Coliform

 

ENZYME SUBSTRATE COLIFORM TEST

-By Method 9223 B 

Scope:

Enzyme substrate tests use hydrolyzable chromogenic and fluorogenic substrates to simultaneously detect enzymes produced by total coliforms and Escherichia coli (E. coli). In this method, total coliform bacteria produce the enzyme β-d-galactosidase, which cleaves the chromogenic substrate in the medium to release chromogen. Most E. coli strains produce the enzyme β-glucuronidase, which cleaves a fluorogenic substrate in the medium to release fluorogen. The release of chromogen indicates that coliform bacteria are present, and the release of fluorogen indicates that E. coli are present.

-Standard Methods for the Examination of Water and Wastewater

Method List

Analyte List

*Please contact our project management team for more information about reporting limits and other specific project needs.

MEMBRANE FILTER TECHNIQUE FOR MEMBERS OF COLIFORMS

-By Method 9222 D 

Scope:

The membrane filter (MF) technique is reproducible, can be used to test relatively large sample volumes, and usually yields numerical results more rapidly than the multiple-tube fermentation procedure. It is useful in monitoring drinking water and various natural waters. However, the MF technique has limitations, particularly when testing waters with high turbidity or large numbers of noncoliform (background) bacteria. If heterotrophic bacteria interference occurs, for example, sample results may need to be invalidated and new samples collected.

The MF technique may be used to test drinking, surface, ground, swimming pool, and marine waters. Do not use it to test primary wastewater-treatment effluent unless the sample is diluted, because the high turbidity level may clog the membrane filter before sufficient sample has been filtered. Chlorinated effluents should have low counts and turbidity. Also, do not use the MF technique to test wastewater containing high levels of toxic metals or toxic organic compounds (e.g., phenols) because the filter may concentrate such substances, thereby inhibiting coliform growth. For non-wastewater samples, high turbidity levels may clog the filter and high heterotrophic-bacteria concentrations may interfere with coliform growth on the filter, possibly requiring the use of multiple filters per sample and/or various sample dilutions.

Standard Methods for the Examination of Water and Wastewater

Method List

Analyte List

*Please contact our project management team for more information about reporting limits and other specific project needs.

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