Aquasafe WSL50 Pro, Instruction Manual

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SECTION 8: COUNTING COLIFORMS AND
RECORDING THE RESULT
Note the temperature that the incubator has been set for.
Following incubation, switch off the power and remove the petri dishes from the
incubator.
Place the petri dishes on a flat, level surface.
Remove the lids and count all the yellow colonies, irrespective of size. Use the
eye glass, if necessary. Count the colonies within a few minutes of removing from
the incubator, as the colours are liable to change on cooling and standing. Ignore
those colonies that are not yellow e.g. pink & transparent colonies.
Once the number of yellow colonies has been determined, and assuming
that 100 mL of sample was filtered, this number of colonies equals the
number of coliforms per 100 mL. Where samples were incubated at
35°C, the count is of Total Coliforms, whilst for those incubated at
44.5°C, the count is for Faecal (thermotolerant) Coliforms.
Record the results using the record sheets (if provided in the kit)