Richard Arconti 
Our health and safety depend on having access to water that is free of harmful microorganisms. However, contaminants such as coliform bacteria can make their way into well water, making it unfit for human consumption. While most coliform bacteria are not harmful, fecal coliform or E. coli in well water can pose a significant health risk to humans. But how to test for coliform bacteria in well water to know if you are at risk?
In this article, we’ll explore what coliform bacteria are, how they get into well water, the common sources of contamination, how to test for them, and the solutions to eliminate it.
What Is The Acceptable Level Of Coliform Bacteria In Drinking Water?
The Environmental Protection Agency (EPA) has set a maximum contaminant level (MCL) for total coliform bacteria of zero per 100 ml of water for public water systems in the United States.
The MCL levels are determined based on the number of positive samples for total coliforms or for both total coliforms and Escherichia coli or fecal coliforms, depending on whether the violation is acute or monthly. A water system cannot have more than 5% of its samples test positive for total coliform bacteria in a single month.
Note that the presence of total coliform bacteria is not a health risk by itself, but is rather used to indicate if other potentially harmful bacteria are be present
What Are Coliform Bacteria?
Coliform bacteria are a diverse group of bacteria commonly found in the environment, including soil, vegetation, and the feces of animals and humans. They are helpful as an indicator of other disease-causing organisms in the water.
Coliform bacteria can be classified into three main groups based on their characteristics: total coliform, fecal coliform, and E. coli. So, how different are they from each other?
1. Total coliform bacteria
Total coliform bacteria can include both fecal coliforms and non-fecal coliform bacteria, such as those found in plants and soil. The presence of total coliform bacteria in drinking water can indicate that the water has been contaminated by organisms that may cause disease, and further testing is usually required to identify the specific type of bacteria present.
2. Fecal coliform bacteria
They are typically found in the intestinal tracts of warm-blooded animals and humans. Their presence in well water indicates that the water has been contaminated with fecal matter, which can contain harmful pathogens that pose a risk to human health.
3. E. coli bacteria
The presence of E. coli bacteria in well water typically indicates fecal contamination from either animals or humans. This can occur due to various sources, including agricultural runoff, septic system failure, or malfunctioning sewage systems.
Some strains of E. coli can cause illness in humans, ranging from mild diarrhea to more severe infections such as urinary tract infections and bloodstream infections. In particular, some strains of E. coli, such as O157:H7, can produce toxins that cause severe and even life-threatening illnesses. This usually affects vulnerable populations such as young children, the elderly, and those with weakened immune systems.
Coliform Bacteria Symptoms In Humans
While most types of coliform bacteria are not harmful, some strains can cause health problems. Here are some common symptoms of coliform bacteria infection in humans:
- Diarrhea
- Abdominal cramps
- Nausea
- Vomiting
- Fatigue
- Fever
- Dehydration
- Headache
- Loss of appetite
It is important to note that symptoms may vary depending on the type of coliform bacteria present and the individual’s immune system. Some people may not experience any symptoms at all.
However, infants, young children, elderly individuals, and people with weakened immune systems are at a higher risk of developing severe symptoms and complications. If any of these symptoms persist or worsen, seek medical attention immediately.
How Do Coliform Bacteria Get Into Well Water?
Coliform bacteria can enter well water in several ways. They can be carried by rainwater or surface water that seeps into the ground and contaminates the well water. They can also be introduced into the well water by faulty or outdated well construction, including improper casing or sealing. Additionally, if the well is located near a septic system, the bacteria can seep into the well water through cracks in the well or the surrounding soil.
Common Sources Of Coliform Bacteria In Well Water
There are several sources of coliform bacteria in well water. Some of the most common sources are:
- Aging or cracked well caps: Older wells or the ones with cracked caps can allow surface water to enter them and contaminate the water with coliform bacteria.
- Agricultural practices: Using fertilizers and pesticides in agricultural areas can seep into the groundwater and contaminate the well water.
- Animal waste: Well water can be contaminated by animal or human feces if animals or livestock are in the area.
- Badly-maintained septic systems: Wastewater from poorly maintained septic systems may leach into soil and contaminate wells.
- Faulty plumbing: Water in the well could be contaminated if there was a problem with the plumbing in the house or other structures nearby.
- Heavy rainfall: After a downpour, floodwaters, and runoff might seep into the ground and contaminate the well with coliform bacteria.
- Human activity: Human activity, such as bathing or washing clothes, can also contaminate the well water if the water is not adequately treated or disposed of.
