| Bacterial Water Quality Testing:
A Rising Tide Project for Grades 9 and 10
Introduction and Background |
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| Main
Standards
Addressed Biology
I Standards
Methods Safety Sample Collection Sample Preservation & Storage Bacterial Analysis Calculations Classroom
Activity
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 Why Monitor Water Quality? Fecal Indicator Bacteria Water Quality Standards As human beings, we are constantly dependent on our intake of water to maintain our health and well being. Our bodies are 60% water. In South Carolina, much of our drinking water is taken from our rivers, lakes, and streams. As a result, it is very important to establish that our surface waters have adequate purity. To determine this, environmental scientists monitor many physical, chemical and biological characteristics such as the water's temperature, turbidity, dissolved oxygen content, and abundance of fecal coliform bacteria.. Fecal coliform bacteria are used to assess the quality of water because their presence is well correlated with the many waterborne disease-causing organisms or pathogens. These include bacteria, protozoans and viruses and can cause diseases such as gastroenteritis, dysentery, typhoid fever, and cholera. Although fecal coliform bacteria are not necessarily pathogenic, they indicate the likely presence of pathogens and hence are referred to as indicator organisms. Their abundance is typically expressed as the number of colony forming units detected in 100 milliliters of a sample or CFU per 100 mL. Federal and state governments have set acceptable levels of fecal coliforms to provide guidelines for evaluating water safety. Fecal coliforms are naturally present in the intestines of warm-blooded animals and hence in their solid wastes. Solid wastes from pets, livestock and wildlife can enter water bodies after rains run waste materials off the land. Other sources of fecal coliforms include sewage treatment plant effluent, leaking septic systems and sewer pipes. Most fecal coliforms die within days of release into the water bodies although some scientists have reported that fecal coliforms can survive in sediments of river bottoms and even reproduce. The presence of fecal coliforms in high quantities is interpreted as evidence of fecal contamination from warm-blooded animals and indicates the possible presence of pathogens. High levels are also associated with other water quality impairments including cloudy (or turbid) water, unpleasant odors, eutrophication (nutrient pollution) and an increased oxygen demand. Members of three bacteria groups: coliforms, enterococci and fecal streptococci, are used as indicators of possible sewage contamination because they are commonly found in human and animal feces. Although they are not necessarily harmful themselves, they indicate the presence of pathogenic (disease causing) bacteria, viruses, and protozoans that also live in human and animal digestive systems. Therefore, their presence in streams, lakes, and rivers suggests that pathogenic microorganisms might also be present and that swimming, drinking, or eating shellfish from those waters might be a health risk. Due to the great expense and time required for testing every pathogen, scientists instead measure one of the indicator groups of bacteria to assess the sanitary quality of a water body. The most commonly tested fecal bacteria indicators are total coliforms, fecal coliforms, Escherichia coliforms (E. Coli), fecal streptococci, and enterococci. All but E. coli are composed of a number of species of bacteria that share common traits such as shape, habitat, or behavior. E. coli is a single species in the fecal coliform group. Total coliforms are a group of bacteria that are widespread in nature. All members of the total coliform group can occur in human feces, but some can also be present in animal manure, soil, submerged wood, and in other places outside the human body. The South Carolina Department of Health and Environmental Control (SC DHEC) has issued water classification and standards for all bodies of water in South Carolina. In South Carolina's coastal region, the majority of our drinking water comes from surface waters including regional rivers and lakes. Each water body has been given a classification which establishes which activities, such as boating, swimming or drinking, must be protected. A set of water quality criteria have been established for each classification. The classifications and water quality criteria are described in "Water Classifications and Standards" (R.61-68). DHEC Bureau of Water For example, the Waccamaw River has been assigned to the classification Freshwaters (FW) which is defined as "freshwaters suitable for primary and secondary contact recreation and as a source for drinking water supply after conventional treatment in accordance with the requirements of the Department (DHEC)." These waters are suitable for fishing, swimming, and the survival and propagation of a balanced indigenous flora and fauna. The water quality criteria which assure that these uses are protected are listed below: CLASS FW WATER QUALITY STANDARDS
*Lakes only: Not to exceed 25 NTUs provided existing uses are maintained. The following are federal water quality standards promulgated by the US Environmental Protection Agency (US EPA) for indicator bacteria. These standards can be found in the US EPA's publication "Ambient Water Quality Criteria for Bacteria" (1986). FEDERAL STANDARDS FOR INDICATOR BACTERIA
At this time, E. Coli is recommended by the US EPA for freshwater testing and Enteroccocus for marine waters because these bacteria provide a better correlation with body-contact related illnesses than fecal or total coliforms. For historical reasons, many state standards (see above for South Carolina) still employ fecal coliform levels. Although the US EPA has not set standards for total coliforms, some states have promulgated their own. For example, the state of California has a set for its marine waters as shown below. South Carolina does not have standards for total coliforms. Total Coliforms as Per California Code for Ocean Water Quality Single Sample Maximum Allowable Density
Geometric mean of at least five weekly samples during any 30-day period
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