Water Education - Water Quality

The Importance to Test for Total Coliforms and Fecal Coliforms in Water

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To put it briefly, these organisms are good indicators of the potential contamination of a water source. Coliform bacteria have been used to evaluate the general quality of water. Testing for coliform bacteria is faster and cheaper than testing for specific organisms and pathogens. U.S. Public Health Service established a standard in 1914. Coliforms include all aerobic and facultatively anaerobic, gram-negative, non-spore-forming bacilli that, when incubated at 35 C, can ferment lactose and produce gas (CO2) within 48 hrs. Fecal coliforms are the coliform bacteria that originate specifically from the intestinal tract of warm-blooded animals (e.g., humans, beavers, raccoons, etc.).

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They are cultured by increasing the incubation temperature to 44.5 C and using somewhat different growth media. Two other groups of bacteria that are present in feces are: fecal streptococci and Clostridium. Clostridia spores can survive a long time during adverse conditions. This genus occurs naturally in soils and polluted waters; it is not used for monitoring purposes. Fecal streptococci and enterococci are terms that have been used interchangeably; however, there are some differences between the two groups.

Coliform organisms are used as indicators of water pollution. The coliform organism is a very common rod-shaped bacterium, not thought of as disease causing to humans. Because pathogenic bacteria in wastes and polluted waters are usually much lower in numbers and much harder to isolate and identify than coliforms, which are usually in high numbers in polluted water, total coliforms are used as a general indicator of potential contamination with pathogenic organisms. However, many coliform bacteria live in the soil, and these organisms may be the source of those that appear in the water, especially surface water. Fecal coliforms, on the other hand, are more specific because they refer to the coliforms that live in the intestinal tract of humans and many other animals.

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