- Improper well construction: If the well is not constructed correctly, it can allow surface water to enter the well and contaminate it with coliform bacteria.
- Nearby landfills: Coliform bacteria can contaminate well water through the leaching of landfills into groundwater.
- Water treatment system failure: If the water treatment system is not working properly or maintained, it can allow coliform bacteria to pass through and contaminate the well water.
How Do You Test For Coliform Bacteria
Testing for coliform bacteria in well water is a straightforward process that can be done either at home or in a lab.
Home DIY Test
Fortunately, DIY tests are available for homeowners to test their well water for coliform bacteria.
The basic test for coliform bacteria involves adding a small sample of water to a test tube containing a nutrient broth that supports the growth of coliform bacteria. The test tube is left at room temperature for a designated period, typically 24-48 hours.
If coliform bacteria are present in the water sample, they will ferment the nutrients in the broth and produce gas, which can be seen as bubbles or turbidity in the broth. If the water turns orange, coliform is present. If it stays the same color, there are no coliform bacteria detected.
However, it’s important to note that this is a presumptive test, meaning it cannot differentiate between total coliform and fecal coliform bacteria, which are more specific indicators of fecal contamination and potential health risks.
Therefore, if the presumptive test is positive for coliform bacteria, additional testing is recommended to determine the presence of E. coli and assess the potential health risks associated with the water sample.
Note: The basic home test is not considered as reliable as laboratory testing methods. It should be used only as a preliminary screening tool.
Lab Test For Total Coliform
If you want the most accurate and reliable test, use a certified laboratory to analyze your water sample. Importantly, the laboratory will conduct a series of tests to determine the presence and concentration of total coliform bacteria, fecal coliform bacteria, and E. coli. This way you won’t have to guess or wonder if the bacteria is harmful – the test will give you all the info.
Laboratory Well Water Test Kit Best For Bacteria
Tests for dozens of other common harmful contaminants
Designed specifically for well water
The most commonly used method for testing is the membrane filtration method. This method involves filtering a water sample through a special membrane that retains bacteria, which is then incubated on a nutrient agar plate. After incubation, the resulting bacterial colonies can be identified and counted, providing a more precise measure of bacterial presence and concentration in the water sample.
It’s important to note that laboratory testing can provide a more comprehensive assessment of water quality and potential health risks beyond just bacteria. A well water report will test for dozens of other substances.
Tips For Collecting Your Water Sample
After you receive your bacteria test kit, it is important to follow water collection best practices. Since coliform bacteria are naturally present in the environment, it is possible for you to contaminate the sample. Any contamination of your water sample can lead to a false positive.
To ensure an accurate test result, here are some tips to follow:
- Disinfect your faucet surface area with diluted bleach or rubbing alcohol
- Wait at least 5 minutes to let the disinfectant dissipate
- Turn on your tap and let it run for 30 before collecting your sample
- Wear clean rubber gloves if you have them available to avoid cross-contamination
- Turn on cold water supply and slowly collect your sample so it does not overflow
What To Do If Your Well Water Tests Positive Coliform?
If your well water tests positive for coliform bacteria, it’s essential to take immediate action to address the issue and ensure the safety of your drinking water. Here are some steps you can take:
Shock chlorination treatment
This treatment involves adding a high chlorine concentration to the well water to kill any bacteria present. The chlorine is flushed out of the system by running the water for several hours. This treatment is often recommended as the first step to eliminating coliform bacteria from the water system.
UV purification system
UV purification systems use ultraviolet light to kill bacteria and other microorganisms in well water. These systems are installed at the point of entry to the home and require regular maintenance. UV purification systems effectively eliminate coliform bacteria and other harmful pathogens from well water.
Boiling water
If your well water tests positive for coliform bacteria, boiling the water for at least one minute before consumption can be a temporary solution. However, it’s essential to have your water retested for the specific strains of coliform bacteria present to determine the appropriate treatment method.
In any case, it’s recommended to consult a certified water treatment professional to determine the best course of action for your specific situation.
How Often To Test Your Well Water For Coliform
The Environmental Protection Agency (EPA) recommends that private well should be tested for coliform bacteria at least once a year. Since private well water is not regulated like city water, a consistent testing schedule is critical to ensure safe and healthy drinking water.
You should test your well more frequently under the following circumstances:
- Significant land development or mining activity is occurring near your well water supply
- A natural disaster like flooding, earthquake or hurricane takes place
- You have high-risk individuals or newborns in your home
- Noticible changes in appearance, taste, or smell of your well water
- You have an aging or deteriorating well
