Chlorine is a chemical used to disinfect water. Chlorine is extremely reactive, and when it comes in contact with microorganisms in water it kills them. Chlorine is added to swimming pools to keep the water safe for swimming. Chlorine is available as solid tablets for swimming pools. Glendale's drinking water treatment plants use chlorine in a gas form because of the large volumes required.
Chlorine is very effective against algae , bacteria and viruses .
Protozoa are resistant to chlorine because they have thick coats. Protozoa are removed from drinking water by filtration . Coliform bacteria are bacteria normally found in the intestines of warm-blooded animals. Coliform bacteria are present in high numbers in animal feces. Disinfection is the application of a chemical to kill most, but not all, microorganisms that may be present.