2022 Volume 45 Issue 1 Pages 29-39
An environmental standard on the number of coliforms in public rivers was set in 1970 to indicate fecal contamination, but its low indexability has been a problem. In this study, we investigated the usefulness of the hydrophobic gridded membrane filter (HGMF) method using CHROMagar-ECC nutrient agar and the Colilert method for the simultaneous enumeration of coliform bacteria and coliforms, in addition to the prescribed method based on notification No.94 in 2011 of the Ministry of the Environment that can only detect coliform bacteria. From the results of the survey in the Yamato River system, we found that the three methods showed a certain consistency of results, and that the HGMF and Colilert methods were capable of identifying the sites with high contamination levels which could not be determined from coliform counts alone. We also verified how the accuracy of a new environmental standard would change when the current environmental standard is revised from the coliform group count to the Escherichia coli count, and we found that many points on effectiveness that had not been realized with the current standard are expected to be realized after the standard after the revision.