Trace2O AquaSafe WSL25 Plus, Instruction Manual

Page: 39 / 85

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).