What are coliform bacteria?

Coliform bacteria are commonly found in soil, on vegetation, and in surface waters. They also live in the intestines of warm-blooded animals and humans. Some coliform bacteria strains can survive in soil and water for long periods of time. Coliform bacteria will not likely cause illness in most people; however, because coliform bacteria are most commonly associated with sewage or surface waters, the presence of coliform bacteria in drinking water indicates that other disease-causing organisms (pathogens) may be present in the water source or its distribution system.

There are three different groups of coliform bacteria, and each has a different level of health risk:

  1. Total coliform bacteria are commonly found in the environment and are generally harmless. If only total coliform bacteria are detected in drinking water, the source is probably environmental, and fecal contamination is not likely. If environmental contamination can enter the system, however, that suggests there may be a way for pathogens to enter the system. Therefore it is important to determine the source and resolve the problem.
  2. Fecal coliform bacteria are a sub-group of the total coliform group. They are found in great quantities in the feces of people and animals. The presence of fecal coliform in a drinking water sample often indicates recent fecal contamination — meaning that there is a greater risk that pathogens are present than if only total coliform bacteria are detected.
  3. E. coli is a sub-group of the fecal coliform group. Most E. coli are harmless and are also found in great quantities in the feces of people and warm-blooded animals. Some strains, however, may cause illness. Some of these common waterborne illness symptoms include diarrhea, vomiting, headache, and cramps (acute gastrointestinal illness). Populations at highest risk to this ailment are: the very young, the very old, and persons with compromised immune systems. The presence of E. coli in a drinking water sample almost always indicates fecal contamination of the water supply, and so E. coli outbreaks usually receive a lot of media attention. Many food borne outbreaks have been caused by an especially virulent strain of E. coli known as E. coli 0157:H7 which can cause serious illness or death.

E. Coli and Total Coliform Regulations

The current federal drinking water regulations for public water supplies (EPA) and bottled water (FDA) set forth requirements for the detection and prevention of E. colicontamination of both types of drinking water.

The current respective total coliform maximum contaminant levels are:

  • Public Water Supply: no more than 5 percent confirmed positive total coliform samples from a public water supply which samples 40 or more times per month.
  • Bottled Water: zero confirmed positive total coliform samples from a finished bottled water product or its source water.

Both public water and bottled water regulations have a zero tolerance for E. coli.

A violation of the total coliform standard by a public water supply requires correction of the deficiency, notification of the responsible state authorities, notification of the public within 30 days, and may call for increased monitoring. An E. coli violation by a public water supply involves these same measures as well as public notification within 24 hours and boil orders.

A bottled water producer in violation of either the FDA total coliform or E. coli standards of quality will be prohibited from releasing the finished product into the marketplace or using a contaminated source until the violation is corrected. In addition to public notification, the contaminated bottled water product must be recalled from the field and destruction of the product is required.

For further detail see: A Comparative Microbial Safety Assessment of Public Water Supplies and Bottled Water

Jack West is the Chairman of the Board of Trustees of the Drinking Water Research Foundation (DWRF) in Alexandria, Virginia. With over 30 years of experience in the bottled water industry, he is now an advisor on drinking water quality issues.

CDC: “A Survey of the Quality of Water Drawn from Domestic Wells in Nine Midwestern States” 9/2004

City of Lacey, MI: “Coliform Bacteria and Drinking Water Fact Sheet”
Michigan Dept of Environmental Quality Water Division “Coliform Bacteria and Well Water Sampling Fact Sheet”

Federal Register: FDA Proposed Amendments to CFR 21 parts 129 and 165; Vol 73, No. 181, pg 53775, September 17, 2008

Federal Register: EPA Ground Water Rule; Vol 71, pg 65574, November 8, 2006

FDA Bottled Water Coliform Bacteria Final Rule, May 29, 2009 Code of Federal Regulations Title 21 Chapter 1, Subchapter B, Part 165, Subpart B Section 165.110 Bottled water(2,B, E. coli.)

The Revised Total Coliform Rule (RTCR) State Implementation Guidance—Interim Final. Office of Water (4606M), EPA 816-R-14-004, December 2014. Last accessed 1/27/2015.