Message-ID: <Pine.SOL.3.91.960925155600.391D-100000@fox.ksu.ksu.edu> Date: Wed, 25 Sep 1996 16:06:15 -0500 From: kerry miller <mailto:astingsh@KSU.EDU> Subject: Re: Potable drinking water To: Multiple recipients of list DEVEL-L <mailto:DEVEL-L@AMERICAN.EDU>
Most current literature focusses on chlorine (bleach) or iodine as chemical methods of water sterilization. Here's a fragmnet I clipped from a U S Forest Service report:[...]During the past 10 years, scientific knowledge about what is required to kill or remove Giardia cysts from a contaminated water supply has increased considerably. For example, it is known that cysts can survive in cold water (4 deg C) for at least 2 months and that they are killed instantaneously by boiling water (100 deg C) (23,24). It is not known how long the cysts will remain viable at other water temperatures (e.g., at 0 deg C or in a canteen at 15-20 deg C), nor is it known how long the parasite will survive on various environment surfaces, e.g., under a pine tree, in the sun, on a diaper-changing table, or in carpets in a day-care center.
The effect of chemical disinfection, such as chlorine, on the viability of Giardia cysts is an even more complex issue. It is clear from the number of waterborne outbreaks of Giardia that have occurred in communities where chlorine was employed as a disinfectant that the amount of chlorine used routinely for municipal water treatment is not effective against Giardia cysts.
Therefore, when one cannot boil drinking water, chemical disinfectants such as iodine or chlorine should be used. This will provide some protection against Giardia and will destroy most bacteria and viruses that cause illness. Iodine or chlorine concentrations of 8 mg/liter (8ppm) with a minimum contact time of 30 minutes are recommended. If the water is cold (less than 10 deg C or 5O deg F) we suggest a minimum contact time of 60 minutes. If you have a choice of disinfectants, use iodine. Iodine's disinfectant activity is less likely to be reduced by unfavorable water conditions, such as dissolved organic material in water or by water with a high pH, than chlorine. [...]
I find it hard to imagine that 1 or 2 ppm K-permanganate would do better than this.
A WWW site that is worth looking at for more on these matters is Rev Tim's Holy Trauma Water Kitchen http://www.fc.net/~tdeagan/water/index.html
kerry ˙˙˙˙˙˙˙˙On Wed, 25 Sep 1996, Benedict Tisa wrote:
> We are seeking information fro a project in Nepal. At the Living River
> Health Serves, they are interested in using potassium permanganate to
> make dirty river water potable. It has been suggested that a 1:500,000
> dilution is needed, but this makes the water quite purple. Is this the right
> dilution or can it be used at 1:1,000,000. How long does it take before it is
> drinkable ? Does this kill cysts like giardia ? What else needs to be done if
> the water is turbid?
>
> Any information would be helpful. Please send any comments to the list
> in general or to me: mailto:benedict_tisa@jsi.com
>
> Thanks in advance for every ones help
>
> Cheers,
>
> Benedict Tisa
> Communication Advisor
> OMNI Project
>