Fecal-coliform bacteria are a group of bacteria that inhabit the intestinal tract of warm-blooded animals. The presence of fecal-coliform bacteria in water indicates fecal contamination of the water by a warm-blooded animal and harmful bacteria associated with fecal contamination may also be present.
Elevated levels of fecal-coliform bacteria in streams and rivers are a result of fecal contamination from warm-blooded animals. Humans, dogs, cats, cows, as well as wildlife such as geese, deer, and beavers are all examples of possible sources of contamination. The pathways these bacteria take to get into streams and rivers are varied and depend on which sources contribute and the hydrologic conditions. Fecal-coliform bacteria from cattle might be washed into a stream from a pasture during rainfall, geese and ducks might defecate directly into a stream or river while feeding, and bacteria from human sources may enter the water as a result of sewage spills, leaking sewer lines, or malfunctioning septic systems.
Pathogens are disease-causing organisms such as some types of bacteria, viruses, and protozoans. Consumption of, or recreational contact with, water contaminated with feces of warm-blooded animals can cause a variety of illnesses. Minor gastrointestinal discomfort is probably the most common symptom; however, pathogens that may cause only minor sickness is some people may cause serious conditions or death in others, especially in the very young, old, or immuno-comprimised. Monitoring for pathogens is typically only cost efficient after there is a known outbreak.
A microbial indicator organism is a microbe that is usually harmless, found in high numbers, and originates from the same sources as the pathogens whose numbers you are interested in obtaining. Monitoring for indicator organisms is usually much easier and more cost effective than actually monitoring for the disease causing organisms. Pathogens typically occur in very small concentrations, so routinely monitoring for pathogens is analogous to looking for a needle in a haystack. Field sampling and laboratory methods for measuring pathogens are very time consuming, expensive, and sometimes put the analyst at more risk for being infected by the pathogen. Separate tests must be performed for each individual pathogen and frequently cost more than $1,000 per analysis.
Bacteria are a natural component of all rivers, lakes and streams and most bacteria are harmless, however, certain species of bacteria in groups such as Campylobacter, Salmonella, and Shigella can cause sickness in humans. The most common side effects of these sicknesses may include a short period of vomiting and/or acute diarrhea. Some bacteria such as the recently discovered strain of E. coli (0157:H7) can cause hemorrhagic colitis, a serious illness that can lead to complications such as kidney failure. Other waterborne diseases that can affect humans are caused by parasites and viruses-which are also associated with elevated levels of bacteria in the water. Those most at risk for the serious side effects associated with these waterborne diseases are the very young, old, and immuno-compromised.
The presence of fecal-coliform bacteria in waters does not directly affect fish consumption, however, when fishing it is often difficult to avoid some contact with the water. Any body contact with water that has elevated fecal-coliform bacteria levels increases the likelihood that a person may be exposed to or accidentally ingest water from the river. This is especially true if the person has open cuts or wounds or if eating or drinking is involved.
Fish consumption advisories are issued by the Georgia Department of Natural Resources (Ga DNR) and are based on an analysis of chemical and metal concentrations in fish tissue. Currently, the Ga DNR advises fishermen to limit consumption of Rainbow Trout and Largemouth bass caught from Buford dam to Morgan Falls Dam to one meal per week and Carp caught from Morgan Falls Dam to Peachtree Creek to one meal per week.
Levels of fecal-coliform bacteria in a river or stream can be influenced by many factors. The most common causes for elevated levels of fecal-coliform bacteria are due to runoff associated with storms, however, leaking sewage lines or spills from treatment plants can also cause levels to increase. Fecal-coliform concentrations are typically higher (1) during and after rain events, (2) on tributary streams than in the Chattahoochee River, (3) further downstream in the Chattahoochee River than near Buford Dam, (4) during the summer recreation season than during the winter months, and (5) at night rather than during daylight hours.
