|Fecal Coliform Bacteria and Illinois Streams
A letter from Bob Mosher, Illinois EPA
|We are not responsible for errors or omissions.|
When boating, regardless of water depth, wear a PFD!
Recently, fecal coliform bacteria have been a news item that has attracted the attention of recreational users of Illinois' streams and rivers as well as the general public. Just what are these organisms and what is their significance to canoeists, fishermen, and others whose hobbies or vocation put them in contact with water? I'll try to explain this from the background of our water quality monitoring activities at the Illinois Environmental Protection Agency.
Fecal coliforms are bacteria that originate in the intestinal tracts of all warm blooded organisms. They serve their hosts in several ways, gain their nourishment from leftover food molecules in the intestine, and are a natural and healthy presence in the body. When feces are passed out of the body, billions upon billions of these bacteria go along. In fact, well over half the bulk of feces may consist of bacteria, many of which are classified as fecal coliforms. Hence, a cow flop, deposited in a stream, could send the fecal coliform count of the water into the hundreds or thousands of bacteria cells per 100 milliliters (mL) of water, the most common way that fecal coliform concentrations are expressed.
This ignoble lifestyle makes fecal coliforms an excellent environmental indicator. When we find them in the environment we know where they came from - human or animal waste - and we are alerted to the potential presence of pollution. Interestingly, fecal coliforms can't be distinguished between humans and animals or between types of animals once they get into streams and rivers although the circumstances surrounding a particular site could provide hints as to their origin. In themselves, fecal coliforms aren't generally thought to be harmful, but other microorganisms potentially associated with them definitely are. Enteric diseases, meaning those diseases associated with the digestive system either as a mode of contraction or that the disease affects this part of the body, may be present along with the fecal coliforms if an infected person or animal contributed waste to the water body.
Diseases no longer very common in this country such as typhoid and cholera are enteric in nature and could be (and usually are) contracted from drinking water contaminated by fecal matter from someone who already has the disease. This was a huge problem before cities protected their water supplies. Hepatitis causing organisms as well as those that cause "stomach flu" or diarrhea in mild to severe forms are what generally come to mind in this country today when one thinks of water borne enteric diseases.
How many people actually get sick because of contact with disease organisms in Illinois streams? The answer is unknown. It's extremely difficult to determine the source for ailments like stomach flu. Proving that a case of diarrhea came from a recreational visit to a stream isn't high on the list of communicable disease outbreaks that health experts attempt to trace. How often diarrhea is contracted from whole body contact with streams is anybody's guess. Tracing disease contraction at swimming beaches is more realistic and several studies have been done but here the source of the disease was most likely another swimmer, very possibly one that hadn't passed toilet training yet.
Modern sanitation was designed to resolve many of these problems. Waste is treated at a sewage treatment plant where the incoming sewage contains literally millions of fecal coliforms per 100 mL. The fecal coliforms (and other organisms) in the finished product, or effluent, of the plant are typically reduced by a thousand fold or more by the rigorous biological breakdown process and final clarification. Without further disinfection, fecal coliform counts of 1,000 to 20,000 cells per 100 mL are expected. Septic tanks, when properly functioning, work about the same way. When chlorination or other means of disinfection is applied, the counts are reduced to less than 400 cells per mL.
But if sewage treatment is so efficient why do we sometimes have high fecal coliform counts in our waters?
Many sewage treatment plants are not required to disinfect their final effluents. The toxicity of chlorine, by far the most often used disinfectant, isn't good for streams in its own right. Within the last ten years, regulations were passed that restrict the amount of chlorine that may be discharged and also allowed an exemption to fecal coliform standards. In order to protect recreational users from undue exposure to disease organisms, a water quality standard of 200 fecal coliform cells per 100 mL of water normally applies to Illinois streams during the recreational season: May through October. However, where it is demonstrated that recreational use is highly unlikely due to shallow depths or other factors that make a stream physically impossible to swim in, and, no public water supply exists on the stream within a distance of concern, sewage treatment plants may obtain an exemption from disinfection. No bacteria standard applies in these receiving streams. The rule expressly protects all recreational waters and tributaries that may threaten these waters. Effluents to these waters must be disinfected and then dechlorinated. A site-specific review process is applied to all dischargers seeking disinfection exemptions to ensure that potential or existing recreation is protected.
If disinfection exemptions are tightly regulated, how are larger streams and rivers impacted by fecal coliforms? What about other sources?
Animal waste is everywhere. Feed lots, pastures, urban areas saturated with pet waste and even concentrations of wildlife (flocks of geese are notorious) may be major sources of fecal coliform contributions to our surface waters. These fecal coliforms and potential tagalong organisms enter streams and lakes by a route known as non-point source pollution. Rainfall washes feces into the water where the bacteria persist for a time. This prospect isn't a new problem. Imagine what happened when a thunderstorm hit after a herd of bison finished grazing next to a stream in pre-settlement Illinois. You get the picture.
