Ref ID : 1101
Elaine F. Munoz and Melvin P. Silverman; Rapid, single-step Most-Probable-Number Method for enumerating fecal coliforms in effluents from sewage treatment plant. Appl.Environ.Microbiol. 37(3):527-530, 1979
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A single-step most-probable-number method for enumerating fecal coliforms in sewage treatment plant effluents is described. The method requires the use of only one lactose-based broth medium and a single incubation temperature of 44.5 degrees C, and it can be completed in 18 hr or less, as compared with up to 72 hr for the standard most-probable-number method. The appearance of growth is the sole criterion used for designating positives, which can be determined either by increases in the electrical impedance ratio of inoculated medium, as compared to an uninoculated control using a Bactometer model 32, or by visual examination of inoculated medium for turbidity. In trails with 53 samples of unchlorinated sewage treatment plant effluent, fecal coliform counts by the single-step most-probable-number method, throughout a range of less than 10 to almost 10E7 fecal coliforms per 100 ml of effluent, were in excellent agreement with counts obtained by the standard most-probable-number procedure. Similar agreement was obtained in comparative trials with 31 chlorinated effluent samples from two sewage treatment plants. Overall, 87% of 452 positives were confirmed as containing fecal coliforms. The applicability of the single-step most-probable-number method to automated sewage treatment plant operations is discussed.