Sources of Coliform Bacteria Contamination in Home Well Water
Coliform bacteria are common in the environment, present in the soil and intestines of animals, and are generally not harmful. However, they are one of the most common water contamination problems in home well water.
The presence of these bacteria in well water or spring water usually indicates that the water may be contaminated with germs that can cause disease. These germs can even contaminate well water without any change in taste or odor to the water. Therefore, the US EPA recommends annual testing of residential water wells for coliform bacteria.
Generally, the two categories of coliform bacteria found in well water are total coliform and fecal coliform or E. coli.
Detecting total coliform in a water source doesn’t necessarily mean the water is contaminated, but it can indicate that more harmful bacteria, like fecal coliforms or E. coli, may be present.
If you detect fecal coliforms or E. coli in your well water, start by disinfecting your system and locating the source of the contamination.
Sources of Coliform Bacteria Contamination
When tests detect only total coliform (without fecal coliform or E. coli), the contamination most likely entered the system from the environment, often during construction, plumbing, or water main repairs.
Because there are so many different ways to introduce bacteria into the system, the original well construction can often be the cause of an ongoing bacterial problem that can last for many years.
If fecal coliform or E. coli are detected along with total coliform in drinking water, they are most likely coming from sewage that has entered the drinking water. Waste from humans, rodents, or farm animals can be a principal source of bacteria in the water.
Runoff from agricultural fields, animal feedlots, sewers, or septic systems often causes contamination. Additionally, the overuse or improper storage and disposal of chemicals can poison and contaminate drinking water if they are in close proximity to your well.
Testing For Bacteria
We recommend this state-certified lab water check test for proper testing of fecal coliforms and E. coli. This should be strongly considered when purchasing a new home or after constructing a new well.
What To Do If Fecal Coliform Is Detected
If E. coli or fecal coliform are detected in the drinking water, the first step should be an emergency chlorination that lasts two to five days. At the same time, a system is being disinfected, it is recommended to vigorously boil the drinking and cooking water for one minute before using it.
It is also very important to continue testing the water because if anything happens to the chlorine residual, or if the chlorine demand changes and the consumer doesn’t know about it, the water can become unsafe again.
Prevention of Bacterial Contamination
Construct your well at least a foot above ground level or build a mound of dirt around it to prevent rainwater or chemical runoff from pooling nearby and seeping into the system. Also, if you are constructing a new well, it is important to minimize the proximity of possible sources of contamination—the further away, the better!
- Septic Tanks, 50 feet
- Livestock yards, Silos, Septic Leach Fields, 50 feet
- Petroleum Tanks, Liquid-Tight Manure Storage, and Fertilizer Storage and Handling, 100 feet
- Manure Stacks, 250 feet
Be careful about storing or disposing of household or lawn care chemicals and wastes, or consider using organic alternatives that will break down before reaching your groundwater. Take steps to reduce erosion and prevent surface water runoff, such as constructing a simple swale or using plants to stabilize slopes.
It is especially important to address these risks before they become an issue, as it will help save money in the long run. Keeping up-to-date records of well installations, repairs, and water tests will help you keep ahead of potential issues.
Introduction to the Problem
Coliform bacteria make up a large group of microorganisms commonly found in soil, surface water, and the intestinal tracts of warm-blooded animals, including humans. While most coliforms are harmless, finding them in drinking water signals a potential presence of disease-causing organisms, making them a serious public health concern.
Water professionals use total coliform bacteria—including fecal coliforms and Escherichia coli (E. coli)—as indicators of possible contamination. When these bacteria appear in drinking water, it suggests that pathogens may have entered the supply and pose a risk of illness. To reduce this risk, communities must regularly test and treat water sources to detect and eliminate contamination.
