Chlorine disinfection

Alex Castillo castillo at
Mon Sep 15 10:05:16 EST 1997

Cysts of parasites (amoeba, Giardia, Cryptosporidium, etc.) are usually
chlorine-resistant. Now, they are a lot larger than bacteria as well, so
you may want to add chlorine to a final residual Cl concentration of 2-3
ppm, and also buy a filter which will take care of parasites, if you are
treating water for drinking purposes.

Now, to answer your question, the dilution you have to prepare will depend
upon whether you want to treat drinking water or make a disinfectant
solution. If it is for drinking, you may not want to go beyond 2-5 ppm
residual chlorine. If it is for preparing a disinfectant, then 100-200 ppm
will work ok, but keep in mind that bacterial spores and cysts of parasites
(parasites do not form spores) are more resistant.

rayzzz at wrote in article
<rayzzz-ya02408000R1309970916260001 at>...
> Hi--
> Can someone tell me: what is the proper ppm of chlorine to water (so I
> make the right household bleach dilution, bleach being, of course, a 5%
> solution already) in order to kill amoeba? What is the dilution to
> high level sterilization (kills spores)?
> I have heard that a certain dilution is best, and above that it is not as
> effective. Is this correct, or if not, what leeway do I have?
> Thanks very much. Please email me. 
> Katherine
> Take the zzz out of my address to write to me. 

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