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E-M:/ Re; E. Coli taints Red Cedar

Enviro-Mich message from anne.woiwode@sfsierra.sierraclub.org

     Enviro-Mich:  The following came in response to the posting on the Red 
     Cedar River and E.coli:
There is a bit of confusion in this story.  E coli is measured in what 
is called MPN (most probable number) of e coli cells in a 100 ml 
sample.  This is a statistical calculation based on the number of 
confirmed e coli presence in 3 sets of five test tubes.  Each of the 3 
sets of five gets innoculated with  with the sample, the first set is a 
1:10 dilution the second set 1:100 dilution of the original sample and 
the third is a 1:1000 dilution of the original sample.  The number of 
positive tubes (after a period of incubation) gives your MPN number.
The highest allowed for swimming is 200. 

        The author also noted that the Detroit Wastewater plant, for     
        example, has an MPN discharge limit to the Detroit River of 30.

     Anne Woiwode

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