Contaminated Water: Causes, Signs & Types

Instructor: Adrianne Baron

Adrianne has a master's degree in cancer biology and has taught high school and college biology.

Water contamination happens more frequently than we would like. In this lesson, learn about various causes, signs and types of water contamination that can occur.

Contaminated Water

Have you heard the simplified adage that you should drink eight glasses of water a day? This is a goal you hit on most days, but today is a little different. Your area was recently hit with very violent weather and you're concerned that you may have contaminated water.

Water whose color is altered due to contamination
contaminated tap water

This is water that is physically changed or has the presence of certain chemicals or microbes.


Flooding and other results of storms can cause chemicals and microbes from the ground to make their way into the water. Roads are sometimes damaged and washed away during flooding, which can damage water mains and pipes allowing contaminants to make their way into the water.

Another cause of water contamination is run-off from everyone's yard or nearby farms. You love the fact that the people in your neighborhood work hard to keep their lawns beautiful, but the fertilizers and pesticides that they spray on them could contaminate the water. When the lawn is then watered, the contaminants can seep into the ground, affecting the water supply (particularly in well water areas).

While you are checking the mail, you mention your concerns about the drinking water to one of your neighbors. She has the same concerns due to some nearby construction. She explains that construction crews could hit a water main, which would allow microbes (tiny organisms such as bacteria) and other contaminants from the soil to make their way into the water.

Water main breaks can allow contaminants into the water supply
Picture of a water main break

This is particularly concerning since the water is already treated once its in the water mains going to the houses. This is supposed to be the clean water ready for consumption and use.


Concerned, you do some research and find that there are four major categories of water contaminants: physical, radiological, chemical and biological.

Physical contaminants refer to things that alter the physical nature of water. This could include sediment suspension or soil erosion that change the clarity or other aspects of the appearance of water.

Radiological contaminants refers to radioactive particles in the water, meaning the particles have an unbalanced number of protons and neutrons, making them unstable. These contaminants have been linked with cancer. You're not too worried though as you don't live near any chemical plants that may be releasing unstable chemicals in the ground or water supply.

Chemical contaminants are from chemicals that you commonly find in your home or in businesses like the fertilizers and pesticides discussed earlier. It can also include chemicals that occur naturally such as nitrogen and chlorine.

Biological contaminants are living organisms that contaminate water. Some of the most common biological water contaminants include bacteria and parasites that cause disease.


So what signs could let you know if your water might be contaminated? The first thing you can do is simply look at the water. Water should be clear and colorless. If the water is cloudy or you can see anything floating in it, then it is contaminated. If it has a color to it such as yellow, orange or brown, then there is definitely something in there.

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