According to the U.S Environmental Protection Agency, coliform bacteria are common in the environment and are often not harmful in of themselves. However, the presence of these bacteria in well water or spring water can indicate that the water may be contaminated with disease-causing agents such as parasites, viruses or bacteria. Since testing for pathogens such as the bacteria, protozoa, and viruses that make people sick can be difficult, total coliform bacteria are tested for instead. Total coliforms are indicators and are more common and easy to grow.
Coliform bacteria are organisms commonly found in soil or vegetation and in the intestinal tracts of warm-blooded animals. This group of bacteria has long been an indicator of the contamination of water and possible presence of intestinal parasites and pathogens. The coliform bacteria are relatively simple to identify, are present in much larger numbers than the more dangerous pathogens, and react to the natural environment and treatment processes in a manner and degree similar to pathogens. By observing coliform bacteria, the increase or decrease of many pathogenic bacteria can be estimated.
E. coli is a type of fecal bacteria that originates from human and animal wastes. During rainfalls, snow melts, or other types of precipitation, E. coli may be washed into creeks, rivers, streams, lakes, or ground water. When these waters are used as sources of drinking water and the water is not treated or inadequately treated, E. coli may end up in drinking water. A presence of E.coli usually indicates a more serious contamination condition than the presence of total coliform alone.
Properly constructed and maintained water wells usually do not test positive for total coliform or E.coli. A presence of coliform in a deep water well usually indicates that the well is under the influence of surface water, or is being contaminated by septic systems, or other industrial or commercial waste water systems.
In some cases new wells or wells that have recently had work performed such as a pump repair, can test positive for coliform due to improper sanitizing of the tools and equipment used during the repairs. If this is the case it is advisable to shock chlorinate the well and pressure system and repeat the test for coliform.
In many cases the water is not contaminated at all but the sample taken was accidentally contaminated during the sampling, producing a false-positive. It is relatively easy to accidentally take a contaminated sample. If you think your water is safe and your well is in good condition, you might consider re-testing the water. Use a sterile bottle and take caution to avoid contaminating the sample by touching the inside of the cap or bottle with your hands, or allowing foreign particles to accidentally get inside the sample bottle.
If your water is contaminated and tests positive for total coliform and/or fecal bacteria you can take one of the following steps:
Boil all water intended for consumption or use a filtration system that can remove bacteria to safe levels.
Disinfect the well, pressure tank and household piping and fixtures thoroughly with chlorine bleach. Wait several days to a week until all chlorine is gone from your system and repeat the coliform test.
Monitor your water quality to make certain that the problem does not recur.
Try to identify the source of the problem (such as a defective well seal, or cracked casing) and fix it.
If the well is too expensive to repair, investigate the feasibility of drilling a new well or install a disinfection unit, which can use chlorination, hydrogen peroxide, ultraviolet light, or ozone to kill bacteria and viruses.
If your water source is a community system on well water there are federal and state laws that apply. All community public water systems, as well as non-community public water systems (public systems that do not serve a residential population such as a gas station or restaurant on a private well), must submit samples for coliform bacteria testing on a regular monthly basis. Failures to submit samples, meet the maximum contaminant level (MCL), and report non-compliance are all violations of the total coliform rule.
The maximum contaminant level is based on the presence or absence of total coliforms in a sample. A very small water system may have one coliform positive sample per month and still remain in compliance with the regulation.
Each state may have its own unique requirements for disinfection and water quality monitoring of public or private water systems. Check with your state water agency to determine what is required in your state.
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