ETV Verification Statement: Analysis of Total Coliforms and E. Coli in Drinking Water. Colifast, Norway

摘要

The U.S. EPAs 1989 Total Coliform Rule (TCR) sets both goals and legal limits for the presence of total coliform (TC) and Escherichia coli (EC) in DW. To summarize, the TCR states that the objective for water utilities is for zero TC organisms to be present in DW samples, and no more than 5% of all DW samples collected by a utility can test positive for TC. In order to comply with the TCR, water utilities need coliform detection technologies that are able to detect TC and EC at concentrations of one organism (org) per 100 milliliters (mL) of DW. While it is difficult to determine if a single target organism is present in 100 mL of water, when approximately half of the analyzed replicates are positive and half are negative, the density of the organism has become adequately low so that a positive result can be considered single organism detection. Therefore, for the purpose of this verification, the objective was to prepare a series of spiked DW dilution sets (labeled A, B, C) that provided 50 -25% positive results for TC or EC (depending on which is being targeted) using the reference method(s), and compare the results from the reference method with those produced by the tested detection technology.