Coliform Bacteria in Drinking Water Supplies

WHAT ARE COLIFORMS? TOTAL COLIFORMS, FECAL ARE COLIFORM BACTERIA Coliforms are bacteria that are always COLIFORMS, AND E. COLI HARMFUL? present in the digestive tracts of animals, The most basic test for bacterial Most coliform bacteria do not cause including humans, and are found in their contamination of a water supply is the test disease. However, some rare strains of E. wastes. They are also found in plant and soil for total coliform bacteria. Total coliform coli, particularly the strain 0157:H7, can material. counts give a general indication of the cause serious illness. Recent outbreaks sanitary condition of a water supply. of disease caused by E. coli 0157:H7 have generated much public concern about this “Indicator” A. Total coliforms include bacteria that organism. E. coli 0157:H7 has been found organisms are found in the soil, in water that has been in cattle, chickens, pigs, and sheep. Most of Water pollution caused by fecal influenced by surface water, and in human the reported human cases have been due contamination is a serious problem or animal waste. to eating under cooked hamburger. Cases due to the potential for contracting of E. coli 0157:H7 caused by contaminated B. Fecal coliforms are the group of the diseases from pathogens (disease- drinking water supplies are rare. causing organisms). Frequently, total coliforms that are considered to be concentrations of pathogens from present specifically in the gut and feces fecal contamination are small, and of warm-blooded animals. Because the the number of different possible origins of fecal coliforms are more specific pathogens is large. As a result, it is than the origins of the more general total not practical to test for pathogens coliform group of bacteria, fecal coliforms in every water sample collected. Instead, the presence of are considered a more accurate indication pathogens is determined with of animal or human waste than the total indirect evidence by testing for coliforms. an “indicator” organism such as coliform bacteria. Coliforms C. Escherichia coli (E. coli) is the major come from the same sources as species in the fecal coliform group. Of the pathogenic organisms. Coliforms five general groups of bacteria that comprise are relatively easy to identify, are the total coliforms, only E. coli is generally usually present in larger numbers not found growing and reproducing in COLIFORM TESTING than more dangerous pathogens, the environment. Consequently, E. coli is and respond to the environment, considered to be the species of coliform Testing for bacteria is the only reliable way wastewater treatment, and water bacteria that to know if your water is safe. You cannot treatment similarly to many is the best tell by the look, taste, or smell of the water pathogens. As a result, testing if disease-causing organisms are in it. for coliform bacteria can be a indicator of fecal The New York State Department of Health reasonable indication of whether pollution and other pathogenic bacteria are the possible recommends that well owners test their present. presence of water for coliform bacteria at least once pathogens. a year. If you have experienced bacteria problems in the past, it is recommended that you test your well more frequently. WHEN SHOULD I TEST? • contaminant seepage through the well casing - cracks or holes in the well cas- Late spring or early summer are the best times ing allow water that has not been filtered to test your well, since coliform contamination through the soil to enter the well. This is most likely to show up during wet weather. seepage is common in the wells made of Coliform Whether your test results are positive or nega- concrete, clay tile, or brick tive, understand that the sample you collected Bacteria is just a “snapshot” of your well’s water quality. • contaminant seeping along the outside The more samples you have tested, the more of the well casing - many older wells were In confident you can be about the quality of the not sealed with grout when they were water you are drinking. constructed Drinking • well flooding - a common problem for WHAT DO THE RESULTS MEAN? wellheads located below the ground in Water If coliform bacteria are present in your drinking frost pits that frequently flood during wet water, your risk of contracting a water-borne weather. Supplies illness is increased. Although total coliforms LONG-TERM OPTIONS FOR DEALING can come from sources other than fecal mat- WITH BACTERIAL CONTAMINATION ter, a positive total coliform sample should be OF A WELL considered an indication of pollution in your well. Positive fecal coliform results, especially • Connecting to the regional public water positive E. Coli results, should be considered system, if possible indication of fecal pollution in your well. • Inspecting wells for defects and repairing them if possible WHAT SHOULD BE DONE IF COLIFORM • Constructing a new well BACTERIA ARE DETECTED IN A WELL? • Installing continuous disinfection equip- ment When coliforms have been detected, repairs • Using bottled water for drinking and food or modifications of the water system may be preparation required. Boiling the water is advised until disinfection and retesting can confirm that For further information contact contamination has been eliminated. A defec- New York State Department of Health, tive well is often the cause when coliform Center for Environmental Health bacteria are found in well water. at 518-402-7650 or 1-800-458-1158 WHAT KINDS OF DEFECTS CAN or [email protected] ALLOW CONTAMINATION? • a missing or defective well cap - seals New York State around wires, pipes, and where the cap Department of Health meets the casing may be cracked, letting in contaminants 3226 12/04.

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