Significance of Test Parameters

  1. Total Coliform - it was recognized that most genera in the total coliform group occur naturally in soil, vegetation, and water in addition to feces, making them unsuitable indicators of fecal contamination.

    • Total coliforms were used as a surrogate for E. coli, primarily because routine methods to distinguish E. coli from other coliform bacteria were not available in the past.
    • It was not until the mid-20th century that more specific methods for the thermotolerant coliforms (previously referred to as fecal coliforms), which include E. coli and members of the genera Klebsiella, Enterobacter, and Citrobacter, were developed.

  2. Fecal Coliform - (now also called thermotolerant coliform) Fecal Coliform bacteria indicate the presence of sewage contamination of a waterway and the possible presence of other pathogenic organisms.

    • The presence of fecal coliform bacteria in aquatic environments indicates that the water has been contaminated with the fecal material of man or other animals.
    • At the time this occurs, the source water may be contaminated by pathogens or disease producing bacteria or viruses, which can also exist in fecal material.
    • Fecal coliform like other bacteria can usually be killed by boiling water or by treating with chlorine. Washing thoroughly with soap after contact with contaminated water can also help prevent infections. Gloves should always be worn when testing for fecal coliform.
    • Membrane filtration is the method of choice for the analysis of fecal coliforms in water.

  3. E. coli - As early as the 19th century, E. coli was recognized as a good indicator of fecal contamination. It was identified as the only species in the coliform group found exclusively in the intestinal tract of humans and other warm-blooded animals and subsequently excreted in large numbers in feces (approximately 109 per gram).

    • In addition to being fecal specific, E. coli do not usually multiply in the environment and have a life span on the same order of magnitude as those of other enteric bacterial pathogens, both of which are qualities of an ideal indicator.
    • E. coli are also excreted in the feces in high numbers, making detection possible even when greatly diluted.

http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/escherichia_coli/significance-importance-eng.php
http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/coliforms-coliformes/significance-importance-eng.php