Bacteria and other Microbial Contaminants
On occasion, the Minnesota Pollution Control Agency (MPCA) will post advisories at
Lake Superior's Minnesota beaches due to high levels of bacteria in the water. The
MPCA began monitoring bacteria levels at these beaches in 2003 with funding from
the U.S. Environmental Protection Agency (EPA). The MPCA established this
monitoring program with the mission and intention of warning the public about high
levels of bacteria and advising when contact should be avoided.
Unfortunately, no one has yet developed an automated sensor or a quick process to determine the presence of disease-causing pathogens, although a lot of progress is being made by researchers. So we still have to collect water in sterile bottles, either by hand or by using automated samplers. The water is then brought back to laboratories where it is tested to determine if indicators for pathogens, such as E. coli, are present, and at what level. To further complicate matters, it is extremely expensive to assay for specific microorganisms that may actually make you sick. There are just far too many types of bacteria, viruses and protozoans to look for, and most of the time they aren't present at high enough levels to detect anyway. |
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Indicator Organisms In almost all cases of water-borne illnesses the disease causing organisms, technically called pathogens or pathogenic organisms, come from untreated human waste or feces (Yes - we mean poop). The most common illness associated with swimming in and ingesting contaminated water is gastroenteritis, which can cause nausea, vomiting, abdominal cramps, fever, headache, and diarrhea. Other illnesses associated with swimming in such waters include eye, ear, nose, and throat infections. Direct testing for pathogens is expensive and impractical, because the pathogens are rarely found; they usually occur sporadically and mostly at low levels. Instead, public health agencies look for the presence of "indicator" species — so called because their presence indicates that fecal contamination may have occurred. The two most commonly used indicators for recreational waters are fecal coliforms and E. coli. These are bacteria that live in the lower intestines of warm-blooded animals, including wildlife, farm animals, pets, and humans, and are excreted in their feces. In fact, they may constitute a significant fraction of fecal waste. The indicator bacteria themselves are not usually pathogenic, but their presence can indicate sewage contamination, perhaps accompanied by disease-causing pathogens. Although still somewhat pricey (usually in the $15-30 range per sample), the cost of indicator monitoring is feasible and public health agencies have used total coliforms and fecal coliforms as indicators since the 1920s. |
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The US EPA and State of Minnesota have established several standards to use as criteria for posting beach advisories to protect public health. Fecal coliform levels have been used for decades as the prime indicator, but the E. coli level is now being phased in by most States at EPA's recommendation. The MPCA will likely adopt the E. coli standard for beach monitoring in 2006. In many programs, such as for the Lake Superior Beach Monitoring Program, both indictors were monitored until the 2006 recreation season when only E. coli was used. |
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In water-contact recreation waters —
The routine test for our drinking water microbial purity is the total coliform assay which includes the fecal coliform group as well as other coliforms that can live outside of mammalian bodies in the environment. This test is used because it is more conservative since we want to know if the drinking water system has been contaminated with soil bacteria due to pipe breaks or leaks. The standard for this test is less than 1 coliform colony per 100 mL of water (a bit less than a half cup). This means that if the water plant gets a "hit" in their daily monitoring, they have to resample and immediately attempt to fix a potential problem. Here is some more information on area drinking water monitoring. How long do these microbes persist in the water? This is an excellent question. There is no simple answer, but it is now well known that bacteria, including pathogenic species, may survive for weeks in water and sediment and possibly even in fecal pellets from wildfowl that have sunk to the bottom. Cold temperatures actually enable the organisms to survive even longer than in warmer temperatures where they may be degraded or eaten by other microorganisms and protozoans more quickly. Sources of microbial contamination It can come from lots of different places:
Additional information and local data A limited amount of fecal coliform data are being collected for Tischer, Chester and Kingsbury Creeks as part of the DuluthStreams project. These data are located in this downloadable spreadsheet. Additional data for other streams may be available in the REPORTS pages (linked from the top of each webpage in the Streams section). Monitoring data for Duluth area beaches and recreational areas may be found at MNBeaches.org — the website developed by DuluthStreams staff for the Minnesota Pollution Control Agency's Minnesota Lake Superior Beach Program that was initiated in summer 2003. The focus of this program is to provide timely information about Minnesota's Lake Superior swimming beaches and recreational-use waterways. Here you will find information about swimming beach monitoring efforts, beach advisories, and fecal coliform and E. coli test results from local beaches. The information is collected by county environmental and health departments and the Minnesota Pollution Control Agency. DuluthStreams staff serve on the Technical Advisory Committee for this program. |
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The vast majority of bacteria in streams and lakes are 'good' bacteria. They do
not cause diseases and are necessary for healthy ecosystems to function properly.
Some of the bacteria, however, have the potential to cause disease or illness.
When the amount of disease-causing bacteria, or pathogens, rises and reaches
certain levels, humans should avoid contact. EPA and the MPCA have established
standards for posting water-contact advisories to protect human health.
