Drinking Water Micro PT Question

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Drinking Water Micro PT Question

Postby kchapman1 » Wed May 01, 2013 2:06 pm

Does anyone know if the micro testing is still required to be the 4 negative, 3 +/+ and 3 +/- configuration? Or is the PT provider allowed to mix that up a little?

Question from a small lab in Oregon
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Re: Drinking Water Micro PT Question

Postby eaturner » Tue May 28, 2013 12:43 pm

Hi Keith,
The micro PT requirements for drinking water are as follows:
9) The ten-sample set shall be assigned lot numbers and randomly composed of samples as follows:
Two to four samples containing an aerogenic strain of Escherichia which will ensure positive results for total coliforms, fecal coliforms and E.coli.when analyzed by any of the USEPA approved methods.
Two to four samples containing an aerogenic strain of Enterobacter species and/or other microorganism which will ensure positive results for total coliforms and negative result for fecal coliforms and E.coli. when analyzed by any of the USEPA approved methods.
One to two samples containing Pseudomonas species and/or other microorganism which will ensure negative results for total coliforms, fecal coliforms and E.coli. when analyzed by any of the USEPA approved methods.
One to two samples which do not contain any microorganism which ensure negative results for total coliforms, fecal coliforms and E.coli. when analyzed by any of the USEPA approved methods.
10) Laboratories analyzing qualitative sample sets for more than one method in a particular study shall obtain a unique ten-sample set for each method reported as specified in Footnote 9.

Elizabeth Turner
Elizabeth Turner
Small Lab Advocate
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