Fecal coliforms and the disease organisms they may be associated with aren't at all happy about being excreted into the world of sunshine because, fortunately for us, it's the beginning of the end for them. The UV light in sunlight is a very effective disinfectant - if the sunlight can get to the microorganism. Muddy water or pockets of decayed leaves create shelter which allows them to survive longer. Predatory creatures such as protozoans feed on the bacteria, further reducing their numbers. Another good thing is that reproduction of these organisms is inhibited outside of the warm, dark, food rich conditions of their original habitat. The Agency has studied the demise of fecal coliform bacteria once they are in a stream and we have identified a die-off factor which can be used to estimate the natural cleansing of a stream. We use this value to predict the influence of fecal coliform bacteria downstream of a sewage treatment plant that is being considered for a disinfection exemption.
So, how does the Illinois EPA monitor fecal coliforms and what is our reaction to something like the recent findings that tributaries to the Mackinaw River in Central Illinois had relatively high fecal coliform levels? The Agency collects data at slightly more than 200 stream stations across the state at the rate of nine samples per station each year regardless of weather or flow conditions. This is a very extensive monitoring network as compared to other states. A fecal coliform analysis is almost always included among the water quality parameters monitored. This means that each year we look at approximately 1800 fecal coliform results. What we find is fairly consistent. When rains cause streams to rise and discolor, fecal coliform levels dramatically increase. Fecal coliforms are correlated with increasing turbidity or solids content of the water. This makes sense because rains that are heavy enough to erode and suspend soil particles are also washing fecal matter from the surface of the land into the water. Heavy rains also sometimes overburden sewage collection systems and cause overflows that may contain high fecal coliform concentrations. There is a first-flush effect. The first part of a storm causes a large part of the fecal contamination to enter the stream. Later, there is not so much left to wash in and fecal coliform levels begin to decline.
Our data show that most of the collections made during the year find that fecal coliform levels are at or near zero and meet the water quality standard. The remaining samples, collected during wet weather, may show fecal concentrations up to 100,000 cells per 100 mL or more. This is true throughout the state regardless of the water body. The lone exception is that our station on Lusk Creek in far southern Illinois rarely exceeds the standard. Why? This is one of our few streams that has an entirely forested watershed. The force of the rainfall is tempered by the trees and the slowed-down runoff is filtered by the leafy forest soils.
The Mackinaw River, a prime recreational stream, has an Agency monitoring station located near Green Valley. In the twelve months between October 1994 and September 1995, the most recent period for which data is available, one of the nine fecal coliform samples collected exceeded the water quality standard. On May 1, 1995, however, the fecal count was 4,900 cells per 100 mL. The turbidity on this date was 66 mg/L (average: about 4 mg/L) and the total suspended solids count was 816 mg/L (average: about 50 mg/L).
Conclusion: this sample was taken after a rain event. The usually clean Mackinaw was up and muddy. Along with the soil particles came bacteria that in all probability, given the location, came from livestock. Efforts to control non-point pollution continue, but certainly, while we have a long way to go in improving livestock waste runoff, the problem will never entirely disappear.
It may be true that there are isolated cases where inadequately treated human sewage enters streams as has been postulated at some of the towns in the Mackinaw basin. This problem is much less extensive than in years past because more and more towns now have sewage treatment systems. Where "wildcat" sewers (a collection system for sewage that doesn't have a treatment plant at the other end) are suspected of contaminating a stream, the Agency will respond by conducting a study to verify the source of the fecal coliforms. This is usually the old reliable upstream/downstream method. If the stream is contaminated downstream of a suspected source and the upstream water is not affected, the source is implicated. At the same time, Agency investigators will check out other possible sources such as feed lots that may be having an impact. If the upstream water is also contaminated, we have to look for a possible non-point source. Not all towns without a treatment plant are automatically suspect. Properly functioning septic tanks are a valid alternative, especially for very small communities.
What can one do to reduce the risk of exposure to microorganisms in water? Avoid contact when bacterial levels are known to be highest, immediately after rainfall events that have caused the stream to rise significantly and turn muddy. Waters near urban areas are more likely to have human-associated microorganism present than waters in rural areas. Always wash hands with soap before eating and after contact with the water. The route of exposure is the ingestion of water through nose or mouth or by eating food with unwashed hands. Properly cooked fish will be safe to eat because the heat of cooking will kill microorganisms.
The Illinois EPA is actively engaged in preventing fecal coliform contamination of recreational streams and lakes. Information on disinfection exemptions for specific sewage treatment plants as well as the regulations that allow these exemptions is available from us. Non-point pollution control information is also available, sometimes on a site specific basis. Write the Agency in care of the Planning Section of the Division of Water Pollution Control at 1001 North Grand Avenue East, Springfield, IL 62794-9276 or call 217-782-3362.