Total Coliform and E. Coli Bacteria (Limit = Absent per 100 ml)
The organisms in the total coliform group are called indicator organisms. That is, if present, they indicate that there is a possibility, but not a certainty, that disease organisms may also be present in the water. When absent, there is a very low probability of disease organisms being present in the water. The ability of the total coliform test to reliably predict the bacterial safety of water relative to the hundreds of possible diseases that might be present is critical since it is impossible, in a practical sense, to check separately for every disease organism directly on a monthly or a quarterly basis. The presence of only total coliform generally does not imply an imminent health risk but does require an analysis of all water system facilities and their operation to determine how these organisms entered the water system.
Escherichia Coli (e-coli) is a specificspecies (subgroup) within the coliform family. They orginate only in the intestines of animals and humans. They have a relatively short life span compared to more general total coliform. Their presence indicates a strong likelihood that human or animal wastes are entering the water system, and have a much higher likelihood of causing illness.
For more information, please refer the following NH DES fact sheets:
WD-DWGB-4-1 Interpreting the Presence of Coliform Bacteria
WD-DWGB-4-2 Causes of Bacteria in Water Samples