Evaluation of the relationship between two different methods for enumeration fecal indicator bacteria： Colony-forming unit and most probable number

Evaluation of the relationship between two different methods for enumeration fecal indicator bacteria: colony-forming unit and most probable number

Most probable number (MPN) and colony-forming unit (CFU) estimates of fecal indicator bacteria (FIB) concentration are commonmeasures of water quality in aquatic environments. Thus, FIB intensively monitored in Yeongsan Watershed in an attempt to comparetwo di erent methods and to develop a statistical model to convert from CFU to MPN estimates or vice versa. As a result, the significantdi erence was found in the MPN and CFU estimates. The enumerated Escherichia coli concentrations in MPN are greater than those inCFU, except for the measurement in winter. Especially in fall, E. coli concentrations in MPN are one order of magnitude greater thanthat in CFU. Contrarily, enterococci bacteria in MPN are lower than those in CFU. However, in general, a strongly positive relationshipare found between MPN and CFU estimates. Therefore, the statistical models were developed, and showed the reasonable convertingFIB concentrations from CFU estimates to MPN estimates. We expect this study will provide preliminary information towards futureresearch on whether di erent analysis methods may result in di erent water quality standard violation frequencies for the same watersample.