Coliform Bacteria In Drinking Water

Water that is found in the natural environment is usually contaminated with numerous different chemical and biological agents.  When water is removed from the natural environment and used for drinking water - as is the case with well water - it is important that the water is free from organisms that can cause illness.  One of the most common drinking water contaminants - especially in rural water supplies - is coliform bacteria.

What Are Coliform Bacteria?

Coliform bacteria are a large group of bacteria that are found in very high concentrations in the fecal matter of warm blooded animals such as dogs, deer, and humans.  Some coliform bacteria can cause disease in humans, but most do not.  But, when any coliform bacteria are detected in a water supply it is a clear indication that the water has been contaminated with animal fecal matter.  Fecal matter may contain other, much more dangerous organisms.  So, coliform bacteria are classified as an indicator organism.  The presence or absence of coliform bacteria suggests the presence or absence of more dangerous disease-causing agents in the water.

How Do Coliform Bacteria Get Into A Water Supply?

Coliform bacteria are most commonly found in surface water sources such as lakes, rivers, ponds, and streams and in well water.  Coliform bacteria typically enter a surface water source when rainwater washes animal waste into the water.  Grazing cattle and other livestock may defecate directly into small streams that are tributaries to larger rivers and lakes.  Sometimes coliform bacteria are discharged to natural waterways when human sewage treatment plants fail to properly disinfect the sewage before it is discharged.

Coliform bacteria may enter a well water supply in a number of different ways.  If a well cap is below the level of the surface, rain water may wash animal fecal matter into the well.  If a well casing is cracked or if the well was improperly built, contaminated ground water may enter the well below the level of the surface.  Very high coliform levels may be detected in well water when the casing is cracked and when a septic system weeping bed has been located too close to the well.

Are Coliform Bacteria Dangerous To My Health?

There are a number of coliform bacteria that can directly cause disease in humans.  E. coli is a good example of this.  The presence of coliform bacteria though suggest fecal contamination of the water supply which may suggest the presence of other, more dangerous organisms such as intestinal parasites.

How Is Coliform Bacteria Tested?

In North America a coliform bacteria test is very easy to have done and in many jurisdiction it is a test which is offered for free or for a minimal fee.  After running the water in the home for several minutes, a sample of water is taken in a special container that contains a bacterial preservative.  This sample is then taken immediately to the laboratory.  The sample is plated on a petri dish that contains food for the bacteria.  This petri dish is then incubated at a warm temperature to help the bacteria to grow quickly.  Wherever a single bacteria was present, a large colony will now exist.  These colonies are counted.  The results of a coliform bacteria test are usually reported as CFU/100ml - this translates as "colony forming units per 100 millilitres".

How Much Coliform Bacteria Should I Have In My Water?

The answer to this question is zero, however, the limit to the number of coliform bacteria in your water varies by jurisdiction.  Some places in North America will consider water safe as long as it contains fewer than 5 CFU/100mL.  The U.S. Environmental Protection Agency has a maximum contaminant level of zero for coliform bacteria as can be seen here.

How Can I Remove Coliform Bacteria From My Drinking Water?

There are a number of ways to remove bacteria, including coliform, from your water.  The easiest, most affordable, and most effective way for a homeowner to protect their water supply from these bacteria is to us a UV System.  A UV system is a metal cylinder that houses a UV lamp.  Water flows through the steel chamber and any bacteria are exposed to high amounts of UV radiation.  This radiation kills the bacteria making them harmless.  Popular residential UV systems are made by TrojanUVMax, Sterilight, and UV Pure.