Marker of faecal contaminantin is -

Coliform organisms are considered as indicators of faecal contamination . This is because 1.coliform organisms are constantly present in abundance in huma intestine.they are foriegn to potable water.hence their presence indicate faecal conatamination. 2.they are easily detected by culture methods as small as one bacteria in 100 ml of water,whereas other methods of detecting pathogens are complucated and time consuming. 3.They suvive longer than the pathogens which tend to die out more rapidly than coliform bacilli. 4. Coliform bacilli has greater resistance to forces of natural purification than the water borne pathogens. If the coliform organisms are present in a water sample the assumption is probable presence of intestinal pathogens. Parks textbook of preventive and social medicine.K Park. Edition 23. page no:720,721