LaMotte MF 3-0035 - Manual (Page 5)

prepared dish. Make sure that there are no air bubbles between the filter and the
pad. Cover the dish with a lid. Tape the lid to the dish bottom with clear tape.
Incubation
15. Incubate the dish in a warm place or in an incubator. If using an incubator,
incubate at 35°C for 18-24 hours. If an incubator is not used, place the dish in a
place that will be at constant, warm temperature. Do not place it in direct sunlight
or over a direct heat source, radiator, furnace duct etc. The dish may be placed
near one of these sources or in a warm spot in a kitchen. Allow 24-48 hours for
growth to begin. Once growth has begun, incubate for an additional 24 hours
for complete growth.
16. Once the incubation is complete, count the colonies. Colonies are normally
reported as Colony Forming Units (CFU) per 100 mL of water. Refer to the
ColiQuant MF Colony Color Guide.
Interpretation of Results
17. To determine the result as E. coli or Fecal Coliform, count the blue colonies.
Disregard any light-blue, blue-green or white colonies. Refer to the ColiQuant
MF Colony Color Guide.
To report the result in terms of E. coli or Fecal Coliform per mL of water: Divide
the number of colonies by the original sample size
To report the results in terms of E. coli or Fecal Coliform per 100 mL of water: Multiply
the number of colonies by 100. Then divide by the original sample size. (Most states
use this measurement to report water quality results.)
18. To determine the result as General Coliforms count the number of pink to red
colonies.
To report the result in terms of General Coliforms per mL of water: Divide the number
of colonies by the original sample size
General Coliform colonies
per mL (CFU/mL)
# Colonies
Amount of sample used
=
E. Coli or Fecal Coliform
Colonies per mL (CFU/mL) # Colonies
Amount of sample used
=
E. Coli or Fecal Coliform
Colonies per 100mL
(CFU/100mL)
# Colonies x 100
Amount of sample used
=
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