Technical Report No. 177
Roger S. Fujioka, Nipapun Kungskulniti, Samuel S. Nakasone
The most recent edition of Standard Methods proposes the use of the presence-absence (P-A) test to assay drinking waters for Coliform bacteria and the membrane filtration (MF) method using two new media (M-HPC, R2A) to determine the concentrations of total heterotrophic bacteria in drinking water samples. These two methods were used to analyze selected samples of Honolulu’s drinking water which were being routinely analyzed for coliform bacteria and total heterotrophic bacteria tested by traditional methods from the Honolulu Board of Water Supply (BWS) and the Hawaii State Department of Health (DOH). Over a thirteen-month period, 200 water samples obtained by the BWS and 18 samples obtained by DOH were also analyzed for coliform bacteria using the P-A test and for total heterotrophic bacteria using the MF method by the laboratory at the University of Hawaii. The comparative results show that the P-A test is more sensitive than the most probable number (MPN) (P <0.01) and the MF methods (P <0.05) in recovering coliform bacteria. Moreover, the MF method using either the M-HPC or R2A media is more efficient in recovering total heterotrophic bacteria than the pour plate method (P <0.01). The P-A test for coliform bacteria and the MF method for total heterotrophic bacteria were determined to be feasible and reliable methods when applied to drinking water samples from Honolulu. These two new methods were recommended for use by the BWS and DOH.