There are many types of microorganisms that cause diseases, and they are collectively called pathogenic microorganisms. The pathogenic microorganisms present in drinking water can be roughly divided into three categories: bacteria, viruses, and protozoa.
Bacteria are prokaryotes, and common pathogenic bacteria include pathogenic E. coli, tuberculosis, dysentery, typhoid, and cholera. Although many pathogenic microorganisms have been able to be detected directly, environmental microbiologists often use indicators that indicate that organisms can pollute water bodies as human pathogens. To date, E. coli is considered the most suitable indicator microorganism. E. coli can cause parenteral infections and acute diarrhea in drinkers. In daily water quality testing, the total number of colonies and E. coli groups are used as indicators to indicate the degree of inactivation of bacteria in the water. Long-term practice shows that as long as the number of E. coli detected in 1L of water is less than three, drinkers are less likely to contract intestinal diseases.
Viruses are a class of non-cellular microorganisms that contain only nucleic acids (DNA or RNA) and must be observed under an electron microscope. Common viruses in drinking water include enterovirus, gastroenteritis virus, hepatitis A virus, poliovirus, and adenovirus. Hepatitis A virus can cause liver dysfunction, hepatitis and other diseases.
Protozoa are the most primitive, simplest, and lowest single-cell animals in the animal kingdom. The number of outbreaks caused by Giardia flagella and Cryptosporidium was the highest. Both Giardia and Cryptosporidium can expose contacts to chronic chronic diseases and diarrhea and diarrhea.