Fecal contamination of water is evaluated by

Coliforms are E. coli (faecal) and Klebsiella (non-faecal). E. coli is the most typical faecal coliform. They are chosen as the indicators of faecal pollution of water because, They are constantly present in abundance in the human intestine. They can be easily detected by culture methods. they tend to survive longer than the pathogens. they have greater resistance to forces of natural purification than waterborne pathogens. Park's Textbook of Preventive and Social Medicine, 25th edition, Page No. 780