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Guide to Emergency Water Purification

When a natural disaster, such as a hurricane, earthquake or tsunami strikes, one of the first resources to be threatened is the public water supply. In 2010, the earthquake in Haiti left thousands without access to clean drinking water and cholera broke out all over the country. Recently, in 2011, a large earthquake struck Japan, damaging a nuclear plant in Fukushima. Since then, traces of radioactive iodine have been found in the tap water in nearby areas. Many residents in cities across the U.S. have faced a boil water advisory at least once in their lifetime. Some water supplies have been affected by natural gas drilling in certain areas as well.

During emergencies, people must be wary of what is in their drinking water. Both natural and man-made environmental disasters can cause water to become contaminated with bacteria, viruses, cysts (giardia and cryptosporidium) and toxic chemicals. Bottled water is often the solution, when access to safe tap water is limited. Convenience stores in areas where boil water advisories have been issued have been known to run out of bottled water. Boiling water is not the most convenient way to handle a water shortage, but it is a safe bet when there are no other alternatives. However, boiling is just one of several methods of water purification during emergencies. 

Water Purification by Boiling 

Boiling water is a feasible method of water purification if a source of heat is available. This method renders viruses, bacteria and other micro-organisms inactive. Though they are still present in the water, they are unable to cause waterborne illness. To ensure that the water is safe, you should filter it through a paper towel, cloth or coffee filter to remove large dirt and sediment particles; then allow it to boil rapidly for 10 minutes. At higher altitudes, raise the boiling time by one minute per 1000 feet above sea level. Boiling is effective for small quantities of water, but for larger households or for purposes where a larger quanity is needed, you may want to try another method.

Chemical Water Treatment

To chemically treat water, place drops or tablets of the chemical being used into the water, swish it around to aid in dissolving, and allow it to sit for 30 minutes, once it has dissolved. The effectiveness of treatment depends on the cloudiness, pH and temperature of the water. If the water is especially cloudy or has large particles floating in it, you should filter it using a paper towel, cloth or coffee filter first, to remove dirt and sediment. The colder the water, the less effective the treatment will be. If the temperature is below 40 degrees Fareinheit, double the contact time. It is best if the water is at least 60 degrees before treating. One downside to chemical treatment is that it affects the taste of the water. Municipal tap water supplies are usually treated with harsh-tasting chemicals, which is why many people choose to purchase home water filters to remove them. However, chemical water treatment has long been an effective method of water disinfection, and remains effective in certain emergency situations. To lessen the harsh taste of chemically treated water, you can pour it back and forth between containers after it has been treated, or add a pinch of salt or flavorings. Whatever your method of treatment, there are many different solutions available on the market, so make sure to follow the manufacturer's instructions. The two chemicals most used as water disinfectants are iodine and chlorine.

For more information about boiling and chemical treatment as methods of water purification during emergencies, visit the EPA website.


Iodine is one of two types of chemical water disinfection, and has been shown to be more effective than chlorine at inactivating cryptosporidium and giardia cysts. It is light sensitive and must always be stored in a dark bottle. Iodine works best if the temperature of the water is at least 68 degrees Farenheit. People with thyroid problems, people on lithium, women over 50 or women who are pregnant should consult their doctor before using iodine as a method of water purification. Some people are allergic to iodine as well. In that case, chlorine is a viable alternative.


Chlorine is a chemical water treatment available for people who are allergic or unable to ingest iodine. Most municipal water treatment plants use chlorine as a disinfectant. Recently, however, scientists have begun to probe the possible negative consequences of prolonged chlorine exposure. It has been linked to respiratory aggravation and asthma and may be carcinogenic over time. Because of this, many people have installed water filters in their home, which remove chlorine. However, it does remain feasible for use in emergency situations, where no other method of purification is available.

UV light

UV radiation affects the microorganisms in water, by altering the DNA in their cells, impeding reproduction and rendering them inactive. It does not physically remove them from water; but it does prevent them from causing waterborne illness, should they be ingested. Unlike many other methods of water filtration, UV light sterilizes the water without using harsh-tasting chemicals or producing waste water. Inline UV water filters attach directly to your water line, and are great for purifiying the water throughout your home during boil water advisories or other types of emergencies. For UV filtration outside the home, you can use a portable UV lamp like the Emergency Steripen to purify small amounts of water for drinking.

Emergency water filters 

Katadyn manufactures several different types of water filters for outdoor and/or emergency use. Frequent outdoor travelers, hikers and campers use the Katadyn MyBottle water purifier, which can be dipped directly into lakes, ponds, streams, and other freshwater sources, removing 99.9 percent of bacteria, viruses, protozoa and other water impurities, bad tastes and odors. The Katadyn Mini Ultralight microfilter is even able to remove radioactive particles. These water filters tend to be more expensive than your average home water filter, but in case of emergencies, they are well worth the expense.

Katadyn water filters are used by the US military, NATO, international militaries and relief organizations like the Red Cross during environmental disasters or emergencies where safe drinking water is scarce. Both the Katadyn Gravidyn and the Doulton Gravity Fed water filter system will provide clean water for larger groups of people in times of crisis. These systems don't require connection to a tap or pumping, because they use gravity to push the water through the filter into the lower reservoir. For maximum filtration, in emergencies with a very large number of victims, you may want to invest in a Katadyn Expedition KFT water filter system. This filter system uses a very advanced Katadyn KFT ceramic depth filter element, which has a long-lasting filter life of 26,000 gallons and may be cleaned several times before needing replacement.

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