The effect of storage on the coliform andBacterium colicounts of water samples. Overnight storage at room and refrigerator temperature

This investigation has been concerned with the changes that occur in the coliform and faecalcolicontent of water samples on storage at room and refrigerator temperature for 20–24 hr. On examination by a seventy-tube method, using twofold diminishing volumes, twenty-three out of 151 samples of water stored overnight at room temperature showed a significant increase in the presumptive number of conform organisms and twenty-nine a significant decrease. Of the same number stored in the refrigerator, ten showed a significant increase and twenty-six a significant decrease. Of 111 samples examined for faecalcoli, eight showed a significant increase on storage at room temperature and twenty-nine a significant decrease. Of the same number stored in the refrigerator, seven showed a significant increase and fifteen a significant decrease. The effects of the source of the water, the time of year and the original number of coliform organisms in the sample were examined. The present investigation has shown that in a considerable proportion of samples a significant change in the conform and faecalcolicontent does occur on overnight storage at room or refrigerator temperature. It may, perhaps, be safe to store samples under some conditions for shorter periods, but this is a matter for future investigation.