Harmful Bacteria Found in Water
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In the Ozarks, a disease-causing bacteria is present in 30 to 50% of household wells.

What are bacteria?

Bacteria are microscopic organisms that come in many different shapes and forms. Bacteria can cause infections from tuberculosis to strep throat and many others. However, not all bacteria are harmful. They are an important component to nutrient cycling; bacteria assist in decomposition of dead organic material and make the nutrients once again available to larger organisms. Many bacteria are beneficial to humans—for instance, we use certain bacteria to make fermented products like cheese and yogurt. Bacteria inhabit nearly all environments, from hot springs to cold artic habitats. In humans, bacteria reside normally throughout the body, including the skin and the digestive tract. In rivers and lakes, bacteria are most commonly found along the shoreline and within the bottom sediments. Although they are found, bacteria are typically not as abundant in the open waters of rivers and lakes.

What is E. coli?

The bacterium Escherichia coli (E. coli), belongs to a group of bacteria known as coliforms. These bacteria naturally reside in the intestinal tracts of mammals where they assist in the digestion of food. However, they can cause severe health problems when ingested in large amounts. See the following site for more information on E. coli: http://medic.med.uth.tmc.edu/path/00001497.htm

E. coli can be found in rivers and lakes polluted with animal waste. Due to its potential health hazards, this bacterium is commonly measured in area waters. If it is found, other harmful intestinal bacteria could also be present. E. coli does not live long outside of the body, so any amount detected in streams is an indication of a recent pollution event.

What level of E. coli is unsafe?

The Environmental Protection Agency has established a safety level of 265 colonies of E. coli per 100mL of water sample. Waters with readings above this level are unsafe to swim in and to drink. Waters with readings below this level are considered safe for “full body contact”. Even if below this safety limit, as a usual rule, water from local lakes and streams should not be ingested intentionally. Drinking water from the city is monitored regularly for E. coli and is safe to drink. Individuals with wells should have their wells tested periodically for E. coli.

How do agencies measure the bacteria levels in water?

A number of different tests can be used to determine how much bacteria is in the water. Usually, a sample is collected (100mL in size), and this sample is then taken back to a laboratory where the analysis is conducted.

In one type of test, the 100mL sample is poured through a paper filter, leaving the bacteria on the top of the paper filter. This filter is then placed in a container that contains enough nutrients for the bacteria to grow. The container is incubated, and then the number of bacteria colonies is counted.

Another test called the Colilert Defined Substrate Test is used to detect E. coli. In this test, the water sample is put into certain nutrients and chemical agents. If coliforms are present, the sample will turn yellow, and the number of yellow colonies can be counted. The sample can also be viewed under special UV lights to see if the sample is fluorescent, which indicates that E. coli are present. This is the method used by local health departments. The maximum number of colonies that can be counted with this method is 2419, so any sample with a count of 2419 can be assumed to contain more.

Where are the bacteria coming from?

Bacteria such as E. coli live in the intestines of animals. Because of this, common sources of E. coli in waters are animal waste runoff and sewage. According to the Greene County Health Department, E. coli in recreational water can come from the following sources:

  • Urban and agricultural runoff
  • Malfunctioning onsite sewage treatment systems (septic tanks, lagoons, etc.)
  • Sewer overflows (both sanitary and combined sewers),
  • Wild and domestic animal waste
  • Human fecal accidents in the water

Sometimes, E. coli/bacteria will increase in a body of water after a rainstorm of increased runoff. Other spikes in the data could result from events described in the bullets above.

Many bacteria are common to waters. Bacteria live on the surfaces of plants and aquatic animal as well as in the soil substrate of lakes and rivers. These bacteria are important to the functioning of the river ecosystem.

How can we determine where the bacteria have come from?

One way to see where the bacteria are coming from is to take water samples at different locations on a river/creek. For instance, if you take a water sample upstream from a suspected source (a leaking septic tank, for example), then take a water sample below this site, you can compare the levels from both samples. If the value of bacteria is higher downstream, you have good evidence that the septic tank was a source of the elevated bacteria levels.

DNA analysis can also help determine bacterial sources. According to the University of Missouri’s FAPRI (Food and Agriculture Products Research Institute) Environmental Report, “DNA source tracking techniques are used to obtain patterns of the coliform colonies and compare them to patterns of known species including humans, cattle, poultry, dogs, horses, hogs, and wildlife” (Shoal Creek Watershed Project 2002).

Solutions to Bacteria in Water

This section discusses what both the local agencies are already doing and what the individual citizen can do to decrease harmful bacteria in local waters. A list of important contact numbers is provided at the end of this section. If you need more information concerning these issues, or if you want to find out about current bacteria levels, feel free to call these local agencies.

What are local agencies/authorities doing to prevent bacteria contamination in our local waters?

Locally, health departments and the United States Geological Service are involved in monitoring bacteria levels. These health departments measure the water for bacteria regularly during the summer months, because this is the time that people will be recreating in the water. Most of the health departments begin their monitoring for bacteria in mid-May and continue through August. If an event occurs such as a wastewater overflow, the health department will then start monitoring the river where the contamination occurred. The health departments also will issue a “whole body contact” ban on a particular river/creek if the E. coli levels are higher than the 235 colonies/100 mL safety limit (Goddard 2002). This means that swimming is not allowed, and other activities, like fishing or canoeing, should be done cautiously.

Local and state governments are involved in programs which try to lower the amount of bacteria in the water. Runoff into streams can be lessened by planting more shoreline vegetation and by keeping farm animals further away from the water. Other programs work with owners/operators of septic tanks and sewage treatment plants to ensure that no raw sewage is ever released into a local waterway.

If you are connected to city utilities, the water that reaches your house faucets has gone through a purification process. Microorganisms from the water have been removed by a sand filter, and the water has been disinfected through the use of chlorine or ozone. Drinking water from the city is perfectly safe to drink and information concerning the quality of your town’s drinking water is available through city utilities or your local water treatment plant.

What can you do to fight harmful bacteria in our local waters?

The best thing that you can do to help lower harmful bacteria levels in our local waters is to stay informed. This summer, you can call your local health departments to see what the bacteria readings are at your favorite recreation spot. You can also contact local agencies that have resources and programs concerning bacteria in our local waters. See a list of contacts.

If you own a septic tank, a farming operation, or property with a waterway running through it, you can work to prevent releases of bacteria into the water. By properly maintaining your septic system, keeping animals further away from the stream, and by planting vegetation close to the shore, you can help lower bacteria levels

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Missouri Department
of Natural Resources

Missouri Watershed Information Network (MoWIN)
Send comments to: mowin1@missouri.edu
205 Agricultural Engineering
Columbia, MO 65211
Phone: (573) 882-0085
Toll Free: (MO only): 1-877-H20-shed (426-7433)
Fax: (573) 884-5650

Page last updated August 26, 2008