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  • Writer's pictureBaileigh Higgins

How to disinfect contaminated water in Urban Areas

Updated: May 16, 2023

Today’s survival tip is simple but also crucial to one’s survival during any kind of emergency: How to disinfect contaminated water. There are several methods available, and today we deal with the most common. Please note today’s tips are mostly for urban use and assume some access to amenities.


Boiling is considered the world’s oldest method for disinfecting water; it is also among the most effective. As the water temperature increases, pathogens are killed by the heat. For most pathogens, inactivation occurs at temperatures below the standard boiling point of 100°C.

  1. Bring the clear water to a rolling boil for 1 minute (at elevations above 6,500 feet, boil for 3 minutes).

  2. If the water is cloudy, filter it through clean cloths or allow it to settle, and draw off the clear water for boiling.

  3. Let the boiled water cool.

  4. Store in clean containers.

  5. Add a pinch of salt for every quart or liter boiled.


  • Batch volume is dependent on the pot used for boiling

  • Very effective

  • Relatively inexpensive

  • Accessible to everyone

  • Quick and simple


  • Turbid water should be pretreated before boiling (for example, filtration)

  • Boiling may not be appropriate for chemically contaminated water as the concentration of some contaminants will increase after boiling

  • Pots used for boiling may need to be replaced over time

  • Some people dislike the taste of boiled water as boiling allows dissolved oxygen to escape, causing a flat taste (can be improved by vigorously stirring or shaking)

Chlorine Bleach:

If you are unable to boil your water, you can disinfect it with household chlorine bleach. (Warning: do not use bleach that contains any additives or scents.)

  1. If the water is clear, add 1/8 teaspoon of unscented bleach to one gallon of water, stir well, and allow the water to stand for 30 minutes before using.

  2. If the water is cloudy, filter it through clean cloths or allow it to settle, and draw off the clear water for disinfection. Add ¼ teaspoon of unscented bleach to one gallon of water, stir well, and allow the water to stand for 30 minutes before using.

  3. The water should have a slight chlorine odor. If not, repeat the dosage and allow the water to stand for an additional 15 minutes. If the treated water has too strong a chlorine taste, allow the water to stand exposed to the air for a few hours or pour it from one clean container to another several times.


Iodine solution, crystals, or tablets can kill viruses and bacteria and is easy to use (though it is not effective against more resistant organisms like Cryptosporidium). The downside is that it gives the water an aftertaste.

  1. Follow the directions provided on the product, as the amount used will vary for the solution, crystals, and tablets.

  2. Using warm water, if possible.

  3. Add the iodine to the correct amount of water in your container. Mix the iodine well with the water, ensuring some of the solutions also coats the lid and threads if using a screw cap bottle.

  4. Allow the water to sit for 30 minutes after the iodine has fully dissolved before using it. If your water is cold (below 40 F), wait 60 minutes before using it.

Ultraviolet Light Water Purifier:

Ultraviolet (UV) water purification lights can be used to kill bacteria, protozoa, and viruses.

  1. Before using this method, filter the water through a cloth to remove any solid particles. The light won’t be able to sanitize the interior of such particles.

  2. It also may not be effective if the water is cloudy.

  3. UV lights may be built into water bottles, but one common format is a pen-shaped light powered by batteries. Turn the light on and drop it into a container with the water. Swish the light around in the water for a couple of minutes, according to the manufacturer’s instructions. Remove the light from the water after the proper period of time. It’s now safe to use.

Use a Water Purification Filter:

Water purification filters can remove bacteria and protozoans from the water. A carbon filter gets rid of some chemicals and any weird tastes. Be sure to read the instructions for correct use and to understand what it will and will not remove. You do need to ensure particles in the water do not clog the filter. Allow cloudy water to settle for several hours. Pre-filter the water through a pre-filter or cloth, then pass the pre-filtered water through the water purification filter.

These are the easiest and most basic methods for disinfecting water. You can also try water purification kits and tablets. These will be available at outdoor and camping shops. A good thing to mpObviously, there are more, but these are the most basic. Do not be tempted to try non-water liquids as a substitute for the real thing. In all but the direst of situations, these will only worsen your health:

  • Alcohol - Dehydrates.

  • Urine - Contains harmful body waste.

  • Blood - May transmit disease. Also has high salt and iron content.

  • Seawater/Sea Ice. Contains 4% salt. It takes more water to rid your body of the waste from seawater than what you get from it, dehydrating you further.

In short, use your head, remain calm, and there’s a good chance you’ll be able to find drinkable water. Tune in next time for tips on finding and disinfecting water in the wilderness - an entirely different kettle of fish… or is it water?

A Blog Post by Baileigh Higgins


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