LaMotte MF 3-0035 - Manual (Page 6)

To report the results in terms of General Coliforms per 100 mL of water: Multiply the
number of colonies by 100. Then divide by the original sample size.
19. To determine the result as Total Coliforms count the number of dark
purple/blue and pink to red colonies.
To report the result in terms of Total Coliforms per mL of water: Divide the number of
colonies by the original sample size
To report the results in terms of Total Coliforms per 100 mL of water: Multiply the
number of colonies by 100. Then divide by the original sample size.
20. If there are more than 80 CFU (colonies) of one color, the result should be
recorded as Too Numerous To Count (TNTC). If the E. coli colony count is less
than 80, even though there are more than 80 total colonies of all colors and
types the E. coli may be counted and reported. Record TNTC for coliforms or
non-coliforms that are present at greater than 80 CFU.
21. Presence/Absence
The presence of at least one dark blue/purple or pink/red colony at least 0.5 mm
in diameter indicates the sample is total coliform positive. The presence of at least
one blue/purple colony indicates the sample is positive for E. coli. The presence
of at least one pink/red colony indicates the sample is positive for general
coliforms.
Clean up
Empty the filtered water from the collection container (F) into a sink. Clean the funnel
before the next use by rinsing with alcohol. The white filter pads (C) and the funnel (B)
can be sterilized by microwaving for 1-2 minutes. Dry the funnel with a clean paper
towel before microwaving. Place the white filter pads on a clean paper towel to
microwave. The white filter pads should be saved and reused.
Total Coliform Colonies
per mL (CFU/mL) # Colonies
Amount of sample used
=
Total Coliform Colonies
per 100mL (CFU/100mL) # Colonies x 100
Amount of sample used
=
6
General Coliform colonies
per 100mL (CFU/100mL)
# Colonies X 100
Amount of sample used
=