Abstract
Bacteriological control of water supplies frequently involves examination of samples which have been shipped considerable distances. All editions of Standard Methods for the Examination of Water and Sewage provide for icing samples during shipment. Berry, 1 Jordan and Irons, 2 , Hale and Melia, 3 Albert, Hinman and Jordan, 4 Eijken, 5 Huss, 6 and Rector and Daube 7 reached conclusions which are not in agreement. Berry found little difference in the Escherichia coli count of iced and uniced samples and no appreciable multiplication of this group in stored samples. Boruff and Buswell 8 reported that a sample of water analyzed immediately showed more viable bacteria than after shipment iced about 100 miles (1–2 days in transit). Warm polluted water iced even for 12 hours underwent a distinct decrease in count. Their work would seem to indicate that the type of sample would largely determine the changes which would take place. Icing a sample of warm polluted water might cause more profound changes than icing a sample of cold water in the winter.
The work here reported involved 5 different types of water: (1) polluted surface water; (2) water to which soil had been added; (3) diluted sewage; (4) sterile distilled water inoculated with pure cultures; and (5) tap water inoculated with pure cultures. The technic in general was to divide the sample into 3 portions for storage at 3 different temperatures—in the refrigerator at about 4° C., at room temperature from 20.5 to 21.8° C., and in the 37° C. incubator. These incubation temperatures cover about the range to which samples might be subjected between time of collection and analysis.
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