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7 <br /> C <br /> Issued: 0/18/87 <br /> MICRO SOP-P19 <br /> o If the number of colonies per plate exceeds 300, report as "too <br /> numerous to count (TNTC)" and for calculating the density, use the <br /> value of greater then 300 0300). For example, if a plate at the 10-2 <br /> di ution is TNTC, caleglate the density as greater than 3.0 x <br /> 10 CFU/ mL (>3.0 x 10 CFU/ mL). <br /> a If there is no plate with at least 30 colonies, go ahead and calculate <br /> the density using the highest plate counts but remember that <br /> statistically these counts are only estimates. <br /> o if colonies grown are spreaders and are exceeding one-half of the total <br /> plate area, the plate will be difficult if not impossible to count. In <br /> the extreme case, it is not used but is reported as uncountable. <br /> o Colonies can be counted on representative portions of plates if <br /> spreading colonies constitute less than one-half of the total plate <br /> area and the colonies are well distributed in the remaining portion of <br /> _ the plate. <br /> o Plates that are uncountable because of missed dilution, accidental <br /> dropping, contamination, should be described in a comments section. <br /> z <br /> F <br /> t References <br /> 1. <br /> Environmental Protection Agency. 7970. Microbiological <br /> Methods for Monitoring the viroriment, Water and wastes. <br /> t EPA-600/8-78-017. USEPA. Waahington, DC. <br /> 2. American Public Health Association. 1905. Standard Methods <br /> for the Examination of water and Wastewater. 16th Edition. <br /> - E <br /> APHA. Washington, DC. <br /> e <br /> Prepared by: <br /> Carl W. rken recher, Jr. <br /> Research Microbiologist <br /> Approved Vey: AL <br /> Frank . Phil ips+ <br /> section Supervisor <br /> --- --— _ --__---___- <br /> ----- ------Environmental Toxicology-and Information Services <br /> t CWE/F%P/egg/Micro SOP`s <br /> - 5 - <br /> �,tet <br />