Q: Test vol for crypto IFA

wick at cris.com wick at cris.com
Thu Feb 13 08:49:37 EST 1997


I am interested in finding out the "equivalent original water-sample volume" 
that is  examined by labs performing the IFA for cryptosporidium. This value, 
I believe, would be equal to  (original water sample vol.) (fraction of packed 
pellet that was floated) (fraction of floated sediment that was actually 
examined by IFA), or simply the (F V R) value presented in the EPA ICR 
Microbrial Laboratory Manual. 

I would be most interested in hearing from anyone testing raw (source), 
finished and backwash test samples. I realize that the actual volumes will 
vary somewhat depending upon turbidity. However, preliminary calculations 
suggest approx. 10L for raw, 50L for finished, and 5L for backwashes samples. 
Does this seem correct???

Jim Wick

"Don't precipitate more than you can resuspend"






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