Disinfection
refers to the selective destruction of disease-causing organisms.
All the organisms are not destroyed during the process.
In the field of wastewater treatment, the three categories of human enteric organisms of the greatest consequence in producing disease are bacteria, viruses, and amoebic cysts.
Diseases caused by waterborne bacteria include typhoid, cholera and bacillary dysentery.
Diseases caused by waterborne viruses are poliomyelitis and infectious hepatitis.