Many human pathogens (disease-causing organisms) can be transmitted by water, especially when it is contaminated by human sewage or other animal fecal matter. However, even when they are present in a water supply, most pathogens occur in such small numbers that testing for them is difficult and often inconclusive. Instead, the Coliform Bacteria test is used to ascertain if a water supply is adequately protected from potential contamination by pathogens. This is accomplished by checking for the presence of bacteria from the coliform group.
These “indicator bacteria” are abundant in soil, surface water, and animal feces (including human sewage), but are not normally found in ground water. This analysis can also be used to check the effectiveness of disinfection systems (chlorinators, Ultra-violet, etc).
New Wells, Repairs, Power Outages
Coliform bacteria are often temporarily introduced into a well during the well and water system construction process, any time the well or water system is opened for repairs, or when a power outage results in loss of pressure to the water system. For this reason it is a good practice to disinfect the well and water system with chlorine bleach. Disinfection instructions are available at the lab upon request.
Bacteria in Springs
Interpretation of test results for springs, especially unprotected springs, is difficult, since they often contain coliform bacteria naturally. The MPN test can, however, give you some idea of the extent of contamination from vegetation and animal sources.
For routine monitoring of drinking water. Tells you whether bacteria are Present or Absent.
Most Probable Number (MPN)
Gives an estimate of the number of bacteria in the range often found in contaminated wells (1.0 – 200.5 per 100 mL).
Swim Water MPN
Gives an estimate of the number of bacteria in the range often found in surface water.
(2 – 1,600 per 100 mL — higher ranges are available, contact us for prices).
For assessing whether a water source (spring, creek, etc.) is contaminated with sewage. (Fecal coliform analysis, up to 160,000 per 100 mL)