The indicator agents to determine fecal pollution of drinking water is:

Ans (d) E. coliRef: Park 23eJ P 720-21* Ideally, drinking water shouldn't contain any organism known to be pathogenic.* The primary bacterial indicator recommended as a bacteriological indicator is the coliform group of organisms as a whole. These include both fecal and non-fecal organisms.* Typical example of the fecal group is E. coli (single best indicator) and of the non-faecal group, Klebsiella aerogens.Reasons why foliform organisms are chosen as indicators of fecal pollution rater than the water borne pathogens directly* Constant presence of coliform organisms in great abundance in human intestine. These organisms are foreign to potable water. Therefore their presence is looked upon as evidence of fecal contamination.* They are easily detected by culture methods* Longer survival as compared to other water borne pathogens* They have greater resistance to the forces of natural purification, as compared to water borne pathogensOther Indicators Include* Faecal streptococci: Faecal streptococci regularly occur in faeces, but in much smaller numbers than E. coll. Their presence is regarded as important confirmatory evidence of recent faecal pollution of water.* Cl. perfringens: They also occur regularly in faeces and their spores are capable of surviving in water for a longer time than organisms of the coliform group. So, the presence of spores in the absence of the coliform group, suggests that faecal contamination occurred at some remote time.