Sources of Contamination
Coliform bacteria can enter drinking water through various sources, including human or animal waste, contaminated soil, and surface water. Fecal coliform bacteria, including E. coli, are typically found in the intestinal tracts of warm-blooded animals and can be introduced into water supplies through improper waste disposal, agricultural runoff, or other environmental factors. Animal waste, in particular, can be a significant source of contamination, as it can contain high levels of coliform bacteria.
Additionally, septic systems and other wastewater treatment systems can also contribute to the contamination of water supplies if not properly maintained. Understanding the sources of contamination is crucial in preventing the introduction of coliform bacteria into drinking water.
Private Water Systems
Private water systems, including wells and springs, are more susceptible to coliform bacteria contamination due to their proximity to potential sources of contamination. Shallow wells, in particular, are more vulnerable to contamination from surface water and soil.
Weather conditions, such as rainy weather, can also contribute to the contamination of private water systems. Proper maintenance and testing of private water systems are essential to prevent surface water contamination.
The EPA recommends testing private water systems for total coliform bacteria at least once a year, and more often if the system has a history of contamination. By taking proactive steps to prevent contamination and regularly testing and treating drinking water, households can reduce the risk of illness associated with coliform bacteria.
Detection and Testing
Detecting coliform bacteria in drinking water is crucial in ensuring water quality and safety. The Environmental Protection Agency (EPA) recommends regular testing of water samples for total coliform bacteria, including fecal coliform and E. coli. Testing typically involves collecting a water sample and sending it to a lab for analysis.
If the initial result is positive, repeat samples may be collected to confirm the presence of coliform bacteria. In some cases, additional testing may be necessary to determine the source of contamination and to identify the most effective treatment options.
Boiling or disinfecting the water can be an effective way to kill coliform bacteria, but it is essential to address the underlying source of contamination to prevent future occurrences.
Health Risks
The presence of coliform bacteria in drinking water can pose significant health risks, particularly for vulnerable populations such as the elderly, young children, and people with weakened immune systems. While most types of coliform bacteria are harmless, some strains of E. coli can cause serious illness, including bloody diarrhea, stomach cramps, and vomiting.
Fecal contamination, in particular, can indicate the presence of disease-causing organisms, making it essential to take prompt action to address the issue. In severe cases, coliform bacteria can cause life-threatening illnesses, emphasizing the need for regular testing and treatment of drinking water.
Resources:
- U.S. Environmental Protection Agency. (n.d.). Private drinking water wells. https://www.epa.gov/privatewells
Frequently Asked Questions (FAQs)
1. Where are coliforms commonly found?
They are typically present in soil, surface water, and the intestines of warm-blooded animals. Their presence in drinking water often signals possible contamination.
2. How do these bacteria get into well water?
They can enter through cracks in well casings, faulty seals, surface runoff, or nearby septic systems that aren’t properly maintained.
3. Can exposure make you sick?
Yes. While total coliforms are generally not harmful, certain strains like E. coli can cause gastrointestinal illness, especially in children, the elderly, or those with weakened immune systems.
4. Is their presence in tap water dangerous?
Not always, but it indicates that your water system may be vulnerable to harmful pathogens. Further testing is usually required to determine health risk.
5. What’s the difference between total and fecal coliforms?
Total coliforms are a broad category found in the environment, while fecal types (like E. coli) specifically originate from the intestines of humans or animals.
6. Can these bacteria survive on surfaces?
Yes. They can live on damp surfaces such as sinks or kitchen counters, especially in unsanitary conditions.
7. How do you test for contamination?
Use certified home test kits or send a sample to a local water testing lab. Testing is typically done through membrane filtration or enzyme substrate methods.
8. What should I do if my water tests positive?
Begin with shock chlorination and retest. You may also need to inspect and repair your well system to prevent future contamination.
9. How often should private wells be tested?
Test at least once a year, or more frequently if you notice changes in water taste, odor, or clarity, or after flooding or repairs to the system.
10. Are these bacteria removed by filters?
Yes, many filtration systems using UV, reverse osmosis, or chlorination can effectively remove or kill bacteria present in the water.
