Chemical purification of water

There are a number of ways to purify water in the wilderness. You can utilize: chemical purification, boiling, or ultraviolet light. You can use a commercial filter. And, you can even make and use your own filter on the spot. Yes, I’ve seen this on Youtube, but I’m a little unsure about this DIY method of water purification.

Image by doug88888 via Flickr

In this post I will limit my discussion to using chemicals to purify water. There are four types of chemicals that can be used for water purification in the wilderness. I will briefly discuss each one giving pros and cons.

Chlorine

Pros

It effectively kills bacteria.

Cons

It may not kill Giardia cysts in normal concentrations.

Halazone Tablets

Pros

Inexpensive;

Convenient.

Cons

Requires 6 tablets per liter;

Contact time is one hour minimum;

Bad flavor;

Effectiveness of tablets diminishes when in contact with warm, humid air.

Superchlorination-dechlorination

Pros

Highly effective;

Results in water with practically no taste.

Cons

Inconvenience of two-step process: adding high chlorine concentrations, then removing chlorine with peroxide;

Chemicals can destroy clothes and gear if spilled.

Iodine

Pros

Effectively kills bacteria and cysts;

Relatively short contact time;

Convenience of tablets;

Less offensive taste compared to other chemicals;

Bad taste can be removed with flavor crystals, vitamin C tablets or ascorbic acid.

Cons

Cannot be kept longer than 3 to 6 months;

May not be used by people allergic to iodine, by people with active thyroid disease or by pregnant women.

An advantage of all chemical methods of water purification over other methods is the low weight and bulk of the products.

One disadvantage of all chemical water purification methods is that they don’t remove floating debris or sediment.

Make sure, when using chemicals to purify water that you use the correct concentrations as indicated on the packaging and that you observe the proper contact time. Observing religiously these two factors will better guarantee that the bacteria and cysts will be killed. Also, if the water is cold, as in high-altitude streams, longer contact times are required.

Having access to potable water in the wilderness is essential. Purifying water with chemicals is a cheap and effective method of doing that. You just might want to try chemical purification.

by Richard Davidian, Ph.D.

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