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AWWA WQTC65858
- Statistical Analysis of Microbial Data Obtained by Serial Dilution - Agar Plate Methods
- Conference Proceeding by American Water Works Association, 11/01/2007
- Publisher: AWWA
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Plating techniques for microbial enumeration continue to be important quantitative performance assessmenttools used during drinking water compliance testing (e.g. routine coliform analysis)and bench- and pilot-scale performance demonstrations (e.g. aerobic spore removal). Whileconsiderable statistical analysis of these methods historically has been limited to quality controland method development, the analysis of experimental data and laboratory proficiency can alsobe enhanced by the correct analysis of variability in the data. This paper presents a simpleframework for assessing method-associated errors in the quantification of bacteria by membranefiltration - agar plate methods and provides a preliminary discussion of probabilistic models thatmay be used to quantify uncertainty in plate-count data. Simple recovery experiments forBacillus subtilis spores and Escherichia coli are presented to demonstrate the occurrence andquantification of method-associated errors. This type of analysis of method errors is essential forlaboratories, water suppliers, and engineers, particularly in demonstrating regulatory compliance. Includes 11 references, tables.