Coliform Bacteria

What are coliform bacteria?


Coliform is a family of bacteria common in soils, plants and animals. The coliform family is made up of several groups, one of which is the fecal coliform group, which is found in the intestinal tracts of warm-blooded animals including humans. The presence of fecal coliform in drinking water is evidence that human or animal waste has been or is present. This is cause for concern because many diseases can be spread through fecal transmission.

  • The presence of some fecal material in lakes, ponds and rivers is to be expected as part of the environment in which we live. As long as the level of fecal coliform bacteria is low, swimming is relatively safe.
  • In drinking water, however, any fecal coliform presence is a warning sign that action should be taken.

Where are coliform bacteria 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 coliform bacteria enter my water?

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. Also, reduced pressure or suction in long water lines, or drawing in soil water at the joints are sources as well.

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.

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.

If my well has bacteria, should we drink bottled water?

If you have unsafe levels of coliform bacteria you should obtain an alternative source of drinking and cooking water until the problem is solved. Don’t neglect to solve the problem. Most bottled waters are not free of bacteria, but they should be free of coliforms. In the U.S., the Food and Drug Administration administers commercial bottled water quality.

The source (bottler) should be able to give you information on the quality of the batch of bottled water you are using. Another source is water hauled from a nearby public water system that is tested to be safe for drinking. It is important that water jugs or tanks used to haul water are themselves very clean and free of coliform bacteria or chemicals.

What types of treatment devices will make the water safe for consumption?

If treatment is necessary, there are a number of ways of addressing bacteriological concerns. Disinfection is the removal of infectious agents. Disinfection should not be confused with sterilization, which is the complete inactivation of living material.

Biological contaminants are most effectively eliminated through chlorine disinfection, filtration, ultraviolet irradiation, and ozonation. All methods must be properly designed for the intended use and properly maintained. Additionally, bacterial analysis of the treated water must be made with sufficient frequency to ensure adequate treatment.

What about bacteria in public water systems?

About 40,000 of the 210,000 ground water-supplied public water systems reporting via the Federal Reporting Data System have had microbial violations, indicating bacterial presence in their ground water, wells, or distribution systems during the last five years. Smaller systems and non-community systems tend toward violations from source water contamination.

Contamination of distribution systems results from cross contamination and backflow events, and from bacterial growth within a system. Some septic systems, displaced by rising ground water pressure or flooding, may become hydraulically connected to wells. They are the most frequently reported causes of contamination in ground water disease outbreaks associated with the consumption of untreated ground water in the U.S. Other sources are animal feedlots and the like.

If my water is clear and smells OK, is it safe?

You cannot directly smell unsafe bacteria or protozoa. They can only be detected using tests designed for that purpose. You should check your water quality regularly. Some sources of odors are bacteria or septic, or the presence of chemicals. It is a good idea to take your nose seriously. Have the water tested.

What if my water is brown, or black, or smells bad?

The water may not be unsafe to drink, but you should test it just in case. Also test for “iron bacteria” or biofouling, iron, manganese, and sulfur. Water treatment methods are available to provide clear, odor-free water. Check with several water treatment professionals for options.

How common are water problems?

“Pure” water does not exist – all natural water contains some gases and minerals. All natural waters, regardless of their source (surface or ground water), are likely to contain some microbial organisms. A few cause disease; some impart taste, odor, or turbidity (cloudiness) to the water; others are beneficial.

The acceptability or desirability for the presence of these materials in water is usually a matter of individual preference. Many people develop a tolerance for drinking water of poor taste, odor, or appearance, and they believe their water supplies do not need treatment. They should still have their water supply tested every year or after well and/or pump service. If a water quality problem is present, it can usually be remedied with the appropriate water treatment equipment. Changes in taste, odor, or turbidity of the water may be the first signals of a water problem.