Coliform organisms may gain access to water from many sources, among which are excretions from human beings, animals, amphibians and birds; surface runoff and the multiplication of non-fecal forms (antrobactor, aerogens) on fibrous and vegetable substances in water. Most fish usually do not contain coliforms in their intestinal tracts unless they live in sewage contaminated waters.
The coliform group of organisms includes by definition “all aerobic and facultative, anaerobic, Gram negative, non-spore forming, rod shaped bacteria that ferment lactose with gas formation within 48 hours at 35° C”.
The coliform group embraces organisms of diverse origin among which the best known are:
(a) escherichia coli (E. coli) strains which are usually, but not always, of fecal origin, and
(b) intermediate and aerobacter aerogens strains which are usually, but not always of soil, vegetable or other non-fecal origin.
E. coli has been frequently proposed as a more specific and reliable indicator of fecal pollution than the broader coliform group. Nevertheless, there is still enough doubt as to the significance of various types of coliform organisms that their differentiation in routine water analysis is unwarranted.
Season has been reported to be a major factor in the occurrence of coliforms in well water, higher counts being reported for warmer months and lower counts for the colder months. Many investigators have also been concerned with the percolation of polluted water through the soils and the likelihood that ground waters will become substantially infected.
The distance pollution travels from bored latrines to ground waters depends mainly on the velocity of the ground water flow. This distance varies with soil structure, gradient of the water table and other factors. Some investigators believe that the safe distance between bore hole latrine and ground water source is the distance represented by about eight days of ground water travel.