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Bacteria in Water Supplies Part 1: Problem Bacteria and How to
Test for Them John M. Jemison, Jr., Extension water
quality and soil specialist Introduction Bacteria are single-celled organisms commonly
found in soil, on our bodies, on leaf material and in water. There may be
over a million cells per gram of soil. Bacteria serve many functions in
nature. They help break down matter (decomposition) and transform it through
chemical reactions. "Pathogenic" bacteria can cause diseases such as
typhoid, dysentery and cholera. If these bacteria are in drinking water,
they can cause serious health problems. In one instance, in Missouri, four
people died and 243 people became seriously ill from drinking water with a
dangerous strain of Escherichia coli (Geldreich et al., 1992). While surface waters commonly support bacteria,
most groundwater supplies don't. This is because the conditions for
bacterial growth (food, oxygen, warm temperatures and favorable pH) are not
often found in groundwater. Yet many well water samples still show bacteria
are present. Bacteria are the most common contaminants found in drinking
water wells in Maine. In this fact sheet,
we explain how bacteria can get into your water supply and how to test your
water for bacterial contamination (part 1). In part 2 of this series, we
explain how to safely disinfect a well. Types of Bacteria Any of several thousand types of bacteria (both
non-pathogenic and pathogenic) can contaminate your water supply. Water
testing labs use a single procedure, the total coliform bacteria test, to
find out whether the water is free of bacteria. First, they filter a water
sample and incubate it. If bacteria are there, they will grow under ideal
lab conditions. After incubation, the colonies of bacteria are counted. Most coliform bacteria do not transmit diseases
but they are a very common group of bacteria. They are used as an indicator
that harmful bacteria may be present. If there are coliform bacteria present
in the water supply (one or more colonies/l00 milliliters of water, as
indicated on the total coliform analysis), then the water is declared unsafe
to drink. If your sample comes back with high coliform counts, this means
that the water entering the well is not being filtered enough by the soil.
Here are some ways contaminated water may enter a well:
The most important thing to remember is this: If
your well is properly constructed and the quality of water feeding the well
is free of bacteria, you should have no coliform bacteria in the well. If total coliform bacteria are present, the
Health and Environmental Testing Lab (HETL) will check for E. coli bacteria
also. These bacteria come from the gut of warm-blooded animals. If they are
present, there's a chance that animal or human waste is entering your water
supply. You'll need to find out the source. You may need to test for
detergents to find out if septic waste is the culprit. Whatever the bacterial source, do not drink
water with any coliform bacteria present. The water supply may have
disease-causing organisms. Your only alternative is to boil the water for at
least a minute before cooking or drinking (Plowman, 1989). Bacteria Tests If you have a private source of water (drilled or dug well or spring), it is up to you, as the homeowner, to test the water. Dug wells and springs are more likely to be contaminated than drilled wells. The main reason is that they may not be well built. Dug wells may collect water that has not moved through enough soil to naturally filter out the bacteria. However, drilled wells can be contaminated, too. A drilled well may not be well sealed into the bedrock, or have water flowing down the side of the well casing. You should test your well every year for
bacteria. The cheapest test is a simple bacterial test from the Health and
Environmental Testing Lab in Augusta (In 2001, this test cost $12.)
Water test A (a $20 test) gives information on bacteria, plus nitrates and
nitrites. It covers all major water quality problems that have an acute or
short-term health effect on humans. All other contaminants generally have a
long-term effect on human health. A more complete test is water test B ($40).
This provides you with data on bacteria and nitrates (nitrites) plus pH,
iron, manganese, hardness, chloride and fluoride. Use this test every couple
of years to keep a record on your water supply quality. If there are noticeable changes in color,
smell, or if anyone in your family has had chronic illness, it would be good
to test the water for bacteria. Also, if your well has been flooded or
repaired, it is important to test the well for bacteria (Mancel et al.,
1991). How to Test for Bacteria These are the steps to test your well for
bacteria:
These are the important steps for a good water
test. If you use another lab, make sure it is a state-certified lab. Water
treatment companies will often offer free on-site water testing, but no one
can test for bacteria on site. Understanding Water Test Results You will receive water test results in the
mail. Depending on which test you do, it may take a few days to a few weeks
to get the results. If you suspect that your water is contaminated, do not
drink the water without boiling it, or drink bottled water. Your bacteria test results will tell you
colonies of bacteria per 100 milliliters of water. If you have one or more
colonies, the water will have to be disinfected. (See Bulletin #7115,
“Bacteria in Water Supplies, Part 2: How to Disinfect Your Well”.) If you
have a lot of bacteria, the lab will report this as "TNTC" or too numerous
to count. If your water sample comes back with 0
colonies/100 milliliter, your water should be safe to drink. The water is
coming from a water source free of bacterial contaminants, and the well is
apparently sound. Other Bacterial Problems Another major bacterial problem comes from iron
bacteria. Iron bacteria are common organisms that cause water quality
problems. They are not pathogenic (disease-carrying) bacteria, but cause
some nuisance problems. These organisms often form a grayish or red/orange
gelatinous material in pipes, toilets and wells, Hydrogen sulfide gas is
often a byproduct of these organisms. It gives your water a distinctive
rotten egg odor. Hydrogen sulfide gas is in the water if you
detect a sulfur smell. Use Test I from HETL ($25). This test will determine
if you have iron bacteria in your water. Iron bacteria is treated with a
disinfectant (see Bulletin #7115, “Bacteria in Water Supplies, Part 2: How
to Disinfect Your Well”). Testing Swimming Water for Bacteria There are also tests to determine bacteria
levels in swimming pools, rivers and lakes. One $24 test, Test K from the
Health and Environmental Testing Lab in Augusta, measures fecal coliform
bacteria against state standards for swimming. For more information on water quality, water
testing or other issues contact your UMaine
Extension county office. For more information on treating bacterial
contamination, see Bulletin #7115, "Bacteria
in Water Supplies, Part 2: How to Disinfect Your Well." References
This material is based on work supported by the U.S. Department of Agriculture, Extension Service, under special project number 94-EWQI-1-9231. © 2002 Published and distributed in furtherance of Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment. Call 800-287-0274 or TDD 800-287-8957 (in Maine), or 207-581-3188, for information on publications and program offerings from University of Maine Cooperative Extension, or visit www.extension.umaine.edu.
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Last
Modified:
04/29/08
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