Question

protozoa can be easily killed by heat and freezing, but not by chlorination. Explain the reasons

Answer 1

Protozoa are relatively large micro- organisms, they are easier to filter out than bacteria and viruses. Drinking water is disinfected to destroy or inactivate the micro-organisms that are not filtered out. Chlorine is the most common disinfectant in the world. But after chlorination process also some of the protozoans such as cryptosporidium protozoa can live in the guts or small intestines of humans and other mammals. They pass into the environment through their faeces as cysts or oocysts. Protozoan cysts and oocysts are bigger than bacteria or viruses. They have a hard shell that helps them survive a long time in the environment and protects them against chlorine.