There are many contaminants in dirty water. Microorganisms may be present and can be pathogenic (disease causing). You should know about the 3 main types of microorganisms that may be in water, how to test for bacterial content of water and also how to kill microorganisms.
Types of microorganisms:
Complete this summary of microbes:
The answers can be found here.
Some microbes can cause disease. Do some research to find out about these and complete the sheet below. It contains some good information about some common water-borne diseases.
Now try this question sheet to check your understanding about microbes.