Water Quality Indicators: Total Fecal Coliforms

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How to use this page: This is an indicator page. Examine this page for detail on the indicator and use that information to establish a metric for the indication of water quality. This is the final step in examining a sustainable community for its environmental attributes, water sub-attributes, and finally a water indicator. After completing this page, please go back and review other indicators and see discern metrics and weights for the AHD process.


Why are Total Fecal Coliforms and indicator of Water Quality?

Fecal coliforms are bacteria that live in the digestive tract of warm-blooded animals and are excreted via feces. In themselves, fecal coliforms generally do not pose a danger to people or animals but they indicate the presence of other disease-causing bacteria such as those that cause typhoid, dysentery, hepatitis, and cholera. Unlike fecal coliforms, disease causing organisms generally do not survive in the environment long enough to be detected in water. This makes their direct monitoring very complicated, expensive, and difficult. Consequently, scientists have turned to fecal coliforms as an indicator. The theory behind such a measurement follows that if a fecal contamination event is present, the source water could have been simultaneously contaminated by pathogens which can also exist in fecal material. The presence of fecal contamination is an indicator that a potential health risk exists for individuals exposed to this water. Fecal coliform bacteria may occur in ambient water as a result of the overflow of domestic sewage or non-point sources of human and animal waste. Fecal coliforms are a common problem among states and areas where livestock is prolific and/or waste treatment is insufficient and leaks or dumps material containing fecal coliforms into a body of water that is a surface drinking water source for a town or city.

What level of Total Fecal Coliforms should a sustainable community have?

If high numbers of fecal coliform bacteria are found in a sample of stream water, one may conclude that there has been recent fecal contamination, although not necessarily human in origin. Other intestinal bacteria, such as streptococci or enterococci, may have a stronger correlation to human sewage, but no indicator has been identified that is exclusive to humans. The ratio of streptococci to fecal coliform was once thought to determine human versus animal fecal contamination. But, this is no longer though to be reliable because streptococci do not persist long in an open water environment, making it difficult to assess true concentrations. Enterococcal bacteria seem to be consistently associated with human sewage and subsequent diseases, but testing for these organisms involves a lengthy and complicated procedure.

Despite the fact that they can not be linked directly to contamination by human sewage, fecal coliform bacteria counts are often used to regulate surface waters for recreational use, shell fishing, and potability (ability to be safely consumed). Federal regulations stipulate maximum allowable numbers of these bacteria for various uses. If fecal coliform counts are high (over 200 colonies per 100 ml of water sample) in the river or stream, there is a greater chance that pathogenic organisms are also present. A person swimming in such water has a greater chance of getting sick from swallowing disease-causing organisms, or from pathogens entering the body through cuts in skin, the nose, mouth, or the ears. Diseases and illnesses such as typhoid fever, hepatitis, gastroenteritis, dysentery, and ear infections can be contracted in waters with high fecal coliform counts.

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Where to go now that you have reviewed an indicator:

Now that you have reviewed an indicator you should create a metric (see Step 4 of the Analytical Hierarchy Processes) that indicates the importance of this indicator in your decision process. Keep this step in mind as you go through one of the other indicators below. Once you have chosen a metric for each of your indicators, you should decide how they collectively measure the sustainability of water by weighting each indicator (see Step 5 of the Analytical Hierarchy Process). These will be applied in an algorithm (see Step 6 of the Analytical Hierarchy Process) to give you the final measurement for Water and Sustainability.



Author: Shawn Dayson Shifflett