Using Bleach for Water Disinfection

[Hiking Malto]

As promised, here is some helpful information on using bleach as a water disinfectant against giardia. It comes from an leading expert in the field. Keep in mind that this applies to Regular bleach that has 5.25% sodium hypo.
1) Is bleach effective against giardia? Yes, but it takes a long time. (See below)
2) Effect of water temperature. Colder water will take longer than warmer water. He recommends 1.5x the time for very cold water to be on the safe side.
3) Water hardness and organic material will negatively impact effectiveness.
4) Bleach will destablize over time. Don't expect three year old bleach to be as effective as fresh. Light and heat will also negatively effect the bleach.
5) Organic or muddy water should be filtered as much as possible. They recommend in emergency situations to filter using a sock or other material before using bleach.
6) Recommended Usage.
a) Filter water with a cloth to remove organics.
b) Apply bleach 2-4 drops per qt.
c) Let stand for 20 minutes (30 if cold)

Based on this I have decided to start using bleach, currently don't use any filtering or chemicals. Even if I have to drink some of the water prior to 30 minutes, I have decreased to total probability and number of organisms. I am going to store the product in a white bottle and try to keep it out of the heat as much as possible. I will also try out a coffee filter to remove to organic material.

Wanted to pass this on because this could be a cheap, quick to treat and effective way to keep the giardia bugs at bay.

[Ben Crowell]

Thanks, Greg, for that post — very interesting!

[John S.]

http://ohioline.osu.edu/b795/b795_7.html

low levels of chlorine, normally used to disinfect water, are not an effective treatment for giardia cysts. A chlorine level of over 10 mg/1 must be maintained for at least 30 minutes to kill giardia cysts.

http://www.cdc.gov/healthywater/drinking/travel/backcountry_water_treatment.html

[EndoftheTrail]

Thanks, Greg.

Water sources up in the Sierras, etc. are often cold. For ease of use, I make it a point to scoop water and pour through a mesh coffee filter, add 5 drops of bleach per liter, and wait the 30 minutes (and not bother guessing whether water is warm enough for a shorter treatment period).

Some may view the next step as overkill for clean mountain streams, but I like to drink my water through the Aquamira Frontier Pro filter — 2 oz. wt. penalty a fair price to pay for clarifying the water, improving its taste (including the elimination of any chlorine taste) — plus blocking out any stubborn protozoa cyst.

Good to know also that chlorine has a limited shelf life. I use chlorine periodically for my laundry — so the bottle on my laundry shelf won't ever be more than a few months beyond the purchase date.

[Steven McAllister]

I use to use chlorine bleach to treat water. I know use Aqua Mira because I think it tastes a little better and is a little more convenient and precise for backpacking.

Hints with Chlorine or Chlorine Dioxide:
Shaking the container from time to time during treatment is supposed to help the process. This is important if you are in a hurry and may want to drink before the recommended treatment time.

Opening the top of the container for several minutes after treatment will allow much of the treatment(gas) to escape, making the water taste a little better.

[Ike Mouser]

Is it ok to use a folded bandana as prefilter, then wear it? Or should i let it dry in the Sun and the UV rays kill the bad stuff on it.

I want to use bleach and my aqua mira but i need a prefilter that is easy to use and avoids contaminiation to myself/my gear.

[Steven McAllister]

According to a government water treatment site, small quantities of the organisms you should be concerned about are harmless. The amount you come in contact with from a bandana would probably way below this count.

Swimming in contaminated bodies are "usually" harmless, but that depends on how much of the water comes in contact with eyes, nose and mouth.
So I wouldn't worry about a damp bandana, unless the water is really disgusting.

[Unknown abc]

I use my bandanna for pre-filtering.

[EndoftheTrail]

Bandanna can work, and since you'll be treating the water after filtering through the bandanna, you likely won't need to worry about baddies transmitted from the bandanna into the water.

I prefer mesh coffee filter over cloth or paper though. With fine mesh, you pour the water straight through — all done in a couple of seconds. With cloth or paper, water takes much, much longer to filter through — which can be extremely annoying when mosquitoes and black flies are attacking…

You can either cut out a piece of mesh coffee filter — or make a water scoop with integrated mesh coffee filter".

[Author]

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