Emergency Disinfection of Drinking Water

AEX-317
Agriculture and Natural Resources
Date: 
05/17/2019
Karen Mancl, Professor, Food, Agricultural and Biological Engineering

Storms, floods, and water line breaks can all cause disruptions in drinking water supply. Camping and hiking spots in remote areas may have unsanitary water supplies. Most importantly, traveling outside the United States poses a risk to travelers, since water treatment is not as reliable in other countries.

Boil water before drinking is the standard recommendation. The boil water call is for good reason, since consuming contaminated water can make people very sick. Boiling water for just a minute is extremely effective at killing bacteria and parasites that can make people sick. When is doubt, drink boiled water! Any heat source—electric or gas range, camp stove, wood fire and even a microwave oven—heats water to boiling temperatures and kills disease-causing microbes.

What if I can’t boil the water?

If the power is out or you are traveling, boiling water might not be feasible. Other disinfection options are available.

Chlorine bleach can be added to water to kill microbes. Chlorine does not kill microbes on contact, so you must wait at least 30 minutes before drinking the water. After disinfection, the water will have a strong chlorine smell and taste. Also the water should be very clear. Particles in the water help protect and hide microbes from disinfection, increasing the chance they will not be killed by the chlorine and will make you sick. If the water source is cloudy, more chlorine will be needed to disinfect it (Table 1).  

Table 1. Recommended Chlorine Bleach Dose to Disinfect Water in an Emergency from the Centers for Disease Control and Prevention.
Bleach Clear water Cloudy water
5.25% 1/8 teaspoon in 1 gallon ¼ teaspoon in 1 gallon

Mix thoroughly and let stand for 30 minutes.

Disinfection tablets containing chlorine or iodine are available for campers and travelers to disinfect a small volume of water. Many different companies market disinfection tablets (Figure 2) that can be easily added to water bottles. Always follow the directions on the package.

Popular disinfection tablets available to purchase Homemade solar water disinfection methods.

Figure 1. Some of the popular water disinfection tablets on the market. Photo: Alex Gulsby, on 99boulders.com/best-water-purification-tablets.

Figure 2. Solar bags available on the market and clear plastic water bottles placed in the sun for hours used to disinfect water in an emergency. 

Sunlight is an amazing disinfectant and is the key to solar disinfection (SODIS).  Ultraviolet light kills pathogens on contact. To use sunlight to disinfect water, the water must be very clear and placed in the sun in clear containers. Clear plastic water bottles, plastic bags or specialized technology, like the Puralytics SolarBag, can be used for solar disinfection (Figure 2). The water should be exposed to sunlight for at least four and up to 10 hours to kill microbes.

In an emergency, boil water for 1 minute before drinking. If boiling is not possible, adding chlorine bleach or disinfection tablets works to clean water. However, adding chemicals to water changes its taste and, while safe, may not be palatable. For extended emergencies, disinfecting batches of water in the sun is a low energy solution.

To learn more:

Elmaksoud S.A., N. Patel, S.L. Maxwell, L.Y. Sifuentes and C.P. Gerba. (2014). Use of household bleach for emergency disinfection of drinking water. Journal of Environmental Health. 76(9):22 -25.

McGuigan, K.G., F. Mendez-Hermida, J.A. Castro Hermida, E. Ares-Mazas, S.C. Kehoe, M. Boyle, C. Sichel, P. Fernandez-Ibanez, B.P. Meyer, R. Ramalingham and E.A. Meyer. (2006). Batch solar disinfection inactivates oocytes of Cryptosporidium parvum and cysts of Giardia muris in drinking water. Journal of Applied Microbiology. 101:453-463.

No endorsement is intended for specific products or businesses that are mentioned in this fact sheet. The authors and OSU Extension do not represent or endorse the quality of any products in this fact sheet. Ohio State University Extension specifically disclaims any liability to readers of any kind for loss or damage of any nature whatsoever and however arising, whether due to inaccuracy, error, omission, or any other cause, regardless of who is at fault, due to the use of the information herein.