What is coliform bacteria and where does it come from?
Coliform bacteria are microscopic organisms. They originate in the intestinal tract of warm blooded animals and may also be found in soil and vegetation.
Human Influences that cause an increase in coliform bacteria:
Why care about coliform bacteria?
Drinking Water Information
How do I find out if there is coliform in my water?
If you rely on a public water system, then your water is tested often for coliform bacteria and other pollutants. If any coliforms are found in a public water supply, the supplier is required to notify the public within 24 hours. With this notification, you will be instructed on how to treat your water until the public water system is cleaned and tests free of coliforms. Most water companies will send out an annual Consumer Confidence Report which discloses contaminants found, possible health effects, and the water’s source. This report is generally sent in July with your water bill. If you do not receive a report, contact your water company for this information.
If you have a private water system (private well) then you are responsible to ensure your drinking water is safe for human consumption. Test for coliform at least once a year. Also test your water if you have a new well or pump installed, or if there are any environmental changes that might affect your well, such as flooding or a new feedlot operation near your well. To test for coliform bacteria contact a certified testing lab near you. A coliform test will cost approximately $10-30.
What is the drinking water standard for coliform?
The established standard for bacteria in drinking water includes total coliforms, fecal coliforms, and E. coli. Municipalities that collect less than 40 total coliform samples per month may have no more than one sample that tests positive. Those collecting over 40 samples per month are required to have no more than 5% test positive. No samples should test positive for fecal coliform or E. coli. There is no standard for private wells, nor is any testing required, which means the owners of private wells must test their own water.
How can I treat water that contains coliforms?
In a public water system if coliform is found, the supplier will notify users within 24 hours and will immediately disinfect the water supply by putting chlorine into the system. If certain types of coliform bacteria have been found the water supplier may issue a "Boil Order" notice. This means the decontaminating and re-testing of the water supply may take several days, during which you should boil all water for several minutes before any uses that involve ingestion. Follow the instructions provided by the water supplier.
If you find coliform bacteria in your private well system the first thing you will need to do is determine whether the source of contamination is in the well or inside your home in the water system. Test the well itself (or as close to the well as possible). If it contains coliforms the well is contaminated, if not, then the source of contamination is probably in the plumbing system. If the results from the water from the well return as uncontaminated, but the tap water results read as contaminated, the contamination source may be an inadequately maintained treatment system. Charcoal filters, and many other point-of-use systems at the faucet or in a refrigerator water system can harbor bacteria. To avoid this filters should be maintained and replaced according to the manufacturer's directions. Other possible sources of contamination may be cross connection with irrigation water or back siphonage (reverse flow) from garden hoses.
Consider possible contamination sources (e.g., faulty septic system, storm runoff, livestock waste runoff). Correct these problems, if practical, before installing permanent water treatment equipment. Well water can be treated by "shock chlorination". This method circulates a strong chlorine solution throughout your water system. It may also remove biological material collecting in your plumbing system. For more information about well water and coliform bacteria view the fact sheet Coliform Bacteria.
Escherichia coli (E. coli)
Escherichia coli (commonly known as E. coli) is a single species in the fecal coliform group. It is a bacterium that is found in the intestines of humans and other warm blooded animals. E. coli does not occur naturally in soil and vegetation. It will only enter water from fecal contamination.
Why care about E. coli?
According to the United States Environmental Protection Agency (USEPA) E. coli is the best indicator of health risk from water contact in recreational waters. The presence of E. coli in water is an indication of recent contamination from sewage or animal wastes, which may have many disease-causing organisms. Although most strains of E. coli are harmless, E. coli O157:H7 is a cause of foodborne and waterborne illness. This strain was first recognized as a source of illness in 1982, when people were getting sick from it in ground beef. Since then, most infections have been from undercooked ground beef, but some have gone waterborne.
What are some health concerns of E. coli in water?
Although most strains of E. coli are harmless, E. coli O157:H7 is one that causes serious illness by producing a powerful toxin. Symptoms of infection usually take 2 to 4 days to appear, but may take as many as 8 days. Symptoms often include severe diarrhea (sometimes bloody) and abdominal cramps. However, these symptoms are common to a variety of diseases and E. coli O157:H7 may not be the cause of infection. In some people (children under 5 and the elderly particularly) an infection can cause a complication referred to as hemolytic uremic syndrome. In this syndrome red blood cells are destroyed and kidneys fail. Approximately 2%-7% of infections lead to this complication. It is a life-threatening condition that usually needs to be treated in an intensive care unit.
How is E. coli monitored?
Most water companies will send out an annual Consumer Confidence Report which discloses contaminants found, possible health effects, and the water’s source. This report is generally sent in July with your water bill. If you do not receive a report, contact your water company for this information.
If you have a private water system please see the section, How do I find out if there is coliform in my water?