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This science fair project was done to find out the amount of bacteria in water coolers. The testing was done by comparing water from water coolers and tap water.


The water from a water cooler will contain more bacteria than tap water.

Scientific Terms

Contaminants, microbes, fluoride, chlorine


Bacteria in water coolers and tap water

Water is very important for humans and all living organisms. But the water that we drink also comes with various types of contaminants in the form of microbes and minerals. Among the common minerals found in water are calcium and magnesium. Fluoride is also added to the water to help prevent disease and protect against tooth decay.

A lot of money is spent on bottled water and water filters. Bottled water and filtered water may be bacteria free, but when the water enters the water cooler, it will get contaminated with many types of bacteria. This is because bacteria grows and multiplies quickly in places with high levels of moisture.

Tap water on the other hand contains chlorine. Chlorine is very effective at killing bacteria such as E. coli and other microbes found in water. Chlorine is intentionally added to water by water utility boards, to kill bacteria and prevent water borne diseases from spreading. However, too high a dosage of chlorine in the water can also cause other health problems.

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Complexity level:
Project cost ($):
Time required:
1 day to prepare, 5 days for science fair project
Material availability:
Easily found
Safety concerns:

The bacteria should be destroyed before being disposed of. Pour some bleach into the petri dish to kill all the bacteria before disposal.