Microbial Contamination in Drinking Water: Sources & Control

Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Microbial contamination in a community's source of drinking water can be very harmful to the entire population. Discover how microbial contamination of drinking water is controlled, and explore the sources of coliform bacteria, and its more dangerous subtype, E. coli 0157:H7, and giardia, which causes diarrhea when in humans. Updated: 10/03/2021

Clean Drinking Water

What many people in the West take for granted is having the ability to turn on the tap and get clean drinking water, clean water to bathe in, and clean water to wash their clothing in. This is more of a luxury than it is a standard across many parts of the globe, where contaminated drinking water leads to a whole host of issues for the population at large.

This lesson will outline some of the things that are often found in contaminated drinking water and what can be done about it.

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  • 0:07 Clean Drinking Water
  • 0:39 Coliform Bacteria
  • 3:41 Giardia and Viruses
  • 4:58 Methods of Control
  • 5:47 Lesson Summary
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Coliform Bacteria

When we think of contaminated drinking water, we tend to focus on many different things. For example, there can be chemicals seeping into the water from industrial plants nearby, heavy metals occurring naturally or from pollution, or there may be fecal waste washing into our drinking water.

While industrial chemicals and heavy metals are a major concern, one of the biggest concerns is finding pathogenic, or disease-causing, microbes in drinking water. Some of these microbes, such as bacteria, may occur in nature and seep in naturally, while others are a result of human sewage or industrial farming techniques.

Regardless of the source of contamination, natural or otherwise, one of the most common bacteria found in the soil and the intestinal tract of animals is known as coliform bacteria. The subtype of coliform bacteria found in the intestinal tract of animals is known as fecal coliform bacteria, where the word fecal refers to the feces produced by these animals.

What's interesting to note is that the coliform bacteria found in your gut rarely cause you any trouble. They are basically looking for a place to eat, live, and reproduce. That place just happens to be your intestinal tract.

However, every now and then, a type of dangerous, toxin-producing, coliform bacteria known as E. coli 0157:H7 can cause bloody diarrhea and even kidney failure in people who ingest this deadly microbe by eating or drinking contaminated food or water.

Regardless of whether they are potentially deadly or non-harmful, coliform bacteria are super important in helping to determine if drinking water has been contaminated.

Since you're now well aware of the fact that coliform bacteria can be found in human and other animal feces, it shouldn't surprise you that we sometimes look for coliform bacteria in drinking water supplies as a proxy for figuring out if the drinking water has been contaminated by other dangerous pathogens found in and spread by feces.

You can liken what we do here to the following example. If you were to take a cup of coffee, you'd notice that it has a brownish-black color and a specific smell. Well, if you were to pour even that small cup of coffee into a much larger gallon of absolutely clean water, that water would turn slightly brown and would smell a bit differently. Even if you were blindfolded and only noticed a change in smell, you could, by extension, guess the water had turned brown because it smells like coffee.

Likewise, when coliform bacteria gets into the drinking water system, we know that, by extension, it's not just the coliform bacteria that are in there. There are likely to be other pathogens in the water system as well.

Giardia and Viruses

One of these pathogens may be Giardia. Giardia is a protozoan parasite that causes diarrhea in some humans who ingest it. This parasite, you guessed it, is spread through feces-contaminated material, including water.

The one cool thing about Giardia is that if you were to look at it under the microscope, you'd never forget its alien-looking shape. It sort of looks like it has two big eyes sticking out and watching you, taunting you about the fact that something so little can cause you so much trouble.

However, feces-contaminated drinking water has even smaller pathogens that can cause as much, if not more, problems for you. These pathogens are viruses. The most famous of which are known as noroviruses. These are the viruses that are the most common cause of viral gastroenteritis in humans. Meaning, they are the number one cause of the stomach flu.

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