e-mail: jhardman@zoominternet.net
What are coliform bacteria? Coliform bacteria originate as organisms in soil or vegetation and in the intestinal tract of warm-blooded animals (fecal coli). 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. Thus by observing coliform bacteria, the increase or decrease of many pathogenic bacteria can be estimated.
Where are they found? The many sources of bacterial pollution include runoff from woodlands, pastures and feedlots; septic tanks and sewage plants; and animals and wild fowl. Domestic animals contribute heavily to the bacterial population. Many coliform bacteria enter natural streams by direct deposition of waste in the water and the runoff from areas with high concentrations of animals or humans.
How could they enter a water system? The most likely sources come from where the water is used, the spigot, sink, or unclean containers. Another source includes backflow from a contaminated source, a sink-top carbon filter, bucket of water, or puddle at the end of a hose. Do you have your dog tied to the well casing? It's a pretty safe bet that you will never pass a coliform test if he is defecating and urinating on the well. Is there landscaping around the well? If so, the level to which you have brought the landscaping up to the top of the well and covered the 1' of bare casing that is to be sticking out of the ground, could contribute to bugs from the mulch climbing right into the top of the well. Does it have a bug resistant cap? You could be creating your own problem. In rare cases, the formation (aquifer) that the well is drilled into could be contaminated, but in spite of the news media and the EPA's constant bleeting to make you think all wells are sub standard and suspect, this is very rare.
Why test for coliform bacteria? While most coliforms are not pathogens, they serve as indicators of the microbial quality of water. Public health officials have tested for total coliform bacteria and fecal coliform bacteria for most of this century as a way of checking the quality of water.
Pathogens – the bacteria, protozoa, and viruses that make people sick – can be rare and difficult to detect even if they are present in the water. Total coliforms are indicators and are more common and easy to grow. Testing for them provides a margin of safety. Pathogens may not be present if coliforms are, but it would be wise to look for problems just in case.
Total coliforms are mostly natural residents of soil and water. Fecal coliforms are those that are usually found in the fecal material of animals. Their presence usually means that the water may be contaminated by sewage effluent. Finding the source of the problem and correcting it is very important.If I have bacteria in my well, where do they come from? Many experts in public health and water supply used to think that the subsurface was some kind of giant filter that trapped microorganisms before they could get to ground water, resulting in an effectively sterile water resource. However, we now know that many types of bacteria are native or adapted to saturated sediments and rock, and are indeed present in significant numbers in most water supply aquifers, even deep formations.
Given time and a route (soil and rock provide plenty of both), bacteria will migrate into and take up housekeeping in an aquifer. The environment is really rather nice- quiet, lots of surface area, often adequate carbon sources, and moderate temperatures with little environmental change.
Drillers and pump installers/servicers can also introduce microorganisms during their activities, but should not be considered the primary source of native microorganisms. There is no practical way at present to say for certain what is the source in any one well- maybe someday, but not yet. "Non-native" coliform bacteria or "protozoa" of potential health concern such as Giardia and Cryptosporidium are most likely introduced from the surface.Where else could coliform bacteria come from? Don't always blame the water first. Who sampled the water and how? How sanitary are your practices in food handling, personal hygiene, etc.? Do children wash regularly? Did the cat just use the litter box and is now sitting on the counter? Did you just wash off fresh vegatables from your garden in the sink, and brush the back of your hand against the faucet as you worked, thus infecting the faucet? While uncomfortable and personal subjects to some, these are more likely routes for contamination than the water itself.
Will coliform bacteria make us sick? Maybe, maybe not. Coliforms are not one kind of bacteria, but many. They are defined by what they do- grow on the sugar, lactose (the same as found in milk), and employ enzymes to help them use this sugar.
Most coliforms are harmless residents of soil and will not make people sick. Some strains of E. coli, the most common fecal coliform bacterium (usually living in animal fecal material), may be pathogens. Some found in food have been lethal. Their presence should be taken very seriously.
Your immune system also determines whether or not you will become ill. People become accustomed to the natural bacteria in their water while guests used to other water may have some discomfort or diarrhea. Immunocompromised individuals may become ill under circumstances where people with normal immune systems would not and such individuals should be very careful of the water they drink.
