratched or cloudy bottles should be replaced, as clouding and scratches prevent the UV rays from reaching the water properly (see reference 2, chapter 5, section 3).

Less Common Methods

• Coagulation by adding chemicals such as alum to the water causes very small particles such as clays and viruses to clump together. This makes them heavy enough to settle out of the water (see reference 2, page 26). This method is primarily used by trained personnel in emergency situations.

  Ozone, lime juice and other acids are used to chemically treat water, but these methods are impractical for home or recreational use to kill all pathogens (see reference 1, chapter 7, sections 4.5, 4.8).

  Filtration by sand and charcoal are commonly used to treat drinking water on a community level. Water treated with sand or charcoal filtration usually requires additional disinfection (See reference 2, page 27).

Warnings

• • The Environmental Protection Agency recommends using twice the chlorine or iodine to treat cloudy water (see reference 3).
  • Iodine is unsuitable for long-term use due to possible adverse health effects (see reference 2, chapter 7, section 4.1).
  • Cloudy water should not be treated with the solar treatment method.
  • The solar treatment method is most effective in the tropics.
  • Exercise care when treating your own drinking water; some pathogens may not be completely destroyed.