[Dioxin-l] Re: Poor efficacy of residual chlorine in drinking water distribution

[david bell]

Hi Pat
perhaps you can explain the wording of the abstract to me: I have not seen 
the paper, and do not know what information it contains.

>microorganisms remained relatively
>     unaffected in water from the distribution systems tested

I understand this-

>except for Escherichia coli

Can you please explain to me what this means ? Does this not mean that E 
coli is affected by water from the distribution systems tested ? Is this not 
the wording of the abstract ?

If E coli is disinfected, is this not a good thing ?

If other bacteria and viruses are not inactivated, that is clearly a 'bad 
thing'; but you don't make the 'bad thing' better by adding another 
pathogen, E coli, to the mix.

david

>Dear Mr. Bell,
>
>I urge you to give the abstract of the study by Payment (1999)  a
>more careful reading.  You have interpreted it to say that "E coli is
>inactivated by residual chlorine throughout the distribution
>system."  This differs considerably from the actual wording of the
>abstract, as follows:
>
>     "Except for Escherichia coli, microorganisms remained relatively
>     unaffected in water from the distribution systems tested. When
>     sewage was added to the water samples, indigenous thermotolerant
>     coliforms were inactivated only when water was obtained from
>     sites very close to the treatment plant and containing a high
>     residual chlorine concentration."
>
>You then note, " Given that E coli is a principal contaminant of
>sewage (and in turn the water supply system), and can be highly
>pathogenic (eg E coli 0157), this abstract can easily be used to
>  make a case for chlorination of water supplies."   With this, I
>  would suggest that you have missed a major finding of the study:
>
>     "Clostridium perfringens was barely inactivated, suggesting that
>     the most resistant pathogens such as Giardia lamblia,
>     Cryptosporidium parvum, and human enteric viruses would not
>    be inactivated. "
<snip>
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