Premium
Effects of Sunlight on Coliform in Water Samples
Author(s) -
Standridge John H.
Publication year - 1986
Publication title -
opflow
Language(s) - English
Resource type - Journals
eISSN - 1551-8701
pISSN - 0149-8029
DOI - 10.1002/j.1551-8701.1986.tb01176.x
Subject(s) - sunlight , environmental science , coliform bacteria , zoology , toxicology , biology , bacteria , genetics , physics , astronomy
The results of tests conducted by the Wisconsin State Laboratory of Hygiene to determine the effect of sunlight on coliform bacteria in bottled water samples are described. On a clear, early spring day in Wisconsin, sunlight caused a reduction in coliform bacteria levels after only 30 minutes of exposure. Complete die‐off occurred after approximately 3 hours. Samples placed behind a window, such as in a car or truck or on the windowsill of a laboratory, also exhibited a dramatic decline in coliform levels, especially in late June, when complete die‐off occurred after 1–2 hours of exposure. Additional tests under various sky conditions and during different seasons led to similar results. Although no die‐off occurred on days when there was heavy cloud cover, it did occur on hazy days. To ensure accurate coliform test results, water utility personnel should be careful not to place sample bottles in direct sunlight, such as sunlight entering through laboratory windows or through car windows.