There are several ways of measuring numbers of fecal-coliform bacteria in streams. The method used to determine the numbers reported on this web site involves a relatively new method recently approved by the United States Environmental Protection Agency (USEPA). It involves the collection of water from the river water using sterile equipment and adding a chemical called MUG. This mixture is then poured into a container that separates the river water into equal-sized compartments. The container is sealed and incubating for 18-22 hours. The river water in the compartments containing coliform bacteria and E. coli (which is a type of fecal-coliform bacteria) will change color. The number of compartments which turn yellow indicates the most probable number (MPN) of total coliform bacteria in the stream while the number compartments which fluoresce under ultraviolet light indicates the number of E. coli present in the stream at the time that it was sampled.
In an urban watershed, there is not a general rule as to the best time to go into the water. Many studies have shown that fecal-coliform bacteria levels are highest during and after rainfall. The turbidity (degree of cloudiness) of the water has also been suggested to be a relatively good indicator of the microbiological condition of the water. However, elevated levels of fecal-coliform bacteria have been observed in metro Atlanta streams during dry conditions and when the water was relatively clear. In general fecal-coliform bacteria concentrations are higher during and after rainfall, higher in tributary streams rather than the mainstem and higher during the summer rather than in the winter. Georgia's water quality rules and regulations state that "the state of Georgia does not encourage swimming in surface waters since a number of factors which are beyond the control of any State regulatory agency contribute to elevated levels of fecal coliform."
There are federal and state standards and criteria for fecal-coliform bacteria in water but presently no county or city standards. The specific standard depends on the water use designation (whether the waterbody has been legally classified as drinking water supply, fishing, or swimming) and the time of year (summer verses winter). The recreational water standard in Georgia for fecal-coliform bacteria is a geometric mean of 200 colonies per 100 ml of stream water year round. From May to October, the time when most water recreation occurs, waters designated drinking water supply and fishing also have a 200 colonies per 100 ml standard, however, during the winter fecal-coliform bacteria levels in waters classified for drinking water supply and fishing cannot exceed 1000 colonies per 100 ml. Usually these numbers are based on a geometric mean of at least 4 samples collected over a 30-day period. A geometric mean is similar to an average and is used because it is a more accurate estimator of the median of fecal-coliform bacteria counts. The USEPA has suggested that all states begin using E. coli, which is a specific type of fecal-coliform bacteria, rather than the general fecal-coliform group because E. coli have been shown to be a better indicator of disease causing bacteria. The criterion based on E. coli levels suggested by the USEPA is 177 colonies per 100 ml for recreational water.
Water suppliers routinely test their raw water for high levels of fecal-coliform bacteria and take numerous steps including filtration and chlorination to insure that the water which leaves treatment plants are free of all microorganisms, however, several large outbreaks of waterborne diseases have resulted when faulty equipment allowed contaminated water to enter the public drinking supply.
The USEPA has estimated that fecal-coliform bacteria concentrations of 200 bacteria per 100 mL would cause 8 illnesses per 1,000 swimmers at fresh water beaches and 19 illnesses per 1,000 swimmers at marine beaches. Paddlers, anglers, and waders are probably at even a smaller risk since they probably come in contact with water less than swimmers. The 200 colonies per 100 mL limit is routinely exceed in many metro-Atlanta streams and sometimes exceeded in reaches of the Chattahoochee River. Exceedences in the Chattahoochee River generally occur more frequently in the areas further downstream from Buford Dam, and most often in the reaches downstream of the Palisades Park Unit.
By definition a river is a moving body of water. Water-quality conditions within a certain reach or at a certain point along a river can vary and are dependent on water-quality conditions upstream of or within the tributaries which join the river along the reach. However, day-old readings may be a useful tool to determine whether or not someone wants to have body contact with water in the Chattahoochee River, especially if one considers the several weeks or months of previous data collected at a site and is aware of the weather conditions prior to recreational activities. Day-old readings will not provide warning of sewage spills nor changes in water-quality conditions caused by rainfall that has occurred during the previous 24-hour period.