Thursday, October 31, 2019

Pasteurizing Your Water

The general answer given for killing the germs in your water is to boil the water for a period of time. But I came across an interesting article at Blue Collar Prepping which pointed out that you can actually do the same through a pasteurization process. The article explains:
      The boiling point of water is 212° F or 100° C, but the pasteurization point of water is 149° F or 65° C. That's a tremendous amount of savings of both time and energy, and can be easily achieved through solar cooking techniques as well as the traditional "pot on the fire" method.

     However, a significant drawback to pasteurization is that, unlike boiling,  there is no visual indicator for when water has reached that point. This is easily corrected with the purchase or manufacture of a Water Pasteurization Indicator, or WaPI.
The remainder of the article discusses how the WaPI works and how to use it.

     This is an intriguing idea because bringing water to boil requires far more energy than what the difference in temperature would indicate. The boiling comes from the water going through a phase change from liquid to gas; phase changes take a lot more energy than simply heating the water. It is also helpful to those living at higher altitudes, because the boiling point of water is lower at higher altitudes, and so the recommended boiling times are longer--meaning you are using even more energy to boil the water.

    In looking for more information on the topic, I came across this article, "A SUMMARY OF WATER PASTEURIZATION TECHNIQUES" (PDF) by Dale Andreatta, Ph. D., P. E. The author writes:
      Contrary to what many people believe, it is not necessary to boil water to make it safe to drink. Heating water to 65° C (149° F) for 6 minutes, or to a higher temperature for a shorter time, will kill all germs, viruses, and parasites. This process is called pasteurization.

      In this document we describe several pasteurization techniques applicable to developing countries. Pasteurization is not the only technique that can be used to make water safe to drink. Chlorination, ultraviolet disinfection, and the use of a properly constructed, properly maintained well are other ways of providing clean water that may be more appropriate, particularly if a large amount of water is needed. Conversely, if a relatively small amount of water is needed, pasteurization systems have the advantage of being able to be scaled down with a corresponding decrease in cost. In other words, if you have only a little money, you can use pasteurization to get a little clean water, perhaps enough for a family but not a village. As always, the selection of the right system should be based on local conditions. 
The article also describes how the Water Pasteurization Indicator (WaPI) works, and describes several improvised methods to pasteurize water including using a solar box cooker, a flow-through pasteurizer, and "solar puddle" which can be scaled up to provide water for a large number of people.


  1. Great link. That deserves a more prominent place on the Internet.

    1. Thanks. I'd never heard of water pasteurization before I came across the Blue Collar Prepping article.


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